9. Maintenance
This section summarizes the procedures for
inspecting and changing the components of the
control head. It also describes calibration of the
pressure gauge.
9.1 Operating incidents
9.1.1 Wrong level shown
Causes Corrective action
Level regulating
ring in wrong
position.
Adjust the level gauge (see
section 9.4, on page 29).
Damaged spring. Change the control head
assembly (see section 7.1, on
page 20).
9.1.2 Valves operate at a pressure lower
than 0.5 bar
Causes Corrective action
Pressure gauge out
of order
Check that the pressure
gauge is operating properly
(see section 9.3.1, on page
27). Replace it if necessary
(see section 9.5.1, on page
30).
Valve out of order Replace the valve (see section
9.5.1, on page 30).
Foreign body
present on the
valve seat
obstructing the seal
If the foreign body is ice, warm
the valve with a jet of nitrogen
or dry air until it disappears.
If the body is of a different
kind, carefully open the flap
and blow nitrogen or dry air
onto the seat of the valve then
closed the flap (see <field/>,
1). This operation may require
the valve to be dismantled
(see section 9.5.1, on page
30).
Figure 9-1: Blowing out the valve's seat.
9.1.3 Valves constantly operate at a high
flow rate
Causes Corrective action
Pressure-building
valve open
Close the pressure-building
valve. This valve must always
be kept closed unless liquid is
about to be withdrawn.
Pressure-building
valve leaking
Replace the pressure-building
valve (see section 9.5.2, on
page 31).
Poor quality
vacuum, causing a
lot of liquid to
evaporate
Contact your local
Cryopal
representative.
9.1.4 Abnormally high evaporation rate
under standard temperature and
pressure
Causes Corrective action
Pressure-building
circuit leaking
Locate the leak (see section
9.3.4, on page 29). Make the
fitting leak-proof again (see
section 9.5, page 30) or
contact your local
Cryopal
representative.
Poor quality
vacuum
Contact your local
Cryopal
representative.
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