Don’t Let Thermal Expansion Cause Excessive Piping Stress: Part 3, How to Inspect Your Piping to Prevent Problems
This is the final installment in a three-part series on thermal expansion and piping stress. The first article provides a primer on the basics of the thermal expansion and contraction found in industrial facilities. The second article focuses on the importance of proper stress analysis and good engineering to mitigate the risks of thermal expansion to piping and equipment. This third article describes how to spot problem areas in your plant before pipe damage and ruptures occur.
What to Look for During an Inspection
Start your inspection by ensuring that your existing process systems incorporate the practices of good piping engineering design.
- Verify that your “hot” equipment has room to grow. The thermal expansion of tanks and pumps should have been accounted for in the stress analysis calculations before installation. But the safety factor may have been reduced if ancillary equipment is replaced without considering thermal expansion.
- Pay special attention to equipment that is now operating at temperatures higher than originally designed as a result of a process change. Tanks and pressure vessels are often repurposed in the oil and gas industry, chemical plants, and food processing operations.
- Check for thermal contraction if any equipment is now being used at temperatures colder than the process engineer designed for.
- Verify that piping connected to hot equipment has multiple bends to absorb the equipment growth.
- Confirm that expansion loops are located in every pipeline that has two anchors on the same straight run of pipe.
- Know the direction of thermal expansion. This helps when performing these tasks:
- Making sure that piping connected to hot equipment will not strike a fixed obstacle as the equipment grows.
- Inspecting the drain valves, instrument connections, and sample points mounted close to obstacles. During thermal expansion, these may strike an obstacle and break.
Older systems may need some maintenance to minimize pipe stress.
- Look for shoes that have fallen off the pipe rack steel. When the line cools, the resulting contraction forces can damage the steel and the piping.
- Make sure that guides have the proper bracing to prevent lateral movement.
- Remove the stops in spring supports to allow the spring to move as the pipe moves.
Check the Drawings
Piping isometric drawings show predicted movements, which is valuable information when performing your inspection. The drawing may have a note like shown in the following image:
Careful review of the drawings and stress analysis results is also critical for new installations. Your process engineer should work closely with the piping engineering firm to consider all aspects of your site’s thermal expansion and contraction in order to reduce piping stresses and equipment damage. During construction, do a thorough walk-around regularly to catch problems early.
Everyone is responsible for safety and for asset protection. This series of articles will help you know what to look for regarding thermal expansion and contraction. And if you have questions or doubts about your equipment and piping, don’t hesitate to ask for support.
Matrix Technologies is one of the largest independent process design, industrial automation engineering, and manufacturing operations management companies in North America. To learn more about thermal expansion and pipe stress analysis, contact Chris Mach, PE, Senior Consultant (Team Leader) in the Process & Electrical Design Department.