Maintenance - Emerson Fisher 634 Instructional Manual

normal operation. Simply select the fracture disk
(key 4) of the appropriate color from Figure 5
according to the desired shatter pressure.
11. The Type 634M shutoff valve can have
considerable unbalance, thus causing the shatter
pressure to vary approximately 2 psig / 0.14 bar
per every 100 psig / 6.9 bar of inlet pressure
change. Select the fracture disk (key 4) of the
appropriate color from Figure 5 according to the
desired shatter pressure in combination with the
inlet pressure.
The lowest pressure of the fracture disk
(key 4) chosen according to step 10
or 11 must be higher than all normal
operating pressures of the regulator
and system being protected. regulator
pressure characteristics such as
lockup, boost and proportional band
must be considered as part of normal
operating pressures.

Maintenance

All key numbers mentioned in this section appear in
Figure 6.
Types 634 and 634M shutoff valves are normally
open. They close only when the fracture disk (key 4)
shatters. Frequency of maintenance depends upon
the severity of service conditions and the requirements
of government regulations. Parts must be replaced
as necessary. Use only Emerson-authorized
replacement parts.
!
Personal injury or equipment damage
may be caused by sudden release of
pressure or explosion of accumulated
gas. To avoid such injury or damage,
isolate the shutoff valve from system
pressure and relieve all internal pressure
before starting disassembly. releasing
downstream pressure from a closed
Type 634 or 634M shutoff valve does not
release inlet pressure from that shutoff
valve. Since there is no longer an intact
fracture disk in a shutoff valve that has
been closed, make sure no downstream
pressure is allowed to act on the
diaphragm during maintenance.
note
warning
Types 634 and 634M
Preparing for Maintenance
1. Isolate the shutoff valve from both upstream and
downstream pressure.
2. Release trapped pressure from both the inlet and
outlet ends of the body (key 1) as follows:
• Where a pipe plug (key 15) is installed in the
body side tapping, use the valves provided in the
system to bleed off pressure. Do not unscrew the
pipe plug.
• Where a tank valve (key 15, not shown) is
installed in the body side tapping, remove the
tank valve cap. Push in on the tank valve stem
until all trapped pressure bleeds out, making
sure the gas bleeds to a safe location. Then,
replace the cap.
replacing fracture disk
1. Complete the procedure for preparing
for maintenance.
2. Remove the disk retainer (key 3) from the upper
casing (key 2) and snap ring (key 14) from the
disk retainer.
3. Shake any loose fragments out of the disk retainer
(key 3), and remove any remaining fragments
from the upper casing (key 2) and body cavities
so as not to hinder diaphragm (key 6) action upon
reassembly. Install a new fracture disk (key 4) and
secure it with the snap ring (key 14). Remark the
disk retainer if the replacement fracture disk has a
range different from the range of the fracture disk
originally shipped from the factory.
4. If necessary, replace the O-ring (key 21) used on
the disk retainer (key 3).
5. Apply a suitable thread lubricant to the threads
of the disk retainer (key 3), and install it into the
upper casing.
6. Test for leakage after assembly.
replacing Plug assembly, diaphragm
or o-rings
1. Complete the procedure for preparing
for maintenance.
2. Remove the pipe plug, cap screws, upper casing
(key 2) and hex nut (keys 2, 11, 12 and 13) from
the fracture disk (key 4) end of the stem (key 10).
5