MAXIMIZING THE MILK HARVEST A Guide for Milking Systems and Procedures Prepared by the Milking Machine Manufacturers Council of the Equipment Manufacturers Institute 10 S. Riverside Plaza Chicago, Illinois 60606-3710
Chapter 1 The Cow Chapter 2 The Milking Machine Chapter 3 The Operator Chapter 4 Vacuum Production and Control Chapter 5 Pulsation Systems and Purpose Chapter 6 Milking Units Chapter 7 Moving Milk From Claw to Receiver Chapter 8 Milking-Time Automation Chapter 9 Cleaning and Sanitizing Chapter 10 Certification of Service Technicians Chapter 11 System Start-Up, Analysis and Scheduled Maintenance Chapter 12 Glossary
Preface
About the Milking Machine Manufacturers Council The Milking Machine Manufacturers Council (MMMC) is part of the Equipment Manufacturers Institute (EMI). EMI is the trade association for manufacturers of agricultural, construction, forestry, materials handling and utility equipment.MMMC members meet voluntarily to discuss and respond to industry-wide challenges and opportunities. Through the council, members often provide resources, research funding information and educational materials that benefit dairy farmers. For example, MMMC develops national standards proposals that are reflected in the design, installation, testing and operation of milking systems.Other programs include: development of a typical certification and training program for technicians who install and service milking systems; design of a two-way communication protocol for transmitting dairy records to and from farm computers and a records processing center; collection of milking equipment sales data which companies use to forecast sales and set production schedules.The most recognized MMMC activity, however, is this book. First published in 1965 under the name, "The Modern Way to Efficient Milking," it has been updated and reprinted on a regular basis with over two million copies sold. The book serves as a ready resource on the design and operation of milking systems. Milking machine dealers, high school teachers, college lecturers or instructors, extension personnel, veterinarians, sanitarians and many others use the book in their work with dairy farmers. Furthermore, the book is a resource used by dairy farmers for training their milking staff.Under a new title, "Maximizing the Milk Harvest: A Guide for Milking Systems and Procedures," the 14th edition of the book is completely revised with new chapters and subject areas. It has incorporated a global flavor by using, in part, international standards terminology and international technical standards. These global features, however, are adapted to North American dairy practices.
Introduction
The milking system is the most important equipment a dairy farmer owns. It "harvests" the cash crop - milk. It comes into intimate contact with every cow two or more times a day. It's used 365 days of the year-no matter what the weather, and even when the calendar says it's a holiday.
The milking system often is misunderstood. That's why the Milking Machine Manufacturers Council (MMMC) provides this book to help dairy farmers, and those with whom they work, understand how milking machines and systems function.
A milking system alone does not harvest the milk. The cow and operator are equally important. Getting all three components to function harmoniously is the key to an efficient and successful milk harvest. The first three chapters of this book take a look at this three-legged stool-cow, machine and operator-to show how each leg supports the other two.
The remaining chapters discuss the milking system itself, as well as milking-time automation, cleaning and sanitizing, service technician certification, milking system analysis and maintenance. The final chapter is a glossary that brings meaning to many terms used throughout the book.
Chapter 1 The Cow
In the rush to get cows milked, many people often forget that, first and foremost, a cow is a mother producing milk. Certain practices enhance milk production and harvest, and others impede it. Basic knowledge of the physiology of lactation and mastitis sheds light on why cows are milked the way they are-both in terms of machine design and proper milking procedures.
How Milk is Made
The udder contains small cell-like milk sacs, known as alveoli. These resemble microscopic balloons (approximately one million per cubic inch) and are surrounded with blood vessels that bring in the raw material for milk production.
Cells that line each milk sac actually make the milk which then collects inside the alveoli. This is a continuous process during a cow's lactation period. Milk secretion rate can be limited by pressure when the udder is full of milk-just one reason why cows must be milked regularly and completely.
Lowdown on Letdown
A cow wouldn't think of letting down her milk if it weren't for a small gland at the base of the brain called the pituitary. This gland secretes a hormone, oxytocin, which travels through the bloodstream to the udder. In the udder, oxytocin stimulates a contraction of the tiny muscles surrounding the milk-filled alveoli. These tiny muscles act like rubber bands that squeeze the milk out, forcing the milk into the duct system, much like squeezing water out of a sponge.
There is an internal udder pressure that varies from 0.1 inches mercury above atmospheric pressure at the end of milking to between 0.4 and 1.4 inches just before milking. When the cow is properly stimulated before milking, this positive pressure can increase to 2 or 3 inches of mercury above atmospheric pressure.
Milk then flows by milk pressure from the alveoli and gravity through the udder cistern and into the teat cisterns. Here, the combined action of pressure within the udder and the vacuum within the milking unit withdraws milk from the teat cistern. Without oxytocin and the involuntary "squeeze" on the alveoli, little of the milk stored in the udder could be harvested.
The release of oxytocin (Chapter 3) and the resulting letdown is a conditioned reflex. In nature, this reflex is triggered by the calf. With machine milking, its triggered by routine and pleasant actions that the cow associates with milking - massage of the teats and udder, removal of a few streams of milk by hand or environmental sounds, such as turning on the vacuum pump.
Milking time should be a consistent, habitual routine. The cow should not be frightened or excited before or during milking because such stress results in the release of hormones that interfere with normal milk letdown.
Some easy-milking or early lactating cows will begin to leak milk from their teats when they hear milking-time noises or as milking time approaches. It is recommended that they should be placed early in the milking order to take advantage of this quick response.
The stimulation of milk letdown, which results in increased udder pressure, sometimes lasts no longer than five to seven minutes. Cows should be milked quickly and efficiently to minimize the amount left unharvested in the udder.
Complete milking is important to production. Residual milk consistently left in the udder will retard future milk production in the alveoli and subsequent milk secretion for harvesting. However, it's equally important not to over milk the cow; the milking machine should be removed when milkout is complete.
The Mastitis Menace
Mastitis remains the most common and expensive disease of dairy cattle throughout most of the world. It exists wherever there are cows. The disease is linked to many aspects of dairy herd management including level of nutrition, cow husbandry at calving, bedding management and milking procedures. The risk of new mastitis infections is higher in high-producing cows, faster milking cows, and greatest in all cows at the start of the dry period. In fact, it is estimated that one-third of the cows in every dairy herd would have mastitis unless a few simple and effective control procedures are followed.
What is mastitis? Mastitis is an inflammatory reaction of the mammary gland in response to a traumatic injury or to the presence of infecting microorganisms that have gained entrance into the udder. In the vast majority of cases, it is caused by microorganisms.
Infections may be clinical or subclinical, depending on the degree and severity of the inflammation. Clinical mastitis is characterized by visible abnormalities in the udder or milk. These may vary greatly in severity during the course of the disease.
Subclinical mastitis is far more subtle and cannot be detected by visual observation. However, it can be identified by conducting tests with milk samples to detect the presence of infective microorganisms or the products of inflammation such as somatic cells.
At one time, it was possible to predict with some confidence a relationship between somatic cell count in the bulk tank and the incidence of clinical mastitis. However, bulk tank cell count information is becoming a less useful investigative tool as the incidence of subclinical mastitis in many herds has fallen due to effective control measures.
Somatic Cell Count
Individual cow cell counts are more useful than bulk tank cell counts. But they, too, are often low even when clinical mastitis is present. More and more reliance must be placed upon clinical records when investigating a herd mastitis problem.
However, these new findings do not minimize the effect of subclinical mastitis in a herd. Many people do not fully appreciate the prevalence and economic importance of subclinical mastitis because the milk looks normal. But subclinical mastitis warrants attention for the following reasons:
Microorganisms that cause mastitis live on the cow, her udder, and in her surroundings. They are very tiny forms of life and cannot be seen with the naked eye. The microorganisms that most frequently cause mastitis can be divided into four groups as follows:
Contagious: Sources of contagious microorganisms are the udders of infected cows. Because infected udders are the chief reservoirs of these microorganisms, transmission from infected to uninfected quarters occurs mainly at milking time. Such organisms are well adapted to growing in the udder, usually establish subclinical infections of long duration, and are shed in milk from infected quarters in large numbers.
Environmental: Dairy herds in which contagious mastitis has been controlled sometimes have a higher incidence of clinical mastitis caused by environmental microorganisms. These microorganisms are abundant in the surroundings in which cows live, including manure, soil, bedding, feedstuffs, water and plant material. The prevalence of mastitis in cows infected with these organisms is usually less than 5%; thus, environmental mastitis often has very little effect on bulk tank somatic cell count. Housed cows are at greater risk of infection with environmental microorganisms than cows on pasture, and clinical cases increase with confinement during winter months.
Udders should be clipped as necessary to remove long hair and to reduce the amount of dirt, manure and bedding that adhere to hair and skin. Clipped udders are more easily cleaned and dried.
Opportunistic: This group of bacteria includes over 20 species of staphylococci other than Staphylococcus aureus. They are commonly referred to as Staphylococcus species or coagulase-negative staphylococci. Although they are often the most frequently isolated bacteria in the herd, infections with these microorganisms are usually mild and elicit only a slight increase in somatic cell count. Cell counts may approach one million per milliliter in subclinically infected quarters. Clinical symptoms are rarely exhibited, are mild, and are limited to clots and flakes in milk.
Other: A wide variety of other microorganisms may also cause mastitis. Infections with some of these organisms are often due to poor treatment procedures. Occurrence of infection is usually low, but outbreaks may occur when conditions develop that increase exposure to them.
Chapter 2 The Milking Machine
Milking machines started to replace hand milking about 100 years ago. To better understand how milking machines function, it helps to take a look at the action involved in the hand milking process. At the bottom of a cows teat is an opening called the teat canal. This canal is held closed by a group of muscles known as a sphincter. When harvesting milk, the teat canal must be forced open to establish milk flow out of the teat.
Compared with Hand Milking
In the hand milking process, milk flow is accomplished by using the thumb and forefinger to pinch off the milk at the upper end of the teat as the other fingers squeeze inward and downward. The squeezing action increases the pressure within the teat and forces the teat canal open, allowing the milk to pass through it. Since the size and resistance of the teat canal varies among cows, milk flow rates will vary from cow to cow.
