4 General Technical Specification of Bhilai Steel Plant, SAIL ...

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General Technical Specification
For sections where the gas tight isolating device can not be provided, provision to insert
blind flange at outlet of gate valve shall be made.
Sectionalizing / isolation for purging of fuel gas lines may be done with Spectacle blinds.
Gas tight butterfly valves may be used for isolation near consumption points requiring
frequent and quick operation. These can be valves with gas tight seating or eccentric
valves for gas tight isolation.
Emergency quick shut off valves shall also be double eccentric butterfly valves.
For fluid lines with working pressure over 16 kg/cm2 (g), valves of DN 300 and above
shall be provided with by-pass arrangement or depressurisation arrangement for pipe
sections.
Selection of Actuators for Isolating devices:
Manually operated shut-off gate valves of size DN 300 to DN 450 for low pressure lines
shall have gear drive. For high pressure lines, gear operator shall be provided as per
manufacturer’s recommendations for limiting the operating torque to acceptable limits.
Gate Valves of size DN 500 and above shall be provided with electric actuators. Electric
actuators for fuel gas lines shall be of flame proof design if located in gas zone/in shop.
In the interplant area these actuators need not be flame proof. Position and torque limit
switches shall be provided on actuators. Manual over ride shall also be available in
actuators.
Goggle valves shall have electrical actuators for disc/ plate movement and electro
hydraulic drive for flange separation. Manual arrangement for valve operation shall also
be provided with gear and chain operation from convenient location. The hydraulic power
pack for the valve shall include one motorized pump and one manual pump. Encased
design goggle valve with vent shall be used at locations closed to buildings.
Electrically operated gate valves for gas pipelines of smaller diameter are recommended
to be used only if they are incorporated in the automation scheme.
All valves located remotely, requiring frequent operation and / or with automatic control
shall be provided with electric drives, electro- pneumatic drive, solenoids etc.
Check valves shall be used in piping system where unidirectional flow is required. For
small size pipes below DN 50, lift check valves shall be used. For DN 50 and above,
swing check valves or dual plate check valve shall be used. Lift check valves shall be
used only in horizontal pipeline. It should not be used in vertical pipeline. For low
pressure gas lines dual plate check valve will be used.
The Pressure Regulating valve shall be of globe / needle type, with material
specifications, dimensional standards etc. as per the relevant Piping Material
Specification (PMS) for the service for which the valve is intended.
001 For Compressed Air
Pressure regulators of sizes up to DN 50 shall be complete with a prefilter having 40
micron porous bronze filtering element in shatterproof plastic or glass container,
pressure regulator and pressure relief arrangement to prevent overpressure at
downstream of the regulator.
Gases & Liquid Fluids
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GS-02