PIPE RACK PIPING

 PIPE RACK PIPING

• Pipe racks are open-frame structures with braces that are adopted for the modular construction. In some applications, the steel pipe racks are encased in concrete for fire protection; however, this is not designed to offer structural support.pipe rack frame using the steel-concrete hybrid composite frames with the monolithic rigid beam-column connections; frame with the mechanical joints having detachable laminated joints with assembly and disassembly capability to cope with sudden design changes; or pipe rack structure implementing prestressed precast frames. The braces, which were inevitable with steel pipe rack frames having pinned joints, are removed with rigid joints. The proposed fast track method can even remove the necessity for correcting frames when the needs for the design changes arise.

• It connects all equipment with lines that cannot run through adjacent areas. Because it is located in the middle of the most plants, the pipe rack must be erected first, before it becomes obstructed by rows of equipment. Pipe racks carry process, utility piping and also include instrument and electrical cable trays as well as equipment mounted over.

Lines on pipe rack shall be arranged properly based on service and size as well as fluid content.

Pipe racks are the main highway in a process facility.

The Pipe racks connect all the equipment with piping that cannot run through the equipment areas.

Pipe racks are usually located in the middle of process plants.

If the racks are located in the middle of the plant then they have to be erected first, before becoming surrounded by process equipment.

Pipe racks support not only process piping but also utility piping, cable, and instrument trays as well as any equipment that is supported from and over the pipe rack such as air coolers.

Pipe racks require considerable planning and coordination with all disciplines to facilitate not only a logical design but also to reduce construction costs.

Data required for pipe rack development include

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Plot plan

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P&IDs

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Piping and plant specifications

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Construction materials

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Fireproofing requirements

Pipe rack development requires the following inputs:

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Line-routing diagram

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P&ID

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Line list

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Plot plan

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Plant layout specifications

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Client specifications

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Fireproofing requirements

Once the number and size of lines plus a 25% allowance for future requirements and the amount of cable trays and any relief line requirements have been established, the rack size can be determined.

Pipe rack development requires the following inputs:

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P&IDs (process and instrument diagrams)

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Indicates line sizes

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Shows insulation requirements

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Indicates equipment sequences

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Process line list

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Shows line temperatures

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Shows insulation requirements

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Plus will show any other line relevant information in the remarks column

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PFDs (process flow diagrams)

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Shows operating temperatures

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Shows insulation requirements

On completion of the line-routing exercise, the development with regard to pipe rack width, bent spacing (vertical columns and horizontal structural member), numbers and levels of rack can then be finalized.

Process Lines

Predominantly process lines are to be kept at lower tier. Hot process lines on upper tier.

Utility Lines

Utility lines for water, steam, air etc. shall be located on upper tier.

 

Grouping Hot and Cold Lines

Generally the hot lines and cold lines shall be kept apart in different groups on a tier. Keep hot, non insulated, lines at a higher elevation than cold lines. Hot lines should be located near the outside to allow for expansion loops. Un-insulated lines with possibility for ice build-up, shall not be run above walk ways.

Large Size Lines

Generally the bigger size lines shall be kept nearer to the rack column to reduce load on rack columns. Water lines more than 30″ shall not be routed over pipe rack, these shall be routed  underground.

Small Size Lines

Small pipes should be grouped together to simplify support design. Locating small pipes between large pipes shall be avoided especially when the large lines are hot.

Branches

Gas, Steam and vapor branch lines must be taken from top of headers. Liquid lines may branch from the top or bottom.

Vents and Drains

Vent all high points and drain all low points on rack piping.

Typical guidelines for pipe racks include the following:

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Use line spacing charts to make sure all lines can be maintained within the rack.

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Determine pipe-rack elevations, normally the bottom level of the rack is 15 ft. (500 mm) above the grade, depending on mobile equipment used to access pumps and equipment located under the rack.

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Flat turns for branch piping are not permitted. If the rack runs north-south, then all east-west branch pipe running to and from equipment, such as pressure vessels, tanks, rotating equipment, etc. must run, usually, 3 ft. (1 m), above or below.

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Allow space for cable trays and instrument pipe.

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Check with adjacent areas to determine if they have any lines that run along a section of pipe rack.

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Allocate sections on rack for certain pipe, for example, steam and other hot pipes, that may require loops to be located on one side of the rack.

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Group utility pipe.

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Group process pipe.

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Process and relief piping should be placed next to the large-diameter piping and utility piping and positioned in the center of the rack.

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Cooling water piping should be located to one side of the rack, that side being where there are more branches to and from the equipment.

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Locate piping with orifice taps to outside of rack for maintenance/accessibility.

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Large-diameter piping should be located on the outside of the rack to reduce the bending moment on the beam. Check if future pipe-rack expansion is planned before using flat turns.

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If flanges are located in the pipe, one must make sure that any flanges on adjacent piping are staggered to minimize spacing.

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All insulated pipe should sit on shoes.

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Small pipe that may not span the distance between bents (columns) may be supported from larger-diameter pipe if acceptable to client.

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Loading at anchors on the pipe rack must be given to structural engineers so they can design the steelwork accordingly.

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In a multilevel rack, steam and condensate piping are on the top level along with other utility piping except cooling water, which is on the first level close to the equipment they serve. The preferred location of the electrical cable tray is on the top level with the alternate being outside the first level.