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

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General Technical Specification
supplementary steel structures to properly secure and support all pipe hangers,
supports, restraints, etc.
- Provision shall be made for support of piping which may be disconnected during
maintenance work. All large pipes and all long pipes shall have at least two
supports each arranged in such a way that any length of piping or valve may be
removed without any additional supports being required.
- Supports, guides and anchors shall be so designed that excessive heat is not
transmitted to the building steel. Supporting steel shall be of structural quality.
Perforated, strap, wire or chain shall not be used. Support components shall be
connected to support steel by welding, bolting or clamps. Bolt holes shall be drilled
and not gas cut. Structural steel work for supporting shall be designed on the basis
of a maximum design stress of 1265 kg/cm2. Pipe attachments coming in direct
contact with pipes having surface temperature above 400 0 C shall be made of alloy
steel. Use of insulating materials like asbestos between pipe clamp and pipe
surface to meet the above temperature limitation shall not be permitted. The
maximum spacing between two consecutive supports shall be not more than as
specified. Pipe hangers and supports shall be capable of supporting the pipelines
under all conditions of operation. They shall be capable of supporting the pipelines
under all conditions of operation. They shall allow expansion and contraction
without over stressing the piping system or overloading the terminal equipment due
to variation in supporting effort. Rigid supports or hangers shall be permitted only
for pipes with small movements. For hot lines, spring hangers shall be used. The
maximum permissible load variation on the terminals of sensitive equipment
between hot and cold conditions shall be limited to 6%. Variability in load between
hot and cold conditions expressed as a percentage of the design load shall be
taken as the criteria for spring selection for spring hangers. Variable spring hanger
shall be set at cold conditions so that they take design load under operating
condition after the designed thermal expansion has taken place.
Spring shall be encased in suitable cages and the hangers shall be provided with
spring locking arrangement, external load and movement indicator and turn buckles
for load adjustment. All the rigid hangers shall be provided with turn buckles for
vertical length adjustments. Hanger rods shall be subjected and designed for tensile
loads. At locations of high axial or lateral movement, suitable arrangement shall be
provided to permit the swing. The swing from vertical position shall be within 4 0 .
Double nuts and locknuts shall be used for hanger rods and bolts in all cases.
Hangers shall be designed so that they can not become disengaged by
movements of supported pipe.
- The supporting structures at each support points shall be designed for the highest
of the following loads to take into account the extra load during hydraulic testing.
- 1.25 times the maximum load under operating condition
- Weight of pipelines full of water (combined weight of pipe, insulation, valve
attachment etc. plus weight of water)
- Weight of pipeline full of water as above plus any cold reaction as anticipated.
- Where the piping system is subjected to shock loads such as thrust imposed by the
actuation of safety valves, hanger design shall include provision of shock absorbing
Gases & Liquid Fluids
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GS-02