Pipe Rack and Pipe Track

This blog offers a concise overview of pipe rack and pipe track design, highlighting their key differences. It covers width calculations for pipe racks, civil loading considerations, various types and shapes of pipe racks, and essential design and review points for effective pipe rack or pipe track design.

Introduction

A pipe rack serves as the backbone of a process unit, linking all equipment with lines that can’t traverse adjacent areas. It supports not only process and utility piping but also accommodates instrument and electrical cable trays, along with equipment mounted above.

Due to its central location in most plants, the pipe rack needs to be erected first to avoid being obstructed by rows of equipment that are installed later.

Key Differences Between Pipe Rack and Pipe Track

A pipe rack features overhead piping supported by structural steel or concrete bents, allowing for vertical spacing and easy maintenance.

In contrast, a pipe track consists of above-ground piping resting on concrete sleepers, positioned at grade level for direct ground access.

The primary data required for detailed development of a pipe rack and pipe track

• Plot Plan
• P&ID’s
• Utility distribution diagram
• Line list (Insulation thickness, operating temp. etc)
• Client Specification
• Construction Materials (Concrete or Steel)
• Fire proofing requirements

Pipe Rack and Pipe Track Design

• To initiate the design process for pipe racks, the first and most crucial step is to create a line-routing diagram. This diagram serves as a schematic representation of all process and utility piping systems, illustrated on a draft of the plot plan. Also known as a planometric drawing, it visually represents the layout of these lines without detailing exact locations or interfaces, helping to identify the most congested areas.
• The second step involves analyzing this schematic to pinpoint the most congested areas. From here, you can arrange process and utility piping to determine the necessary width of the pipe rack, including the number of tiers required.
• Third step is to make sure about client requirements, stated in their specifications or feed documents provided, and same shall be checked and taken care in pipe rack design, while deciding width of pipe rack as well as tiers etc.
• Moreover, each pipe rack should allow for future space requirements. To accommodate potential expansions or modifications, the total width of the rack should include an additional 20% for racks up to 16 meters wide, and 10% for those wider than 16 meters. The client’s specifications should dictate these future space considerations.
• Typically, pipe rack widths are set at 6m, 8m, or 10m for single bays, and 12m, 16m, or 20m for double bays, with a maximum of four tiers. Generally, the spacing between pipe rack portals or bays is 6m, but larger pump sizes or installations beneath the rack may necessitate increasing this spacing to 8m.

Calculating Width of Pipe rack

The width of the pipe rack is estimated as per below equation,

W = (f x n x s) + A + B

f = Safety factor
= 1.5 if pipes are counted from the PFD
= 1.2 if pipes are counted from P & ID.
n = Number of lines in the densest area upto the size of 18 Inch
s  = 300mm (estimated average spacing)
= 225mm (if lines are smaller than 10 Inch)
A = Additional width for
(1) Lines larger than 18 Inch
(2) For instrument cable tray/duct
(3) For electrical cable tray
B = Future provision
= 20% of (f x n x s) + A

Different Shapes of Pipe Racks

• All plants are divided into manageable sections according to the pipe rack design. Pipe racks come in various shapes, including ‘straight’, ‘L’, ‘T’, ‘U’, ‘H’, and ‘C’ or ‘Z’.
• The choice of shape or configuration depends on the overall layout of the facility, the arrangement of equipment, and the physical conditions of the site. Each pipe rack is strategically designed to accommodate the incoming and outgoing piping lines effectively.

  

Once the width of the pipe rack is determined, maintaining the appropriate clearance beneath it is crucial.

For units, a minimum clearance of 4 meters must be maintained both longitudinally and transversely. In offsite areas, this minimum clearance is reduced to 2.2 meters in both directions.

Additionally, road clearance requirements stipulate 7 meters for main roads and 5 meters for secondary roads.

These guidelines are general standards and should always align with specific client requirements.

Key Considerations for Pipe Rack Design

Key considerations for pipe rack design include the following:

Position of Lines:

• Process lines should be placed on the lower tier, while utility and hot process lines should be on the upper tier.
• Hot and cold lines are generally positioned at the edge of the rack for expansion loop feasibility.
• Flare lines are placed on the top tier.
• Lines with orifice plates should be appropriately positioned.
• Large pipes should be placed thoughtfully.

Future Space:

• Every pipe rack should account for future space requirements. The total width should include an additional 20% space for future expansion or modification for rack widths up to 16 meters, and 10% for rack widths above 16 meters. Client requirements, as stated in feed or specification documents, govern future space needs.