In the hand milking process, milk flows out of the teat because the thumb and forefinger are used to increase pressure inside of the teat. In the machine method, however, milk flows from the teat because the pressure around the outside of the teat is lowered by vacuum and the greater internal udder pressure forces the milk through the open teat canal.
Both methods have the same end result: the creation of a pressure differential between the inside and outside of the teat. This differential is needed to overcome the closing forces of the teat canal.
The First Machines
Early attempts at milking machines tried to imitate the squeezing action created by the hand during the manual process. However, these crude devices did not function well and tended to cause injury to teats.
Suction used. Suction was first used in 1851 as the basis of a mechanized method for harvesting milk.
This idea was the first attempt at removing milk from the teat through the use of vacuum and is the forerunner to todays milking machines. However, hand milking remained the prevalent method into the early part of the 20th century.
Need massage. The problem with early attempts at using vacuum to milk cows was too much blood and body fluid congestion within the teat. The wall of the teat contains arteries and veins that allow blood fluids to collect in large quantities when the teat is exposed to vacuum.
Milking machine inventors quickly learned that, if vacuum was to be used successfully, a means for massaging blood and fluids out of the teat was necessary to ensure proper blood circulation. The development of the double-chambered teatcup in 1892 and the introduction of pulsation into the milking process provided the solution.
The massaging action on the end of the teat, created by the closing of the teatcup liner (also known as an inflation), helped the blood to flow up the veins for a more normal circulation.
Today's Milking Machines
The basic principle of machine milking is dependent on lowering air pressure by removing air from the milking system. This is done by the vacuum pump (see Chapter 4).
The pulsator alternately allows air at atmospheric pressure into the space between the liner wall and the shell, then removes this air by opening a port into the vacuum system (see Chapter 5).
When the pulsator shuts off the atmospheric air flow and the vacuum level is re-established in the area between the liner and the shell, the liner opens and milk flows from the teat canal. This is the milk phase of the cycle.
During the rest phase, the pulsator allows air at atmospheric pressure into the space between the liner and the shell. The difference in air pressure between the vacuum level within the liner and the atmospheric air pressure outside the liner causes it to collapse and massage the teat.
This process of mechanical milking - milk:rest, milk:rest, milk:rest - is continued throughout the milking.
Mastitis and the Milking Process
Milking machines and milking time management are intrinsically linked to mastitis prevention and control because a lactating cow is at risk of infection during and just after milking. A combination of good milking management and correctly functioning milking equipment helps to keep mastitis levels low.
Poorly functioning milking machines and poor milking time management may affect udder health in three main ways: (1) poor milking routines may expose the teat to infective organisms; (2) milking changes the teat or teat canal in ways that may encourage the multiplication of bacteria at the teat end especially if proper maintenance or routines are not followed; (3) milking can assist the movement of pathogens into or through the teat canal, especially toward the end of milking.
Figure 1. Conventional Teatcup.
Here's a closer look at all three effects.
1. Exposure to infective organisms. The milking machine can serve to transfer mastitis-causing microorganisms from cow to cow via the teatcup liners. Milking routines are recommended that will allow cows with infected quarters to be milked last to reduce this type of cross contamination.
The machine may also contribute to cross infections within the same udder (from an infected quarter to an uninfected quarter) by aiding the transfer of microorganisms across the milking cluster. New types of milking units, such as larger capacity claws, flow-directional claws, quarter-milking claws, or valved claws, may be of value in reducing such infections.
2. Changes to the teat or teat canal. Mastitis researchers agree that the main way in which milking machines will influence the level of exposure is likely to be their direct effect on the health of the teat canal and the skin of the teat. In other words, a damaged teat is more likely to harbor infective microorganisms.
The milking machine, although not the only cause, may affect the teat condition, and therefore new infection rate, by changing the integrity of the teat canal (which is the primary physical barrier to infection) or by changing the teat tissue. Faulty pulsation, over milking, and improper removal techniques (see Chapter 3) may contribute to teat damage and need to be avoided.
3. Movement of bacteria into or through the teat canal. The action of the milking machine can contribute to "impacts" - droplets or slugs of milk propelled against the teat end with sufficient force to penetrate partway into, or sometimes through, the teat canal. These "impacts" usually occur only when certain combinations of cyclic and irregular vacuum fluctuations are generated within the individual cluster at milking. Greatest risk occurs when bursts of air are allowed into the unit by operator procedures.
The most important effects of these within-the-cluster vacuum fluctuations are an increase in cross contamination between teatcups and an increase in the rate of new mastitis infections. These fluctuations generated within the individual cluster are the only ones known to be related to mastitis infections.
Cyclic vacuum fluctuations at the teat end result from the combined effects of pulsation and the presence of liquid within the short milk tubes and barrels of the liners. They occur because milk in transit impedes the free movement of air into and out of the liners as they open and close.
Irregular vacuum fluctuations generated within a cluster are caused by sudden air leakage past one or more teats and often are also accentuated by the presence of milk within the cluster. They may result from events such as liner slips, vigorous machine stripping or abrupt cluster removal.
These vacuum fluctuations are the reasons why tiny droplets of milk may impact against the end of the teat at very high velocity. Such droplet impacts may contain mastitis-causing microorganisms and increase the risk they may penetrate the teat canal.
Factors such as pump capacity, sensitivity of the vacuum regulator and size of airlines or milklines have little or no effect on the rate and extent of such vacuum drops within the individual cluster. However, they may affect the rate of recovery to the normal milking vacuum after the air leakage has been stopped.
Machine and operator related problems can be reduced by effective training of operators (see Chapter 3), competent system evaluation and service (see Chapter 10), and a regular program of equipment maintenance and service (see Chapter 11).
Chapter 3 The Operator
While the cow makes the milk and the machine harvests it from the cow, the two would never come together without the third leg of the stool-the operator. The cow and the milking system can function only as well as the operator allows them to. That's why its important for everyone who milks cows to understand proper milking procedures and the reasoning behind these recommendations.
Far more important than the milking machine is milking management-the way the machine is used and maintained.
Proper Milking Procedure
Preparing the teats and udder for milking has a two-fold purpose: to stimulate milk letdown and to reduce the number of contaminating microorganisms on the skin (see Chapter 1). Good preparation will reduce contamination of milk, decrease strippings, increase milk yield, shorten milking time and reduce the spread of potential mastitis-causing microorganisms.
A summary of recommended milking procedures follows.
Provide a clean, stress-free environment. The environment of the cow should be as clean and dry as practical. Even the best designed and maintained milking equipment cannot overcome a dirty environment. The three essential conditions for bacteria to thrive are moisture, temperature and food. Bacteria can multiply to enormous numbers in MUD (Manure, Urine and Dirt).
Check foremilk and udder for mastitis. Feel the udder to check for signs of clinical mastitis - hot, hard or enlarged quarters. Use a strip cup in stanchion barns or a plate in the parlor floor to examine foremilk for clotty, stringy or watery milk.
Milk should never be stripped directly onto the hand as this can spread microorganisms from teat to teat and cow to cow via contaminated hands.
Wash teats with a warm sanitizing solution. Correct washing and massaging of the teats sends a signal to the brain and causes the release of oxytocin, the milk letdown hormone, into the bloodstream. This hormone then travels to the udder where it stimulates the muscle fibers surrounding milk-secreting tissues to contract and cause milk letdown (see Chapter 1).
The ultimate goal of udder preparation should always be to milk clean, dry teats. Use of a bucket and rag for washing is not recommended. Preferably, use a low pressure hose and try not to wet the udders. The milking of wet udders and teats will lead to increased mastitis and higher bacterial counts in the bulk tank.
Use a premilking teat dip (optional: recommended in situations where a high level of environmental contamination of the teats is likely). Early research has indicated that predipping with a germicidal teat dip reduces udder infections caused by environmental microorganisms by 50 percent. However, teats disinfected in this manner must be dried thoroughly before teatcups are attached to avoid contaminating milk with germicide residues.
Only teat dips with label instructions for predipping should be used. Recommended predipping procedures are: clean teats, forestrip, predip teats, allow recommended contact time (usually 20 to 30 seconds), and dry teats with an individual paper towel to remove germicide residues, and attach teatcups.
Dry teats thoroughly. Use of excessive water to wash teats and udders, and failure to carefully dry the skin, result in water laden with microorganisms draining down and being drawn into teatcups. Such organisms may cause mastitis and will lower milk quality.
Regardless of the method used to prepare the teats and lower surface of the udder, these surfaces must be dried thoroughly before teatcups are attached. Single service paper towels are preferred, though cloths for each individual cow may be used if they are thoroughly laundered and dried between milkings.
Attach teatcups within one minute. Teatcups should be attached as soon as teats are full of milk, usually within one minute after udder preparation begins (this makes maximum use of the milk letdown hormone, oxytocin). Attach and adjust teatcups carefully to avoid the entrance of excessive air into the milking system. Improperly aligned milking units may block milk flow, increase strippings and slip more often.
It is important to minimize slipping or squawking of teatcups because liner slips contribute to machine-induced infections in the uninfected quarters of previously infected cows.
Shut off vacuum before removing teatcups. Remove teatcups just as the last quarter milks out. Vacuum should always be shut off before teatcups are removed. Otherwise, there is an increased risk of infection. A minute or two of over milking with a properly functioning machine does not necessarily predispose the udder to mastitis. However, research has shown that most machine-induced infections occur near the end of milking, and more teat damage occurs with over milking.
Dairy operators often ask the question, How should a quarter that milks out ahead of the other quarters be handled? It should be remembered that front quarters usually milk out early because they have less milk. The fact that front quarters normally have less mastitis than hind quarters, even though front teats get over milked more, tells us that over milking by itself is not a major cause of mastitis. Nevertheless, over milking should be minimized. Over milking causes more teat congestion, edema and teat lesions. It makes no sense to deliberately over milk cows when it has been shown to cause more teat damage. Automation, such as automatic cluster removers, reduces the risk of over milking.
Dip teats. Dipping teats with a safe and effective teat dip immediately after milking is perhaps the single most important thing a dairy farmer can do to reduce the rate of new infections. The entire teat should be covered with dip.
