Changes

===How the milk machine works===

===How the milk machine works===

The milk machine works by having a collapsible ‘’’liner’’’ within a solid ‘’’pulsation chamber’’’. The liner forms a seal at the top of the teat and connects with the ‘’’short milk tube’’’ to deliver milk to the ‘’’claw piece’’’ of the ‘’’cluster’’’. Via the ‘’’short pulsation tube’’’, the pulsation chamber has an alternating vacuum/atmospheric air delivered which causes the milk liner to open and close beneath the level of the teat. When vacuum is present within the pulsation chamber, there is an equal pressure with that in the short milk tube, which has a constant vacuum supply to facilitate movement of milk away from the udder. The equal pressures means the liner is open and milk is drawn out. Conversely when atmospheric air is introduced into the pulsation chamber, the pressure differential causes the liner to collapse and the teat no longer to be exposed to the vacuum. This allows blood flow to return to the teat necessary to prevent teat damage and is called the ‘’’massage phase’’’. A constant vacuum applied to the teat, as in the early parlour designs, causes a vast amount of soft tissue trauma which would cause untold levels of mastitis.

The milk machine works by having a collapsible '''liner''' within a solid '''pulsation chamber'''. The liner forms a seal at the top of the teat and connects with the '''short milk tube''' to deliver milk to the '''claw piece''' of the '''cluster'''. Via the '''short pulsation tube''', the pulsation chamber has an alternating vacuum/atmospheric air delivered which causes the milk liner to open and close beneath the level of the teat. When vacuum is present within the pulsation chamber, there is an equal pressure with that in the short milk tube, which has a constant vacuum supply to facilitate movement of milk away from the udder. The equal pressures means the liner is open and milk is drawn out. Conversely when atmospheric air is introduced into the pulsation chamber, the pressure differential causes the liner to collapse and the teat no longer to be exposed to the vacuum. This allows blood flow to return to the teat necessary to prevent teat damage and is called the '''massage phase'''. A constant vacuum applied to the teat, as in the early parlour designs, causes a vast amount of soft tissue trauma which would cause untold levels of mastitis.

===Movement of Milk===

===Movement of Milk===

All four short milk tubes meet at the claw piece, and from there the milk mixes and goes into the ‘’’long milk tube’’’. All the long milk tubes from each individual cluster contribute to the milk transfer line which delivers the milk to the ‘’’receiver vessel’’’. Some parlours may have more than one receiver vessel. The location of the milk transfer line is important as this determines the vacuum level required to move the milk. In a ‘’’low line parlour’’’, the milk transfer line runs below the level of the udder and requires a lower vacuum level of 38-40kPa. This compares to a ‘’’high line parlour’’’ which has the milk transfer line above the level of the udder. In this scenario, extra energy is required to life the milk to this level so a greater vacuum is required at somewhere around 46-50kPa. Once the milk reaches the receiver vessel, often another smaller vacuum pump is present known as a ‘’’milk pump’’’ to transfer the milk from the receiver vessel to the bulk tank. This pump is triggered when the milk level in the receiver vessel reaches a pre-determined level.

All four short milk tubes meet at the claw piece, and from there the milk mixes and goes into the '''long milk tube'''. All the long milk tubes from each individual cluster contribute to the milk transfer line which delivers the milk to the '''receiver vessel'''. Some parlours may have more than one receiver vessel. The location of the milk transfer line is important as this determines the vacuum level required to move the milk. In a '''low line parlour''', the milk transfer line runs below the level of the udder and requires a lower vacuum level of 38-40kPa. This compares to a '''high line parlour''' which has the milk transfer line above the level of the udder. In this scenario, extra energy is required to life the milk to this level so a greater vacuum is required at somewhere around 46-50kPa. Once the milk reaches the receiver vessel, often another smaller vacuum pump is present known as a '''milk pump''' to transfer the milk from the receiver vessel to the bulk tank. This pump is triggered when the milk level in the receiver vessel reaches a pre-determined level.

===Vacuum pump and interceptor===

===Vacuum pump and interceptor===

===Vacuum reserve===

===Vacuum reserve===

Vacuum reserve is the amount of extra vacuum generated by the pump so that when air enters the system a stable vacuum is maintained. If air does not enter the system, the regulator lets air in so vacuum levels do not increase (see section on the regulator below). Inadequate reserve can lead to vacuum fluctuations in the system which is a risk for mastitis. Additionally ‘’’liner slip’’’ or units falling off cows during milking may be seen. The vacuum reserve is regularly measured as part of a ‘’’static parlour test’’’.

