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

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General Technical Specification
- Matching faces of flanges shall be perpendicular to the axis of pipelines. Use of
gaskets of unusual thickness to fill gap between flanges shall not be allowed.
- For horizontal pipes, the flanges shall be erected such that top two bolt holes are
displaced by half pitch from the vertical axis of the flange.
- Flanges of adjoining pipes shall be located in staggered manner.
- Flanged joints shall be laid as close to the support as possible.
- Bends for steam pipes shall have a radius of not less than three
times the nominal pipe dia unless otherwise specified.
- In general pipes are to be joined by butt welding. However, steam service
pipelines 40 mm & lower sizes shall be joined by socket welding.
- For insulated pipe, steel protectors for the insulation shall be provided at
points where the pipe is supported on rollers, slides or other equipment where
contact with such members is required outside the insulation.
- In case the location of spindle wheel of valves is not clearly shown in the
erection drawings, the same shall be located in a manner as to facilitate easy
operation from ground level of nearest operating platform.
- For making pipe bends/ elbows at site using hot/ clod bending process, the
decrease in the pipe thickness shall not be more than 15% of the pipe thickness.
- After erection of pipelines, the holes made in the walls shall be covered with
bricks & mortar. A gap of 10 to 20 mm shall be kept between wall and the pipe
for the movement due to thermal expansion. The gap shall be filled with felt/
asbestos.
- Holes made in the roof shall be covered with removable CGI sheets.
- The trenches for pipes shall be covered with removable chequered plate covers/
concrete slabs as per the drawings.
- All pipeline branches not connected to equipment shall be closed using blank
flanges and gaskets.
03 Welding of pipelines
- All pipelines shall be joined by welding. Flanged joints shall be used for
connecting the pipe with equipment, valve or fitting.
- Electric arc welding shall be used for joining pipes, support, structures, etc.
- All manufactured pipes shall be joined by butt welding. Large dia pipes,
fabricated from sheets, shall be joined by fillet welding using semi- bandages
attached to each section being joined.
- Welding shall be done by qualified welders. Code of practice as per relevant
Indian Standards shall be followed for the welding procedure, use of electrodes,
etc.
- Proper edge preparation and preheating of edges to be welded, whenever
required, shall be ensured before welding.
- After every 50 butt welded joints of gas pipeline, one test sample shall be welded
by the same welder. Tensile teat and bend test shall be performed as per IS
:814 to check the strength of welding. Four test samples shall be made from the
test piece, two each for tensile and bend test.
Gases & Liquid Fluids
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GS-02