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

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.

Branch clashes due to thermal movement.

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. When expansion loops are required, lines should be grouped together and located on the outside of the rack.

First Line Location

Set the distance from the first line in the rack to the vertical column center line. Column sizes are furnished by the civil/structural engineers.

Flare Header

Many relief headers must be located above the top level of the rack to allow the line to drain to the blow-down drum. The designer should avoid locating the line over the centerline of the column for
support so that the columns can be extended for future rack expansion. Following figure shows suggested location for the relief header that does not impede future expansion.

Sloping Lines

Sloping pipes, such as flare headers and drain lines, should be located together and the routing established at an early stage in the design period to prevent difficulties which may occur if other process and utility lines are routed first. Sloped lines can be carried on cantilevers attached to pipe rack columns. To obtain the required change in elevation at each bent, cantilevers may be attached at the
required elevation. Alternately, a series of cantilevers can be attached at the same elevation and the slope obtained by using shoes of different sizes. This method leads to fewer construction problems.

Slot for Electrical Tray Conduit

When the electrical conduit trays are located on the top level and a row of motor driven pumps is located beneath the rack at grade, a 6-in (150-mm) slot should be provided to allow the conduit to run in the most direct manner and avoid running to the outside of the rack and back to the pumps.

Access to Valves on Pipe Rack

Shut-off valves at utility headers are located inside the rack area in the horizontal position, directly above the header if room permits. Isolation valves shall preferably be accessible from deck or platform. However, if this is not possible, valves shall be positioned such that access from temporary facilities is obtained.

Operating valves must be accessible from platforms or by chain operators. The location of the valve must also permit the chain to fall free of obstructions that would hamper operation.

Fire water ring main isolation valves shall always be accessible from deck or platform. Pressure relief devices (relief valves, rupture discs) shall be accessible and installed for easy removal from deck or permanent platform. Relief valves shall be installed with the stem in the vertical position. Other valves may be tilted, as long as the
stem is above horizontal position. When ESD valves are installed as isolation valves, they shall be located as close as possible to the fire/blast partition.

Dead Spaces

Piping must be routed to avoid dead spaces because space in the pipe rack is limited once the design is set. The designer should ask area designers to identify which lines can run within their areas in order to minimize pipe runs in the pipe rack. During the early stages of pipe rack development it can subjected to multiple line location changes for which consideration is necessary prior to firming up the rack design.

Sensitive Lines

Ensure very hot lines are not run adjacent to lines carrying temperature sensitive fluids, or elsewhere, where heat might be undesirable.

Field Welds

Keep field welds and other joints at least 3 inches (75mm) clear from supporting steel or other obstruction. Allow room for the joint to be welded

Hose Station Near Rack

Vertical Drops

The vertical drop of lines outside the rack, although usually 2 ft (610 mm), is once again set by the average Line size in the unit. If the average line size is 2 in, a 12- in (300-mm) drop may be sufficient.