Vacuum reserve is the amount of extra vacuum generated by the pump so that when air enters the system a stable vacuum is maintained. If air does not enter the system, the regulator lets air in so vacuum levels do not increase (see section on the regulator below). Inadequate reserve can lead to vacuum fluctuations in the system which is a risk for mastitis. Additionally '''liner slip''' or units falling off cows during milking may be seen. The vacuum reserve is regularly measured as part of a '''static parlour test'''.

===Sanitary Trap===

===Sanitary Trap===

===Regulator===

===Regulator===

The regulator is a valve present on the vacuum system to try and maintain a constant vacuum level in the system. Air is extracted at a constant rate by the vacuum pump. Normally, air enters the system from various parts of the milking machine such as when the clusters are attached to the cow’s udder. If the vacuum reaches a certain level, the regulator valve will open to let air into the system to maintain vacuum stability. When air is entering the system from other parts of the machine, the regulator will have to extract relatively less to maintain this stability. Air enters via filters which need to be regularly cleaned in order for the regulator to function correctly and prevent excess particulate matter entering the vacuum system. Occasionally the source of the air may be outside the building to reduce the amount of matter entering the system – a so called ‘’’clean air system’’’.  

The regulator is a valve present on the vacuum system to try and maintain a constant vacuum level in the system. Air is extracted at a constant rate by the vacuum pump. Normally, air enters the system from various parts of the milking machine such as when the clusters are attached to the cow’s udder. If the vacuum reaches a certain level, the regulator valve will open to let air into the system to maintain vacuum stability. When air is entering the system from other parts of the machine, the regulator will have to extract relatively less to maintain this stability. Air enters via filters which need to be regularly cleaned in order for the regulator to function correctly and prevent excess particulate matter entering the vacuum system. Occasionally the source of the air may be outside the building to reduce the amount of matter entering the system – a so called '''clean air system'''.  

During milking, the regulator should be constantly heard to be letting air into the system. Failure to do so may be indicative of an inadequate vacuum reserve or a problem with the regulator.

During milking, the regulator should be constantly heard to be letting air into the system. Failure to do so may be indicative of an inadequate vacuum reserve or a problem with the regulator.

===Teat Liners===

===Teat Liners===

The teat liner is the only part of the parlour that has direct contact with the cow and is therefore a potentially very important fomite for spread of mastitis pathogens. The more liners are used, the more they get worn. Cracks may appear which may harbour pathogens. Additionally, the elasticity of the liner is also affected which can be detrimental to teat health. Therefore it is important that liners are changed at sufficient time periods. The liner life depends on the type of liner with ‘’’rubber’’’ liners lasting 2,500 milkings (or 6 months, whichever is sooner) whilst ‘’’silicone’’’ liners last 10,000 milkings. Rubber liners are more widely used, whilst silicone liners are more expensive. Various designs of liner are available on the market (e.g. triangular). Some parlours require specific liner types such as those that have an [[Automatic Disinfection and Flushing (ADF)|ADF]] system installed.

The teat liner is the only part of the parlour that has direct contact with the cow and is therefore a potentially very important fomite for spread of mastitis pathogens. The more liners are used, the more they get worn. Cracks may appear which may harbour pathogens. Additionally, the elasticity of the liner is also affected which can be detrimental to teat health. Therefore it is important that liners are changed at sufficient time periods. The liner life depends on the type of liner with '''rubber''' liners lasting 2,500 milkings (or 6 months, whichever is sooner) whilst '''silicone''' liners last 10,000 milkings. Rubber liners are more widely used, whilst silicone liners are more expensive. Various designs of liner are available on the market (e.g. triangular). Some parlours require specific liner types such as those that have an [[Automatic Disinfection and Flushing (ADF)|ADF]] system installed.

===Automatic Cluster Removal (ACR)===

===Automatic Cluster Removal (ACR)===

#* This last step is to remove any residual disinfectant from the hot wash.

#* This last step is to remove any residual disinfectant from the hot wash.

With circulation cleaning, it is important that the entire pipe is disinfected. In order to achieve this, the wash solution needs to be agitated. This is facilitated by the use of ‘’’air injectors’’’ which inject regular bursts of air to cause the agitation. Air injectors help ensure the entire surface of the pipe is covered and make parlour washing more effective.  

With circulation cleaning, it is important that the entire pipe is disinfected. In order to achieve this, the wash solution needs to be agitated. This is facilitated by the use of '''air injectors''' which inject regular bursts of air to cause the agitation. Air injectors help ensure the entire surface of the pipe is covered and make parlour washing more effective.  

