ANDERSON GREENWOOD
MARVAC FIGURE 121 PRESSURE AND VACUUM RELIEF VALVE
INSTALLATION AND MAINTENANCE INSTRUCTIONS
SAFETY PRECAUTIONS
Read and understand this instruction manual
before installing, operating or performing
maintenance on Figure 121 pressure and
vacuum relief valves. Follow all precautions
and warnings noted herein when installing,
operating or performing maintenance on this
equipment.
NOTE
This manual is issued for guidance only and does not
affect our standard terms and conditions and our
product limited warranty, all of which are available on
request.
Read Anderson Greenwood Marvac general instructions before continuing
1 INSTALLATION
Figure 121 pressure and vacuum relief valves
must be mated with the appropriate flange.
1. These valves must be gasketed and bolted
to a flat machined horizontal flange. Bolts
must be tightened uniformly to ensure a
good seal.
2. This valve does not contain any internal
packing. Therefore, internal checks should
not be necessary.
3. It is recommended that carbon steel valves
be given a coat of paint immediately after
installation is complete. Apply paint to
external surfaces only.
2 MAINTENANCE
(during atmospheric venting period)
WARNING
The relief valve must be isolated from tank
pressure before servicing. All gas must be
blocked and pressure vented safely. Wear
appropriate gloves and/or breathing apparatus if
hazardous vapors are present.
© 2017 Emerson. All Rights Reserved.
Emerson.com/FinalControl
VCIOM-01934-EN 15/12
Refer to Figure 1
1. Remove weather hood (item 3) and vacuum
cover (item 7), inspect O-ring in vacuum
cover for damage and replace if necessary.
2. Remove pallet assembly to inspect pallet
seating for wear and replace if necessary.
3. To replace damaged/worn items from pallet
assembly (see recommended spares):
a. remove nut from pallet stem, remove
support disc, diaphragm and backing disc
b. clean pallet surface and threads
c. replace with new parts
d. reassemble in reverse order
4. Inspect valve seat (item 2) for wear and
regrind or replace where necessary.
5. Clean seating surface thoroughly with
suitable solvent and apply a thin smear of
light spindle oil.
6. Generally clean the inside of the valve,
remove all foreign matter and repaint
exterior where possible to prevent
corrosion.
7. Replace pressure pallet on pressure seat
and vacuum pallet (with lead disc if fitted).
8. Replace weather hood, secure with hand
nuts.
9. Replace vacuum cover and replace sealing
washers if necessary, secure with screws.
NOTE
The efficiency of the valve depends on maintaining
good seating surfaces. Therefore, maintenance
periods should be adjusted to suit service conditions.
