SPI Supplies
29
SPI-DRY Critical Point Dryer
(d)
Re-assemble in reverse order, using a new O-ring.
7.1.6
Gauge Maintenance
There are two gauges on the CPD: A temperature gauge that reads from 0
– 100 C, and a pressure
gauge that reads from 0
– 2300 psi (or 0 – 160 bar).
Figure 7.2: Gauge Mountings
(a)
Thermometer Gauge
a. Remove the thermometer gauge and push-fit plug assembly, with O-ring seal, by rotating
and pulling.
b. Inspect and clean the O-ring, and replace if needed.
c.
Grease the O-ring lightly before re-fitting. If the thermometer is suspect, it can be checked
in water against a laboratory thermometer.
NOTE: In operation, there is a slight thermal lag between the true temperature inside the
pressure vessel and the reading on the thermometer if heating or cooling is carried out
rapidly. The use of a thermal transfer grease between the thermometer stem and the
pressure vessel will reduce this lag.
(b)
Pressure Gauge
a. Using a well fitting, open-end wrench on the hexagonal sectioned gauge stem, unscrew
and remove the pressure gauge. Do not use an over-sized wrench, or attempt to remove
the pressure gauge by rotating the gauge head.
b. Replace the fibre washer before refitting the pressure gauge. After replacing the pressure
gauge, tighten the gauge stem to a torque of 20 ft. lb. It may be necessary to use a
different thickness of fibre washer, or several washers, to achieve the correct tightness
while maintaining the correct gauge orientation.
7.1.7
Liquid Transfer Boat Maintenance
To prevent blockages, regularly strip and clean the transfer boat drain valve as follow:
(a) Remove the screw in the end of the transfer boat.
(b) Extract the valve slider and spring.
(c)
Clean out the drain hole using a 1/32” diameter drill.