Often circulation cleaning is performed semi-automatically.

Often circulation cleaning is performed semi-automatically.

===Milk cooling===

===Milk cooling===

It is of great importance that milk is cooled as soon as possible to limit bacterial overgrowth. This is facilitated by the use of a ‘’’plate cooler’’’. The plate cooler is placed between the receiver vessel and bulk tank and cools the milk so that when it enters the bulk tank, it is close to the storage temperature of 4°C. Using a counter current mechanism, cold water runs in the opposite direction to the flow of milk and heat is transferred from the milk to the water. The surface area is maximised to increase the efficiency of this process by the use of several stainless steel plates separating the milk and water. Once in the bulk tank, the temperature is maintained at 4°C ready for collection by the dairy milk tanker.

It is of great importance that milk is cooled as soon as possible to limit bacterial overgrowth. This is facilitated by the use of a '''plate cooler'''. The plate cooler is placed between the receiver vessel and bulk tank and cools the milk so that when it enters the bulk tank, it is close to the storage temperature of 4°C. Using a counter current mechanism, cold water runs in the opposite direction to the flow of milk and heat is transferred from the milk to the water. The surface area is maximised to increase the efficiency of this process by the use of several stainless steel plates separating the milk and water. Once in the bulk tank, the temperature is maintained at 4°C ready for collection by the dairy milk tanker.

===Types of parlour===

===Types of parlour===

Herringbone is the most common type of parlour seen in the UK. Cows face at a slight angle to the milker who is located in a “pit” between two lines of cows. The milker has good access to the cow’s udder with this system being at the level of the waste/chest region. One disadvantage is that a cow that is slow to milk out delays the release of the rest of the cows in the line.  

Herringbone is the most common type of parlour seen in the UK. Cows face at a slight angle to the milker who is located in a “pit” between two lines of cows. The milker has good access to the cow’s udder with this system being at the level of the waste/chest region. One disadvantage is that a cow that is slow to milk out delays the release of the rest of the cows in the line.  

In this system, there can either be one milking unit per cow position, or one unit which is shared between the two lines. The latter is known as a ‘’’swingover’’’ parlour. Although cheaper to install due to fewer units required, this type of parlour is slower to operate. Usually longer parlours are necessary with this setup. Both of these systems can also be seen in rapid exit parlours (below).

In this system, there can either be one milking unit per cow position, or one unit which is shared between the two lines. The latter is known as a '''swingover''' parlour. Although cheaper to install due to fewer units required, this type of parlour is slower to operate. Usually longer parlours are necessary with this setup. Both of these systems can also be seen in rapid exit parlours (below).

====Trigon====

====Trigon====

====Rotary====

====Rotary====

Rotary parlours are good for large herds due to the large throughput of cows possible. Cows may face the inside (‘’’external rotary’’’) or outside (‘’’internal rotary’’’) of the circle depending on the particular design. For a large rotary there should be at least three operators for an effective milking routine. One for udder preparation, the second for unit attachment and the third for [[Post-Milking Teat Disinfection (PMTD)|post milking teat disinfection]].

Rotary parlours are good for large herds due to the large throughput of cows possible. Cows may face the inside ('''external rotary''') or outside ('''internal rotary''') of the circle depending on the particular design. For a large rotary there should be at least three operators for an effective milking routine. One for udder preparation, the second for unit attachment and the third for [[Post-Milking Teat Disinfection (PMTD)|post milking teat disinfection]].

===Tied Stalls===

===Tied Stalls===

====Dynamic tests====

====Dynamic tests====

Dynamic tests are performed when cows are being milked. The main aim is to measure vacuum fluctuations at the teat end which may not always be suggested as a problem by the results of the static test. Milk flow can also be measured which may reveal problems with bimodal milk flow, suggestive of problems with udder preparation and/or milk let down. It is during such tests that ‘’’liner slip’’’ may be noticed.

Dynamic tests are performed when cows are being milked. The main aim is to measure vacuum fluctuations at the teat end which may not always be suggested as a problem by the results of the static test. Milk flow can also be measured which may reveal problems with bimodal milk flow, suggestive of problems with udder preparation and/or milk let down. It is during such tests that '''liner slip''' may be noticed.

<gallery widths=100px heights=100px perrow=3 caption="Dynamic Parlour testing">

<gallery widths=100px heights=100px perrow=3 caption="Dynamic Parlour testing">