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 line from the main valve
diaphragm. Point tubing in a direction to prevent
damage or burns.
3. Back off temperature setting by turning the tempera-
ture knob. A setscrew in the adjusting knob locks the
setting. Loosen the setscrew to turn the knob.
4. If used in conjunction with a spring pilot make sure
the spring adjustment has the spring pilot open.
5. Slightly open the shut off valve in the steam supply to
the main valve and allow pressure to build.
6. Increase the temperature setting on the pilot until
steam passes from the open end of the copper tubing
line.
7. Back off temperature setting and the steam flow
should stop. A slight leakage is OK.
8. Repeat several times.
9. If the pilot does not start and stop the steam supply it
should be repaired or replaced.
10. If the pilot responds properly the problem is elsewhere
in the system.
TEMPERATURE PILOT
Temperature Pilot Testing
lbf-ft
N-m
Bottom Cap
80 – 90
108 – 122
Housing to Body
100 – 120
136 – 163
Model AP-4A: Air
150 – 170
204 – 231
cover to housing
Before removing sensing probe, the system must be
drained and pressure relieved and cooled, unless a
separable well is provided. Failure to follow this
procedure may result in serious burns.
!
CAUTION
Temperature pilot bulb will be inserted in the heated fluid.
Before immersing check compatibility of copper bulb with
the heated fluid. Failure to follow this caution may result
in serious burns.
!
CAUTION
This test is done using live steam. Point tubing in a direction
to prevent property damage or burns. To prevent serious
burns, wear heat resistant gloves. Failure to follow this
warning may result in property damage, personal injury or
death.
!
CAUTION
Tightening Torque: Models AP-1A and AP-4A Air Pilots
20
9. Inspect and clean all parts and gasket sealing areas.
Replace any worn or damaged parts.
• Reassemble using non-hardening sealant on the
plug threads.
• Note: The hollowed out end of the stem goes
against the ball.
10. To service the upper end of the pilot:
• Mount it in a vice with the top up.
• Unscrew and remove the upper housing.
11. Remove upper diaphragm button, diaphragm(s) and
lower diaphragm button.
Note: Model AP-4A has 2 sets of diaphragms and a
pusher spacer mounted between them.
12. Inspect and clean all parts, replace diaphragm(s) and
worn or defective items.
13. Diaphragms should be biased down by using air
pressure in the top port before finally tightening
housing to body.
14. Install stem with the counterbore end facing the ball.
(See magnified view of the stem and ball below.) The
flat end of the stem should face the lower diaphragm
button.
Air Pilot Disassembly (cont’d)
