QDa turbo makes grinding noise and slows to a stop too quickly when venting - WKB1864

SYMPTOMS

• When powering-off QDa, the turbo pump makes a grinding noise and slows to a stop far more quickly than normal
• A loud grinding noise is heard while the instrument performs the vent cycle

ENVIRONMENT

• ACQUITY QDa Mass Detector (Performance)

CAUSE

The ballast valve on the rotary pump is open, allowing air back into the turbo pump when venting. 

FIX or WORKAROUND

Ensure that the ballast valve on the rotary pump is closed before powering-off the QDa.

ADDITIONAL INFORMATION

Unlike all other Waters mass spec systems, the rotary pump turns off as soon as the vent sequence starts. Air is allowed into the analyzer through a solenoid in a controlled manner. When the ballast valve on the rotary pump is open, air will backstream through the rotary pump in an uncontrolled manner, causing the turbo to slow very quickly. Over time, these conditions can damage the turbo.