CHECK-UP ON PREVENTIVE MAINTENANCE FOR HYDRAULIC PRESSES

Checking on your hydraulic press to keep it in good working order is more than just smart operating procedure, it can actually pay-off for manufacturers. By knowing when a hydraulic press is running well or is in need of attention, and by consistently conducting preventative maintenance, the lifespan of a press can be significantly increased to maximize your investment. The key is to get to know your machinery and develop a written preventive maintenance schedule that will help you keep your equipment in peak condition for many years to come.

A QUICK CHECK A DAY
There are a variety of small tasks that can be performed each day to keep equipment up and running. The daily maintenance checklist below will give you an idea of how you can get started:
? Look for oil leaks on all the hydraulic lines. A very small leak can turn into a very big mess. Tighten any leaking fittings and clean up any excess oil. Keeping your press clean will help to locate any new leaks as they develop and will keep your press running cooler.
? Measure the fluid level of the oil and top it off if necessary. Most presses will have an oil tag affixed to the machine describing the type of oil to be used.
? Check for loose bolts around the tooling area; some die?s can cause vibrations and shocks that can loosen bolts over time.
? Make sure there is enough lubrication on guided platens. Some bushings will have fittings that should be greased to keep a small film of lubrication over the rod. Do not over grease or dirt will accumulate and cause the bearing to wear prematurely. Other bushings will have a check valve-type fitting, which have graphite impregnated into the bronze and require very little maintenance. Use a small amount Mobil Viscolite or similar to spread the graphite onto the rod; the rod should be and somewhat dry. Never put grease into this type of bearing.
? Let the machine warm to operating temperature, then check the oil temperature (which should be 120 deg F).
? Make sure the press ram is moist but not dripping oil.
? Check the light curtains function. Break the beam while the ram is traveling down. The press should stop immediately. Breaking the beam on the upstroke may not stop the press. Your owner?s manual will provide the proper function.
? Keep the work area clean to ensure safety and prevent accidents.

Additional measures performed throughout the year will help maintain a healthy press.

OIL MAINTENANCE
Not maintaining proper oil levels and quality will quickly reduce the life of a machine. Dirt and heat are especially destructive to a press. Keeping your oil in new condition is fairly easy to do and will help ensure longer press life.
Best operation temperature, as mentioned previously, is about 120 deg F. Oil temperature can be maintained by either air or water coolers. Probes are inserted into the oil reservoir and temperature maintained by the use of a thermostat. The air coolers use a radiator to separate the heat with the use of an electric fan moving the air through the cooler. Dirt and dust tend to collect in the vanes of the radiator and prevent the airflow from traveling at maximum capacity, so it?s important to keep the radiator clean.

To help keep the unit clean, you can attach a common filter, like the ones used for heating and air conditioning, to the heat exchanger. Yearly inspection is recommended for:
? Water cooled systems function much in the same way air coolers except that water travels through the vanes.vThe method for the water could be city water, chillers or roof top mounted exchangers. To inspect, remove the end caps to check for clear passages and flush with cleaning solvent if necessary.

? Roof top mounted units tend to collect dust and dirt, that can result in clogging of the exchanger and produce rust. Placing a filter in line will help remove any fine particles.

? Water Chillers dissipate heat well because the inlet temperature can be adjusted and anti-rusting agents can also be added to the water.
? Oil sampling needs to happen to determine filters need to be changed. From this sample you can tell how many particles of different sizes are in the oil, if the oil has water in it, as well as the lubricity properties. In most cases it is not necessary to change oil but certain additives may be needed. From the oil sampling you can also determine if the oil filters are being changed at proper intervals.

You can also tell from the results if the correct micron level of filtration is being used. Simple hydraulic systems only require code 10 filters, which result in a cleanliness level of 20/18/15. More complex systems that have proportional or servo valves require code 03 filters, which have a cleanliness level of 16/14/12. Several companies can perform this test and maintain records for you.

PRESSURE
If your press is in good working condition with no leaks, it should build to the maximum required pressure in one-half to one second. A pressure buildup of two to three seconds may indicate a problem with a pump, valve or motor. Pressure problems are usually pump-related, although the issue could also stem from the relief valve working too slowly. Look for dirt or grit in the line and also check to see that the valve is not open too wide. Additionally, if the press motor is not producing sufficient revolutions per minute (RPM), a drop in pressure could occur.

ELECTRICAL MAINTENANCE
Electronics today are very dependable, but do not last indefinitely. Coils that are located on valves normally have a life cycle of three million strokes, and relays typically have one million strokes. Replacing them before they fail can decrease or eliminate hours of troubleshooting, resulting in less down time. Installing an hour meter and non re-settable cycle counter will help to maintain accurate records and can help with scheduling maintenance.
Check your control wiring annually to make sure all connections are tight and that the wiring is in good condition. Place loose wiring in wire ways or tie them with wire ties. Unused wires or spares should be capped off or removed. Remove any dust or dirt from enclosures.

Developing a preventive maintenance checklist ? daily, monthly and yearly ? that is right for your press is the key to detecting issues at an early stage to avoid potential costly fixes later on and keeping your press at optimal performance for years to come.

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Thomas Lavoie is the applications manager and Carl Jean is the service manager at Greenerd Press & Machine Company, Inc., 41 Crown Street, PO Box 886, Nashua, NH 03031, 603-889-4101, Fax: 603-889-7601, www.greenerd.com. Lavoie has been with Greenerd for 14 years in various positions, with applications engineering being his specialty. Jean has been with Greenerd for 33 years. He built and supervised the construction of all Greenerd presses for 23 years and has been service manager the last 10 years. He is an expert on the subject of presses and how to maintain and build them for longevity.