Troubleshooting and repair of a reciprocating compressor

air compressor

The compressor is quite complicated technical equipment, as it is used, it has the right to wear and break. In this article, we will consider all the methods of maintenance and operation for its maximum prolongation of life. To repair the compressor with your own hands, if it still broke and it is possible.

The reliability of compressor equipment depends largely on timely and high-quality maintenance. A large number of failures of piston compressors is a consequence of poor-quality cleaning of compressed air (abrasive dust, water, and other inclusions). The use and timely replacement and cleaning of filter elements will delay the repair of the compressor for a long time.

The main reasons why an air piston compressor breaks down are:

  • Unfavorable operating conditions
  • Scheduled maintenance is not performed.
  • Not competent staff

To ensure high-quality maintenance, operation, and repair of the compressor with your own hands, you must solve all the above points.

The main difference between maintenance and compressor repair is that during the repair, certain parts are forced to be replaced, and during maintenance, parts are replaced as required, depending on their actual condition.

 

Principle of operation and components

The compressor is a device for increasing pressure and moving gas to the required source ( spray gun, grinding machines, screwdrivers, airbrushes, and any other pneumatic equipment). The main demanded equipment in the body repair was the compressor piston, oil type. In piston, the volume of working chambers is changed by means of pistons, reciprocating.

They have a different number of working cylinders and distinguish them according to the following structural arrangement:

  • Horizontal
  • Vertical
  • Oppositional
  • Rectangular
  • V and W shaped
  • Star-shaped
Main design flaws: incomplete balance of their moving parts, the presence of a large number of friction pairs, etc. All this is the cause of failure and subsequent repair.

Before you repair the compressor yourself, you need to study its technical structure. In the photo below the scheme of a single-stage compressor, piston group.

  1. Crankshaft
  2. Housing
  3. Connecting Rod
  4. Piston Pin
  5. Piston
  6. Cylinder
  7. Valve
  8. Cylinder head
  9. Valve plate
  10. Flywheel
  11. Omentums
  12. Crankshaft bearings

On the body near the electric motor, there is an automation unit called a prostate. With it, you can adjust the compressor. It is possible to lower the inflated pressure or raise.

 

Malfunction of the reciprocating compressor

If you find any defects (the appearance of knocks, jamming rubbing parts, strong heating, increased consumption of lubricant, etc.), it is necessary to make repairs.

Determining the type and amount of repair is important to establish at the stage of diagnosing the condition of the object before repair. Malfunctions of the compressor can be divided into two groups: technical malfunctions (working part of piston group and malfunctions of an electric equipment). Below are the most common failures:

  • The compressor (electric motor) does not start
  • The motor hums and does not rotate
  • The compressor does not gain momentum
  • Knocking in the cylinder-piston group
  • The cylinder is too hot
  • The performance dropped
  • High Vibration

The compressor (electric motor) does not start

The compressor does not turn on, the most common problem. The main and commonplace, which can be in this breakdown, is there is no voltage in the network. The first thing to check is the plug and the wire for the break, supplying the electric motor. Using a special “screwdriver tester”, check whether the voltage is applied to all phases. Check the fuse if there is one. Make sure that the starting capacitors are operational (single-phase compressors have a voltage of 110V).

 

Pay attention to the level of pressure in the tank (receiver). Perhaps the pressure is sufficient and the automation does not start the compressor, as soon as the pressure drops to a certain level, the electric motor will start automatically. This is not a breakdown, many forget about this nuance and survive ahead of time.

A non-return valve can also become a problem if the compressor does not turn on. Also, a faulty automation unit (warning switch), affects the breakdown (on and off), possibly the button on the block itself has become unusable.

If the electric motor does not start to buzz, buzzes do not gain the necessary turns or stops during operation, this does not always mean a breakdown.

The basic malfunctions of the electric motor which can prevent it to correct uninterrupted work:

  • Low motor power (insufficient mains voltage)
  • Loose connections, poor contact
  • A non-return valve (leaks), thereby creating a back pressure
  • Incorrect start of the compressor (see operating instructions)
  • Wedged piston group (due to lack of oil level, overload)

If the electric motor of the compressor does not turn on at all and does not emit sounds, this indicates the following:

  • The mains fuse has tripped
  • Overload protection has tripped
  • Poor contact in the electrical circuit (malfunctioning wiring)
  • The worst, the electric motor burned (often there is a characteristic smell)

 

Knocking and crashing into the cylinder and piston group

One of the reasons for the compressor failure is the faulty piston group. Recognize the defect of this system is simple enough. Usually, they are accompanied by a thud, a rumble, a grating and other sounds of a metallic character. If the compressor knocks, then its injection part is faulty, where there are many metal parts that interact with each other. Because of their friction and wear, there are extraneous noises and unpleasant sounds.

