Design of Pipe Rack involves considerable planning and cor-ordination with other engineering groups. Rack Design involves following activities.
- Pipe rack width calculation.
- Pipe tiers elevation calculation.
- Pipe rack piping layout
- Accessways on pipe rack
- Cable tray arrangement
- Future Space
- Spacing between rack beams
- Pipe rack loading to civil
- Flow meters in pipe rack
- Pipe supports on pipe rack.
- Utility stations from pipe rack
- Expansion loops on pipe racks
Racks shall be designed to give the piping shortest possible run and to provide clear head rooms over main walkways, secondary walkways and platforms. Predominantly process lines are to be kept at lower tier. Utility & hot process lines on upper tier.
Generally the top tier is to be kept for Electrical cable trays (if not provided in underground trench) and Instrument cable ducts/trays. Cable tray laying to take care of necessary clearances for the fire proofing of structure.
Hot lines and cold lines shall be kept apart in different groups on a tier. Bigger size lines shall be kept nearer to the rack column.
Spacing Between Pipes
Minimum spacing between adjacent lines shall be decided based on O.D. of bigger size flange (minimum rating 300# to be considered), O.D. of the smaller pipe, individual insulation thickness and additional 25 mm clearance, even if flange is not appearing. Actual line spacing, especially at ‘L’ bend and loop locations, shall take care of thermal expansion / thermal contraction / non-expansion of adjacent line. Nonexpansion / thermal contraction may stop the free expansion of the adjacent line at ‘L’ bend location.
Anchors on the racks are to be provided on the anchor bay if the concept of anchor bay is adopted. Otherwise anchors shall be distributed over two to three consecutive bays. Anchors shall be provided within unit on all hot lines leaving the unit.
Battery Limit Valves
Process lines crossing units (within units or from unit to main pipeway) are normally provided with a block valve, spectacle blind and drain valve. Block valves are to be grouped and locations of block valves in vertical run of pipe are preferred. If the block valves have to be located in an overhead pipe-way, staircase access to a platform above the lines shall be provided.
Branches in Headers
Stubs in sea water shall be from top of main header.
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