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Pressure relief safety valve

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  • 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

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    esOil RefineryPetro-ChemicalPulp & 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 AIn Service

    PSV BIn Service

    PSV BIsolated

    PSV AIsolated

    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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