On Vacuum Pumps and Milking Machines

Today, vacuum pumps are indispensable to the dairy industry, where they are used in milking machines and other common dairy equipment.  The integration of the vacuum pump in milking machines is an interesting evolution.


The creation of the modern milking machine actually took place over many years of trial and error. As the industrial revolution of the 19th century swept through industry, many recognized the potential efficiencies of mechanical milking machines, but farmers were resistant to the idea. And no wonder!  Milking machines that would be horrific by modern standards were used as late as the 20th century. They used catheters and tubes made of “pure silver, gutta percha, ivory, and bone”.  The first true vacuum pump milking machines were developed in 1851 in England and 1859 in America, however they did not use the large, industrial-size vacuum pumps of today.  Instead, they used a rudimentary “hand cranked suction pump [that] drew milk from all four teats at once”.  Just picture Greg Focker explaining this at Thanksgiving dinner!  Fortunately, in 1898, the USDA approved a foot-pedal-powered milking machine that allayed farmer’s concerns about harming their valuable livestock.  As you can see, it took about 50 years for an acceptable mechanical milking machine to be developed.

Modern Milking Machines

The modern milking machine has become a standardized device.  Its goal is to collect milk from a cow by vacuum suction. These milk extraction systems are comprised of several components including vacuum pumps, reserve tanks, vacuum regulators, pipelines, and pulse tubes.  In addition, pulsators that alter the force of vacuum on the cow are used, as are various valves, which control the flow and suction.   No proper system would be complete without milk tubes and receivers that transport the milk from the vacuum pump system to a bucket, pump, pipeline, and so on.

The Role of Vacuum Pumps

Essentially, vacuum pumps are used to evacuate (remove air) the pipelines and tubes connecting the milking machines to the cows.  By removing the air molecules from the system, its overall pressure is reduced well below atmosphere*.  Then simple vacuum physics takes over and the higher pressure milk flows through the lower pressure pipelines from the cows to the milking receptacle.

Interestingly, a key component of the vacuum pump milking machine is the use of an interceptor.  The interceptor is fitted to the primary vacuum line and acts to prevent solid and liquid material from getting sucked into the vacuum pump.  As one can imagine, the absence of the interceptor would be detrimental to the performance and longevity of the vacuum pump, and thus to the milking machine.

As with any vacuum system, limiting downtime on a milking application relies on the use of both the proper ancillary equipment (interceptors, particulate traps and filter, etc.) as well as proper system maintenance including vacuum pump oil changes, pipeline preventative maintenance/cleaning, and leak detection and prevention.

Atmosphere or atmospheric pressure (the pressure all things are exposed to in everyday life) is one level of vacuum or pressure.  Typically pressures above atmospheric pressure are expressed in common measurements, such as pounds per square inch (PSI), whereas pressures below atmosphere are expressed in atmospheres (atm), inches or mm of mercury, pascal (Pa), or torr.  Stay tuned for our next blog where we’ll discuss pressure measurements in greater detail.

If you have questions about how to keep your vacuum based system in tip top shape, feel free to contact us at United Vacuum for assistance.

The way vacuum pumps actually work, if you have never considered it, is by lowering the pressure to below-atmospheric levels. When the vacuum pumps are switched on, the air pressure inside the lines and tubes drops, making a difference between the atmospheric pressure and the pressure inside the lines. This difference is call the “vacuum level”, and that’s measured by a mercury manometer. (You may recognize the word “manometer” from getting your blood pressure checked.) The unit of measurement for pressure is sometimes still referred to as mm of mercury (a literal description, if you think about it), but the international standard to measure the vacuum level of milking equipment is the Kilo PAscal (Kpa). For point of reference, 1 mm Hg = 0.1333 Kpa.

That basically covers the role of vacuum pumps in milking machines and dairy operations. Hopefully, that clears up any questions you might have.

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