Download Pressure Relief Valves

XI. Maintenance (Contd.)
Determining the Correct Limit
Washer Length
9. Install the limit washer with the chamfer down
and reassemble the valve as described in Steps 2
through 4.
Determine the correct limit washer length (see Figure 35)
as follows:
10. Measure the lift of the valve and compare it with the
required lift as given on the restricted lift nameplate
(-0.000”, +0.005” [-0.000 mm, +0.127 mm]). Take
one of the following steps, based on the results, if
the lift is not correct:
1. Assemble the disc (6) and disc holder (8) (installing
the bellows gasket and bellows, if applicable) as
follows:
• If the actual lift is less than required, machine the
limit washer as necessary to obtain the required
lift. (Machine chamfer, deburr and polish before
installation into the valve.)
ATTENTION!!
Do not use an impact wrench on bellows valves.
• If the actual lift is greater than required, obtain a
new limit washer, and return to Step 7. (Machine
chamfer, deburr and polish before installation into
valve.)
• Place the guide over the disc holder barrel and
connect the spindle (15) to the disc holder (8).
• Install the eductor tube (40) in base (1), if
applicable.
11. Once correct lift is obtained, disassemble the valve.
• Install the adjusting ring (3) below the seat.
ATTENTION!!
2. Install the guide gasket (10), and insert the disc
assembly from Step 1 into the base (1).
Ensure the limit washer has been chamfered to
fit over the radius of the disc holder (8). The limit
washer must be installed so that the chamfered end
is mating to the back face of disc holder.
3. Install the bonnet gasket (12) and bonnet (11)
(leaving out the spring assembly at this time).
4. Tighten the stud nuts (14) to compress the bonnet
gasket (12).
ATTENTION!!
5. Place a dial indicator on the bonnet (11) and
over the spindle (15) and then zero the indicator.
Measure total lift by pushing the disc (6) upward.
Subtract the required lift of the valve from the
measured lift to find the required limit washer length.
Check all dimension requirements for each valve. Do
not interchange internal parts or use a different base
after a set of parts has been custom-fit.
6. Machine the limit washer to the required length.
For bellows Type D and E valves, check the outside
diameter and, if necessary, emery cloth down to
.680˝ (17.3 mm) maximum diameter in order to
avoid interference with the bellows threads.
7. Machine the inside chamfer, deburring and polishing
as required.
8. Disassemble the valve.
ATTENTION!!
Guide
Guide
Required Lift
Bellows
Limit Washer
Limit Washer
Measured Lift
Disc Holder
Bellows Ring
Bellows Gasket
Limit Washer Length
Conventional
Disc Holder
Bellows
Figure 35: Determining Lift and Limit Washer Length
38 | Dresser Consolidated®