VHS-4, VHS-6 and VHS-250 Diffusion Pumps - Ideal Vacuum ...

DRAFT 3/9/05
3.7 Heater Replacement
3-8
VHS-4, VHS-6 and VHS-250 Diffusion Pumps
Refer to Figure 3-5 (VHS-6 and VHS-250) and Figure 3-6 (VHS-4) for this procedure:
1. Turn off the power to the diffusion pump and disconnect the power supply.
2. Remove the heater cover and the insulation from the bottom of the diffusion pump.
3. Label the heater wires for proper location during installation.
4. Disconnect the terminal leads.
Use two wrenches when loosening (one on each nut) to prevent excessively torquing
and possibly breaking the heater terminals.
5. Remove the nut holding the heater clamp.
6. Lower the entire heater unit from the pump and replace the defective heater.
7. Coat the boiler stud with an anti-seize compound such as FEL-PRO C5A or common
milk of magnesia.
8. Support the heater unit by the heater clamp, line up the hole with the boiler stud, and
push the unit up against the boiler plate.
9. Finger-tighten the nut to hold it in place.
10. Tighten the heater clamp bolt to a torque of 250 inch-pounds.
11. Replace the heater insulation and cover.
Heater Element
647306125 2200 W, 120 V
647306175 2200 W, 208 V
647306225 2200 W, 240 V
Figure 3-5 VHS-6 and VHS-250 Heater Mounting