Teat dip cups must be kept clean and sanitary, and leftover teat dip should never be poured back into the original container.
Teat spraying, which is an alternative to teat dipping, is acceptable if the entire surface of the teat is covered thoroughly with the teat dip. Unfortunately, many milking operators only spray from one side and don't cover the entire teat.
Training Employees
When owners don't do the milking themselves, they must take the time to properly train their employees in the art of milking. Owners must never assume that their employees know as much about milking as they do, or that they'll use the same procedure for milking.
Start by asking a new employee what he or she already knows about: how a cow makes milk; how a cow gets mastitis; how a milking machine works; and what is a proper milking procedure. Then explain to the employee the things that he or she does not seem to understand. People will be more apt to follow proper milking procedures if they understand the reasoning behind them. They'll avoid rough treatment of cows if they know that it reduces the flow of milk. They'll dry udders thoroughly if they believe that wet udders may lead to increased mastitis and lower milk quality.
Operator's Responsibility
No matter who milks the cows, the dairy owner/operator has the ultimate responsibility of making sure the three-legged stool-cow, machine and operator has all legs securely on the ground. To do a continually good job of milking, dairy farmers must have an intuitive nature. They must keep their eyes and ears open for anything out of the ordinary.
An alert operator will immediately suspect that the milking system is overloaded or malfunctioning if teatcups fall off, if there's a slow return to operating vacuum levels after air enters the line, or if cows are uneasy.
An alert operator will check the cleaning and sanitizing system and check for cracked or torn tubes if bulk tank bacteria counts go up. An alert operator will schedule regular maintenance, not just emergency calls, with a certified service technician.
An alert operator will continue to seek help from a veterinarian, milking machine service technician, county extension agent, extension dairy specialist or other management specialists.
Remember... You have this team of resource specialists available for improving herd management. They can help improve your milking performance or reduce your mastitis problems.
Chapter 4 Vacuum Production and Control
The basic principle of machine milking is to lower the pressure outside the teat through the use of vacuum. That's why a properly functioning vacuum pump and system are so crucial to maximizing milk harvest.
Vacuum Basics
The term "vacuum" means pressure below atmospheric pressure. When air molecules are removed from an enclosed space (for example, by a vacuum pump), air pressure is reduced in that space. The difference between atmospheric pressure and the reduced pressure within the system is measured as the vacuum level.
Vacuum levels measured on a mercury manometer are expressed by the term inches of mercury (for example, 12" Hg). The higher the vacuum level in the manometer tube, the lower the air pressure acting on the surface of the mercury, meaning the mercury can be pushed higher up the tube by the atmospheric pressure acting on the open end of the mercury column.
In the milking system, there are two vacuum levels that need to be adjusted and monitored: the milking vacuum and the nominal vacuum.
Milking vacuum is the mean vacuum level found in the milking cluster during the period of main milk flow of a representative group of cows. It should be about 11" or 12" Hg of vacuum in the claw. The teat canal is fully opened at this vacuum level for most cows. The milking vacuum will vary slightly among cows due to differences in their milk flow rates.
Nominal vacuum is the vacuum level within the milking system measured at the vacuum gauge. It should be adjusted to provide a milking vacuum of 11" or 12" Hg for most milking systems today. See table below for general guidelines.
Approximate Settings for the Nominal Vacuum Level at the Vacuum Gauge
Highline (No Automation) 14"-15" Hg Weigh Jars (Center Mount) 13.5"-14.5" Hg Lowline (Direct to Line) 12.5"-13.5" Hg
Note: The actual vacuum setting depends on the average milking rates of cows in a herd and the number and type of extra components fitted between the cluster and the milkline or recorder jar. When end-of-milking indicators, ACRs, and milk meters are used, the vacuum should be set perhaps 0.5" Hg higher.
The correct vacuum level is essential in extracting peak performance from the milking system. If the milking vacuum level is too high (above 15" Hg), it may have the following effects.
Increased machine strip time. High vacuum may cause the unit to "ride up" on the udder and pinch off or restrict milk flow. As a result, dairymen may complain that it is sometimes necessary to pull down on the unit toward the end of milking and massage the udder by hand in order to completely milk out the cow.
Teat lesions. Teat lesions, such as hyperkeratosis, are aggravated by high vacuum or extreme over milking that creates a higher pressure differential across the teat end and adds stress to the teat tissue.
Increased teat congestion. A high vacuum level tends to cause more blood congestion in the teat end. This increases the tissue swelling which can reduce the size of the teat canal. A smaller teat canal means longer milking times. Over a period of time, the teat end can become hard and rough.
If the vacuum level is too low, it may cause the following.
Unit fall-off. Low vacuum levels cause units to fall off because not enough suction is provided to hold the unit on the teats. Unit fall- off most commonly occurs during high milk flow.
Liner slippage. Low vacuum can cause the weight of the unit to pull down on the teat which will break the teat seal around the mouthpiece of the liner. When the liner slips on the cow's teat during milking, air can enter the unit and cause the milking vacuum level to decrease.
Slow milking. Low vacuum results in slow milking because the teat canal is not fully opened and because of the lower pressure difference available to force milk out of the teat.
American Standard Method measures volume of Atmospheric Air (14.7#/sq. in. Absolute)
The old New Zealand Method measured volume of air at 15" Hg Vacuum (7.35#/sq. in. Absolute)
Vacuum Pumps
The vacuum pump is the heart of any milking system. While milking systems differ in design and construction, they all need an adequate vacuum pump - whether milking ten or 1,000 cows. Many dairy farmers make the mistake of using a pump that is too small for their system. They save money on the initial purchase but may lose a great deal more from decreased production. Recognizing the importance of an adequate and efficient vacuum pump can save a great deal of time and money.
Airflow ratings. To understand how vacuum pumps work, it helps to have an understanding of airflow ratings. Vacuum pumps are rated by cubic feet per minute (CFM). The CFM of a pump indicates how many cubic feet of air it can move per minute at sea level.
There are two methods used to measure the CFM capacity of vacuum pumps: the American Standard Method (ASME) and the New Zealand Method. The American Standard method measures air flow at standard atmospheric pressure, and the New Zealand method measures air flow at one half of atmospheric pressure. Therefore, one CFM under ASME equals two CFM under the old New Zealand method.
Recently, vacuum pump manufacturers have agreed to use the ASME method for rating pumps industry wide. However, many older pumps were rated by the New Zealand method. Keep this in mind when comparing older pumps with new pumps.
Vacuum pump sizing. When sizing a vacuum pump, all of the components in the system that will admit air during operation must be considered. As a rule, pumps are sized by accounting for the amount of air admitted into the milking system during the milking operation plus a 50 percent reserve which provides for accidental air admittance and the deterioration of parts.
The table gives the minimum values for each component based on industry averages. Even though these values are adequate for most systems, checks should be performed on a regular basis. Atmospheric air pressure is less at higher elevations; therefore, vacuum pumps will have less capacity. The table provides the estimated correction factors (based on elevation) to use when rating pump capacity.
The table listing the minimum CFM requirements for pipeline milking systems indicates that the minimum required for any system is 35 CFM. There are two reasons for this minimum value - air flow reserve and system wash requirements.
MINIMUM CFM REQUIREMENTS Pipeline Milking System
(Vacuum Level 15" Hg)
Note 1: The 50% reserve capacity recommended is included in the table above.
Minimum required for any system (based on 15" Hg) 35 CFM
VACUUM PUMP CAPACITIES Bucket Milking System - Minimum Capacity
MANUFACTURER'S CFM RATINGS FOR VACUUM PUMPS
AT SEA LEVEL
In referring to the following tables the vacuum pump CFM rating is in accordance with ASME. Atmospheric pressures and distance above sea level will change output of vacuum pump.
