The milking machine works on the principal of providing a vacuum that alternates with atmospheric pressure to draw milk from the teats. A continuous vacuum would soon become painful for the cow and cause teat damage and so the pulsating system used to milk provides a cycle that can, when correctly set, remove milk efficiently without damage to the teat or udder.
The correct vacuum and pulsation levels are essential to this process and are checked when a milking machine test is performed. However, even on a day-to-day basis, the milking staff should be aware of how important these correct levels are, what indicates that they are not correct and how to perform a basic test to ensure the correct vacuum characteristics. A low vacuum level would result in under-milked udders and liner slippage and a high vacuum level would quickly lead to teat damage.
When the milking machine is switched on and vacuum permitted to rise to working levels before milking commences, the vacuum gauge in the parlour should read 45-48 kPa for high-line parlours and between 40-44 kPa for low-line systems.