Bell & Gossett HS 601G Pilot Operated Pressure and/or Temperature Steam Regulators Series 2000 - Manual (Page 19)

Air Pilot Bench Tests
1. Isolate the main valve from the steam line. Make sure
the internal pressure is 0 psig and allow the valve to
cool to prevent injury.
2. Disconnect the copper tubing lines and feedback line.
Disconnect the pipe union and remove the pilots. If
more than one pilot is used, unscrewing the 1/4 " NPT
pipe nipples should separate them.
3. Mount individual air pilot in a vice to test.
4. Plug the 1/4" NPT FEEDBACK tapping.
5. Install a 1/8" NPT pipe with a pressure gauge and
shut off valve in the SIGNAL port.
6. Connect a 30 psig air supply to the pilot IN connection.
7. Test for seat and ball leakage.
• Open shut off valve from SIGNAL port.
• Apply air pressure at the IN port.
• Check for leakage from the SIGNAL port. Only a
small amount of leakage is allowable.
• If excessive leakage is indicated replace the ball
and seat. See "Air Pilot Repair."
8. Test for Valve Movement.
• With 30 psig air pressure at the pilot Inlet connection,
close the shut off valve in the SIGNAL pipe.
• Load air pressure on the top of the pilot until pressure
is equal to 1/2 of air supply.
• Slowly open and close the shut off valve several
times, the pressure should be the same each time
the shut off valve is closed.
• The pressure should respond smoothly.
• If the pressure changes each time or if the reaction
of the pressure gauge is jerky, the pilot valve
movement is restricted.
• Inspect the internal components for dirt or wear.
9. Diaphragm test.
AP-1A:
• With a 30 psig air supply to the
FEEDBACK tapping,
the SIGNAL line and IN tapings plugged, check for
air leakage from the top of the pilot.
• If air is leaking, replace the diaphragms.
AP-4A:
• With a 30 psig air supply to the FEEDBACK tapping,
the SIGNAL line and IN tapings plugged, check for
air leakage from the vent hole of the pilot.
• If air is leaking, replace the lower diaphragms.
• With a 30 psig air supply to the top of the pilot, the
SIGNAL line taping, FEEDBACK taping and IN
taping plugged, check for air leakage from the vent
hole of the pilot.
• If air is leaking, replace the upper diaphragms.
• With a 30 psig air supply to the top of the pilot, the
SIGNAL line taping, FEEDBACK taping and IN
taping plugged, check for air leakage from the vent
hole of the pilot.
• If air is leaking, replace the upper diaphragms.
1. Isolate the main valve from the steam line. Make sure
the internal pressure is 0 psig (0 bar) and allow the
valve to cool to prevent injury.
2. Disconnect the copper tubing lines and feedback line.
3. Disconnect the pipe union and remove the pilots from
the main valve.
4. If more than one pilot is used, unscrewing the 1/4"
NPT pipe nipples should separate them.
5. Mount air pilot in vise with bottom up and unscrew
the plug.
6. Remove the bottom plug and brass washer. Remove
from vice and turn upright. The spring, ball, strainer
and stem will drop out.
Note: The bottom portion of Model AP-1A and AP-4A
is the same. Model AP-4A has a small spring spacer
below the spring.
7. Mount the pilot in the vice again with the bottom up.
8. Remove the seat using a 9/16" thinwall socket.
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Model AP-1A Model AP-4A
HOUSING
VENT
HOLE
SPRING
SPACER
BALL
STEM
BODY
DIAPHRAGM(S)
UPPER DIAPHRAGM
BUTTON
LOWER DIAPHRAGM
BUTTON
SEAT
STRAINER
BOTTOM
PLUG
SPRING
PLUG GASKET
SEAT GASKET
Air Pilot Disassembly