Elevation Correction Factors for CFM Rating
Elevation Estimating Factor X (Feet above times capacity at sea sea level) level equals true capacity 0 1.00 1,000 0.96 2,000 0.93 3,000 0.90 4,000 0.86 5,000 0.83 6,000 0.80 7,000 0.77 8,000 0.74
ALFALAVAL AGRI INC. Kansas City, MO
Vacuum Pumps: CFM Ratings Motor Pump Model Pump HP Speed Standard Nominal 15" 14" 13" 12" 11" 10" ---------------------------------------------------------------- 18 1 1525 11 11 12 13 14 14 76 2 935 27 29 31 33 35 36 76 3 1250 36 38 41 43 46 48 777 5 1000 56 60 65 69 74 78 78 5 800 56 60 65 69 74 78 78 7.5 1090 80 86 92 98 104 110 78 10 1270 100 107 115 122 129 137 84 10 760 120 128 138 148 157 164 84 15 950 150 160 173 184 196 206 86 15 760 160 171 184 197 210 219 86 20 950 200 214 230 246 262 274 RVM-9 5 1750 48 52 55 59 62 64 RVM-14 7.5 1750 57 61 64 68 70 74 RVM-16 10 1750 78 84 90 96 101 106 RVM-19 15 1750 109 116 123 130 137 145 RVM-21 25 1750 156 169 180 191 201 212 RVM-23 30 1750 203 220 235 252 270 289 RVM-25 40 1450 250 266 283 299 315 332 RVM-25 40 1750 310 327 350 373 394 414
BABSON BROS. CO. Naperville, IL
Vacuum Pumps: CFM Ratings Surge Motor Pump Model Pump HP Speed Standard Nominal 15" 14" 13" 12" 11" 10" ________________________________________________________________ Alamo 550 20 21 22 23 24 25 Alamo 1200 43 45 48 50 52 55 Alamo 1400 5.5 1150 50 55 60 66 72 77 Alamo 2300 8 1150 84 88 94 99 105 112 Alamo 2800 9.5 1150 101 105 111 116 122 129 Belt Drv 1050 3 780 38 39 41 44 46 48 Belt Drv 1400 5 1130 53 55 58 61 64 67 Belt Drv 2200 7.5 915 80 83 87 92 96 101 Belt Drv 2800 10 1130 101 105 110 116 122 128 Water Ring 12480 7.5 1420 66 69 73 77 80 84 10 1740 82 86 91 95 100 104 Water Ring 12430 15 1100 125 131 139 145 152 159 20 1310 155 163 172 180 188 197 25 1485 175 184 194 203 213 222 Water Ring 12440 25 910 200 210 222 232 243 254 30 1020 225 236 250 261 273 286 40 1210 258 268 283 296 310 324
BOU-MATIC DAIRY EQUIPMENT CO. Madison, WI
Vacuum Pumps: CFM Ratings Motor Pump Model Pump HP Speed Standard Nominal 15" 14" 13" 12" 11" 10" ------------------------------------------------------------------- Oil Vane FR-3A 5 1700 43 46 50 54 57 61 FR-4A 5 1500 48 52 56 60 64 68 FR-4A 7.5 1725 65 70 76 81 86 92 DB-2000 5 610 50 54 58 63 66 70 7.5 855 78 84 91 98 103 110 10 1100 100 108 116 125 133 141 VP-115 5 1300 58 62 67 73 77 82 VP-155 7.5 1750 78 84 91 98 103 110 VP-230 10 1300 115 124 134 144 152 162 VP-330 15 1277 165 178 193 207 217 232 Water Ring VPW-250 15 1750 125 133 141 150 158 166 VPW-330 20 1750 165 175 187 198 209 220 VPW-385 25 1750 183 194 208 219 231 243 VPW-470 30 1750 235 250 266 281 297 313 Lobe BVP-100 5 3169 45 48 51 54 57 60 BVP-140 7.5 2920 70 75 80 85 90 95 BVP-200 10 2060 95 101 107 114 121 128 BVP-400 15 2030 145 155 164 174 184 194
UNIVERSAL DAIRY EQUIPMENT INC. Kansas City, MO
Vacuum Pumps: CFM Ratings Motor Pump Model Pump HP Speed Standard Nominal 15" 14" 13" 12" 11" 10" ------------------------------------------------------------------ 306076 3 1185 35 37 40 44 47 50 306083 3 1185 35 37 40 44 47 50 306154 5 1055 58 63 70 76 83 90 306084 5 1055 58 63 70 76 83 90 306155 7.5 1000 83 91 101 112 124 136 306085 7.5 1000 83 91 101 112 124 136 306120 10 977 118 125 143 159 176 193 306158 10 977 118 125 143 159 176 193 306156 10 977 118 125 143 159 176 193 306122 15 1255 155 177 189 202 216 229 306157 15 1255 155 177 189 202 216 229 Air flow reserve. Vacuum pumps are sized to take into account
the accidental admittance of air during normal operations. By making the minimum requirement 35 CFM, a reserve air flow capacity is automatically calculated for smaller systems.
As a general guideline, there should be enough air flow reserve to handle one milking unit fall-off without exceeding 1-2" Hg drop in vacuum on installations with less than 16 units. In larger systems, the vacuum system should have enough air flow reserve to handle two milking unit fall-offs simultaneously.
WESTFALIA SYSTEMAT - DIVISION OF CENTRICO, INC. Elk Grove Village, IL
Vacuum Pumps: CFM Ratings Motor Pump Model Pump HP Speed Standard Nominal 15" 14" 13" 12" 11" 10" ------------------------------------------------------------------- Oil Vane RPS-2800 5 740 55 61 68 74 80 86 RPS-2800 7.5 1030 83 91 99 107 114 122 RPS-2800 10 1230 110 120 130 138 146 154 RPS-5600 15 660 150 166 177 187 199 210 RPS-5600 20 850 200 222 236 250 266 280 Lobe Air RPD-5 5 4800 50 52.5 54 56 56.5 57 RPD-7 1/2 7 1/2 3600 75 77 79.5 81 83.5 86 RPD-10 10 2500 100 103 107.5 110 112.5 115 RPD-15 15 2800 150 153 157 160 162.5 165 RPD-20 20 3300 200 205 210 215 220 225 RPD-25 25 2800 250 255 257.5 260 262.5 265 RPD-30 30 2030 300 305 307.5 310 312.5 315 RPD-40 40 1400 400 405 407.5 410 412.5 415 System wash requirements. Vacuum powered clean-in-place (CIP)
washing systems for pipelines require adequate vacuum to properly clean. Most CIP systems use an air injector to admit large volumes of air into the system on an intermittent basis. This air admission forms a slug of water that scrubs the milk contact surface. The minimum 35 CFM recommendation provides the built-in reserve needed to maintain the vacuum level during the wash cycle when an air injector is in use.
Vacuum Controller
The vacuum controller admits the necessary air required to maintain a constant vacuum level. During normal operation, air is admitted into the system as units are put on and taken off the cows. As the volume of air changes, the controller will either increase or decrease the amount of air that it admits.
As the operator or milking equipment admits more air, the controller reduces the amount of air it admits. If the operator or equipment admits less air, the controller admits more.
Vacuum controllers are rated in three categories:
The CFM capacity of the controller must meet or exceed the CFM capacity of the vacuum pump at the operating vacuum level.
Sensitivity is defined as the controllers ability to respond to a change in vacuum level and the time it takes to recognize that change. Most controllers on the market today are the servo-diaphragm design which will respond to a vacuum level change of 0.1" to 0.2" Hg or less which occurs for less than 0.2 second.
Airlines
A pipeline milking system (around the barn or in a parlor) is designed and installed with three different types of pipelines, all of which are under vacuum: the main airline; the milkline (see Chapter 7) and the pulsator airline (see Chapter 5).
The main airline is defined as the pipeline that extends from the sanitary trap to the vacuum pump.
This line is important to the milking vacuum stability of the system and, as a result, must be able to move the air necessary to maintain the recommended vacuum level. The line must also be able to move the full volume of air admitted into the system by the air injector during washing. The diameter, length and design of the main airline will influence the system's ability to move the necessary air for both milking and washing.
Sizing the airline. When sizing the diameter of the main airline pipe, the main goal is to keep the vacuum drops (a.k.a. pressure drop, pressure loss, head loss) to less than 0.75" Hg, and preferably between 0.25" and 0.50" Hg. Vacuum pump capacity is reduced by about 5 percent with an increase in vacuum head of 0.75" Hg.
Traditionally, the industry airline sizes are based on the number of milking units in the system. But more recent research has caused a shift in thinking. Recommended practice is to size airline diameter based on:
Number of milking units is no longer considered. For example, given the same number of units, a 3-inch diameter pipe may be adequate if the line is short, whereas a 4-inch diameter pipe will be needed if the line is long.
The table shows the recommended maximum air flow rates for different sized airlines under various conditions.
There is no advantage in installing airlines above the recommendations indicated in the table.
RECOMMENDED MINIMUM PIPE SIZES (Inches Internal Diameter) FOR THE MAIN AIRLINE OF A MILKING SYSTEM Vacuum Pump Approx. Length of Main Airline Capacity (Feet of Straight Pipe) CFM-ASME 20 40 60 80 100 50 2 2 3 3 3 60 2 3 3 3 3 70 3 3 3 3 3 100 3 3 3 3 3 150 3 4 4 4 4 200 4 4 4 4 4 250 4 4 4 6 6 300 4 6 6 6 6 350 6 6 6 6 6 400 6 6 6 6 6
NOTES: The main airline is defined as the pipeline between the vacuum pump and the sanitary trap near the receiver.
These calculations are based on a maximum vacuum drop of 0.5 inches of mercury between the receiver and vacuum pump. The maximum air flowrate is normally from the vacuum regulator to the pump. Whenever additional air enters the milking clusters during milking, however, the maximum air flowrate is from the receiver to the vacuum pump.
This ready reckoner table includes an allowance for the equivalent length (feet of straight pipe) of one distribution tank, one sanitary trap and 4 elbows. If the system includes more than 4 elbows, then use the next pipe length column to the right for every 3 additional elbows.
Low line pipeline
High line pipeline
Chapter 5 Pulsation Systems and Purpose
The rhythmic action of the pulsation is a familiar sound to anyone who has ever milked cows. But pulsation does more than set a beat; it's the element that allows cows to be milked with vacuum machines.
Pulsation's Purpose
The main purpose of pulsation is to limit fluid congestion and edema in the teat tissues during machine milking. It allows the teat to be massaged (see Chapter 2).
The pulsator sets teat massage in motion by alternately introducing vacuum and atmospheric pressure into the pulsation chamber of the teatcup (area between the shell and liner). When air at atmospheric pressure is admitted into the pulsation chamber, the resulting pressure differential across the liner wall causes the liner to collapse beneath the teat.
The collapsed liner applies little or no pressure to the teat wall itself and does not close the teat cistern at any stage of milking. However, the collapsed liner does squeeze the teat hard enough to close the teat canal and provide enough massage to prevent fluid congestion and edema near the teat end.
Contrary to common belief, the collapsed liner does not shut off vacuum at the teat end.
Rates, Cycles and Ratios
There are many different brands and designs of pulsators currently in use on milking machines. All pulsators are valve mechanisms that alternately connect the pulsation chamber of the teatcup to vacuum (milk phase) or to air at atmospheric pressure (massage phase). Pulsation rate is defined as the number of complete pulsation cycles per minute. For example, a rate of 60 pulsations per minute means that the liner opens and closes 60 times in one minute or once every second.
The pulsation rate should be set according to the manufacturer's specifications. Most milking machines operate efficiently with pulsation rates between 45 and 65 cycles per minute. Increasing pulsation rate will not necessarily increase milking speed. Pulsation cycle. A pulsation cycle is divided into four main phases:
Pulsator ratio. Each cycle is described in terms of a ratio of the amount of time spent opening and holding open the liner (phases A and B) and the amount of time spent closing and holding the liner closed (phases C and D).
For example, a 60:40 pulsator ratio means that the vacuum is increasing or at maximum vacuum for 60 percent of the cycle and decreasing and/or at atmospheric pressure for 40 percent. This ratio is often expressed as a percentage of one complete cycle, e.g. 60%.
Milk:rest ratio. This is defined as the ratio of time that milk can flow, within a pulsation cycle, to the time that milk flow is stopped by the compressive load applied to the teat by the closing liner. For example, the milk:rest ratio might be 65:35 for a given liner and a pulsator ratio of 60:40.
