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2. To Fill the Hydraulic Back-Pressure Valve or to
Check the Liquid Level, close both the inlet and
outlet shut-off valves. Operate the relief valve to re-
lieve any pressure in the hydraulic through the vent
pipe. Remove the liquid-level plug and fill to the in-
dicated level. Replace the liquid-level plug. Open
the shut-off valves.
3. The Liquid Level Should Be Checked Regularly,
and the correct liquid level maintained at all times.
The frequency with which the level should be
checked depends upon the conditions of service and
the liquid used in the hydraulic.
4. Preferred Solutions for Filling - These hydraulics
have a liquid capacity of 19.8 pints. The H-4 and H-
9 may be used with wet gas from an acetylene
generator or with dry gas from acetylene or piped
natural gas. The preferred filling solution for each
situation is fully described in the booklet Cold
Weather Care of Acetylene Generating Equipment,
packed with each hydraulic. These instructions ap-
ply equally to all types of fuel gases.
5. If a Flashback Should Occur, check the liquid level
before resuming service, making sure that the liq-
uid is at the correct level, and refill if necessary.
V. MAINTENANCE
Before making any adjustments or repairs on the
hydraulic, close the shutoff valves at the hydraulic
inlet and outlet. Relieve the pressure in the hydrau-
lic by venting it through relief valve.
No repairs should be made to the hydraulic back-
pressure valve proper except those which can be
made by simple replacement of parts. Only standard
parts as listed should be replaced. If any other parts
require replacement, contact your ESAB represen-
tative.
1. To Drain the Hydraulic, remove the drain plug at
the bottom of the hydraulic.
2. Clean and Inspect the Swing-Check Valve at
Regular Intervals. When necessary, replace the
valve. To disassemble the hydraulic for such an in-
spection or replacement, make sure that the shut-
off valves at the hydraulic inlet and outlet are closed.
Then disconnect the unions in the vent pipe and in
the outlet connection. Remove the hex nuts and bolts
that hold the cover plate and gasket to the hydraulic
shell. The shell can then be lowered away from the
inlet pipe, exposing the swing-check valve. Manu-
ally operate the swing-check valve to see that it
opens and closes freely. If necessary, wipe the valve
out with a clean cloth.
Fig. 2 - The sketch above shows the detail of the hy-
draulic support and the method of installing it. Note that
about 2 or 3 inches clearance between the hydraulic
and the wall or supporting structure should be provided.
1. Install the hydraulic in a true vertical position with
the shut-off valves and union connections shown in
Fig. 1. Fit the connection nipples accurately so that
the union joints can be made up without straining
the connection joints at the hydraulic.
2. Support the hydraulic from a wall, building column,
or other rigid structure by means of a U-bolt or band
clamp placed around the lower chamber of the hy-
draulic. Use a spacer block or bracket to allow 2 or
3 inches clearance between the hydraulic and the
wall or supporting structure.
3. Remove the liquid-level plug and fill through this
opening to the indicated level. NOTE: For instruc-
tions as to the correct liquid to use, see the para-
graph, Preferred Solutions for Filling below.
4. After installing the hydraulic, leak test all joints at a
pressure of 20 psi with soapy water. The joints to be
tested include all joints of the hydraulic itself and all
joints made in fitting up and connecting the assem-
bly to the fuel gas service lines. On new piping sys-
tems, the test should be applied with compressed
air or nitrogen before fuel gas is introduced into the
system. Nitrogen only should be used if the hydrau-
lic was installed in piping previously in use for fuel
gas service. Never test for leaks with an open
flame.
If the test pressure causes the relief valve to vent enough
to reduce the test pressure, release the pressure, re-
move the vent pipe connection, and plug the relief valve
outlet until the test has been completed.
IV. OPERATION
1. To Admit Fuel Gas to the Hydraulic Back-Pres-
sure Valve and to the Branch Line, open the shut-
off valves at the hydraulic inlet and at the hydraulic
outlet. TO SHUT OFF THE HYDRAULIC BACK-
PRESSURE VALVE, CLOSE BOTH SHUT-OFF
VALVES.
WALL
LINE
3/8" U-BOLT
3/8" X 2"
BAR
3"