Pipe Spacing:

• Follow pipe spacing charts, standards, or tables for proper spacing on the pipe rack.
• High-temperature lines spacing should consider thermal expansion.
• Fireproofing thickness should be considered when deciding pipe spacing.

Large Size Lines:

• Large lines (14 inches and larger) should be arranged close to the column to decrease the bending moment of the beam.

Anchor Bay:

• Anchors on the racks should be provided at the anchor bay if the anchor bay concept is adopted. Otherwise, anchors should be distributed over two to three consecutive bays.
• Anchors should be provided within the unit on all hot lines leaving the unit.
• Bracing locations should be at anchor bays.

Pipe Route:

• Racks should be designed to provide the shortest possible run for piping and to maintain clear headroom over main walkways, secondary walkways, and platforms.

Trays:

• The top tier should generally be reserved for electrical cable trays (if not provided in underground trenches) and instrument cable ducts/trays. Cable tray placement should allow for necessary clearances for fireproofing the structure.

Battery Limit (ISBL):

• Process lines crossing units (within units or from the unit to the main pipeway) should typically have a block valve, spectacle blind, and drain valve. Block valves should be grouped, and locations in the vertical run of the pipe are preferred. If block valves are located in an overhead pipe-way, staircase access to a platform above the lines should be provided.

These key points ensure a functional and efficient pipe rack design, accommodating current needs and potential future expansions.

Expansion Loops Required on Pipe Rack and Pipe Track

• Expansion loop is provided on the high temperature lines. This information shall be given by stress group. All the loops shall be located around one column only.

Group the lines together and install large size piping and high-temperature piping along the edge of the rack.

• When installing an expansion loop on the condensate line, prioritize a horizontal installation to prevent water hammering. If a horizontal loop is not feasible, follow the recommended alternatives.

Pipe Rack and Pipe Track Loading 

For the effective design of pipe racks, the pipe rack loads must be communicated by the stress group to the Civil & Structural discipline. These loads encompass various cases and should be adequately considered in the civil design process. The key load types include:

Sustained Load (Dead Load):

• This includes the weight of the piping, valves, and insulation materials. It is a constant load that the pipe rack must support at all times.

Thermal Load:

• These loads arise from the thermal expansion of the piping. As the temperature changes, the piping expands or contracts, generating forces that must be accommodated by the pipe rack design.
• Additionally, the reaction force caused by the internal pressure of expansion bellows must be considered. Expansion bellows are used to absorb the expansion and contraction in the piping system.

Dynamic Load:

• These are loads caused by dynamic forces such as vibration of the piping due to flow-induced vibrations, mechanical equipment, or external factors.
• Wind loads also fall under this category, as they can exert significant forces on the pipe rack structure.
• Earthquake loads are another crucial factor, particularly in seismically active regions. The pipe rack design must account for seismic forces to ensure stability and integrity during an earthquake.

Sustained Load (Live Load):

• Live loads are variable loads that may be applied temporarily, such as the liquid load during hydrostatic pressure tests. These tests involve filling the piping system with water to check for leaks and ensure structural integrity.

By considering these various load types, the design process for pipe racks can ensure that the structure is robust, safe, and capable of supporting the operational demands placed upon it. Proper communication and coordination between the stress group and Civil & Structural disciplines are essential to achieve an optimal design.

Key Bullet Points for Any Pipe Rack and Pipe Track Design

• Construction priority.
• Drip legs Location
• Expansion loops & Drop out location for relief valves or big sized valves.
• Bracings at anchor bay locations.
• U/G Lines crossing at Anchor bay location.
• Plan bracing locations
• Flat turns on pipe rack.
• Small Bore Piping with below 2”.
• Slope lines.
• Pipe rack concrete or steel.
• If concrete check for Insert plate requirements.
• Monorail requirements
• Platform requirements for C&A condensate pot access for orifice.
• Pipe rack Interface between two units or between two contractors.
• Pipe rack loading for future space.
• Escape ladders and proper access requirements.
• Relief Headers
• Check for Fire water lines requirements. (Since these are not coming under utility)
• Where possible interconnect adjacent platforms with pipe rack platforms for better access and better escape routes in case of any accidents. Since both the structures are having difference expansion rates, keep gap of 50mm between interconnection.
• Utility stations.
• Electrical & instrument junction box locations check.
• Davit requirements with drop out area.
• Control valve station assembly, Heat tracing steam trap assemblies.
• Check for construction sequence for hydro test on pipe rack pipes. i.e. no of lines at once for hydro test for economic design of pipe rack.