Pulsation Action
A pulsation system can have either simultaneous or alternating action. With simultaneous (or single) action, all four teatcups are on the same pulsation cycle-all four milk at the same time and massage at the same time.
With alternating action, two pairs of teatcups are on the same pulsation cycle-two are milking while the other two are massaging. The unit may be divided so that teatcups on one side work opposite the other side, or so that the front teatcups work opposite the back teatcups.
Millions of cows have been milked with either pulsation action with excellent results. Overall, both research evidence and field experience seem to favor alternating pulsation.
Alternating pulsation provides a more constant flow of milk from the claw since at least one pair of teatcups is always in the milking phase. And, in smaller capacity milker units, alternating pulsation helps increase the vacuum stability within the unit; this advantage is not as important with large capacity units.
Cyclic vacuum fluctuations, which occur inside the milking unit each time the liner opens and closes for milk flow and massage, are present with each type of action. However, given the same claw and liner type, simultaneous pulsation results in greater cyclic vacuum changes within the claw. Alternating pulsation doubles the frequency of the variations but reduces their magnitude.
Simultaneous pulsation usually results in slower opening and closing phases (phases A and C of the pulsation cycle). This is because all four teatcups are being evacuated through one long pulse tube and pulsator valve at the same time.
Dairymen should discuss the advantages and disadvantages of each system before deciding whats best for their operation alternating or simultaneous pulsation.
Pulsator Airline
The pulsator airline loops around the barn or parlor and transfers vacuum to several types of pulsation valves which intermittently evacuate atmospheric air from the pulsation chamber of the teatcup; this action opens and closes the liner to perform the milking function.
The pulsator airline should be looped to prevent any large change of vacuum from occurring at the end of the system. Because these lines will get moisture and milk in them at times, they should be installed so they can be washed during a scheduled service call. Risers are permissible within the vacuum system but must be installed with a drain on the lowest point of the riser.
Sizing the line. The pulsator airline should be adequately sized to cope with the cyclic air flow as the pulsators open to remove the air from between the liners and shells. Vacuum fluctuation should be no more than 1" Hg in the line each time the pulsators operate. If not adequately sized to the number of pulsators installed, the pulsator airline vacuum will fluctuate 1" to 2" Hg in phase with the pulsation cycles.
The pulsator airline sizes suggested by the ASAE S 518 Standard are shown in the table.
Filtered (Clean) Air System. For permanent mounted pulsator systems, atmospheric air should be supplied through a separate filtered atmospheric airline. This helps maintain pulsator performance between service intervals and is highly recommended.
MINIMUM SIZES FOR PULSATOR AIRLINE OF PIPELINE MILKING SYSTEMS (New Installations)
Chapter 6 Milking Units
Of all the components in a milking system, the milking unit is most familiar to the dairy operator. The unit is seen and handled by the operator cow after cow, day after day, to the point where it is attached by habit, with no thinking required by the operator.
Familiarity should not breed complacency. Since the milking unit is the only part of the system that actually comes into contact with the cow, the operator must keep a close eye on it to make sure that it is always harvesting milk to the best of its design capabilities.
While unit attachment is largely dependent on the operator (see Chapter 3), the design and construction of the unit can help to harvest the entire milk crop as quickly as possible. Research suggests that the speed with which a cow is milked may influence total production and herd health.
Unit Attachment
The weight of the unit should provide tension on the cows udder to allow proper positioning throughout the milking cycle. The unit's position is influenced by milking vacuum levels. Many times when the operator complains that the unit is too light or too heavy the problem is actually that the milking vacuum level is either too low or too high.
If the vacuum level inside the unit is too high, or the unit is too lightweight, it tends to draw more teat tissue into the teatcup. This is sometimes referred to as creeping teatcup. When this occurs, the area at the top of the teat and bottom of the udder is closed off, and milk cannot flow from the udder into the teat. As a result, the cow will not milk out without additional force being applied, such as the operator pushing down on the unit. (See page 18.)
If the vacuum level is too low or the unit is too heavy, the unit may tend to fall off the cow, or there may be more liner slips and squawks. (See page 18.)
The construction and design of the unit should allow the weight to be evenly distributed during milking. The weight of the unit should be adjusted and evenly balanced on the cow. If this is not done, uneven or slow milkout may occur. This increases milkout time and, over time, may cause the udder to become uneven. Hose support devices help assure proper unit adjustment.
Unit Detachment
The way in which teatcups are removed is probably more important than when they are removed. The best way is to shut off the vacuum to the claw so that the cups slide gently off the teats without pulling or squawking.
The Claw
The design of the claw affects milk harvest in many ways. Reach. The position of the inlets on the claw should provide adequate and uniform reach to all four quarters. Many cows have udders and teats with a forward slope or tilt. Milk removal may be impaired if one teatcup assembly partially clamps off, thereby restricting milk flow.
Milk inlets. The milk inlets into the claw should be large enough to handle peak milk flow rates. Small diameter inlets and liner milk tubes can cause milk to dam up in the body of the liner, causing the cow to milk more slowly especially during peak flow rates.
Milk outlets. Likewise, the size of milking unit outlets is important for proper milk and air flow away from the claw. A 58" milk outlet and milk hose provide the necessary capacity to move milk and air away from the claw faster while maintaining vacuum stability. Allowing the milk to dam up in the unit creates a turbulent flow which reduces vacuum levels during peak flow rates.
Visibility. A milking unit designed for visibility lets the operator view the milk flow out of each quarter. This allows the operator to make sure that the unit is properly adjusted to the cow and that all quarters are milking properly. Another benefit is to identify the end of milking without pinching the liner stem. Pinching the stem is a very imprecise method for detecting the end point of milking.
The Teatcup
As far as the cow is concerned, the teatcup is the only part of the milking machine that really matters. All the forces applied by the machine to the cow must be transmitted via the teatcup liner to the teat.
The teatcup consists of a rigid outer casing (shell) and a rubber liner (inflation). The inside of the liner, beneath the teat, is connected to continuous vacuum. The outer chamber, or pulsation chamber (between the teatcup shell and the outside of the liner), is connected to the pulsator. During milking, the pulsator alternately connects the pulsation chamber of the teatcup to vacuum or air at atmospheric pressure; this action opens and collapses the liner to milk the cow (see Chapter 5).
The liner, or inflation, plays an important role in maximizing production and minimizing stress on the cow's teat by providing the milking and massaging action necessary.
Dairy producers should follow the manufacturers recommendations when selecting a liner. It is imperative to have liners and shells that match; mismatching liners and shells impairs milking performance because the liner interacts with several components of the milking system, such as the pulsator and milking vacuum levels. Contrary to popular belief, thin-walled, soft rubber liners, which require only a small pressure difference for collapse, may apply a relatively low compressive load to the teat. The load applied to the teat increases with increasing wall thickness, rubber hardness and increasing liner tension.
Liners are made of several different combinations of materials that influence their expected life, or the number of cow milkings obtained. Generally, natural rubber liners last for 600 to 1,000 individual cow milkings. Liners made from a mixture of natural and synthetic rubber last for about 1,200 cow milkings. Silicon liners last for around 5,000 cow milkings.
It's extremely important to follow the manufacturers guidelines on when to change liners. Trying to stretch more milkings out of a worn-out liner is penny wise and pound foolish.
In addition to following the manufacturers guidelines, here are some other indications that a liner is worn out: visual signs, such as holes, bulges, cracks or loss of elasticity; high incidence of liner slips and fall offs; slow milking or milk left behind in the udder (not always due to worn liner). If theres a noticeable difference in milking performance after liners are changed, the liners were changed too late.
A liner's life span is based on many factors. One is the number of times it opens and closes, which reduces the elasticity and the reaction of the liner. When a new liner is put into a teatcup shell, it is stretched to help prevent air leaks and to add tension to the liner. As the liner ages, the tension weakens and the liner opens more slowly.
This slower action means that the liner will start to milk more slowly over time. And the weaker tension affects the compression applied to the teat; blood will not be properly massaged out of the teat and slower milking will result.
The chemicals used to wash and sanitize the system also affect liner life. The chlorine used in pipeline detergents and sanitizers will shorten the life of rubber goods. If liners are used for extended periods of time (more than the recommended life), the surface will start to roughen and harbor bacteria.
Storage is another important factor because liner life can be affected by sunlight, electric motors or other sources of ozone.
Chapter 7 Moving Milk From Claw to Receiver
Once the milking unit has done its job of harvesting milk from the cow's udder, that milk has to be transported from the unit claw to the bulk tank. That transportation system has to be properly sized and designed so milk can be moved quickly without flooding the line or backing up through the milking unit. There also has to be ample room for air flow.
Milk and air flow through the system together, under vacuum, from the time they enter the claw to the time theyre separated in the receiver. Why admit air into the claw?
Air Admission
Controlled air admission through claw air vents helps to stabilize and maintain the vacuum level in the claw. When the unit is first attached to the cow, the vacuum level in the milkline and the claw will be equal. As milk flow is established, the vacuum level in the unit decreases because of the hydrostatic pressure of milk in the long milk tube (or milk hose). The mixture of air and milk in the long milk tube is less dense than a solid column of milk, so the hydrostatic pressure (between the milkline and claw) is reduced.
Without proper air admission, milk will flood the unit which will lower the vacuum and increase the risk of machine-induced udder infections.
Claw air vents should be positioned to inject air on top of the milk, not below the milk surface. Injecting air below the milk surface or using oversized vents increases agitation, which can reduce milk quality by raising acid degree values (delicate protective membranes on fat molecules are ruptured by the agitation). Increased acid degree values lower butterfat content, contribute to off flavors and shorten the milk's shelf life.
Pipeline system flow map
Milk Hose (Long Milk Tubes)
Once milk and air leave the claw, they enter the long milk tubes. The flow pattern in the milk tubes depends on factors such as the tube diameter, the volume of air relative to milk and whether the milk is being elevated.
Long milk tubes commonly come in two diameters, 9/16-inch and 5/8-inch. The wider diameter (5/8) is generally preferred because it moves milk during peak milk flow with less vacuum reduction. The maximum recommended length for milk tubes is 9 feet. However, they don't have to be that long; they should be as short as practical so there are no unnecessary loops and so they hang squarely on the udder without dragging on the floor. Hose support devices help keep the long milk tubes positioned correctly.
