Safety Precaution Definitions; General Information; Operation - Emerson VAREC Series Instruction, Operation And Maintenance Manual

VAREC SERIES 2010B/2020B/3500B PRESSURE AND VACUUM RELIEF VALVE
INSTRUCTION, OPERATION AND MAINTENANCE MANUAL
SAFETY PRECAUTIONS
Read and understand this instruction manual
before installing, operating or performing
maintenance on Varec Vapor Control Inc.
2010B/2020B/3500B series pressure and/or
vacuum relief valve. Follow all precautions
and warnings noted herein when installing,
operating or performing maintenance on this
equipment.
WARNING
Relief valve must be isolated from tank pressure
before servicing. All gas must be blocked and
pressure safely vented.

SAFETY PRECAUTION DEFINITIONS

CAUTION
Damage to equipment may result if this
precaution is disregarded.
WARNING
Direct injury to personnel or damage to
equipment which can cause injury to personnel
may result if this precaution is not followed.

GENERAL INFORMATION

The 2010B/2020B/3500B Series pressure
and/or vacuum relief valves are designed to
protect low pressure storage tanks, sludge
digesters and gas holders from excessive
pressure and/or vacuum. The valve is installed
on the storage tank roof or digester cover.
It may be used in combination with a VAREC
Vapor Control Inc. flame arrester.
The 2010B Series valve relieves pressure
directly to the atmosphere. A weatherhood and
mesh screen protect the pressure pallet and
guideposts. Vacuum pressure is relieved by
inbreathing ambient air.
The 2020B Series valve relieves pressure
through an enclosed outlet adapter. Product
vapors may be piped away rather than relieving
directly to the atmosphere. Vacuum pressure is
relieved by inbreathing ambient air.
The 3500B Series valve is a vacuum relief valve
that relieves negative pressure by inbreathing
ambient air.
CONSTRUCTION
Standard materials of construction include
cast body and cover(s). Pallets are dead weight
loaded with lead or coated steel weights and
include a flexible membrane sealing insert.
The pallet is loosely guided through a center
stem and pallet guide posts.
The "All-Weather" Models 2011B, 2021B and
3501B Series include a special coating on
portions of the pallets, seat rings and guides to
eliminate ice accumulation.

OPERATION

When the internal tank pressure approaches
the valve setting, the pressure pallet begins to
lift. As the pressure exceeds the valve setting,
the pressure pallet lifts off the seat ring.
Excess product vapor is allowed to vent to the
atmosphere or through the pipe away system
adapter, relieving the over pressure condition.
The pallet automatically re-seats as the tank
pressure drops below the valve setting.
If a vacuum within the tank approaches the
valve setting, the vacuum pallet begins to
lift. As the vacuum exceeds the valve setting,
the vacuum pallet lifts off the seat ring.
Atmospheric air is allowed to flow into the
tank, relieving the excess vacuum condition.
The pallet automatically re-seats as the
vacuum drops below the valve setting.
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