CRYOGENIC TURBOEXPANDER TROUBLESHOOTING

•     Seal gas pressure regulator improperly set.

•   Plugged or defective regulator.

•     Worn labyrinth seals causing excessive seal gas consumption.

•     Reset pressure regulator settings.

•   Clean or replace regulator.

•   Contact Air Products

CryoMachinery.

lube oil pump(s).

•   No power or faulty motor.

•   Pump seized.

•     Establish power or replace motor.

•   Look for flow restriction in lines.

•     Defective lube oil heater temperature switch or element.

•   Lube oil heater set too high.

•     Faulty oil temperature control valve.

•     High incoming cooling water temperature.

•     Insufficient cooling water supply.

•   Cooling water isolation valve(s) closed.

•     Disconnect power to lube oil heater and replace switch and/or element.

•   Reduce heater setting.

•     Replace oil temperature control valve sensing element.

•     Decrease cooling water temperature.

•   Increase cooling water flow.

•   Open valve(s) as needed.

•   Oil pump output too low.

•   Clogged oil supply line.

•   Dirty pump suction screen.

•   Dirty oil filter elements.

•     Pump failure to prime at startup.

•   Cooling water isolation valve(s) closed.

•     Rebuild lube oil pump, replacing pump seals.

•   Clean oil supply lines.

•   Clean suction screen.

•   Replace filter elements.

•     Check oil level and that the pump inlet screen is clear of debris. Rebuild oil pump if necessary.

•   Open valve(s) as needed.

•      Oil pressure control valve fouled.

•    Oil temperature too low.

•     Clean pressure control valve and oil lines.

•     Allow heater to heat oil to at least 16°C (60°F) before running pump.

open inlet slam valve.

•     Bearings are frozen and the expander needs to be defrosted.

•     High pressure in turboexpander circuit.

•     Ice formation on slam valve inhibiting motion.

•     Inlet slam valve not reset electrically.

•     Lube oil supply temperature high. Oil cooler fouled or cooling water turned off.

•   Seal gas supply pressure high.

•     Instrument/electrical problem with slam valve or plant control system.

•     Defrost turboexpander to unfreeze bearings.

•     Vent pressure in turboexpander circuit.

•   Defrost inlet slam valve.

•     Reset slam valve on plant control system.

•     Clean oil cooler and/or turn cooling water on.

•     Decrease seal gas supply pressure.

•     Replace or fix solenoid. Check wiring to plant control system.

•   Shaft locking screw in place.

•   Seized bearing/rotor.

•     Tight seals. Insufficient flow or differential pressure to spin expander.

•     One or more bearings are damaged.

•   Install speed probe.

•   Contact CryoMachinery.

•     Check supply flow and pressure to expander.

•     Improperly set gap on speed probe.

•   Defective tachometer or probe.

•     Improperly wired or calibrated tachometer.

•     Desensitizing jumper on tachometer.

•   Set gap per Outline drawing.

•     Obtain and install new tachometer or probe.

•     Check tachometer wiring and recalibrate tachometer.

•     Remove jumper between tachometer terminals 11 and 30.

•     Resistor not installed across signal leads.

•     Speed probe leads switched at tachometer.

•     4-20 mA signal from tachometer incorrectly converted in plant control system.

•     Refer to tachometer wiring diagram.

•     Correct speed probe connections on tachometer. Black is wired to common. See Wiring Diagram.

•     Reprogram plant control system conversion code.

•   Compressor surge.

•     Check process conditions with compressor surge curve.

1. Process temperature, flow, pressure, speed or a combination of the preceding, not at design.
2. Expander or compressor inlet
3. Worn or damaged abradable material on expander shrouds. Seal gas regulator improperly set. A high positive differential pressure results in warm gas bleeding into the process. A high negative differential pressure results in cold gas bleeding out of the process.
4. Both cases will negatively affect expander efficiency.
5. If automatic speed control, the design speed setpoint in the plant control system could be incorrect.

See low inlet pressure above.

Refer to the CryoMachinery Product Definition Specification for proper setpoint.

Refer to the CryoMachinery Product Definition Specification for proper setpoint.

does not respond

to nozzle adjustments.

• Damaged nozzle mechanism.

• Faulty actuator.

• Plant control system control problem.

• Frozen oil in nozzle mechanism.

• Loss of actuator instrument signal.

• Loss of actuator motor power.

Contact CryoMachinery.

Repair or replace actuator.

Check wiring to plant control system.

Check wiring to actuator

Verify power to actuator motor. Verify actuator is receiving instrument signal from DCS. Pull plug-in cartridge and clean expander end thoroughly.

•     Unloading of compressor due to insufficient flow initiating surge condition.

•   Excessive turbine horsepower.

•   False indication of overspeed.

•     Failure of inlet slam valve to close in specified time.

•     Open vent valve on compressor discharge (or open compressor recycle valve if present) to help increase compressor flow.

•     Verify correct turbine inlet temperature. As process cools, speed will decrease. As speed decreases, flow can be increased.

•     Verify alarm and trip setpoints on tachometer and in plant control system.

•     Inspect inlet slam valve for ice formation. Stroke valve to check operation.

•   Damaged impellers.

•     Expander or compressor wheels dirty or eroded.

•     Ice forming on expander wheel due to insufficient expander defrost.

•     Compressor operating in or near surge.

•   Oil contamination (with water).

•   Contact Company CryoMachinery.

•   Contact Company CryoMachinery.

•   Defrost turboexpander.

•     Increase flow by opening expander nozzles or vent valve on compressor discharge.

•   If oil is contaminated, dispose of properly and refill the lube oil reservoir with appropriate grade of oil and additives.

on the inlet slam valve.

•      Ice formation on inlet slam valve inhibiting motion.

•     Valve seat damaged and will not seal tightly.

•   Defrost inlet slam valve.

•   Replace inlet slam valve.

Worn labyrinth seals.

Low seal gas pressure.

Bypassing seal gas interlocks and starting oil pump.

• Contact Company

• See low seal gas pressure

• Remove bypasses to allow pump to shut off when seal gas pressure is low.

mist coming from reservoir demister.

Seal gas atmospheric vents piped to alternate location.

Check if an alternate location is being used to vent the seal gas. Verify that the line sizes are not creating backpressure in the seal cavity and forcing the seal gas into the bearing case.

Low oil temperature (causing high oil viscosity).

Check that oil heater is functioning properly.

• Oil leaking in the piping or lube oil system components.

Oil leaking across seals to process piping due to low seal gas pressure or low seal gas differential pressure across expander seal and pumps not shutting off.

• Close drain valve.
• Check lube oil system for leaks.
• See low seal gas pressure entry.

process temperatures fall.

Open vent valve on compressor discharge (or open compressor recycle valve is so equipped) to help increase compressor flow.

Check resistance at RTD. Replace bearing at next maintenance interval (only for imbedded RTDs).

Faulty probe or actuator.

Replace faulty components.

High oil inlet temperature.

Worn or damaged bearings.

Abnormal operating conditions (high thrust load). Expander overthrust.

See High Oil Supply

Contact Company

Contact Company CryoMachinery. Reduce flow through compressor to increase compressor pressure ratio.