Maintenance of Milking and Milk Handling Equipment

Factsheet - ISSN 1198-712X   -   Copyright King's Printer for Ontario
Agdex#: 410/725
Publication Date: 01/85
Order#: 85-001
Last Reviewed: 07/12
History: Reprinted, July 1989
Written by: G.A. Garland - Head, Engineering Section, New Liskeard College of Agricultural Technology

Table of Contents

  1. Milk Cooler
  2. Refrigeration Unit
  3. Vacuum Pump
  4. Vacuum Control Valves or Regulators
  5. Pulsator
  6. Vacuum Pipeline
  7. Vacuum Reserve Tank
  8. Rubberware
  9. Milk Claw
  10. Milk Pipeline
  11. Milk Receiver Jar
  12. Milk Pump
  13. Testing Equipment


Following a program of preventive maintenance can bring great benefits to the dairyman by eliminating unnecessary service calls and down time, and by minimizing the chance of a major breakdown or permanent damage to a vital piece of equipment. The operator should know not only how his milking system works, but also what regular inspection and servicing it needs to keep it performing at near new efficiency.

A checklist and maintenance suggestions are given below to help the dairyman to keep his milking system in top working condition.

Milk Cooler

  1. Check the agitator motor for grease leaks or noisy operation, also worn shaft shields and bearings.
    • Replace leaking agitator motor seals. Tighten bolts holding motor mounting brackets. Replace worn shaft shields and bearings.
  2. Check the timer to be sure that it will start the agitator motor and advance to the "off' position.
    • Replace timer if not functioning properly
  3. Check the thermometer for accuracy - should read 0° C (32° F) when submerged in ice water. Be sure it is not sticking.
    • Replace thermometer if faulty.
  4. Check milk tank outlet valve for 4. leaks. Plug type valve will have to be refinished.
    • Replace valve "O" ring, if leaking.
  5. Check the running time of the cooler. It should cool to 10° C (50° F) within one hour of first milking and cool to 4° C (40° F) and hold that temperature after the second hour. The blend temperature of the second, third and fourth milking should remain under 10°C (50° F).
    • If running time is too long check and clean condenser coil. Check refrigerant.
  6. Check for foam, churned milk, and frozen milk on the milk surface.
    • The presence of foam indicates air indicates air leaks in the milking system or excessive agitation of the milk;
    • churned milk (clumps of fat floating on the surface) usually is caused by excessive agitation and slow cooling of the milk. Check refrigerant; and
    • frozen milk on the surface or as layers of ice on the bottom of the tank. The freezing of milk can be avoided by turning on the refrigeration when the milk level reaches the level of the agitator blades and setting the tank thermostat so that the milk is cooled to 4° C (38 to 40° F).

Refrigeration Unit

  1. Check condenser coil for dirt or dust - air must flow freely through the coil and exit into the atmosphere.
    • If condensor coil is dirty turn disconnect switch to "off" position, brush wash with milk detergent solution, rinse with tap water from the fan side out and allow to drain for three hours before restarting.
  2. Check refrigeration unit and tubing for signs of leaks (grease spots).
    • Call to the attention of refrigeration service man, any air or refrigeration leaks.
  3. Check refrigerant sight glass after unit has been operating 15 minutes refrigerant should be clear without any indication of foaming.
    • If refrigerant is foaming, have refrigerant added by serviceman.
  4. Check condensor fan motor(s).
    • Call to the attention of refrigeration service man any malfunction of the condensor fan motor.

Vacuum Pump

  1. Check oil level weekly.
    • Fill with correct type of oil recommended by manufacturer. Some oils contain additives which form a sludge when mixed with water and detergent. Do not overfill - excess oil will blow out exhaust.
  2. Check type and tension of belts. Spin pump by hand to see if vanes fall freely, or to detect unusual drag loose pulleys or rough bearings. Check that pulleys are in line.
    • With v-belts care must be taken that the belt section used matches the the correct section pulley, for example, B section belting should not be use on A section pulleys. Tighten drive belts so there is a slight sag on the slack side while running. Repair or replace worn vanes, bearings and drive belts.
  3. Check cleanliness of vacuum pump.
    • Once every six months, or when the pump becomes fouled by milk, it should be cleaned using diesel fuel or a 4:1 kerosene-oil mixture. Approximately two pints of mixture are fed into the suction port while the pump is running. If extensive cleaning is required, the pump can be filled with this mixture and allowed to soak. After the pump is cleaned half a pint of oil should be added through the suction port to ensure thorough lubrication.
  4. Check exhaust pipes.
    • The exhaust pipe must never be smaller than the outlet from the pump, otherwise pressure will seriously limit the performance of the pump. Elbow bends should not be used as they are too restrictive. Bends with large radii are better. A non-return valve should prevent reverse rotation when pump is switched off.
  5. Check capacity of pump with a flow meter.
    • Every six months have vacuum pump capacity checked by service man to help detect wear, leaks or stoppage in the system.

