BOC Edwards 18B4B, Instruction Manual, Page: 35 / 62

Feb 04 Issue A
18B4B Vapour Booster Pumps
PAGE
29
29
OP
ERATION
4 OPERATION
4.1 Introduction
WARNING
Do not pump gases which are
flammable at pressures in the
operating pressure range of the
18B4B pump. If you do, this may
result in an explosion or fire. If in
doubt about the compatibility of
gases with the use of the 18B4B
pump, contact BOC Edwards for
advice.
WARNING
Do not operate the pump when the
cooling-water flow through the
cooling-coils is restricted. If you do,
water in the cooling-coils may boil,
the cooling-coils may fracture, and
hot water and steam which escapes
from the cooling-coils may injure
people.
WARNING
Do not touch any part of the pump
when it is switched on. Avoid contact
between the pump and combustible
materials, plastic materials and
electrical cables. Surfaces of the
pump are very hot and can cause
injury to people and damage to
equipment.
WARNING
If the cooling-water supply fails, allow
the pump to cool before you
disconnect the cooling-water supply
and return pipelines from the pump.
If you do not, steam or water may be
ejected from the cooling coil when
you disconnect the pipelines and you
may be injured.
4.2 Check the insulation resistance of the
heaters
If the heaters in the pump have absorbed moisture
while the pump was switched off, the insulation
resistance of the heaters may be too low. Use the
following procedure to measure the insulation
resistance of the heaters 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 heaters, 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 this procedure to check
the insulation resistance of the heaters before you
reset the RCCB.
1. Measure the insulation resistance (at 500 V d.c.)
between any of the heater terminals (see
Figure 5) 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 heaters from the pump (refer to
Section 5.8). Bake the heaters in an oven at a
temperature of 120
o
C for 12 hours or more.
3. Remove the heaters 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.
• 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.