5. Setting & Testing4. Assembly
8
1. Refer to Figure 1.2 for construction details, and
Figures 1.5 and 1.6 for open lever and packed
lever cap construction details.
2. Verify that all parts required are grouped for assem-
bly. Visually inspect all parts, paying close attention
so that the body and disc seats are clear of imper-
fections and all parts are clean. Special attention
should also be given to the guide, checking for any
dirt or scale in exit holes and undercuts, and making
sure that guide surface is in good condition.
3. All threaded surfaces should be lubricated with
Bostik Never-Seez or equivalent. Sealing surfaces,
such as body and cap gasket, should be lightly
coated with a sealant such as Rectorseal pipe
thread sealant. Use Bostik Never-Seez or equiva-
lent on valves for steam service.
Sliding and bearing surfaces such as disc holder/
guide and disc-to-disc holder contact surfaces
should be left clean and assembled without lubricants.
4. Place disc in disc holder, making sure V-notch is
facing the stem radius. Insert assembly into guide.
Install body and lower guide gasket on the body.
5. Hold guide/disc holder assembly horizontally in
your left hand and insert body, being careful not to
damage disc or body seating surfaces.
6. Mount body/guide assembly vertically in a vise,
gripping body securely by the flats. Install guide
gasket on top of guide flange.
7. Place spring and spring buttons onto stem assembly
and insert into disc holder. Hold in place in vertical
position.
8. Place bonnet over assembled parts and screw
down handtight onto the body. For C and D orifices,
torque the bonnet to the body to 140-160 ft. lbs. For
E, F, and G orifices, torque should be 180-200 ft. lbs.
9. Thread the jam nut onto the spring adjusting screw.
Place spring adjusting screw over stem and into
bonnet. Hand tighten spring adjusting screw until it
contacts spring and lightly compresses it. Compress
spring to the same point as in disassembly, if same
set pressure is required. Install cap gasket.
10. Test the valve according to the procedure described
in Section 5. After testing, install the appropriate
cap or lever assembly.
Testing Procedures
Testing consists of adjusting the valve set pressure,
performing a seat leakage test and a backpressure
test. The set pressure test is always performed first.
Set Pressure Test
1. Set pressure testing must always be performed
using the appropriate test fluid shown in Table 2.
2. Mount valve on test stand, making a note of set
pressure and cold differential test pressure (CDTP).
The valve will be set at the CDTP.
3. Hold the stem tightly and tighten (clockwise) spring
adjusting screw to increase the set pressure. Make
sure stem does not rotate while tightening the
adjusting screw as this can damage seat and disc.
4. Slowly raise test drum pressure and observe the
opening (set) pressure. The set pressure on air and
steam is the point at which it makes an audible
pop. For water, the set pressure is the first continu-
ous flow of liquid that forms a stream approximately
1/16” thick perpendicular to the outlet.
5. If necessary, reduce test drum pressure 25% below
the opening pressure and adjust the spring adjusting
screw. Repeat until the valve opens at the required
pressure, designated as the cold differential test
pressure (CDTP). The set pressure tolerance is
equal to +/-3% of set pressure.
CAUTION: Never adjust the spring when the
pressure under the valve is near its popping point as
the body seat and disc may score and/or gall. Always
lower the pressure in the test vessel at least 25%
below popping pressure before making adjustments.
This will put a loading on the seating surfaces and
prevent rotation and damage.
6. Lock the jam nut in place and pop valve once more
to ensure set pressure adjustment was not disturbed.
PRESSURE RELIEF VALVE TEST FLUIDS
Service Fluid Test Fluid
Air, gas & vapor Air or gas
Steam Steam*
Liquid Water
Table 2
*air may be used for ASME Code Section VIII valves.
!
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