Table 147 Problems and solutions air compressors and the air distribution system

Problem Initial Maintenance Action


Compressor (Ref. 5) Low suction pressures Gauges do not work Excess vibration Cold crankcase heater during compressor operation Loose wiring or frayed wires Leaks on high-pressure side

Air line Leaks

Water in line Oil in line may only be that more air is used; this depends upon the individual application. If air is used as an energy source for motors or tools, the speed of the motor or tool usually depends upon the air pressure, and any decrease in this pressure will affect the performance of the motor. Another thing—controls are particularly affected by oil, water, and dust particles in control air, so it is of utmost importance that the compressor be checked regularly to see that the air cleaner is working as intended. More detail on compressors can be found in Chapter 12 of Ref. 5. Table 14.7 gives a guide to the initial maintenance procedures for air compressors and air distribution systems.

The Manufacturing Equipment System

This section would not be complete without a discussion of some of the more common equipment used in manufacturing. Some of this equipment has unique maintenance requirements, and these must be obtained from the manufacturer. Much equipment, however, is common to many companies or facilities, and this includes motors, ovens, and time clocks.

Motors. Motors can consume excess amounts of energy if they are improperly mounted, if they are not hooked up to their load, or, in the case of three-phase motors, if the voltages in the opposing legs are different. In this last case, the ASHRAE Equipment Handbook states:

With three-phase motors, it is essential that the phase voltages be balanced. If not, a small voltage imbalance can produce a greater current unbalance and a much greater temperature rise which can result in nuisance overload trips or motor failures. Motors should not be operated where the voltage unbalance is greater than 1% without first consulting the manufacturer.5

Look for leaks on low-pressure side; overhaul if necessary Repair or replace

Check mountings and initial installation instructions Check for lubrication problems

Bearings. Bearing wear is one of the more significant failure types in a motor, and this can be avoided by a procedure devised by Harold Tornberg, a plant manager and former industrial engineer for Safeway Stores, Inc. The Tornberg procedure is to connect a stethoscope to a decibel meter and to take readings at both ends of a motor. The reading on the driving end of the motor will usually be 2 to 3 dB above the reading on the inactive end. If there is no difference, the bearings on the inactive end probably need to be lubricated or replaced. If the difference is 5 to 6 dB, the bearings on the active end need to be replaced. If the difference is 7 to 9 dB, the bearing is turning inside the housing, and the motor should be overhauled as soon as possible. If the difference in readings is more than 9 dB, the motor is on the verge of failure and should be replaced immediately. These procedures were developed on motors in use at Safeway Stores and are in use throughout the Safeway system. To adapt these procedures to your facility, buy or make an instrument that allows you to determine the noise level at a particular point. Then survey the motors in your facility using the criteria discussed above. Take one of the motors that the test has indicated as needing repair into your shop, and tear it down. If you find that the failure was worse than these standards indicated, lower the decibel limit needed to indicate a problem. If you find that the failure was not as bad as you thought, raise the standards. In any case, this procedure is one that can be adapted to your needs to indicate bearing failures before they occur.

Ovens. Ovens use much energy, and many standard operating practices are available to help decrease associated waste.6 In describing the initial maintenance actions that must be performed, check the seals, controls,


Examine compressor closely; check gaskets, connections, etc., and replace if necessary Repair

Look for leak at compressor

Look for lubrication leak in compressor refractory, and insulation. The possible problems are shown in Table 14.8. Correcting these will save energy and improve operating efficiency at the same time. Remember also that heat lost from an oven must be removed by the air-conditioning system.

Time Clocks. Time clocks can be used to significant advantage in the control of equipment that can be turned off at regular intervals. But two problems may occur to eliminate any savings that might otherwise be generated. First, people can wire around time clocks or otherwise obstruct their operation. Or maintenance personnel can forget to reset them after power outages. If either of these happens, all the potential energy savings possible with their use will have been lost. These items are included in Table 14.8.

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