What Are The Most Common Repairs For An Industrial Air Compressor?

Most industrial air compressors are worked hard. Used to produce compressed air for pneumatic tools, actuators, grippers, conveyors, and spray systems, if the plant is running the industrial air compressor is running. That often means 24×7 operation.

Modern compressors, especially the rotary screw type, are very reliable. Even with appropriate maintenance though, problems can still arise. Here is an overview of the most common problems you should expect and the repairs that would likely be needed.

Compressor Operation

To understand what might go wrong, a grasp of how industrial air compressors work is needed. The two most widely used types are reciprocating and rotary screw compressors. While these have different methods of compressing the air their basic principles are the same.

A motor or engine drives an air pump. This pulls ambient air in through a filter, compresses it into a smaller volume, and discharges it into a storage tank or reservoir. Typically, in rotary screw compressors, the air also passes through an oil separator to remove oil picked up during compression.

The compressor will turn on and off as needed in response to signals from a pressure switch or transducer, or operate continuously at part or full load using various controls. Protection against overheating in rotary screw compressors and some reciprocating compressors is provided by some form of temperature sensor.

In a reciprocating compressor, the air pump consists of a crank-mounted piston moving up and down in a cylinder. The downstroke sucks air in, after which the inlet valve closes, and the piston rises to compress the air. The outlet valve then lets compressed air escape into the tank.

Rotary screw compressors use a pair of meshed helical screws. These draw air in as they turn, forcing it into an ever-smaller volume before it’s released into the tank. Most rotary screw compressors rely on oil to seal between screws and housing, lubrication, and heat removal.

Common Compressor Problems

Most problems experienced by compressor operators fall into one of these five categories:

  • Compressor will not start
  • Compressor will not shut off
  • Too much oil in the air
  • Low pressure and/or flow
  • Frequent shut-off

The majority of faults stem from problems with sensors, switches, or filters. Here is a closer look at the repairs most needed.

Compressor Will Not Start

Possible culprits include:

  • Faulty switch
  • Faulty pressure transducer
  • Broken belt or drive coupling
  • Unloader valve not working
  • Starter capacitor has worn out
  • Motor has worn out (possibly loose capacitor wires or worn windings)

In each case the repair is to replace the defective component.

Compressor Will Not Shut Off

This indicates either the system is not reaching the required pressure, or the pressure sensor is faulty. Assuming the former, the most likely problem is a blocked air intake filter or faulty inlet valve/controls. In a reciprocating compressor, it may also signify worn piston seals or rings. Another explanation is an air leak somewhere in the system.

Too Much Oil in the Air

In a rotary screw compressor this usually signifies a problem with the oil separator. These require service and/or replacing at regular intervals.

A related problem would be a blockage in the oil scavenge system. Removal and cleaning should be enough to fix this. Look also for problems with the oil check valve.

High oil consumption in a piston compressor usually means worn piston rings, cylinders or that the compressor has been operating unloaded for extended periods of time.

Low Pressure And/Or Flow

If users are complaining about there not being enough air to run equipment, start by looking for leaks in the distribution system. Then, verify that the tank valve is operating correctly. Look also for filter blockages.

Frequent Shutting-Off

This may be due to the compressor getting too hot and activating the thermal cutout. Filter blockage is a possibility, or the temperature sensor itself may be faulty. With a rotary screw compressor verify there is sufficient oil and that it is flowing as it should. Clean heat exchanger fins to help the compressor shed heat.

Another possibility is that the condensate trap is full. Add draining to the weekly or daily to-do list.

Tips For Avoiding Industrial Air Compressor Problems

When production depends on compressed air, it’s vital the compressor runs reliably. Most common problems and repairs are avoidable by carrying out appropriate preventative maintenance. Oil and filter changes are necessary along with regular changing or cleaning out of the oil separators and draining of condensate traps. Also, conduct regular inspections to look for evidence of leaks. If it’s impractical to do this with internal resources, consider asking a distributor about a maintenance contract.

Compressor manufacturers always provide guidelines for how to maintain their equipment. Refer to the manual for details or ask the manufacturer or their representative what they recommend.

Downtime Costs and Repair Costs

Most compressor problems have straightforward fixes. The majority are solved by replacing filters and/or sensors, and these repairs can usually be carried out quickly. The biggest problem with a compressor is the lost production or increase in quality problems that result from a loss of compressed air. The costs of this disruption will quickly exceed the repair costs and more than justify the expense of routine inspection and maintenance.

As a compressor accumulates hours, problems will invariably become more frequent, and possibly also more difficult and time-consuming to repair. At some point, and often earlier than most compressor users recognize, replacement becomes the most economic action. The prudent user prepares for this day rather than waiting until production is brought to a halt!

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