PRESENTATION

ON

PIPE RACK

Contents:

Introduction

Structural Arrangement

Types of Pipe Rack

Primary Data Required

Pipe Rack Design

Load calculation

Example

INTRODUCTION:

Pipe rack is the main artery of any plant. This carries the

pipes and cable trays (raceways) from one equipment to another

equipment within a process unit (called ISBL piperack) or carries the

pipe and cable trays from one unit to another unit (called OSBL pipe

rack). Sometimes you will also find the air cooled heat exchangers on

the pipe rack.

Piperack is a structure made of steel, concrete or mixed supporting :-

- One or more layers of piping.

- Electrical or instrument cable tray.

- Air cooler in certain case.

Structural Arrangement:

Main Cross Beam :

The main cross beam is a horizontal beam connected to two posts to form the portal frame and to support the pipes.

Portal Frame :

The element of piperack forms by two posts and one or more main cross

beams.

Longitudinal Beam :

The longitudinal beam is a horizontal beam connecting two portal frame in

longitudinal direction. Generally, the members are used to support the

lateral forces, intermediate cross beams and post of coolers. Especially to

transmit the horizontal force to the bracing bay.

Width of Piperack :

The width of piperack is the distance between the axis of the posts.

Piperack Spacing :

Piperack spacing is the distance between the portal frames.

Intermediate cross beam :

The intermediate cross beam is a horizontal cross members supported by

longitudinal beams. They are used to reduce the deflection of small pipes.

TYPES OF PIPE RACK :

(A) Continuous Piperack (conventional pipe rack) system

(B) Non-continuous Piperack system

(C) Modular Piperack.

(A) Conventional / Continuous Pipe rack: Continuous Piperack (conventional pipe rack) system: This is essentially a

system where multiple 2-dimensional (2D) frame assemblies (commonly

called bents), comprised of two or more columns with transverse beams,

are tied together in the longitudinal direction utilizing beam struts (for

support of transverse pipe and raceway elements and for longitudinal

stability of the system) and vertical bracing to form a 3D space frame

arrangement. Piperacks supporting equipment such as air-cooled heat

exchangers must utilize the continuous system approach.

(B) Non- Continuous Pipe rack :

This is a system comprised of independent cantilevered, freestanding 2D

frames not dependent on longitudinal beam struts for system stability. This

system, where feasible, should result in lower total installed cost (TIC).

(C) Modular Pipe rack :

Building Modules: Structural Frames completely fitted with

miscellaneous equipment and architectural finishes.

Piperack Modules: Structural Frames completely fitted with pipes,

Cable trays miscellaneous equipment.

Primary Data Requred:

Plot plan.

P & ID.

3D model showing piping layout,

Vendor prints of equipment located on the rack, e.g., air coolers type

exchangers. The vendor prints should include the equipment layout,

mounting locations and details, access and maintenance

requirements,

Electrical and control systems drawings showing the routing and

location of electrical and instrumentation raceways.

Underground drawings.

Pipe Rack Design:

1)Shapes:

There are various shapes of pipe rack like L/T/U/H/Z. These shapes

shall be considered based on the area available.

DEAD END YARD LINES ENTER

& LEAVE ONE END OF THE RACK

STRAIGHT THROUGH YARD LINES CAN ENTER

& LEAVE BOTH ENDS OF THE RACK

L-SHAPED YARD LINES CAN ENTER

& LEAVE NORTH & EAST OF THE RACK

T-SHAPED RACK PIPING CAN ENTER

& LEAVE THREE SIDES OF THE RACK

COMBINATION OF I & T SHAPED RACK

U-SHAPED YARD LINE CAN ENTER

& LEAVE ALL FOUR SIDES OF THE RACK

COMPLEX RACK PIPING ARRANGEMENT

FOR VERY LARGE CHEMICAL PLANT

2) Width of Pipe Rack:

The width will be decided in consideration of the following points:

No. of piping installed on pipe rack,Pipe size,Insulation

thickness.

