MIKE BREEN ON PREVENTIVE MAINTENANCE

Preventive Maintenance:
It’s Summertime — 
Is Your Chiller Working?

by Michael W. Breen

Michael W. BreenActually, summer has nothing to do with concerns about your chiller unit; however, this system and others need to be inspected nonetheless.

Last month, we examined hydraulic systems, from preventive maintenance steps to finding and repairing problems. In this column, we will continue to address the fluid section by specifically discussing spindle head lubrication, chiller units, and cavity systems.

Spindle Head Lubrication Systems

Spindle head lubrication systems are generally found with gear-type spindles or transmissions. These assemblies are closed-loop, like hydraulic systems. The system usually consists of a reservoir, an intake filter or strainer, a pump, a pressure switch, and lines to the transmission or spindle. The transmission itself may contain flow restriction devices and directional tubing.

The pressure switch in a spindle head lubrication system works differently than the switch in a central lube system. This pressure switch is looking for line pressure, too, but this system has pressure continuously. It bathes the gears, shafts, and bearings with a constant flow of oil. The oil is generally light-viscosity. (As always, refer to your machine manual for the correct oil type.)

The spindle head lubrication system is simple to PM: disassemble the reservoir-pump assembly, clean it, change the system filters, reassemble it, and fill it with new oil. Be sure to inspect where the oil is going. After all, that is the main purpose of the system. You will probably have to remove some covers at this point. Then, inspect the lines for leaks from the pump to their destination.

When you reach the transmission, remove the inspection plate. (Do not place your hands in the transmission with the power on! Because of gear reduction, a slight manual rotation of the spindle could cause injury even with the power off.) Look at the bath lines to ensure they are placed in the proper position. They should be over a gear, shaft or bearing. You also will need to inspect the drain and bottom of the transmission housing for blockage and chips. (If you find chips, be sure to remove them. Remember: some flaking is normal.) Close everything and check the system pressure.

Chiller Systems

Chiller systems are slightly different. You will generally see these with cartridge-type spindles and integral spindles. Chiller systems push cooled fluid through a manifold that is wrapped around a component. The heat from the component is transferred to the oil, and the oil is cooled when it is pushed through the radiator. The compressor system keeps the radiator cool.

This system has two parts. The first consists of a Freon™ gas compressor, fan, and radiator. The second has a reservoir, a pump, a filter, a pressure switch, lines, and coolant. This system usually requires minimal maintenance. The compressor does not require much attention, but be sure that the radiator is clean and air flows through it. Then, check the fans and make sure the compressor runs smoothly. There are usually LED indicators to display chiller status. The oil or coolant and the filter should be changed periodically. After inspecting the lines for leaks, you are finished with the preventive maintenance for the chiller system.

Cavity Systems

Preventive maintenance for a cavity-type system is even easier. Cavity systems usually are not pressurized. A good example is the machine tool’s B-axis. Check the level of oil through the sight glass and refer to machine manuals for periodic oil change information. When draining the oil, inspect it for particulate and liquid (coolant) contamination. The oil is a direct indicator of any potential problems with this type of system.

Next time, we will discuss preventive maintenance for the coolant system itself. This assembly is often overlooked; however, there is more to this system than most people realize. Talk to you next month.


Mike Breen, a Certified Electronic Engineer, began as an aircraft electrician in the 101st Airborne of the U.S. Army. With 14 years of experience in machine tool repair, he is presently a Field Service Engineer with Ellison Machinery Company of Wisconsin, where he has held this position for more than six years. He has designed and implemented complete preventive maintenance programs resulting in significant increases in machine performance for many successful companies. 
e-mail mbreen@ellisonwi.com

- July 2000