BOC Edwards EO2K, Instruction Manual

Page: 38 / 62

EO2K, EO4K and EO6K Diffusion Pumps
OP
ERATION
PAGE
32
Issue G 32 Aug 06
4.2 Check the electrical safety of the pump
4.2.1 Check the earth (ground) continuity
Before you switch on the pump, you must check the continuity (resistance) between the earth (ground)
stud on the pump and accessible metal surfaces of the pump.
We recommend that you check the resistance between the earth (ground) stud and several locations on
the pump. Then:
• If all of the resistances are < 0.1
Ω
: continue at Section 4.2.2.
• Otherwise, contact your supplier or BOC Edwards for advice; do not continue to operate the
pump.
4.2.2 Check the insulation resistance of the heaters
If the heater in the EO pump has absorbed moisture while the pump was switched off, the insulation
resistance of the heater may be too low. Use the following procedure to measure the insulation
resistance of the heater before you switch the pump on.
If you have an RCCB in your electrical supply circuit, you do not need to measure the insulation
resistance of the heater because the RCCB will operate to disconnect the electrical supply from the
pump if the insulation resistance is too low. If your RCCB has operated, use the procedure below to
check the insulation resistance of the heater before you reset the RCCB.
Check the insulation resistance of the heater as follows:
1. Measure the insulation resistance (at 500 V d.c.) between the heater terminals (Figure 13, items 2
and 3) and earth (ground). Then:
• Multiply the measured resistance by the number of heaters in the pump, to calculate the
insulation resistance per heater.
• If the insulation resistance per heater is greater than 1 M
Ω
, you can switch on the pump.
• If the insulation resistance per heater is less than 1 M
Ω
, continue at Step 2.
2. Remove the heater from the pump (refer to Section 5.8.1). Bake the heater in an oven at a
temperature of 180
o
C for 8 hours or more.
3. Remove the heater from the oven. Measure the insulation resistance of each heater:
• If a heater has an insulation resistance greater than 1 M
Ω
, you can refit the heater to the
pump: refer to Section 5.8.2.
• If a heater has an insulation resistance less than 1 M
Ω
, repeat Steps 2 and 3 of this procedure.
If the insulation resistance of a heater is less than 1 M
Ω
after the heater has been baked for
24 hours, then the heater is faulty and you must replace it with a new heater.
WARNING
Ensure that you check the earth (ground) continuity as described below before you
switch on the pump. If you do not, there will be a risk of injury or death by electric shock.