Electrical/Instrument cable trays

Space for future lines

How to use space loacated underneath of piperack such as

walkways,Maintenance road,Route for underground piping.

How to use space located above piperack,Such as space for

Equipment,operation/Maintenance floor.

Pipe spacing:

Minimum spacing between adjacent lines shall be

decided based on O.D. of bigger size flange ,O.D. of the smaller

pipe, individual insulation thickness and additional 25mm

clearance.

After calculating total pipe spacing,25% of total is added for

future space.

Total width(W)=Total pipe spacing(X) + 25% of X(Future space)

The total width is thus obtained.

3) Number of Tiers/Levels:

Number of levels on pipe rack mainly depends upon width of pipe

rack.If W is bigger than 6M usually two piperack levels will be

required. The width of the piperack may be increased or determined

by the space requirement, access to equipment arranged under the

piperack.

Line location in Pipe rack:

In One tier pipe rack,Large diameter pipes are kept near pipe

rack column to reduce bending moment on beam. Place

process and relief lines next to these. Lines serving left hand

areas of plant on left, lines serving right hand areas on the right.

The central piperack portion is reserved for utility lines which

may serve both right and left hand areas on the plant.A

centrally placed section of the piperack is reserved for future

lines.

In Two tier pipe rack, utility lines are placed on the top level

and process lines on the bottom level.

Generally Hot lines & Cold lines are to kept at different tiers or

at different groups on a tier. It is advantageous for pipe supports

to group hot lines requiring expansion loops together,

preferably on side of the pipe rack. Horizontally elevated loops

over the piperack are commonly used to minimize the effects of

expansion on hot lines.

Large size lines (14” and larger) shall be arranged close to

the column in order to decrease the bending moment of beam.

Water lines more than 30” shall not be routed over pipe rack,

these shall be routed underground.

4) Span between Portal frames:

Generally piperack span is taken 6m. This may be increased

to a maximum of 8m consideration must be given to:

Smaller lines which must be supported more frequently.

Liquid filled lines requiring shorter span than gas filled lines

Hot lines which span shorter distances than cold lines of the

same size and wall thickness

Insulated lines; small bore, cold - insulated lines due to weight of

insulation must be supported at relatively short intervals.

5) Elevation of pipe rack:

The Elevation will be decided in consideration of the following

Points:

Minimum Head clearance:

Normal overhead: 2.2 meters

Plant roads in trucking areas: 4.8 meters

Rail-road and public main roads: 6.6 meters

In case of muti-stages Pipe Rack. Vertical elevation gap: minimum

1.5 m.

6) Pipe flexibility and support:

Flexibility is also a crucial factor.Pipes are installed during relatively cooler conditions. When a hot fluid passes in the pipe, or when the ambient temperature rises, the pipe expands. The expansion generates enormous force. If only one end of the pipe were connected, the other, loose, end can expand. But generally, in piping both ends are connected. The expansion force acts on equipment or a structure or whatever the pipe is connected to. If it is flexible, the piping system absorbs the expansion and there is no force on to the connected equipment.

Flexibility is provided by expansion loop.The expansion loop should be located in the center of the distance between two anchors.It depends on:

Co-effiecient of thermal expansion of pipe material

Pipe length

Temperature of fluid running through pipe.

Piping Support Elements are used to transmit load to the structure.

Classification of Pipe support:

A) Rigid Support:

Pipe Anchor

Pipe guide

Pipe insulation shoe

Field support

Dummy support

Hanger rods

B) Flexible Support:

Variable spring support

Constant spring support

Load calculation:

Pipe rack loads shall be given by stress group to civil and structural

discipline for pipe rack design.

Sustain load (Dead load):

- Weight of piping,valve and insulation.

Thermal load:

- Load by thermal expansion of piping.

Dynamic load:

- Load by vibration of piping and by wind & earthquake.

Sustained load (Live load):

- Liquid load for hydrostatic test pressure.