Do not run with such a breakdown, if possible, you must eliminate it as soon as you hear the first signs of their manifestation. The basic malfunctions if the compressor has started to knock and loudly work, than before:

  • Crashed worn bearings, connecting rod bushings
  • The bearings on the crankshaft failed.
  • Piston, rings, piston pin worn
  • Worn cylinder
  • Loosen cylinder and head bolts
  • A solid particle entered the cylinder
  • The cooling impeller was loosened on the pulley

In order to repair the breakage data, in simple cases, it is enough to stretch out all the bolts and nuts. If the piston, the cylinder crankshaft or the connecting rod are worn, then a comprehensive overhaul is required. When repairing the piston group it may be necessary to bore the cylinder, if it is badly worn and has external defects, to pick up a repair piston for the new dimensions. The following are the possible defects of the piston system:

  • Changing the diameter of the piston, cylinder
  • Distortion of the form of the mirror of the cylinder
  • Risks, scratches, scuffs on the walls of the cylinder
  • Cracks in the main working part
  • Cracks and breakage of flanges

With prolonged use due to wear, there are risks on the cylinder’s mirror, the inner diameter of the bush under the eccentric shaft increases. During repair, the cylinders are restored by pressing the sleeves into them. Worn bushings under the eccentric shaft are replaced. This repair is quite difficult to do with your own hands without the necessary tools and equipment. Since the most time consuming and the responsible stage is the restoration of the cylinder. Boring is performed on a vertical boring machine using a special tool.

This, as for the cylinder, below we will consider the main malfunctions of the compressor crankcase.

  • Cracks in the walls of the cavities of the crankcase
  • Variations in the size and shape of landing areas
  • Seat folding
  • Crankshaft bearing seats crashed

When these components are worn out, they must be replaced with new ones. The bearing hole is bored on a horizontal boring machine for a larger diameter of the bearings or for pressing the bushing, followed by boring the pressed bushing to the required diameter. Repair of a compressor of this complexity should be done by qualified specialists.

 

 

 

The compressor is very hot

If the compressor is hot, then it indicates a certain malfunction. There can be several reasons for overheating. Starting with simple, it is blocked airflow of the cylinder and crankcase. Check that the impeller is not blocked with foreign objects.

One of the main reasons for the heating compressor is the lack of oil level. Work nodes are working on wear and tear, high friction is created as a result of the heat build-up. With further such operation, the equipment will quickly fail. Check the oil level if it is not enough, you need to top up to the required level.

Malfunctions of valves, as a result of carbonized contamination or their weakening. Can also be clogged air channels.

Look at the pressure level, the automation may have broken down and the compressor “threshes” to a high pressure, this causes overheating. It may be necessary to repair or replace the safety valve.

Try to place the compressor in a cool, spacious place, especially during the hot season. Whatever cooling it does not have, it will heat up much less, which will affect its positive and durable work. “Also do not forget that the air is colder than the fact that it has less moisture and oil impurities.

 

The performance dropped

The drop in performance may be due to several reasons. Clogged, clogged suction air filter. Remove and clean the filter with compressed air or replace it. Basically, in reciprocating compressors, it is made of ordinary foam rubber.

It is possible that somewhere there is a leak of air. Examine all suitable and outgoing tubes and hoses. As in the previous case, wear and malfunction of the valves are possible, this greatly affects the performance. With a sufficiently long use wear piston rings, sealing disappears. In more serious cases, the cylinder and pistons are worn out, scratched or have other external defects, which results in loss of compression and the compressor stops pumping air.

It is worth checking the force of the belt tension, connecting the electric motor and the crankshaft of the piston system. With loosening slippage is possible and the compressor stops to pump the air properly.

 

The oil entering the working chamber

If the oil gets into the working chamber, bad signs are bad enough, of course, it will not lead to a complete breakdown of the compressor, but it can even do damage to paint works and the appearance of defects in painting. The main causes of oil ingress, wherever it does not need: Filled with low viscosity oil, that is, oil is too liquid, it seeps through seals and rings. The oil level is too high. Because of the excess oil, it is squeezed out by force and enters the chamber. Inadequate oil is used. Pour only a special compressor oil.

The piston and rings in the cylinder block worn out. Also, the wear of the cylinder itself affects the ingress of oil into the working chamber. To solve the problem, the repair of the piston compressor is required, as described above.

 

Operation and maintenance of the compressor

A reciprocating compressor, like any technical equipment, requires some maintenance. The proper operation will help prolong the life of your compressor equipment. Let’s consider the basic measures for maintenance, repair, and operation of the compressor.

1. Replacement and cleaning of the air filter. The filter element is mainly made of a non-woven fabric, foam rubber or synthonin. If the compressor is in the same place where the painting of the car is carried out, it is strongly clogged (stuck) with seeds from the paint, varnish, and other paintwork material. The filter prevents the ingress of abrasive dust into the cylinder, the piston and cylinder wear less. As often as possible, change and clean the filter, as this will significantly increase the resource and delay the repair of the compressor.

2. Oil change for air compressor a very important point. Observe the oil level on the special indicator (window) in the compressor crankcase. Working at a small level or without oil entails serious overhaul. Top up to the required level if it is not enough. Periodically it is necessary to completely drain and fill in a new one. Use only special  oil for air compressors.

3. Drain the condensate. An important point in the maintenance of the compressor. The air is saturated with moisture, it inevitably falls with the intake air into the receiver. Over time, accumulates in large quantities. With a large content of condensate, it can be released into air hoses, which leads to defects in painting. Also, due to condensation, corrosion begins inside the receiver. Drain condensate as often as possible, at least once a week, especially during hot and humid seasons.

4. Observe the general condition, periodically blow from dust and other contaminants. Pay special attention to the impeller on the electric motor, the cylinder fins, the air cooler, dust and dust from the paint accumulate as they are used, which reduces the cooling capacity.

5. Inspect the belt drive for wear and tension. When pressing the belt in the middle point, it should not bend more than 12-15 mm. Make a broach of all bolts and nuts. Periodically check the operation of the safety valve, which serves to protect against excessive pressure, due to a breakdown of the pressure switch.

Follow all the above-listed methods and repair the compressor you will delay for a long time.

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