The vacuum pump

mastitis, milking, vacuum pump

During milking, continuous production of vacuum is needed in order to compensate for the milk filling up the pipes and for any leakage of air. If the air and milk flow entering into the system is greater than the pump's capacity, the vacuum will decrease. This will slow down milk flow and cause the milk to build-up in the pipelines, with possible bacterial contamination of the milk and udders as a consequence.

A pump's efficiency is determined by its capacity, which is expressed in litres of air extracted per minute (l/min) at 50 kPa of pressure. The mechanism typically consists of a pump and a motor connected with rubber tubes. Pumps need to be lubricated, which usually includes the use of a recirculation system that allows the oil to be recovered through a hose.

Recirculation system

There are also water-lubricated pumps that use blades to push the liquid towards the pump walls and generate internal vacuum. These are smaller than oil-lubricated pumps (pump and motor in a single unit), are less noisy, and cost less to maintain. However, their price is higher and they require the use of appropriate water (to prevent lime problems).

The pump continuously extracts more air than needed to create a vacuum reserve. A cow’s teats should not be exposed to excess vacuum and a stable vacuum level is very important for their comfort during milking. A regulator allows the controlled leakage of air to keep the vacuum level stable.

Interceptor inputs

The interceptor vessel intercepts foreign bodies and liquids that are sucked into the pump when it is working. Its size should be appropriate for the vacuum flow and its input and output must allow it to work with pipes of up to 110 mm in diameter. It should also include a system to prevent the aspiration of liquid as well as a drain to allow the removal of the water formed by condensation.



Vacuum pump maintenance

  • Rubber connectors must be kept intact, properly tightened (with 3 cm of slack), and free from oil.
  • The motor must be kept free from dirt or dust. The pump's location is critical in this regard. It should not be placed in dirty places, such as close to the routes driven by milk or feed trucks.
Dirty West pump
  • The recirculation filters must be kept clean. These are control points for the pump's lubrication (drops of oil per minute).
  • The water (for water-cooled pumps) must be changed frequently to prevent fouling or lime deposits that could obstruct the hoses or accumulate in the interior.
  • The interceptor must be kept in perfect condition and must be cleaned periodically. Check that there are no vacuum losses through the drainage valve or through any possible dents.
  • The first sections of the vacuum pipe connections should be made of galvanised steel and the rest should be made of PVC. This will prevent the pump's internal temperature from affecting the plastic material.
  • If regulation problems cause excessively high vacuum levels, a pressure switch that can disconnect the pump can be installed.

Types of regulators

  • Diaphragm regulators: respond quickly and maintain a constant vacuum level.
  • Weight regulators: these are not very sensitive and should be replaced.

When selecting a new regulator, choose a model that improves regulation sensitivity and flow consumption. Technical data should be available on the regulation capacity at 50 kPa (in some cases also at 42 kPa).

Location of the regulator             

The regulator should be located close to the sanitary trap so that it can act quickly if any air enters the system during milking. Depending upon the type of regulator, specific requirements must be considered: some regulators work with an independent sensor that must be located in between the regulator and the sanitary trap and at a minimum distance from them. Check the requirements of the manufacturer in case of doubt.

If the regulator is not installed in the vacuum pipe, it must be connected to it using a pipe of the same diameter. For regulators receiving the vacuum variation information through a hose, the hose must be located in the direction of the sanitary trap.

The location of the regulator must allow its inspection and maintenance. Placing it in the milking parlour has advantages for regulation but drawbacks in terms of noise and cleanliness. Placing the receiver vessel outside the parlour offers sensitivity without noise or dirtiness, but does not allow anomalies to be detected (milk entry in splashes, filled unit, etc.). It also increases the length of the milk transfer line.

Maintenance of the regulator

The air filtering system must be kept as clean as possible. Replace the membranes at least once a year (depending on the brand, milking routine, and pump capacity).

Dirty Alfa regulator   Dirty West regulator


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