Expansion Joint Request Through Manufacturer

[ctmecheng]

Hello,

I am currently working on a project where I am designing a piping system in need of expansion joints. The system is large and there is no room for expansion loops, so expansion joints is our best option. However my problem begins dealing with the expansion joint manufacturer.
To start, I modeled my system in Bentley AutoPIPE Advanced, determined my support locations, determined the amount of linear expansion the system would experience and place expansion joints in locations I believed would un-stress the system. The existing system had expansion joints as well and since I did not have any spring constant data for the my new joints, I used the existing joint data as reference. From here I analyzed my system and obtained certain movements for all the joints. From here I contacted a manufacturer and requested a quote and data sheets. I then updated my stress model with the new data a obtained new movements.

My question is, is this the correct way to get expansion joint data from a manufacturer? Is there an important step I am missing? I know this may sound like a trivial question but this is my first time having to design and get quotes from a manufacturer, and I feel like I am going in circles with iterations.

Any help is useful.

Thank you for you time.

 

[DSB123]

Take care with expansion joints. Incorrect installation is what caused Flixborough explosion!!!

 

[XL83NL]

I think your design method is not incorrect, and provides a good start, but it may be better when you look for a required spring constant that meets your system needs (based on the stress analysis), and from there on make up your spec and look for a supplier which can meet that spec.

Nevertheless it's good to get in contact quickly with your, as they have a lot of knowledge on exp joints and can surely assist you in selecting the right type of joint.

In a recent job I did I required an expansion joint with some very unusual, perhaps difficult, requirements. Few suppliers where able to provide a quote, the usual suspects quickly offered a no. In the end only one supplier was able to provide something that met my spec. They were the most expensive ones to offer me an exp joint, but in the end it was the best and only good decision to go ahead with them rather than another supplier which was just off spec, but would not be able to provide the quality and design I required.

It's what you (well, technically your pipes) need that matters, even if that means an unhappy boss because of expenses.

 

[ctmecheng]

XL83NL,

Thank you for the response, it is very helpful.

I should have clarified something in the beginning. I am dealing with a very large diameter system so I cannot pick an item from a catalog to see if it works. I am working with a manufacturer now and they are asking for movements. Well, with the program I am using I have to put in EJ data to see how the EJ is reacting. It was causing much confusion between the manufacturer and I. What I decided to do was look at each section of my system between anchors, figure out the delta L due to thermal expansion, and give the manufacturer that distance. I did this because my train of thought is if I have an EJ that can take up all of the thermal expansion I should end up with a low stress system.

Would you agree with this method?

I am gathering this data now to send to the manufacturer. I can let you know what comes of it once the issue is solved.

Again thank you for your input. It is much appreciated!

 

[XL83NL]

Do you have (significant) thrust loads due to internal pressure? Stress is one, thrust is a major issue to overlook. Only pressure balanced EJ's don't have any real thrust loads, but then again, they may experience significant spring constants due to their complex designs involving a lot of metal.

I understand you can't use catalogue EJ. For detailed stress analysis I did, my experience is that we've always ended up with custom designs. Catalogue EJ's are only used by us for very simple systems, for which analysis can be done using hand rules and straightforward design rules.

 

[ctmecheng]

XL83NL,

There is not any significant thrust loads, the max pressure this system will see will be 15" WC (~0.5 psig). Also this system is very large, 10'-6" in diameter, so I cannot even find an EJ in a catalog this size to even get a starting point.

Would you agree with the approach I took in calculating the amount of thermal growth between anchors and requesting an EJ to absorb that amount of movement?

That is the information I will be giving the manufacturer in hopes I get a properly working system.

 

[met11]

ctmecheng, now I'm just curious. 10'-6" in diameter, how long is that pipe? That's a serious application!

 

[ctmecheng]

Met11,

Yes this is a large exhaust system that is being re-routed to bypass the exhaust stack and go to a Heat Recovery Steam Generator. The new re-route is about 250' in total length.

 

[XL83NL]

Hi ctmecheng, yes, that info is necessary indeed, but also provide him details on the routing, fluid, operating conditions, etc. Saying 'exhaust' I think of high temperatures, so material selection comes into play, especially when the exhaust gas contains corrosive particles.

 

[ctmecheng]

XL83NL,

Yes materials have already been decided through some discussion with the plant engineers. I have given the manufacturer all the things you listed. This makes me feel better about how I have navigated this part of the design. Thank you for talking through this with me. It is much appreciated!

 

[XL83NL]

You're welcome (we have a system for that )