RMDaniel
You posted the following questions & statements:
1. I am looking for a reference on when an expansion loop is required.
2. I mean, I know that it is necessary for high temperature service piping and for straight piping to avoid too much stress.
3. But I cannot find any specific values regarding the minimum temperature and minimum distance such that an expansion loop will be needed in the line.
4. If any of you have guidelines for this, it would really help me in my current project.
Comment:
#1 This is actually two requests in one; location of any/all References related to Expansion Loops, and when are Expansion Compensators required?
So first, you use any search engine on the web and type in “Expansion Loops” and you will get 17million sites. Some might help you but most will not. You first need to know this basics relating to the subject.
#2 Expansion of piping materials (Metallic and non-metallic) will happen to all systems and as the result of all temperatures. You first need to consider the location of the Job Site and the atmospheric temperature at the time of the initial installation as well as the potential temperature for later shut-down events.
Then you need to consider the projected actual maximum (or minimum) Operating conditions. Don’t make the mistake of using the system “Design” Temperature. The Design Temperature is only a theoretical number for use in calculating pipe wall thickness. The pipe will never actually ‘See’ the Design Temperature.
#3 When considering the actual Operating conditions you may have lines with an elevated temperature above the installed temperature or you may have some lines with a negative temperature far below the installed temperature. Examples include, Carbon Steel lines installed at ‘0’ degrees (C or F) and then operating at 600 degrees F (315.5 C) will expand a great deal. The same line in Stainless Steel at the same temperatures will expand almost twice as much. Pipe materials will also react to artic site temperatures and severe negative operating temperatures as well. Sub-Zero temperatures inside or outside the pipe material will cause “Contraction” (the opposite of Expansion) to the same degree as a high temperature.
Next you need to consider the pipe material itself. Different materials have different coefficients of expansion. As noted in the paragraph above Stainless Steel has a higher coefficient of expansion than Carbon Steel. CPVC and Fiber Glass pipe also has a higher coefficient of expansion than Carbon Steel.
See:
Or
Use the correct operation temperature minus the correct installation temperature for the proper expansion/contraction rate times the segment length.
#4 Next you need to consider the options available to compensate for the expansion/Contraction. Loops are a form of configuration and work fine but there are also other ways to solve the same problem. These other ways include other configurations and Engineered Expansion Joints (EEJ).
Other Configurations include:
“I” – With this configuration you have only a straight run but only the one (inlet) end is anchored. The far end is unrestrained and allowed to grow (expand) with the operating temperature. A typical example of this would be a Utility Steam supply line on a loading dock or wharf. The piping at the supply or land end would be anchored but the far end out at the end of the wharf is not anchored because the connections at the far end are just hoses used for cleaning decks and machinery. Between the anchor end and the far end the pipe is guided to maintain position.
“L” – With this configuration you have a natural “L” shape because of the pipe routing. The two legs of the “L” do not need to be equal in length but should be at least 1/3- 2/3. With this configuration it is important to recognize that the ends of the pipe of both legs need to be anchored and any guides on the pipe between the anchor and the connection point of the two legs need to allow for the expansion of the other leg.
“Z” - With this configuration you have the equivalent of two “L” shapes but you do not normally anchor the center of the middle leg. Guides are required for all three legs but again you need to allow for the displacement of the pipe due to the expansion of the three legs.
“U” – This refers to the Loop in a long straight pipe run. At the far end of the two legs attached to the “U” you must have Anchors. A Loop will not work if the ends of the straight run of pipe are not anchored. Between the Anchor and the Loop there needs to be Guides to control the movement of the pipe during the growth and shrinkage during operation.
Engineered Expansion Joints (EEJ):
These come in different styles from very simple to very complex. There is no reason for me to try to explain the different types and how they work. The web site below does that. The point I want to make here is based on my own opinion. EEJ’s are very costly and have inherent problems and can result in high maintenance and costly shutdowns. EEJ’s should never be the first choice and should be avoided when ever possible.
Sometimes its possible to do all the right things and still get bad results
