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

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General Technical Specification
devices of approved design. Vibration control devices shall be part of piping system
design.
- Outdoor piping shall be designed with due consideration to expansion resulting from
exposure to sunlight and care shall be taken to prevent progressive movement of
long pipelines. Outdoor piping may be supported on shoes, saddles or steel
sections. Effect of support friction especially for large dia pipelines shall be
considered and friction forces minimized by suitable arrangement. Piping inside the
trenches shall be supported at intervals on steel sections and the arrangement shall
permit easy maintenance.
02.16 VALVES AND SPECIALTIES
- All valves shall be of approved make and type. All valves shall be suitable for service
condition i.e. flow, pressure and temperature under which they are required to
operate. The valves for high and medium steam service shall have butt welded ends
unless otherwise approved and the internal dia shall be same as that of the pipes to
be joined.
- All gate/ sluice, globe and needle valve shall be fitted with outside screwed spindles
and bolted type glands and covers. Spindle glands shall be of the bridge type
construction and screwed glands will not be accepted. All high pressure valves
having nominal dia more than 150mm, shall have integral steam bypasses concede
to the valve body by means of welded joints.
- All gate/sluice, globe and needle valve shall be provided with hand wheel and
position indicator. The face of each hand wheel shall be clearly marked with words
“open” and “shut” with arrows to indicate the direction of rotation to which each
refers. Arrangement limiting the travel of any valve in the “open” or “shut” position
shall be provided exterior to the valve body. All globe valves shall be designed to
prevent erosion of valve seats when the valves are operated partially opened. Valves
which cannot be operated from the floor or walkways, shall be provided with suitable
extension rods and linkages to facilitate operation from the floor or walkways. Chain
operation will not be accepted for steam valves. Stems shall preferably be arranged
vertically with gland at the top. In no circumstances must the gland be at the bottom.
Valves shall not be installed in an inverted position. The design of valves shall be
such that it will permit packing of glands under pressure. Where required, valve
spindles shall be extended so that the hand wheel is at a height of about 1.0m above
the level of the floor or platform from where the valves are to be operated. Where
required, they shall be provided with head stocks and pedestals of rigid construction
and where gears or bevel wheels are used, these shall be of cast steel or suitable
grade cast iron with machine cut teeth.
- Non return valves on all pumps discharges and steam line shall be of an approved
non slamming type. Draining arrangement shall be made on both sides of the
horizontal non-return valve where such a valve adjoins an isolating valve. Valve
bodies shall be provided with removable access cover to enable the internal parts to
be examined without removing the valves. Valves shall have a permanent “arrow”
inscription on its body to indicate direction of flow.
- Gate sluice valves for low pressure service shall be outside screw rising spindle
type. For these valves wherever necessary, chain operator shall be provided to
operate the valve from the floor or walkways. Larger size gate valves for low
pressure applications shall be provided with bypass and draining arrangement and
valves with dia more than 350mm shall be provided with gear operator.
Gases & Liquid Fluids
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GS-02