Instruction manual

35
VHS-4, VHS-6 and VHS-250 Diffusion Pumps
D R A F T 6 / 1 8 / 1 3
Section 3. Maintenance and Service
3.1 General Maintenance
Diffusion pumps generally require little attention when operated correctly. It is advisable to
perform some periodic inspections to ensure trouble-free operation. By performing simple
preventive maintenance, costly downtime can be avoided. A day-to-day log of pump and
system performance helps indicate the condition of the pump and the need for corrective
action.
3.2 Inspection Requirements
The frequency of inspections depends on the type of system, its operation, and its use.
The maximum interval between inspections is established on the basis of experience.
Agilent recommends that you examine the following items regularly:
✔ When the pump is cold, check the condition and level of the fluid.
❑ Withdraw a fluid sample through the drain and visually check the level of the fluid
through the sight glass. A slight discoloration of the fluid does not affect
performance.
NOTE Always use new O-rings when replacing
fill plugs or the sight glass.
Loss of fluid can be caused by any of the following conditions:
❑ Incorrect venting procedures and/or admittance of excessive air or other gas to a
hot pump
❑ Inadequate water cooling
❑ Prolonged operation at inlet pressures above 10
−3
Torr (1.33x10
-3
mbar)
❑ Failure to reinsert the foreline baffle in the pump assembly
✔ Check the total heater power input.
❑ When the pump is cold and the power is off, ensure that the heater is bolted
snugly to the boiler plate.
❑ Verify that all heater terminal connections at the heater and inside the junction
box are tight and in good condition.