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CROSBY STYLE JQ 4 IN. PRESSURE RELIEF VALVE
INSTALLATION AND MAINTENANCE INSTRUCTIONS
3 GENERAL INFORMATION
3.1 Functional Description
3.1.1 Combination Pressure Relief Device
The Style JQ 4 in. Safety Valve is a hermetically
sealed combination pressure relief device
consisting of a breaking pin assembly in series
with a conventional spring-loaded valve. The
breaking pin assembly is installed as a complete
unit into the base of the safety valve proper. The
breaking pin assembly forms the gasket face for
the flanged connection to the manway cover or
an adaptor flange for connection to piping.
3.1.2 Safety Valve Proper
The safety valve itself is a direct spring-loaded
pressure relief valve with a metal-to-metal
seat or elastomeric seat seals. During an over
pressure event, the breaking pin and both
diaphragms will fail and the valve will open
fully, discharging chlorine until the pressure in
the tank is reduced to a safe working level. At
that time, the valve is designed to reseat and
function as a pressure relief valve. Following
an event, the device must be removed and
reworked according to the procedures outlined
in this manual.
3.1.3 Breaking Pin Assembly
The Breaking Pin Housing (35) is protected by
the Lower Diaphragm (37) which is supported
by the Plunger Assembly (32), Yoke (30) and
Breaking Pin (31). The pressure load on the
Lower Diaphragm (37) is transmitted through
the Plunger Assembly (32), to the Yoke (30) and
thus to the Breaking Pin (31). The Breaking
Pin (31) is a tensile loaded member designed
to break at a predetermined pressure (either
300 psig or 375 psig) on a test stand at
atmospheric pressure. The Breaking Pin (31) is
held in place by two U-shaped Clips (34).
A positive seal is obtained between the
Lower Diaphragm (30) and the Breaking Pin
Housing (35) by creating a compressive load with
the Spanner Nut (33) and its Follower (36).
3.2 Valve Performance Data
3.2.1 Style JQ 4 in. 300 Valve
• Capacity at 10% over pressure (330 psig):
15,242 cfm of free air (60°F, 14.7 psia)
• Breaking pressure of breaking pin:
300 psig ± 15 psig
• Start-to-discharge (set) pressure of
safety valve proper: 300 psig ± 9 psig
• Vaportight pressure: 240 psig minimum
3.2.2 Style JQ 4 in. 375 Valve
• Capacity at 10%
overpressure (412.5 psig): 18,890 cfm of
free air (60°F, 14.7 psia)
• Breaking pressure of breaking pin:
375 psig ± 15 psig
• Start-to-discharge (set) pressure of
safety valve proper: 360 psig ± 10.8 psig
• Vaportight pressure: 300 psig minimum
3.3 Identification and Records
It is suggested that owners who desire
identification stamp their initials on the Base (17)
of each valve and also on the side or bottom
surface of the hexagon nut of the Housing (35).
The Data Plate (20) on the valve should include:
• the name or identifying mark of
the manufacturer
• manufacturer's design or type number
• set pressure, psi (or psi and kPa)
• official flow capacity, cfm air at
standard conditions
• flow rating pressure, psi
• month and year of manufacture or test
• USCG Approval No. 162.018/35/0 on
Style JQ 4 in. 300 valves for barge service
Records should be kept of all tests until the next
retest. Refer to Section 5 for DOT regulations.
3.4 Alterations
WARNING
No alterations to these valves for chlorine barge
service may be made beyond what is allowed in this
manual without the consent of Emerson and the
USCG for the Style JQ 4 in. 300.
4 INSTALLATION
4.1 Care in Handling
Pressure relief valves must be handled carefully
and never subjected to sharp impact loads.
They should not be struck, bumped or dropped.
Rough handling may alter the pressure setting,
deform valve parts and affect valve performance
adversely. When it is necessary to use a hoist,
the chain or sling should be placed around the
valve body in a manner that will ensure that
the valve is in a vertical position to facilitate
installation. The valve should never be lifted or
handled using the lifting lever inlet and outlet
protectors should remain in place until the valve
is ready to be installed on the system.
4.2 Inspection
Pressure relief valves should be inspected
visually before they are installed to ensure that
no damage has occurred during shipment or
while in storage. All protective material, sealing
plugs and any extraneous material inside the
valve body or nozzle must be removed. The valve
nameplate and other identifying tags should be
checked to ensure that the particular valve is
being installed at the location for which it was
intended. The valve seals protecting the spring
setting should be intact. If seals are not intact,
the valve should be inspected, tested and seals
installed properly before use.
4.3 Inlet Piping
Pressure relief valves should be mounted
vertically in an upright position. Installing
a pressure relief valve in other than this
recommended position might affect its operation
adversely. A valve should never be installed on a
fitting having a smaller inside diameter than the
inlet connection of the valve. Inlet piping must be
designed to withstand the total resultant forces
due to the valve discharging at the maximum
accumulated pressure and the expected piping
loads. The magnitudes of the bending moment
exerted on the inlet piping will depend on the
configuration. Many valves are damaged when
first placed in service because of failure to clean
the connections properly when installed. Both
the valve inlet and the vessel and/or line on
which the valve is mounted must be cleaned
thoroughly of all foreign material. The inlet
connection bolts or studs should be drawn down
evenly to avoid straining the valve body with
possible distortion of the base.
5 PERTINENT REGULATIONS
5.1 DOT Regulations
When the Style JQ 4 in. 300 Safety Valve is used
on chlorine barges in the U.S., the regulations
of the USCG-DOT should be consulted. The
concerned reader should see Section (13.2).
5.2 TC Regulations
Regulations similar to those in the U.S. are
promulgated by the Canadian Coast Guard
of the TC. There are some differences and
the concerned reader should consult the
appropriate TC regulations (13.3).
4
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