PIPE RACK WIDTH CALCULATION

PIPE RACK

Pipe racks are frame structures that support pipes and auxiliary equipment in the process areas of industrial plants. Just like loads from the wind and or earthquakes, piping loads can vary greatly from project to project. Clearly, it is difficult to define specific criteria for the design of such structures.

Pipe racks are necessary for arranging the process and utility pipelines throughout the plant. It connects all the equipment (installed at a different location) with lines that can not run through adjacent areas.

Pipe racks are also used in secondary ways, as it also carries the electrical wire, instrument wire, fire fighting systems, lights, etc. Air-cooled or fin-fan type heat exchangers are often supported above pipe racks to reduce the plant space requirements.

Pipe Rack Type

There are mainly three types of Pipe rack-

Steel Structure Type

RCC Structure Type

Sleeper Type (This is also called Pipe Track)

Documents Required for Pipe Rack Development

PFD (Process Flow Diagram)
P&ID (Piping and Instrumentation Diagram)
Line List
Line Routing Diagram or GAD
Over All Plot Plan
Unit Plot Plan
Equipment Layout
Piping Material Specifications
Client Specification
Fire-Proofing Information

Line Placing Criteria for Pipe Rack

Group the utility and process lines.
Keep hot and cold lines away from each other to minimize the heat transfer.
For ease of support to expansion loops, always try to keep the hotlines near to the stanchion or column.
If the lines are heavy, keep those lines near to the stanchion or column to minimize the stress (bending moment) on the horizontal beam or member.
Do not get confused that if the line size is greater the line will be heavier, no it’s not like that, as the gas-filled lines will create less stress on the horizontal beam than the liquid-filled lines.
Once we can compromise with weight, but never ever compromise in case of temperature, always maintain enough space between the lines.
We should avoid keeping a temperature-sensitive process line near high-temperature lines. For example, if the instrument-air line is placed near to the high-temperature line, it will absorb the temperature and can harm the instrument or instrument diaphragm.
We should also avoid keeping the temperature-sensitive lines near to chilled lines, as the other line can absorb the moisture, and further, it can be problematic for that particular line.
In the hydrocarbon and chemical industry, avoid keeping utility lines below the process line (means the process lines will be kept on the first tier and utility lines on the second tier. As in the case of leakage of the process fluid, water may get contaminated (as the water line is a utility line), and it can be harmful to the person.
In the food and pharmaceutical industry, it is mandatory to keep utility lines below the process lines to maintain the purity of the product.
If possible, keep the supply and return lines near each other, as these lines are having minimum temperature difference, and so heat transfer is less. Example: steam and condensate, cooling water supply, and chilled water supply and return.
To balance the width of the pipe rack of different tiers, water, air, nitrogen such lines can be kept on any of the tiers, there is no restriction to such utility lines.
Always try to keep future expansion in the middle of the beam, as it can help initially to reduce the stress in the beam.
Future expansion shall be a minimum of 20 % of the total pipe rack width calculation, and maximum what else comes if space is not a problem.
Make sure that the flanges are staggered to minimize the pipe rack width

While designing pipe rack following considerations have to take care:-

Rack width,
No of levels and elevations,
Bent spacing, pipe flexibility,
Access and maintenance of each item in the pipe rack.

Calculate the width of Pipe rack

w= (f X n X s) + A + B.

f : Safety Factor

1.5 if pipes are counted from PFD.
1.2 if pipes are counted from P&ID.

n = number of lines in the densest area up to size 450NB.

300 mm (Estimated average spacing)
225 mm (if lines are smaller than 250 NB)

A : Additional Width for

Lines larger than 450 NB.
For instrument cable tray
For Electrical cable tray.

s : 300 mm (estimated average spacing)

225 mm (if lines are smaller than 250 NB)

B : future provision

20% of (f X n X s) + A

The pipe Rack width is limited to 6.00 Mtrs. If the width of rack calculated is more then the arrangement shall be done in multiple layers. Normally, 5 to 6 Mtr. spacing is kept in between the column of pipe rack.

Lines placement on the pipe rack

Process lines on lower level, utility lines on top level, instrument and cable trays on utility level or separate topmost level, Heavy lines near columns, Flare line outside rack on cantilever beams or inside rack above top level, steam lines with expansion loops on one side of pipe rack, line s with orifice runs on one side of rack beside columns for maintenance using portable ladder.