The 9 types of compressor failure and hazard analysis are all in it! ! !

The 9 types of compressor failure and hazard analysis are all in it! ! !

1. Common compressor faults-start with liquid

Start with liquid is a problem that easily occurs during shutdown. In the shutdown state, the refrigerant will migrate from the system back to the compressor and be deposited in the lubricating oil.

harm:

 The repeated migration of refrigerant will "wash" off the oil film on the surface of the mechanical parts;

  When the compressor starts with liquid, the lubricating oil will be foamed due to the refrigerant evaporation, which will affect the bearing lubrication

2. Common compressor faults-excessive liquid return

Excessive liquid return of refrigerant is a common problem in operating conditions. It is caused by repeated excessive refrigerant liquid migration back to the compressor when the compressor is running.

 harm:

 The refrigerant liquid dilutes the lubricating oil, causing poor bearing lubrication.

2. Common compressor faults-excessive liquid return

Excessive liquid return of refrigerant is a common problem in operating conditions. It is caused by repeated excessive refrigerant liquid migration back to the compressor when the compressor is running.

 harm:

 The refrigerant liquid dilutes the lubricating oil, causing poor bearing lubrication.

The abnormal force generated by the compressor fluid will cause damage to the scroll (usually damage to the scroll wall on the suction side) and damage to the Oldham slip ring. The liquid hammer damages the mechanical parts, and the generated metal chips enter the motor, which usually causes the motor winding to be short-circuited and burned.

The abnormal force generated by the compressor fluid will cause damage to the scroll (usually damage to the scroll wall on the suction side) and damage to the Oldham slip ring. The liquid hammer damages the mechanical parts, and the generated metal chips enter the motor, which usually causes the motor winding to be short-circuited and burned.

4. Common failures of compressors-oil loss/oil shortage

Loss of oil will result in insufficient oil in the compressor oil sump, and the lubrication of bearings and other mechanical parts cannot be guaranteed. This failure phenomenon usually occurs in the case of poor oil return in the system, which will cause severe wear on all load bearing surfaces.

Poor system oil return can be caused by many reasons:

 Compressor short cycle;

  The pipeline design causes the oil to be trapped in the system and cannot return to the compressor;

  Refrigerant leakage;

  Long-term low-load or partial-load operation;

  For long pipeline systems (pipes longer than 20 meters), there is no proper refuelling;

  Other reasons cause the oil to be blocked in the system, such as the blockage of the oil return hole of the vapor separation or the blockage of the filter, etc.

 5. Common compressor faults-high exhaust temperature

The high exhaust temperature is a fault caused by the compressor's actual operating conditions that have exceeded the compressor's safe operating curve. Due to the thermal expansion effect, the moving and static scrolls will squeeze between each other under the condition of high exhaust temperature, which will cause great contact stress. At the same time, due to the increase in temperature, the lubricating ability of the lubricating oil to the bearing will decrease. In addition, the motor stator may be overheated and burned.

The typical causes of high exhaust temperature are usually:

 The actual operating conditions of the system exceed the safe operating range of the compressor, for example, the suction pressure is too low, or the discharge pressure is too high, or the pressure ratio is too large, or the suction superheat is too high, etc.;

  The system is not clean when evacuated, and there is air or other non-condensable gases;

  Poor heat exchange efficiency of the condenser, or failure of the condensing fan, or dirty condenser fins, etc.;

  The suction refrigerant flow rate is too low, which may be due to insufficient refrigerant charge, or system leakage, or valve not opening normally, etc.;

 6. Common compressor faults-high pressure ratio

The high pressure ratio is a malfunction caused by the actual operating conditions of the compressor exceeding the safe operating curve of the compressor. Under high pressure ratio conditions, a very high pressure difference acts on the fixed scroll, which will cause damage to the top and side walls of the exhaust side of the scroll.

The high pressure ratio can be due to a very low suction pressure, or a very high exhaust pressure, or a combination of the two.

