Desolvation gas flow is unstable when it is set to a high value - WKB236650

SYMPTOMS

• When desolvation gas is enabled and its flow is set to a high value, the readback on the tune page becomes highly unstable
• A clicking sound can be heard coming from the gas handling base plate assembly inside the mass spectrometer
• API gas errors
• Source exhaust trip errors
• The pressure gauge on the nitrogen supply to the instrument drops to low values when desolvation gas is turned on and fluctuating

ENVIRONMENT

• Xevo TQ-S
• SYNAPT G2-Si HDMS

CAUSE

Insufficient supply of nitrogen gas to the instrument

FIX or WORKAROUND

Work with customer facilities to ensure that their nitrogen supply can provide up to 1400 L/hr without substantial drop in pressure.

ADDITIONAL INFORMATION

When desolvation gas flow is set high and the nitrogen supply cannot provide enough gas, pressure in the nitrogen inlet line will drop below trip point, causing the pressure switch solenoid to shut off the flow. When this happens, pressure will quickly build up and thr solenoid will open again. It will continue to cycle in this way, causing large fluctuations of gas flow and clicking noise from the solenoid opening and closing. Also, because the John Guest valve on the waste bottle is pneumatically controlled, nitrogen pressure fluctuations will cause this valve to open and close as well, which leads to source exhaust trip errors.