In the air separation unit, low-temperature liquid is transported by centrifugal cryogenic pump. In order to ensure the reliable operation of the equipment, two sets of low-temperature pumps are generally equipped, one for use and one for standby. During normal operation, the main pump runs at full load, and the standby pump is in standby state under low load operation. Since the working medium temperature of cryogenic liquid pump is about -180°C, the working pressure is very high, and the pump body is installed in the cold box. When the pump fails, it is extremely difficult to maintain. Therefore, how to maintain the stable and reliable operation of cryogenic liquid pump is of great significance.
1.Common faults and cause analysis
|
Fault Condition |
Causes of failure |
|
Cavitation |
low inlet pressure, deviation from the best working point, improper installation height, inadequate cold insulation measures of inlet pipeline, etc |
|
Seal abnormal |
seal aging and abnormal vibration damage seal |
|
Abnormal pumping capacity |
impeller damage, shaft seal leakage, low pump load and speed |
|
Bearing overheating |
excessive lubricating grease, friction caused by improper clearance, shaft vibration caused by shaft bending or poor coupling alignment |
|
Shaft temperature too low |
cooling capacity leaks out |
2.Daily maintenance
|
Maintenance Measures |
Concrete Content |
|
Regular barring |
Before putting into operation, the cryogenic pump needs to be turned manually. When it is out of service for a long time, it should also be turned regularly to ensure its normal operation. |
|
Seal gas put into operation |
Select safe and reliable seal gas, adjust the seal gas pressure according to the standard, and pass the seal gas before the pump starts to ensure that the leakage gas temperature is within the normal range and the bearing temperature is normal. |
|
Full Precooling |
The liquid pump is started under low load. After running at low speed for a certain period of time, the speed is increased step by step, and the pump is cooled by increasing the liquid return flow in the pump. |
|
Lubrication normal |
Select the appropriate brand of lubricating oil, and add the lubricating oil regularly and quantitatively to ensure the normal oil level. |
|
Heating slowly |
When the equipment is shut down, a large amount of cryogenic liquid is left in the pump. In order to prevent overpressure caused by increasing the pressure in the pump after liquid vaporization, the liquid should be discharged in time. After the liquid is drained, the pump should be heated for standby. |
|
Degreasing cleaning |
For the liquid oxygen pump, because the working medium is liquid oxygen, the pump should be strictly degreased during installation. The degreasing agent is perchloroethylene or trichloroethylene solvent. |