Having milk flow down to the milkline is better than having it flow up to an elevated milkline; vacuum at the claw is more stable and milk quality is better with "downhill" milking. That's because it takes vacuum energy to lift the milk against gravity. Consequently, during peak flow of milking, the vacuum at the claw will fall by the extent that milk must be lifted. Then when milk flow decreases near the end of milking, the vacuum at the claw climbs back up. Consequently, vacuum at the claw is low when it should be high for peak flow; and it's high when it should be low at the end of milking to reduce teat congestion.
Lifting the milk also affects milk quality. The higher it is lifted, the larger the rise in acid degree values. This is because, in order to be lifted, milk has to fill the cross section of the milk tube completely; so the tube is filled with little slugs of milk separated by bubbles of air.
Milklines
After moving through the milk hoses, milk and air enter the milkline. The inlets, where milk hoses are connected to the milkline, should be installed on the upper one-third of the line to prevent restrictions from occurring as the milk enters the pipe.
Milk flow. Flow conditions in the milkline are different from those in the milk hoses. And those conditions change frequently because of variations in the number of cows being milked at one time and the amount of milk coming from each cow. Ideally, milk should flow in the lower part of the milkline with a clear, continuous space above for the much larger volume of air to pass over it. In practice, flow typically varies between stratified flow (the preferred condition to maintain a reasonably stable vacuum to the cluster) and slug flow (fluid flowing at uneven speeds which increases acid degree value and the vacuum fluctuations in the milkline).
Under conditions of stratified flow, gravity is practically the sole driving force for milk flow because milklines normally are installed with a slight fall toward the receiver end. The effect of air speed is critical. Above 10-12 feet per second, the drag of air on the milk surface causes it to form waves, the first stage of slug formation. Foam on the milk surface also increases the likelihood of slug formation.
Sizing lines. Milklines are sized to provide ample capacity for both milk and air flow. The diameter of the line required for a given installation is based on the number of milking units.
MAXIMUM NUMBER OF MILKER UNITS PER SLOPE
The figures in this Table are the same as those given in 3-A Accepted Practices because they are the currently accepted national guidelines at the time of publication of this book (February, 1993). These guidelines may change, however, depending on the outcomes of research, funded by MMMC, and the present revision of ASAE standard S 518. The new ASAE standard is likely to replace the performance requirements presently given in 3-A Accepted Practices. MMMC will adopt the new performance and construction guidelines in ASAE S 518 as soon as the revised standard is published.
The sizing recommendations in the chart are based on adequate capacity for transporting milk, as well as air, from the unit. Industry recommendations provide for at least 50 percent of the lines capacity to handle air entering the line. If additional capacity is used for milk flow, air flow will be restricted resulting in fluctuations in the milkline vacuum level during peak milk flow.
Loop and slope. Milklines should be installed in a continuous loop (no dead ends) and should be sloped. Looping the milkline will allow the air to flow in either direction and will help to ensure that the line is properly washed. Sloping the line will aid milk flow toward the receiver during milking, and it will help the system drain properly during washing.
The slope of the line should be a minimum of one inch to every ten feet of pipe (0.8%) toward the receiver. Lower slopes and/or flat spots in the line increase the risk of slugging in a milk line and reduce its ability to drain completely.
Receiver. The receiver, which is under vacuum, receives both milk and air from the system. Its also the place where air and milk are separated. Milk is drawn into the milk pump and released to atmospheric pressure as it travels to the bulk tank. Air continues through the main airline to the vacuum pump where it is discharged to atmospheric pressure.
Chapter 8 Milking-Time Automation
The days of robotic milking, when machines do everything from the time a cow enters the parlor until it exits, aren't commonplace-yet. But there are several automated procedures in use today that have changed the way cows are milked on thousands of farms.
Automatic Detachers
Since milking is such a labor intensive operation, even slight improvements in milking efficiency can add up to significant savings. That's why automatic detachers are the choice in many milking parlors, and even in some stall barns.
With automatic detachers, milking operators don't need to keep running back to cows to see if they're milked out; the machine does it for them. This significantly increases parlor throughput, as measured in cows milked or milk harvested per man hour.
Automatic detacher units are connected loosely to the milking claw, allowing the claw to hang freely as the cow moves and shifts during milking. Based on the rate of milk flow, the detacher detects the end of milking. It then provides positive vacuum shutoff to the claw and removes the claw from the cow.
Advantages of using automatic detachers include: reduced labor and possible elimination of an operator in the barn or parlor; a more consistent indication of end of milking, which is especially important if several people milk the cows; less drudgery and running from cow to cow, making the parlor a more pleasant place to work.
Also available are "end of milk indicators" designed for pipeline systems in stall barns. These detect the end of milking without the automatic detach function. They are designed to be portable so they can be carried easily from stall to stall.
Milk Metering
Up-to-date milk production records help dairy producers make timely management decisions. Electronic milk meters, which tabulate the amount of milk flowing from each cow, give that information at every milking. And, when tied into a herd management computer system, milk production records are automatically summarized into useful reports.
What advantage do daily milk records have over monthly testing? They are more accurate and timely, with 60 records per month (2x milking) versus two. Consequently, they help dairy operators detect problems early so they can take action before a problem can become serious. Cows with lower production may be giving an early warning of health problems, or they may be in heat.
Milk meters can also monitor milk production changes caused by a change in feeding the same day the ration is altered-not weeks later. These are effective, modern management tools.
Animal Identification
As herd sizes grow, it becomes increasingly difficult to identify animals at milking time. This problem is magnified when there are numerous people milking during several shifts throughout the day.
Automatic identification systems can accurately identify animals at each milking and tie the cow number to the production information given by the milk metering system. This reduces labor by eliminating the need to enter cow numbers by hand. And it increases overall record accuracy by removing the chance for human error.
Automatic identification systems can also be tied into herd management computer systems for computerized feeding and other applications on the dairy. Some systems can alert the milking operators to cows that have been treated for mastitis, cows giving colostrum or cows that are due to come in heat.
Each cow is identified by a transponder. The transponder sends a signal via an antenna, either when the cow enters the parlor or when it reaches its individual stall in the parlor.
Backflushing
Since teatcup liners can spread mastitis pathogens from cow to cow, thus increasing the risk of infection (see Chapter 2), automatic backflushing has become an important management tool in many milking parlors.
Automatic backflushing units disinfect the milking cluster between cow milkings. Backflushing with a 15 to 25 ppm (parts per million) iodine solution will significantly reduce the bacteria present on teatcup liners.
Backflushing systems consist of a water rinse followed by a chemical rinse and "contact time" for that chemical to kill bacteria. Then there's a second water rinse followed by a "vacuum or air dry" period. Backflushing takes about one minute and is automatic, either individually as each unit detaches or as a group when the last unit on a parlor side detaches.
Even though automatic backflushing can be an effective practice in the prevention and control of mastitis, it does not replace other good management practices such as post milking teat dipping.
Chapter 9 Cleaning and Sanitizing
As milking equipment becomes more sophisticated, so, too, does the method of cleaning that equipment. Clean-in-place systems have replaced "elbow grease" and brushes on many farms. At the same time, milk quality standards are becoming stricter, with the allowable bacteria count for Grade A milk currently at 100,000 per milliliter. Now, more than ever, dairy producers must pay close attention to their cleaning systems.
The three basic steps of any cleaning process are:
In the manual cleaning process, the brush is used to lift the soil; "elbow grease" is used to break it down; and sudsing detergent disperses the soil load.
These elements are not all present in the clean-in-place (CIP) process. The mechanics of the CIP system must be relied on to properly clean the pipeline.
Requirements of CIP Cleaning
CIP cleaning has certain mechanical requirements that are essential for the successful and effective removal of milk soil. Those requirements are: velocity, volume, temperature, chemical balance, time and drainage.
Velocity: Because the physical scrubbing action and "elbow grease" in the manual process are missing in CIP cleaning, it is essential for adequate velocity to be generated within the system. Velocity is needed to scrub the equipment surface and to lift and carry the soil load out of the pipeline.
Velocity is generated by using air injectors to admit air into the system at timed intervals. This air admission forms slugs of water that scrub the surface and remove the soil. Air injectors may also minimize and/or reduce the amount of water required to wash the system. A reduction in water results in less chemicals needed to clean the system.
Volume: The amount of water used during each cycle influences how well the system cleans and dictates how much chemical is used. During all cycles, the wash vat should never be empty before return water re-enters the vat, and the system should never be allowed to suck air. Insufficient amounts of water cause minimal wash solution contact with the equipment surfaces, potentially leading to fat, mineral or protein buildups.
A table of equipment capacities, from which the proper amount of water can be calculated, should be available from the manufacturer of the milking equipment.
Temperature: The temperature of the water used in each cycle dictates how effectively the chemicals work. During the wash cycle, temperature is especially important because chlorinated-alkaline cleaners do not work as well at low temperatures. If water temperature is not maintained, buildups can occur.
The water temperature during the pre-wash rinse should be between 95 and 110 degrees F. This temperature helps remove the bulk of the soil load and warms the surfaces for the wash cycle. Butterfat will begin to solidify below 93 degrees F.
During the wash cycle, the circulating water temperature ideally should begin at about 170 degrees F and end at no less than 120 degrees F. Excessive heat may also dissipate, burn off, the chlorine in liquid CIP detergents, potentially minimizing protein removal.
The water temperature for the acid rinse should be between 95 and 110 degrees F. Temperatures should not exceed 140 degrees F because extremely hot temperatures can cause the acid rinse solution to evaporate quickly, resulting in mineral deposits.
The sanitizing cycle can use warm or cold water, depending on the product used. Consult the label for proper use directions.
Chemical balance: It is important to use the proper dilution rate for the appropriate chemical during each cycle. Manufacturer's label directions should be followed to attain the proper concentration of chemical. Hard water requires more chemicals than soft water due to the negative effects of hardness minerals on the cleaning action of the chemicals.
