Troubleshooting
4-2
Table 4-1 Troubleshooting
Fault
Probable Cause
Corrective Action
Poor system pressure
Leaks in system, virtual or real
Locate and repair.
High process gas load
Measure gas load, eliminate cause.
System dirty
Clean system to reduce outgassing.
Poor ultimate pressure
Contaminated pump fluid
Examine, clean pump,replace fluid.
Low heat input
Check voltage. Check for continuity,
burned-out element, poor thermal
contact.
Inadequate cooling water flow
Check water pressure. Check tubing
for obstructions and backpressure.
Excessive or too cold cooling water
Check temperature. Adjust flow.
High forepressure
Check for leak in foreline, poor
mechanical pump performance,
breakdown of mechanical pump fluid.
Water in quick-cool coil
Check and remove water.
Low heat input
Check heaters.
Low oil level
Add oil.
Malfunctioning pump assembly.
Check and repair or replace.
Improperly located jets. Damaged
jet system.
Inlet pressure surges
Incorrect heater voltage
Check and correct voltage.
Fluid outgassing
Condition fluid by operating the
pump for a few hours.
Leak in system ahead of pump inlet
Check and correct.
High chamber
Forepressure too high
Check for leak in foreline, poor
contamination
mechanical pump performance,
breakdown of pump fluid, and
incorrect valve operation.
Prolonged operation at high through-
Review operating procedures.
put at pressure above 10
-3
Torr (.133 Pa)
Improper system operation and
Review operating procedures.
air release procedures
Pump will not start
Safety circuits and/or protective
Check utilities, flow switches,
devices prevent contactor from
interlocks. Check thermostat
staying closed
operation.
Slow pumpdown (Pro-
longed cycle after
checking gas goad
conditions)
Summary of Contents for VHS-6
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