Vacuum Control Valves or Regulators

  1. Check the location of regulator.
    • In bucket systems the regulator should be placed in a clean spot on the vacuum line between the reserve tanks and the first stall cock. In milk pipeline systems the regulator should be placed:
      • between the vacuum reserve tank and the sanitary-trap near the milk receiver, or
      • on the vacuum reserve tank.
  2. Check the capacity of the regulator.
    • The regulator must be capable of admitting air at least equal to the capacity of the vacuum pump. All milking systems should be equipped with a vacuum relief valve set 2 or 3 inches higher than normal line vacuum, for safety in event of regulator failure.
  3. Check valve, screen and filters.
    • Regulator valves, valve seats, screens and filters should be dismantled and thoroughly cleaned at least twice a year unless regulators are unavoidable in a dusty location then they should be cleaned more often. Do not oil valves or moving parts since this will only collect dust and dirt and make the valve stick.


  1. Check the pulsation ratio. The pulsation ratio refers to the length of time the inflaction or liner is in the "milking" phase compared to the "rest" phase. This can only be checked by special test instruments.
    • Example pulsation ratios are 50:50 and 60:40. Know what is recommended for your equipment and report any malfunctions to the service man.
  2. Check pulsation rate. The pulsation rate refers to the number of cycles ("milking" phase + "rest" phase = 1 cycle) the pulsator makes in one minute. You can check this with a watch by inserting your thumb inside an inflation when system is operating and counting the number of squeezes per minute.
    • The recommended rate is in the range of 50 to 60 pulsations per minute. This depends on such things as pulsation ratio, vacuum level and type of inflation. Know and follow manufacturer's recommendations to keep these factors in balance. Do not experiment on your own.
  3. Check cleanliness of pulsators. Check pulsator filters and diaphragms.
    • Older type pulsators need frequent cleaning of air inlets and occasional replacement of valve rubber seals. Some can be wahed out regularly, but check manufacturer's recommendations before bringing in contact with water.
  4. Check voltage, look for loose connections and electric shorts on electric pulsators.
    • Report problems to a service man.

Vacuum Pipeline

  1. Check stall cocks for leaks.
    • Tighten or replace faulty stall cocks.
  2. Check drain cocks for leaks.
    • Adjust or replace.
  3. Check line for buildup of residue.
    • Flush vacuum pipeline with hot water and a non-foaming detergent.
  4. Check gasket on sanitary traps for leaks.
    • Adjust or replace.

Vacuum Reserve Tank

  1. Check capacity of tank.
    • Tanks should at least have 5 gallon capacity for each milker unit used.
  2. Check inside tank for rust.
    • Replace tank if necessary.
  3. Check cleanliness and self-drain.
    • Flush to keep clean.


  1. Check short air tubes on milker units.
    • Never milk with holes in pulsator air tubes.
  2. Check inflation or liners.
    • Discard any inflation of liner with holes or cracks. Discard any liner than has passed the number of cow milkings recommended by the manufacturer: for example 1000 cow milkings.
  3. Check storage of rubberware.
    • It is recommended that two sets of liners be kept on hand. One set stored in a lye solution and used on alternate weeks.

Milk Claw

  1. Check air admission hole ("air vent").
    • Clean air vents thoroughly. Slow milking and/or flooding of claw could be caused by blocked air vents. Do not increase vent size.
  2. Check valve, float, claw gaskets and air manifold.
    • Clean and replace any defective claw parts.
  3. Check for vacuum stability during milking with all units in operation.
    • This test will determine if a constant, steady vacuum exists at the teat cup at all times during milking.

Milk Pipeline

  1. Check for proper slope.
    • Maintain slope of 40 mm per 3 m (1 1/2 in. per 10 ft) downward, towards the milk receiver jar from the high point in the line.
  2. Check milk inlets for location and leaks.
    • Maintain inlets in the top third of the pipeline to prevent vacuum fluctuations. Make sure valves close properly to prevent vacuum losses.
  3. Check for leaky couplings.
    • To prevent vacuum losses tighten couplings; clean and/or replace gaskets.

Milk Receiver Jar

  1. Check gaskets, fittings and non-return valve for leaks.
    • Clean and/or replace gaskets. Tighten couplings.
  2. Check electrical probes for corrosion and wear.
    • Report "unexplained" buildups to service man.

Milk Pump

  1. Check bushings, seals and diaphragms.
    • To assure proper performance and sanitation make necessary adjustments or replacements.

Testing Equipment

Dairy farmers may do much to maintain the performance of their milking and milk handling equipment but to locate many faults, regular checks by a person skilled in the use of the necessary scientific testing equipment are necessary.

Milking machine efficiency often deteriorates gradually, unnoticed by the farmer. It is for this reason that it is advisable to have the system tested at least twice a year. These tests are designed to locate faults in the operation of the vacuum pump, vacuum regulator, vacuum gauge, pulsators and inflations. The air reserve is measured and if inadequate the reason for the low reserve is determined.

In many cases, small repairs or adjustments to the equipment on the spot will restore its efficiency.

For more information:
Toll Free: 1-877-424-1300