Time: The length of time that each cycle circulates in the CIP process dictates how effectively the chemicals perform. Inadequate contact time on equipment surfaces can result in milk soil buildup. During the wash cycle, the cleaning solution should circulate for approximately ten minutes. If the wash cycle greatly exceeds ten minutes, water temperature may drop to a level that may cause the soil to redeposit. If the wash cycle falls short of 6 to10 minutes, the chemical may not have enough contact time on the equipment surface to clean properly.
For the acid rinse, the recommended circulation time is five minutes. Again, this time frame should be maintained to give the chemical enough contact time on the surface to effectively lower the pH of the equipment (neutralizing the potential negative effects of chlorine and alkaline residues) and to prevent water spotting. Five minutes also gives the chemical enough contact time to kill bacteria.
Drainage: To prevent milk soil from re-depositing, the pipeline needs to be adequately sloped, and secondary drains are required. Also, the use of diverter valves guarantees that rinse water is not re-circulated during the pre-wash rinse.
CIP Cleaning Cycles
CIP systems are designed with four cycles. All four cycles must be used to assure a clean system and quality milk.
Pre-wash rinse: A clear, clean, potable, tepid (95 to 110 degrees F) water rinse should be flushed through the system to remove the bulk of the soil load. A pre-wash rinse also warms the equipment surface for better cleaning action during the wash cycle.
The initial rinse water should be dumped directly down the drain to prevent re-circulation of the heavy soil load.
Wash cycle: A hot (160 degrees F) solution of a chlorinated-alkaline cleaner should be circulated for ten minutes. Chlorine will aid in soil removal by peptizing proteins while the high alkalinity emulsifies fats. Water temperature should remain above 120 degrees F to prevent milk soil from re-depositing.
Acid rinse: An acid rinse should be applied using water at 95 to 110 degrees F. Daily acid rinse will: neutralize chlorine and alkaline residues (prolongs life of rubber goods); prevent mineral deposits, water spotting and filming (helps prevent milkstones); and reduce the pH of the equipment (inhibits bacterial growth). The reduced pH from the acid rinse will allow chlorine sanitizers to perform more effectively.
Sanitize cycle: The Pasteurized Milk Ordinance (PMO) states that a sanitize solution must be circulated through the system prior to milking to lower bacterial levels on equipment. This cycle should be completed 30 minutes before milking.
Chapter 10 Certification of Service Technicians
As seen in previous chapters, milking systems are complicated and uniquely designed for a highly specialized purpose-milk harvest. How do dairy farmers know that the person installing and repairing milking equipment fully understands the complexities of the system? Answer: By working with certified service technicians.
Because each company's machines are a little different, each manufacturer trains its own service people. But the Milking Machine Manufacturers Council (MMMC) wants to make sure that all training and certification programs contain the same minimum requirements. So, in 1990, it initiated an industry-wide program, "Certification and Training Program for Persons Installing and Servicing Basic Milking Systems."
What does the certification program entail? There is no separate class offered for MMMC certification. Instead, MMMC members complying with the requirements of the MMMC program may refer to their own certification and training program as including the minimum criteria established by MMMC.
How do you know if a manufacturer's program meets MMMC requirements? If specific reference to the MMMC requirements is used by a manufacturer in its verbal or written materials, the manufacturer must state: "The `(Name of Company) Certification and Training Program for Installing and Servicing Basic Milking Systems' includes the minimum requirements developed by the EMI Milking Machine Manufacturers Council."
How can someone be certified? Service technicians who have been employed by an MMMC member dealer for at least 90 days must first complete the training program offered by their manufacturer (at least 40 hours of classroom work). And they must master the knowledge outlined in the MMMC "Training Requirements."
To prove satisfactory completion, the service technician must pass the manufacturer's written and oral examinations, and he or she must demonstrate proficiency in the installation and service of a basic milking system.
How do you know if someone is certified? Technicians who have successfully completed the training program may be given a certificate that confirms their ability to install and service basic milking systems. Certification is good for five years.
After five years, technicians will be recertified if they: complete the manufacturer's applicable special training course(s) which provides Continuing Education Units for recertification; or pass proficiency tests established by the certifying manufacturer.
Certification is automatically cancelled if the service technician: is no longer employed by a dealer of the certifying manufacturer; or fails to meet proficiency requirements of the certifying manufacturer during the five-year period.
Training Program Outline
Manufacturers must include the following information in their training courses in order to meet MMMC certification requirements:
new installation, the owner and operator sign a statement indicating that: all the conditions of the purchase contract have been met; the new milking system is being accepted as being properly installed and operational; the operator's manual has been received and fully explained; appropriate training has been provided; the warranty provisions are clearly understood.
Chapter 11 System Start-Up, Analysis and Scheduled Maintenance
System Start Up and Evaluation
Purchasing milking equipment today should include many factors other than just what brand or model you choose. Upon completion of the installation, proper analysis of all operations should be performed to verify that the equipment is working per manufacturer recommendations. All personnel should be trained in the operation, use, and daily and weekly maintenance responsibilities. A schedule should be established for qualified service personnel to check and verify all aspects of the equipment operation.
Analysis and Scheduled Maintenance
A car driven at 60 mph for ten hours per day will travel more than 200,000 miles in one year. Milking equipment, like the car, has many moving parts that wear over a period of time. This gradual wear may cause the equipment to get out of adjustment and operate less efficiently, thus reducing performance. Impaired performance may translate to more time spent milking cows, less production per cow, herd health complications and lower milk quality.
Many dairy producers have recognized the value of having their milking system serviced on a regular basis. This allows the service technician to make any necessary adjustments and to verify that the equipment is performing properly. Just because the vacuum pump starts when the switch is turned on doesn't mean everything is okay with the milking system. Waiting for equipment to break down is one of the most costly things an operator can do.
The following are some guidelines recommended for milking system maintenance. For more specific instructions, see the maintenance section of the operator's manual for each individual product, or consult a local dealer. And remember that, if a milking system is used many hours a day, the frequency of the following inspections may need to be increased.
Scheduled Maintenance Services for Milking and Cooling Systems
Not all items listed may apply to each milking and cooling system. Consult dealer with questions.
50 hrs 250 hrs 1500 hrs 3000 hrs Each or or or or Milking Daily Wkly Monthly 6 Mos. Yearly
Stray Voltage
Although not directly related to milking equipment, stray voltage can cause concern on dairy farms. It is something to consider when trouble shooting for problems of poor cow behavior or reduced milk production.
Stray voltage is generally understood to mean a low (less than 10 volts), 60-cycle, AC voltage measured between two points which an animal could contact simultaneously to make an electrical circuit. Essentially, it is a small voltage differential between the grounded neutral system and the surface on which the animal stands.
The most common causes of stray voltage:
Although stray voltage has been known to exist for many years, it wasn't until 1982 that it became recognized as a frequent problem on farms in the U.S. Identifying, diagnosing and correcting stray voltage and can be a complex problem for dairy farmers with limited knowledge of electrical distribution, farmstead wiring systems, and the animals' behavioral and physiological responses to low voltages or electric currents.
Cattle, hogs and humans are similarly sensitive to electric current. However, cows are more susceptible to stray voltage because a cow's body impedance (electrical resistance) is lower. Early estimates were that cows could tolerate up to 0.5 to 0.7 volts. More recent and in depth research indicates that animals do not respond the voltage itself but to the current produced by the voltage.
Milk yield may be reduced for a small percentage of cows when cow contact voltages exceed 4 volts. Because the combined electrical resistance of a cow and her contact points is about 500 ohms, then a stray voltage of 4 volts would induce a current of about 8 milliamperes. Current levels below 6 milliamperes have no direct effect on production, reproduction or animal health. Although moderate behavioral changes may occur in animals subjected to current levels between 3 and 6 milliamperes, research shows no evidence that stress hormones are released when cows are subjected to these current levels.
Attempts have been made to associate mastitis with stray voltage. Research indicates only an indirect relationship, however. Mastitis is caused by infection of the teats and udders and not by electricity.
Dairy producers who suspect a stray voltage problem should contact their local utility company, a knowledgeable electrician or an Extension specialist who is familiar with the subject. A comprehensive dairy farm management review, detailing all relevant aspects of the farm, is recommended in any stray voltage evaluation.
The stray voltage analysis should include an investigation of all electrical equipment (both AC and DC powered) which forms part of the milking system. Because of the harsh environment in the milking area, it is not uncommon for short circuits to occur in the network of wires carrying AC or DC power to milking equipment. If milking equipment includes DC power (e.g., pulsator controllers), then tests for the presence of stray DC voltage in the cow environment should be included in the stray voltage analysis.
Equipotential planes, in which all metal stalls and metal reinforcing in the concrete are carefully bonded and connected to the electrical ground system, are recommended for both existing and new facilities. Commissioning of any new milking system should include tests to determine that electrical equipment is properly installed with no unintentional short circuits between the electrical equipment, the stall work and the water lines.
Chapter 12 - Glossary What It Means in Terms of Milking Machines
The milking machine terms defined here are selected from the new International Standard. They are classified according to the general arrangement given below. Some additional, cow-related terms are included in the section on General Terms.
Milking machine. A complete machine installation for milking, usually comprising vacuum and pulsation systems, one or more clusters and other components.
Unit. That assembly of milking machine components which is necessary for milking an individual animal and which may be replicated in an installation so that more than one animal may be milked at one time (e.g. a cluster, long milk tube, long pulse tube and a pulsator plus, perhaps, a recorder jar or milk meter and other individual ancillary components).
Line. A rigid pipeline (usually steel, glass or rigid plastic) that is a fixed part of the installation.
Tube. A flexible hose or tube (usually rubber or non-rigid plastic although it may include a piece of rigid pipeline).
NOTE: The terms line and tube are qualified by their use and place in the following way:
Air: any pipeline used during milking exclusively for air usually, but not necessarily, below atmospheric pressure (e.g. main airline, pulsator airline, atmospheric airline).
Pulse: any pipeline used exclusively for transmitting cyclic pressure changes (e.g. long pulse tube, short pulse tube).
Milk: any pipeline used during milking for a mixture of air and milk (e.g. milkline, long milk tube).
Milking: a term used only to describe the function of a vacuum system or pipeline (e.g. milking vacuum line).