An increase in the pressure ratio will cause the exhaust temperature to increase simultaneously, so usually the failure caused by the high pressure ratio is very similar to the failure caused by the high exhaust temperature. However, under extremely high compression ratio conditions, the mechanical stress will often cause more serious mechanical damage to the scroll.

7. Common failures of compressors-water, steam...

System pollution is one of the main factors affecting system reliability and compressor life. This problem may cause a series of mechanical, electrical, and ice block failures in the compressor.

 Foreign pollutants are usually:

 Water (visible in liquid state);

  Water vapor (not visible, high moisture content);

  Other incompatible substances, etc.

System contamination may be caused by system leakage, for example, evaporator leakage will cause chilled water to enter the system. In addition, many links in the assembly process of the unit, or the use of on-site system maintenance, may introduce dangerous foreign objects, and they are usually related to the control of cleanliness, such as:

 The system is not fully evacuated;

  The cleanliness of other parts of the unit is poor;

  Poor quality of refrigerant or lubricating oil is contaminated;

  The welding process causes system pollution, etc.

Refrigerant R22 is impure and mixed with unknown abnormal substances. Cases:

8. Common compressor faults-reverse rotation

Reversal is caused by the wrong phase sequence of the external power supply wiring. The reverse operation of the compressor will cause the temperature inside the low-pressure shell to rise (may exceed 200°C) and cause the motor to overheat and burn. At the same time, the reverse rotation of the scroll will also cause mechanical damage to the scroll.

Long-term reverse rotation of the compressor will cause a series of mechanical or electrical failures. Therefore, when debugging the system, pay attention to whether the phase sequence is normal. If the following abnormal phenomena occur, the compressor may be in a reverse state:

 No pressure difference between high and low pressure;

  The operating noise of the compressor is very abnormal, which is obviously similar to the noise of metal friction;

  The low-voltage housing temperature rises quickly (the motor protector may trip).

Long-term reverse rotation of the compressor will cause a series of mechanical or electrical failures. Therefore, when debugging the system, pay attention to whether the phase sequence is normal. If the following abnormal phenomena occur, the compressor may be in a reverse state:

 No pressure difference between high and low pressure;

  The operating noise of the compressor is very abnormal, which is obviously similar to the noise of metal friction;

  The low-voltage housing temperature rises quickly (the motor protector may trip).

... ... Potential cause:

 Liquid hammer (the vortex breaks to produce metal chips);

  Failures related to poor lubrication (metal chips due to bearing wear);

  External contamination by foreign matter;

  Other mechanical damage;

  ... ...

9.2. Stator and rotor scavenging causes the motor stator to burn out: during startup or operation, if the stator and rotor scavenges, it will cause the motor to short-circuit and burn.

 Potential cause:

 Main bearing wear caused by poor lubrication (main bearing wear and bearing clearance increase);

  The rotor and stator have poor coaxiality;

  ……

9.3. Burning of motor stator winding coil:

 Short circuit between motor windings①;

  Short circuit between turns of motor winding②;

  Short circuit at the exit of the stator slot ③;

  Short circuit in the stator slot ④;

  Coil short circuit ⑤;

  The lead end is short-circuited ⑥;

Potential cause:

 Impurities and foreign bodies damage the insulation layer of the motor winding;

  Peak voltage or surge current;

  Motor manufacturing defects;

  … …;  9.4. Motor uniformly overheated and burnt out: The three-phase motor burns out evenly, which is usually caused by too high motor stator current or insufficient motor cooling.

Potential cause:

 Blocked rotor, stuck cylinder;

  The voltage is too high or too low;

  Inspiratory pressure is too low;

 Motor overload;

  The compressor starts and stops frequently in short cycle;

  ……

  9.5. Unbalanced three-phase voltage:

 Poor power wiring;

  The three-phase voltage of the power supply is unbalanced;

Lack of phase operation: Under the condition of lack of phase, the star-shaped motor will cause the two-phase winding to be overheated and burned, while the one-phase winding is intact.

… …； Potential cause:

 Poor contact or adhesion of contactor contacts;

  The power wiring is incorrect;