Pressure relief safety valve
Transcript of Pressure relief safety valve
Integral Valve InterlocksApplication Data Sheet
Pressure relief safety valve
In many petro-chemical and chemical plants duplication of process components is used to ensure continuous operation. The aim being to run plants for extended periods of time, years or more, without shutting down.
One of the classic examples of duplication is the use of dual or multiple pressure relief safety valves (PSVs) on process vessels and tanks to ensure safety of operation. An additional requirement of having dual PSVs is that one or more relief valves must always be in service to maintain safety.
There are several ways of ensuring that a PSV is always in service, the simplest being to use standard manual block valves fitted with key operated valve interlocks. The Kirk range of Eagle Valve Interlocks can be supplied to mount directly on to the system block valves with the locks keyed to maintain the operational requirements of a relief valve system.
Quarter-Turn or Multi-Turn valve interlocks being used dependent on the type of valve which they are controlling – Quarter-Turn for ball, plug or butterfly valves or Mutli-Turn for gate, globe or gearbox operated valves.
Please see overleaf for details of operation of a typical dual PSV system. Other key logics can be supplied for multiple PSVs.
www.Kirkkey.comProcess safety Control
Indu
stri
esOil Refinery
Petro-Chemical
Pulp & Paper
Liquefied Gases
Food Bulk Handling
Multi-Turn Valve Interlock
Quarter-Turn Valve Interlock
INITIAL SYSTEM STATUS: PSV “B” is in service and PSV “A” is isolated for maintenance. Valves 1 & 2 are locked closed, valves 3 & 4 are locked open. Key A is held under Supervisory Control.
SYSTEM OPERATION: 1) Key A is issued to an operator from
the Supervisor in the Control Room together with a Permit to Work (PtW)
2) The operator enters Key A into the lock fitted to Valve 1, to unlock and allow the valve to be opened. Key B is removed from the lock to lock the valve open.
3) The operator enters Key B into the lock fitted to Valve 2, to unlock and allow the valve to be opened. Key C is removed from the lock to lock the valve open.
4) The operator enters Key C into the lock fitted to Valve 3, to unlock and allow the valve to be closed. Key D is removed from the lock to lock the valve closed.
5) The operator enters Key D into the lock fitted to Valve 4, to unlock and allow the valve to be closed. Key E is removed from the lock to lock the valve closed.
6) Key E is returned to the Supervisor in the Control Room to signify the operation has been completed.
7) PSV “A” is now in service and PSV “B” is isolated for maintenance.
8) The sequence can be reversed to return to the initial system status.
Interlocking Logic
Operation
Integral Valve interlocksApplication Data Sheet
Interlocking designs can be made to suit any operational Requirements
www.Kirkkey.com
Pressure Relief Safety Valve
The interlocking logic shown illustrates a typical operational sequence for a dual pressure relief system.
D E
CD B
C
A B
E
A
Supervisory Control
Valve 3LockedOpen
Valve 2LockedClosed
Valve 4LockedOpen
Valve 1LockedClosed
Pressure Vessel
To Flare
PSV “A”In Service
PSV “B”In Service
PSV “B”Isolated
PSV “A”Isolated
In ServiceKey Held Isolated
Key A
Key B
Key C
Key D
PSV “B”
PSV “A”
Key E
LegendDual Key Valve Locked Open
Dual Key Valve Locked Closed
Key Free Key Trapped
STEP
1
2
3
4
A
B
C
B
A B C
B
C
B
A
KEYIN
KEYOUT
SequenceControl Unit
H2 Valve CO2 Valve Air Valve
Operating Knob
STEP
1
2
3
4
A
B
C
B
A B C
B
C
B
A
KEYIN
KEYOUT
SequenceControl Unit
H2 Valve CO2 Valve Air Valve
Operating Knob
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