Air Separation Company | FAQs of air separation unit

Air Separation Company | FAQs of air separation unit
1. Reasons for low main cooling liquid level
1 Cause Incomplete heat exchange loss of main heat exchanger increases
The expander has small temperature difference, low efficiency and small expansion capacity
High temperature of air entering the main heat exchanger
The equipment leaks and the cooling loss increases
Too many liquid products are taken out
2. Solution: Reasonably distribute the cooling capacity. If the heat exchanger is blocked, it should be heated and purged completely
Check the expander and handle it
Check and handle the air cooling system and molecular sieve adsorber
Check the cold insulation materials, check the leakage and deal with it
Reduce liquid withdrawal
2. Reasons and treatment for failure of pneumatic diaphragm control valve
2 Cause Diaphragm leakage
Instrument air pressure loss
Valve in manual position
Valve rod is frozen or deformed
Solenoid valve failure or power loss
3 Solution Replace the diaphragm
Adjust the instrument air pressure to normal
Set the valve to the automatic position
Heating and maintenance of valve rod
Repair or replace the solenoid valve
3. Causes and treatment of large vibration of cryogenic liquid pump
2 Cause Cavitation in the pump
The pump operates below the minimum allowable flow
Impeller is blocked and unbalanced
The pump is fixed or the foundation is unstable
Wear of mechanical parts
3 Solutions Improve entrance conditions
Increase the flow to the minimum recommended value
Clean and balance the rotating parts
Improve the fixing method or foundation
Replace worn parts
4. The rated power and pressure of cryogenic liquid pump cannot reach the analysis and treatment
2 Cause Cavitation or gas binding of the pump
Impeller or volute blocked
Unqualified heating before starting the pump, water in the pump
The seal ring and impeller are damaged
The pressure after discharging the system is higher than the rated value
3 Solutions Improve the inlet conditions, clean the inlet filter and exhaust completely
Clean the blocked part
Remove moisture from it by drying heated gas
Replace the damaged part
Check the characteristic curve of pump and discharge system, and improve the system pipeline
5. Startup interlocking conditions of booster turbine expander
1 Lubricating oil pressure > 0.18MPa
2. The exhaust pressure of sealing gas reaches the set value
3 The oil level in the oil tank reaches the specified value
4 Bearing temperature at expander end > 20 ℃
5 Temperature after lubricating oil cooler > 20 ℃
6 Minimum opening of nozzle regulator is 10%
7 Return valve fully open
8 Prelubrication time is more than 10 minutes
9 Low low oil pressure interlock reset
10 Oil pump feedback signal enters DCS
6. Shutdown interlocking conditions of booster turbine expander
1. The speed is higher than 23000 RPM or lower than 10000 RPM
2 Upper limit of bearing vibration at expander side
3 Upper limit of bearing vibration at booster end
4 Upper limit of radial bearing temperature at expansion end
5 Upper limit of bearing temperature at booster end
6 Upper limit of temperature of thrust bearing at expander end
7 Upper limit of inlet temperature at booster end
8 Upper limit of lubricating oil temperature
9 Lower limit of lubricating oil supply pressure (0.15 MPa)
10 Lower limit of lubricating oil pump voltage (lower than 0.85 * 380V)
7. Heating and replacement of expander
2. The operation procedure is used to input all measuring instruments of the system.
Start the seal gas and oil system.
Check the status of relevant valves. V42 closes, V241 closes, V341 opens, and volute purge valve opens
Open the emergency shut-off valve and nozzle
Slowly open V241 to slowly increase the rear pressure of expander to 40KPa (G)
Check the dew point of the outlet gas before starting the heater, and check that the exhaust temperature is close to the intake temperature after stopping the heater
Close V241 after replacement
Close the emergency shut-off valve and nozzle, and finally close V341 and volute purge valve. Enclose the machine body to prevent moist air from entering.