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Gas-tightness Test
When starting up the regulator, and at regular intervals,
check gas tightness as follows:
a. Slowly close downstream cut-off valve.
b. In order to avoid excessive lock-up pressures, close the
valve and simultaneously open the outlet vent tap. In
case of safety slam-shut device being tted, keep this
valve manually open in order to prevent it from tripping.
c. Slowly close the vent tap and read the lock-up pressure
value. An increase in outlet pressure will initially be detected,
after which pressure will stabilize. If, on the contrary, outlet
pressure continues increasing, then the seal is defective.
Check if leak is ascribable to pilot or regulator.
Checking Pilot Gas Tightness
a. Link up together connection A, connection B, a vent tap
and a pressure gauge with appropriate scale.
b. Close connection L.
c. Slightly open vent tap, feed either gas or compressed air
to the pilot through connection S. Pressure gauge will
show the pilot set pressure.
d. Close vent tap and read the lock-up pressure value, which
should be less than 0.4 bar. If this value is higher than
0.4 bar, pilot pad or seal seat are worn out or damaged.
e. Use soapy water to check there are no gas leaks.
Maintenance
CAUTION
personnel to ensure good servicing results.
General Maintenance
a. Disconnect and remove the pilot from the line.
b. Fully unscrew the adjusting screw (key 1).
c. Unscrew the cap (key 3), remove the spring holder
(key 6) and the spring (key 7). Replace the O-rings
(keys 4 and 5).
d. Loosen screws (key 10), remove the upper cover
(key 8) and the lower cover (key 21). Replace the
O-ring (key 18).
e. Lock the stem (key 23) by inserting a key into the notches
and unscrew nuts (keys 20 and 26).
f. Disassemble the parts and replace the diaphragm
(key 14) and the pad (key 22).
g. Unscrew the seat (key 19) and replace the O-ring
(key 17).
h. Use petrol to cleanse the pilot body and all metal parts. Blow
them thoroughly with compressed air and check for clear
holes along the gas conduits. Replace any worn parts.
Reassembly
Reassemble all parts by following in reverse order the assembly
as described above (see General Maintenance section).
As parts are assembled, make sure they move freely
causing no friction.
Make sure to:
a. O-rings and diaphragms should be lubricated by applying
a thin layer of ‘Molykote 55 M’ grease.
Pay attention not to damage them during reassembly. All
other pilot parts require no lubrication.
b. The cover clamping screws (key 10) should be tightened
evenly to ensure proper tightness.
c. Pilot operation, calibration and tightness should be tested
as described in the Gas-tightness test section.
d. Previously disassembled ttings must be connected.
Check for leaks by using suds.
Calibration
See the paragraph Pilot Adjustment on page 10.
(SEE FIGURES 21 AND 22)
Installation
Identical to Type PRX/120, PRX/125 series (see page 16).
Startup
Identical to Type PRX/120, PRX/125 series (see page 16).
Pilot tightness should be tested regularly by referring to the
following procedure:
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