Alveoli. Sac-like milk secreting structures, microscopic in size, consisting of a single layer of cells attached to a base membrane and surrounded by muscular and vascular tissue.
Clinical mastitis. A swollen or inflamed condition of one or more quarters of the udder, or changes in the appearance of the udder secretions (milk) from normal to abnormal. It is frequently associated with infection.
Conditioned reflex. An involuntary reaction that occurs as the result of some routine outside influence.
Ejection of milk. An involuntary reflex action which increases milk pressure within the mammary gland, also referred to as "let-down." Glandular or secretory portion of udder. That part of the gland that receives, from the fine network of blood capillaries, nutrients for secretion of milk.
Oxytocin. The hormone that causes milk let-down.
Pituitary gland. A small ductless gland located at the base of a cow's brain.
Residual milk. The milk left in the secretory portion of the udder at the end of milking.
Sub-clinical mastitis. A low-grade inflammation of one or more udder quarters in which clinical symptoms are not visible even to the most observant milker. Milk composition is changed, however, somatic cell counts are raised and milk yields may be lowered.
2. Types of Milking Machines
Bucket milking machine. A machine in which milk flows from the cluster into a portable milk receiving bucket, connected to the vacuum system, to collect the milk from an individual animal.
Pipeline milking machine. A machine in which milk flows from the cluster into a pipeline that has the dual function of providing milking vacuum and conveying milk to a milk receiver. Weigh jar milking machine. A milking machine in which milk flows from the cluster into a recorder jar under vacuum from a milking vacuum line. Milk is discharged when required from the recorder jar either into a milk transfer line to a milk receiver or into a collecting vessel.
3. Vacuum and Pulsation Systems
Vacuum pump. An air pump which produces vacuum in the system.
Main airline. The part of the pipeline between the vacuum pump(s) and the sanitary trap(s).
Distribution tank. An air vessel or chamber, in the main airline between the vacuum pump (or interceptor) and the sanitary trap, which acts as a manifold for other pipelines.
Sanitary trap. The vessel between the milk system and the air system to prevent contamination by movement of liquid from one to the other.
Milking vacuum line. The pipeline between the sanitary trap and the units in recorder milking machines. This line provides vacuum to the units for milking and may also form part of the cleaning circuit.
Regulator (or Controller). An automatic valve designed to maintain a steady vacuum in a milking system.
Vacuum gauge. A differential pressure gauge to indicate the level of vacuum in the system, relative to atmospheric pressure.
Vacuum tube. The connecting tube between a bucket or recorder jar and the main airline or milking vacuum line.
Vacuum tap. A manually operated valve to permit connection of units or other vacuum-operated devices to the vacuum system.
Pulsator. A device for producing cyclic pressure change.
Pulsator controller. A mechanism to operate pulsators, either integral with a single pulsator (self-contained pulsator) or a system controlling several pulsators.
Pulsator airline. The pipeline connecting the main airline to the pulsators.
Stall cock. A manually operated valve to connect the pulsator to the pulsator airline.
Long pulse tube. The connecting tube between the claw and the pulsator.
4. Cluster
Cluster. An assembly comprising teatcups and claw.
Teatcup. An assembly consisting of a rigid shell, a liner and a short pulse tube and may include a separate short milk tube and connector.
Shell. A rigid shell to retain the liner.
Liner. A flexible sleeve, having a mouthpiece and a barrel, which may have an integral short milk tube.
Short milk tube. The connecting tube between the claw milk inlet and the liner barrel or connector.
Pulsation chamber. The annular space between the liner and the shell.
Short pulse tube. The connecting tube between the pulsation chamber and the claw air nipple.
Claw. The manifold that spaces the teatcups in forming a cluster and connects them to the long milk and long pulse tubes.
Air vent (or air admission hole). A calibrated aperture to admit air into the cluster.
5. Milk System
Long milk tube (or milk hose). The connecting tube carrying the milk away from the claw.
Milk cock (or milk inlet valve). A self-sealing valve to permit routine connection and disconnection of units to the milkline.
Milk inlet. A fixed inlet into a milkline, recorder jar, bucket or other equipment to permit connection of the long milk tube.
Milkline. A pipeline which carries milk and air during milking and which has the dual function of providing milking vacuum and conveying milk to a receiver. Looped milkline. A milkline which forms an enclosed circuit with two full-bore connections to the receiver. High-level milking system. A system wherein the milk inlet to the milkline or recorder jar is more than 4 ft above the cow standing level. Mid-level milking system. A system wherein the milk inlet to the bucket, Milkline or recorder jar is 0-4 ft above the cow standing level. Low-level milking system. A system wherein the milk inlet to the milkline or recorder jar is below the cow standing level.
Recorder jar (or Weigh jar). A graduated vessel which receives, holds and allows measurement of all the milk from an individual animal.
Milk transfer line. A pipeline in which milk is conveyed from the recorder jars to a receiver or collecting vessel under vacuum.
Receiver. A vessel which receives milk from one or more milklines or milk transfer lines and feeds the releaser, releaser milk pump or collecting vessel under vacuum.
Releaser. A device for removing milk from vacuum and discharging it to atmospheric pressure.
Milk pump. A pump for removing milk from vacuum and discharging it to atmospheric pressure.
Delivery line. A pipeline in which milk flows under positive pressure from a releaser or releaser milk pump to a storage vessel.
6. Ancillary Components
Milk meter. A device between the cluster and the milkline for measuring the milk yield of an individual animal in either mass or volume.
Milk flow indicator. A device, usually fitted in the long milk tube, to provide a visual indication of milk flow or flowrate.
Milk flow sensor. A device, usually fitted in the long milk tube, to signal one or more pre-determined levels of milk flowrate.
Initial delay time. The delay time at the start of milking during which the milk flow sensor does not control the operation of an automatic cluster remover (or other pre-set change in vacuum or pulsation characteristics).
Switch point. The threshold milk flowrate (lb/min or kg/min), under test conditions specified by the manufacturer, at which the final delay time starts or the milk flow sensor activates other equipment.
Final delay time. The elapsed time from the switch point to the time of cluster removal.
Take Off or Automatic cluster remover. A device which cuts off the milking vacuum to the cluster, and removes the cluster, based on milk flowrate or time or a combination of flowrate and time.
7. Cleaning and Milk Cooling Equipment
Bulk milk tank. A sanitary storage vessel or vat, usually located in the milk room, used to cool and/or store milk.
Clean-in-place (CIP). The capability to clean the milking system by circulating appropriate solutions through it without disassembly.
Teatcup jetters. An assembly comprising a tube from the washline or the milking vacuum line connected to a manifold and four cups or plugs to which the teatcups are attached during cleaning.
Washline. A pipeline which, during the cleaning process, carries cleaning and sanitizing solutions from the wash vat to the units, milkline or milking vacuum line.
8. Measurement
Vacuum. Any pressure less than atmospheric pressure, specified as the reduction below ambient atmospheric pressure. Vacuum is normally expressed in inches of mercury (for example 12" Hg) or kiloPascals (for example, 40 kPa).
NOTE: The site of measurement should be stated, e.g. pulsation chamber vacuum, claw vacuum.
Nominal vacuum. Vacuum level specified by the manufacturer or installer of the installation (usually, this is the line vacuum indicated by the vacuum gauge).
Working vacuum. The mean vacuum, measured at a stated test point for specified test conditions.
Mean vacuum. Arithmetic mean of all values registered by automatic data acquisition (or the area under the vacuum curve divided by the length of the measuring period when using a curve printer).
Vacuum drop. The difference in vacuum level between any two points in a system, measured as the difference in mean vacuum as defined above or by connecting a differential transducer or manometer to the two points.
Claw vacuum. The vacuum within the claw for specified conditions of liquid and air flowrate.
Free air (or ASME air). Volume of air at ambient atmospheric pressure and temperature.
Expanded air (or NZ air). Volume of air at ambient atmospheric temperature at a given vacuum level.
Vacuum pump capacity. The air-moving capacity of the vacuum pump when it has attained working temperature, at a specified pump speed and vacuum level at the inlet, expressed in volume of free air per minute.
Effective reserve. The reserve pump capacity measured as the air flowrate that can be admitted at or near the receiver in pipeline milking machines, at or near the sanitary trap in recorder machines, or into the airline in bucket machines, to lower the vacuum by 0.6" Hg (2 kpa).
NOTE: This is the reserve air flow capacity available, when the regulator is nominally closed, to cope with unplanned air admission through the clusters during milking.
Manual reserve. The reserve vacuum pump capacity measured at the same position and conditions as for Effective Reserve except that the regulator is disconnected or shut off.
Regulator leakage. The difference between Manual Reserve and Effective Reserve.
NOTE: This is the air flowrate through the regulator, when it is nominally closed, measured under the same conditions as for Effective Reserve.
Teatcup plug. A plug or stopper to simulate the cow's teat and close off the mouthpiece of a teatcup for testing purposes.
Pulsation. Cyclic opening and closing of a teatcup liner.
Alternate pulsation. When cyclic movement of the liners of two teatcups within a cluster alternates with the movement of the other two liners (or, in a cluster with only two teatcups, e.g., for sheep or goats, when cyclic movement of one liner alternates with the movement of the other liner).
Simultaneous pulsation. When cyclic movement of all liners in a cluster is synchronized.
Pulsation cycle. One complete liner movement sequence.
Pulsation rate. The number of pulsation cycles per minute.
Pulsator ratio. The sum of the durations of the increasing vacuum phase and the maximum vacuum phase divided by the duration of the complete pulsation cycle in the pulsation chamber vacuum.
Pulsation ratio. The ratio of the time that the liner is more than half open to the time it is less than half open (expressed as a percentage of the pulsation cycle during which the liner is more than half open).
Milk:rest ratio. The ratio of the time during which milk can flow from the teat (the milking phase) to the time during which milk flow is prevented by the compressive force applied by the liner (the rest phase) within a pulsation cycle. Usually, this ratio is expressed as two numbers which add up to 100, e.g. 65:35.
TITLE; MAXIMIZING THE MILK HARVEST COLLECTION; MILKING MANAGEMENT ORIGIN; MILKING MACHINE MANUFACTURERS COUNCIL DATE INCLUDED; OCTOBER, 1993