Regularly inspecting milking equipment can catch problems

Milking parlor
(Farm and Dairy photo)

While a milking system should have at least a yearly professional inspection, there are many other on farm evaluations that should be done much more often.

The simple routine inspection is intended to help identify possible machine or milking management issues to reduce mastitis, improve teat condition and identify incomplete milking issues. The equipment needed for this milking system inspection include a stopwatch, possibly a level and a high accuracy portable vacuum gauge.

Visual inspection with the milk system off. The first set of inspections is done with the milking machine off. Teat cup liners should be inspected regularly even when they are replaced following manufacture guidelines they occasionally fail early. Short air tubes and inflations need a visual inspection for cracks and distortion where they attach to the claw.

The inflation mouthpiece needs inspected for distortion both out of round and flared up or down. The barrel should also be compared to new inflations to determine that it is not distorted prior to replacement.

Claws have two major inspection points: the air vent and the automatic shut-off valve. Air vents occasionally become blocked with dirt, reducing milking vacuum. Air vents diameter ranges from 0.8 mm to 1.2 mm. Knowing the size of your claws air vents allows you to clean them without causing damage. The claw should let in 7 to 12 liters per minute of air.

Claws with automatic shut-offs help reduce the amount of unintended air and debris entering units during fall off, but these can also effect unit vacuum levels during milking.

While rarely a problem, milk lines should be inspected occasionally to make sure they are still on a 1-2% slope toward the milk receiver and that milk inlets have not been accidently rotated and are still entering in the upper half of the milk line. While you maybe thinking “how could this get messed up,” occasional milk lines are taken apart to replace gaskets or clean lines and don’t get put back the same way they were taken apart.

Dry testing and milk machine operation test. Vacuum level is critical for teat health and milking time. Vacuum gages, regulators and pumps fail over time and should be regularly checked.

The first step is to check the vacuum in the system. The most common problem with dial gauges is in accuracy and failure to increase over standard operation pressure due to wear and not showing high vacuum level. Having a port to test vacuum levels every month can decrease teat health issues.

Once static operation vacuum is tested, leave the test vacuum gauge on and test the vacuum regulator. Regulator testing is first done by testing regulator closure. With all units shut off listen and feel the regulator to determine the air intake hiss. Now open milking units to allow air in until vacuum falls 1″Hg below system operation vacuum check the regulator again, there should be no hiss at the regulator. If regulator still has an air hiss, it needs cleaned. Next conduct a fall off test by having all units closed and opening one unit per 32 units. When the unit opens system vacuum should drop by no more than 0.6″ Hg at unit opening then recover at least partially as vacuum regulator closes. The next system to test is system pulsation. Testing pulsators starts with your ears for uniformity between pulsators but often needs a deeper inspection. Test pulsators with your fingers by taking lines off and feeling for the pulsation, which should feel sharp and clean with definitive starts and stops. Pulsators often fail slowly with a little dirt stopping them from fully opening and closing causing higher levels of vacuum on the teats during the rest phase. With your portable vacuum gauge you may also be able to test claw vacuum. This can either be done with a T connector between the claw and inflation or a 12 to 14 gauge needle through the short milk tube of the inflation. The needle should be long enough to enter the claw and not just be in the inflation. Claw vacuum should be tested over a wide variation of cows, up to 50 per herd. The claw vacuum should be in the range of 10.5 to 12.5″ Hg during peak milk flow. Outside this range may cause teat end damage. While these tests don’t replace a yearly milk system inspection, they may help catch a problem sooner, decreasing the cost or repair and cow health care.


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Jason Hartschuh is an agricultural and natural resources educator for OSU Extension Crawford County. For more information, email or call 419-562-8731.



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