ANDERSON GREENWOOD
4020HP PRESSURE AND VACUUM RELIEF VALVE
INSTALLATION, OPERATION AND MAINTENANCE INSTRUCTIONS
1.0 SAFETY PRECAUTIONS
Read and understand this instruction manual
before installing, operating, or performing
maintenance on the Anderson Greenwood
4020HP Pressure and Vacuum Relief
Valve (PVRV) following all precautions and
warnings noted herein.
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.
WARNING
The relief valve must be isolated from tank
pressure before servicing. All gas/vapour must
be blocked and pressure safely vented. Wear
appropriate protective clothing and breathing
apparatus if hazardous gas/vapours are present.
Use appropriate lifting equipment where required.
3.0 OPERATION
The Anderson Greenwood 4020HP PVRV is a
direct acting vent valve with a spring-loaded
pallet on the pressure side and a weighted
loaded pallet on the vacuum side to keep the
valve closed. When tank pressure or vacuum
acting on the seat sealing area equals the
opposing force acting on the pallet, the valve
is on the threshold of opening. Any further
increase in pressure will cause the pressure
pallet to lift allowing the contents of the tank
to vent through the valve (out-breathing). Any
further increase in vacuum will cause the
vacuum pallet to begin to lift thus breaking
the vacuum by allowing atmospheric air to be
drawn into the tank (in-breathing).
In order for the valve to open and achieve its
design lift, an overpressure will be required.
The 4020HP PVRV has been designed to achieve
this design lift and rated capacity within 10%
overpressure. Set pressures are adjusted by
altering the compression on the pressure
setting spring and set vacuums are adjusted by
varying the weight on the pallet.
2.0 GENERAL DESCRIPTION
The Anderson Greenwood 4020HP PVRV is
employed in gas/vapour service applications
for low pressure storage tanks, vessels
or applications requiring combined low
pressure and vacuum protection with high
capacity flow requirements. This product
helps to prevent damage to the tank and also
prevents the tank’s contents from escaping,
ensuring the safety of personnel and the
surrounding environment.
Pressure/Vacuum valves are designed to limit
the maximum pressure or vacuum that can
exist in a tank due to inflow or outflow of the
tank contents or due to changes in temperature
as a result of environmental conditions.
The Anderson Greenwood 4020HP PVRV
consists of a common inlet connection with
two separate seats, pressure and vacuum. The
vacuum seat draws atmospheric pressure into
the tank being protected and the pressure seat
discharges directly to atmosphere.
• For ease of maintenance, both pressure and
vacuum seats are removable.
• Polytetrafluoroethylene (PTFE)
coated internals are supplied as an
all-weather option.
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