Specifications

16
SERVICE AND MAINTENANCE
58
General
This section contains the information regarding the
l
iquid cylinder care and maintenance. It includes the
particular maintenance procedures for changes to the
operating pressure, service pressure and liquid ser-
vice changes. When performing a procedure that is
described in this section, refer to the previous sec-
tions on operation (Section 8 through 13) for a
components item number and location.
Safety
Before implementing any procedure described in this
section, it is recommended that section 3.0 “Safety”
and Section 18, “Product Safety Bulletins” be read
and fully understood.
O
2
Cleaning
Always keep cylinders clean and free from grease
and oil. This applies not only to containers used in
oxygen service, but also to those used in nitrogen
and argon service.
When repairing containers, use only parts which are
considered compatible with liquid oxygen and which
have been properly cleaned for oxygen service.
(Refer to CGA Pamphlet G.4.1 “Equipment Cleaned
for Oxygen Service”.) Do not use regulators, fittings, or
hoses which were previous used in a compressed air
service. Use only oxygen compatible sealants or
Teflon tape on the threaded fittings. All new joints
should be leak tested with an oxygen compatible leak
test solution.
CAUTION : Before conducting maintenance or re-
placing parts on a cylinder, release container
pressure in a safe manner. Replacement of certain
cylinder parts may also require that the container
contents be completely emptied.
Changing Service
The Dura-Cyl/Cryo-Cyl Series liquid cylinders are de-
signed to hold any of the gas products specified.
They can easily be modified to work as well with ni-
trogen as oxygen. The fittings and decals need to be
changed and the inner vessel needs to be purged.
If a cylinder is changed from inert (argon or nitrogen)
to CO
2
service, the relief valve must be changed to
a CO
2
relief valve.
WARNING: Cylinders used in oxygen service must
not be changed to CO
2
service.
WARNING: Once a cylinder is used in CO
2
service,
it can not be used for other gas products, espe-
cially oxygen or nitrous oxide.
WARNING: Whenever converting a Nitrogen or
Argon cylinder to Oxygen use, inspect the cylinder
to assure cleanliness.
Recommended Inner Vessel Purging
(With a Vacuum Pump)
Before any operation that involves pressure or han-
dling of a cryogenic fluid, be sure that all safety
precautions are taken.
1. Open the vent to remove any pressure that has
built in the inner vessel.
2. Open the pressure building valve to boil away
any cryogenic liquid that remains in the vessel.
3. Warm the inner vessel with warm nitrogen gas
through the liquid valve. Check the gas temper-
ature as it escapes through the open vent valve.
Continue until it is warm.
4. Close the liquid valve, gas use and pressure
building valves.
5. Attach a vacuum pump to the vent valve and evac-
uate the inner vessel to 26 inches of mercury.
6. Break the vacuum to 5 psig (0.3 bar) with high purity
gas as required by the service of the container.
7. Repeat steps 6 and 7 twice.
8. Close all valves and remove the vacuum and gas
purge lines. The container is now ready for filling.