Piping design plays a crucial role in plants and requires precision in its design. The operational agility and efficiency of any facility depend greatly on the robustness and capabilities of the pipes. While these pipes may appear static, they are surprisingly dynamic. Constantly fluctuating loads, extreme temperature differences, varying pressures, and the weight of components exert significant stress that can damage the pipes and cause them to shift.
When the substances flowing through these pipes are hazardous, the consequences can be perilous for the people working in the plant and for the equipment installed. Accurate pipe stress analysis can help you diagnose issues and implement safe and reliable fixes for the plant environment.
This article explains the importance of stress analysis for a safe and efficient plant design, delves into the basics of pipe stress design, and lists common piping design mistakes along with their solutions.
The Significance of Pipe Flexibility and Rigidity
An accurate pipe stress design requires a perfect balance between rigidity and flexibility. Pipes tend to expand when subjected to thermal stresses and shrink when temperatures drop drastically, which directly impacts the connected equipment.
If there is no room for expansion or movement, pressure is exerted on the pipes and the supporting machinery until something gives way. The best way to address this issue is by enhancing the system’s agility with flexible supports, expansion joints, or flexible loops that provide elasticity.
However, too much flexibility is also undesirable. It leaves the pipes susceptible to natural and transient forces like hurricanes, earthquakes, steam hammering, and vibrations.
This is where rigidity plays a vital role. Anchors add rigidity to pipes by breaking the system into independent sections, preventing movements or forces from impacting the other side. They also make the piping systems easier to modify and repair when problems arise. However, overusing anchors can magnify thermal loads, which is why they should only be placed in sections with minimal thermal displacements.
Fundamentals of Piping Stress Design
To achieve a perfect balance between pipe rigidity and flexibility, follow these three basic rules of detailed engineering design:
- Keep pipe stresses below their permissible code limits to avoid damage.
- Allow for large displacements to avoid collisions with adjacent objects.
- Ensure all forces at pipe-machinery connections remain well below the permissible limits stated by the manufacturer.
If you adhere to these fundamental principles, you are likely to achieve the desired balance. However, the combination of pipe routes and supports is complex, and the number of fitting options and bends is extensive. Even with commitment and intent, controlling environmental variables can be challenging. This is where the experience and technological expertise of an agency offering detailed engineering services can help!
Whether you are building a manufacturing facility from the ground up or constructing a petroleum refinery, they can assist you in designing a piping system that ensures the complete safety of your workforce and infrastructure.
How to Get Piping Stress Analysis Right the First Time
Experience can significantly impact the success of piping stress analysis. Experienced companies providing detailed engineering services are familiar with codes, compliance regulations, and processes, and they are equipped with stress analysis software like Bentley and AutoPIPE. This not only reduces time and cost but also ensures accuracy, safety, efficiency, and compliance in piping design.
From accounting for every load to ensuring component strength and making calculations for various pipe layouts, these companies accomplish all competing goals with precision. Their teams investigate potential causes of impending failures and brainstorm possible solutions. Their proficiency and the advanced capabilities of leading software solutions combine to ensure that your design decisions are reliable and sound.
Common Mistakes in Piping Design and How to Fix Them
- Trapping of Pipe Between Two Connections
This occurs when two adjacent pieces of equipment are secured to the floor, and the length of pipe running between them expands due to heat, with no room to grow.
Fix: Stress does not take a straight route. Adding a U-shaped bend or an expansion loop will enable the pipe to flex and grow while relieving stress.
- Expansion Around a Corner When Using Pipe Guides
A straight and long section of pipe is often held up using a series of guide supports. These supports, made with pipe shoes and guiding clips, facilitate movement. Any bend in the pipe disrupts expansion after the bend.
Fix: To enable growth, it is best to cut the clips near the corners, giving the pipe freedom to move in both directions simultaneously.
- Expansion Joints Moving Far Apart
When you have a straight pipe with insufficient space for an expansion loop, using a joint can be beneficial. However, under high pressure, the joint may be pushed outward in both directions.
Fix: Consider adding anchors before and after the section that expands and is attached to the joints. This will eliminate potential dangers.
- Support Lift-off
Pipes that travel long distances vertically need supports at the top and bottom to manage their weight safely. Thermal growth can cause the pipe to lift off the top support, damaging the bottom support due to overloading.
Fix: The best solution is to avoid long vertical runs by breaking them down and allowing each section some room for expansion to prevent support lift-off and damage.
- Damage to Equipment from Connections in Vertical Pipes
For sensitive equipment, even a small vertical run can create misalignment and cause damage. Such issues are challenging to resolve.
Fix: Avoid connecting a vertically laid pipe to any sensitive sections. If unavoidable, a cold spring or a spring can serve as a feasible solution.
Conclusion
Challenges and pitfalls are unavoidable in piping design, but the most significant challenges arise from a lack of proper planning. Making calculated decisions to safeguard the plant and equipment is not feasible without the assistance of an external agency providing detailed engineering services.
Whether it involves a single line of pipe or hundreds of intricate lines, an experienced partner can help you prepare thoroughly, plan thoughtfully, think critically, and design precisely. With a trusted team, you will achieve a much safer plant that keeps your operations running at peak efficiency.
by: Judith Morrison
Morimatsu Dialog provide one-stop technical and fabrication solutions for process modules and skids, offshore topside modules, core process and pressure equipment, heat exchangers, and more.
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