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Smith Flow Control Ltd.
6 Waterside Business Park
Eastways Industrial Estate
Witham Essex CM8 3YQ
United Kingdom

Tel: +44 (0)1376 517901
Fax:+44 (0)1376 518720
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Vessel Closure Lock

Access into pressure vessels is a potentially hazardous exercise. Residual pressure, volumes of residual liquids or gases all can be harmful - typical examples of these potential hazards include pig traps, slug catchers and filter housings.

Locking arm engaged - locking arm releases

Locking the vessel closure in the closed position ensures access into the vessel can be achieved only under controlled safe conditions. The operating key is held in a secure place - e.g. Control Room or Supervisor's office or is retained (trapped) in some other related interlocked item of equipment.

As a minimum, vessel closures are usually interlocked with vessel venting and draining functions - the interlocking arrangement can be extended to incorporate all process items of equipment relating to the vessel's function.

The SFC 'DL3' interlock is adaptable to all types of vessel/access closures and is very simple to use in pig trap applications especially where the closure incorporates a bleed device.

The 'DL3' interlock will be designed to interface with the bleed function to ensure the bleed screw cannot be removed until the interlock permit key has been inserted to unlock the 'DL3' assembly.This key is usually obtained after opening and locking of the vent valve.

When the 'DL3' is incorporated into vessel access safety procedures, total equipment and personnel safety is assured.

Ensure total isolation, venting and draining BEFORE opening vessel closure
Key trapped
Open - Key Trapped


Any type of closure can be fitted with the 'DL3' interlock, regardless of their methods of operation.

Design details can be provided on request.