Glossary

Pipe stress analysis

Pipe stress analysis is the calculation and assessment of the mechanical loading of piping systems under weight, temperature change, internal pressure, external loads and the action of supports and connections.

Also: Piping stress analysis · Piping flexibility analysis · Stress analysis of piping systems

Also known as

Piping stress analysis
Piping flexibility analysis
Stress analysis of piping systems

Three questions a pipe stress analysis answers

A pipe stress analysis answers three questions. Does the line itself hold – do the stresses in the pipe stay below the allowable values of the code? What forces does it pass to its supports and thus to the steelwork? And what forces and moments does it transmit to the nozzles of the connected equipment and machinery?

A fourth result is where the line moves in operation. This decides whether it clashes with steelwork, neighbouring lines or platforms.

When a pipe stress analysis is required

The codes require that a piping system can safely absorb its thermal expansion and its loads. For non-critical lines a simplified assessment is sufficient. A formal analysis is usual as soon as one of the following applies; the exact boundary is set by the code and the project specification.

High or very low temperatures, particularly with large pipe sizes.
Connection to sensitive machinery: pumps, compressors, turbines.
Connection to equipment with limited nozzle loads.
Dynamic loads: pressure surge, discharging safety valves, vibration, earthquake.
Expansion joints or large movements.
Requirements of the operator or the inspection body.

The procedure

It starts with the input: isometrics, the line list with pressures and temperatures, the piping class, the equipment drawings with allowable nozzle loads and a first support concept. From these the calculation model is built and the load cases are applied to it.

The first run is rarely the last. If it shows overstress or excessive nozzle loads, supports are moved or changed in type, or the routing is adapted – until all checks are satisfied. This loop is the real core of the work.

What is available at the end

The result is a report that documents assumptions, load cases and checks traceably, and a set of lists with which other disciplines continue their work. This includes marked-up isometrics showing position and type of every support.

For existing plants, the analysis also answers whether a planned change – a higher temperature, a new connection, a replaced piece of equipment – is possible without modifying the line.

Common misunderstandings

Three assumptions come up again and again, and all three cost money.

Pipe stress analysis is not the wall thickness calculation – the wall thickness is its input.
It is not a step at the end of design: if it follows the steelwork, supports can only be changed at high cost.
It is not finished with the first run – its result is usually a changed support or routing.

What Entracon offers here is on the matching page.

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Overview

Results of a pipe stress analysis and who receives them

Result	Content	Recipient
Stress report	Utilisation per component and load case to the code	Operator, inspection body
Support load list	Forces and displacements for each support	Support design, structural steelwork
Nozzle loads	Forces and moments at nozzles compared with allowable values	Equipment and machinery manufacturers
Displacements	Movement of the line in operation	Piping design, clash check
Spring data	Settings for variable and constant spring hangers	Procurement, erection

Frequently asked questions

Frequently asked questions about Pipe stress analysis

What is the difference between static and dynamic pipe stress analysis?

Static analysis deals with loads that are applied slowly or at rest: weight, pressure, thermal expansion. Dynamic analysis examines time-dependent loads such as pressure surge, vibration or earthquake, where inertia and natural frequencies matter. For many dynamic loads an equivalent static load is sufficient.

Which documents are needed for a pipe stress analysis?

Isometrics or a 3D model, the design data of the lines, the piping class, valve weights, drawings of the connected equipment with allowable nozzle loads, and information on the steelwork available for supporting.

Does every line in a plant have to be analysed?

No. For non-critical lines the codes permit a simplified assessment or comparison with proven designs. Which lines are formally analysed is defined at the start of the project.

When in a project should the stress analysis start?

As soon as routing and equipment layout exist in a first version – and before the steelwork is released. Supports and routing can then still be adapted without rework.

Where the term appears on this site

From the term to the application

Service

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