Design of expansion loop

Dear All

Can any one please advice me, how can the expansion loop be designed for the process piping of size 20"(SA 358 TP321) having temperature 120C and 32Kg/cm2.

Waiting for positive response.

Best Regards

Ikram

Ikram

In order to answer or refer you to an answer it would be productive to confirm what the intent and context of your question relates to:

1. Are you designing the loop (from first principles) for flexibility or performing stress analysis on a new concept?
2. Are you wanting to check an existing loop design or installation?
3. Are you laying out, providing a position and allocating "real estate" for a loop in the design in preparation for downstream formal analysis
4. Have you established that an expansion loop is necessary and why?

2M

Dear 2M

I would like to explain my problem in points to make it clear.

1. We have 20" piping of total 6m length. The piping starts from an horizontal equipment and bend down in 2D (2400mm) and moves straight in the direciton of equipment(from which the pipe started) and ends at nozzle of another equipment (5098mm).

2. In the original scheme the lateral expansion bellow is installed in the 2D piping spool to cater for 6mm lateral expansion comming from the equipment.

3. This bellow has leakage history and leaks once in the 10 years.

4. Now we want to remove the bellow and add an expansion loop.

For this i have asked how to design the expansion bellow of larger size.

I think the problem has been cleared in full and now waiting for your kind response. I may also send you the isometric if you provide me your email address.

Best Regards

Ikram

Ikram,

There are a few select methods of determining the requirements for an expansion loop – both for design and layout. These range from the simplistic to the exhaustive; it depends on the intent, thus alluding to my query.

For a rough check: a simple built-in beam or guided cantilever method would suffice. This entails reducing the piping configuration and your expansion loop to a series of free body diagrams about the guides and anchors.

For a less rough check: using “Spielvogel” piping stress charts / shapes would yield a satisfactory indication of where you are heading in terms of your strategy to replace the EJ.

For a pretty accurate check: use formal stress analysis software to determine code requirements, loadings; thus being exhaustive, responsible and safe.

You may glean a bit more from these references:

www.eng-tips.com/viewthread.cfm? ... 902&page=7

thermacor.com/downloads/document ... -4_001.pdf

books.google.co.za/books?id=mvaJ ... &q&f=false
[Page 217)]

The reason for asking whether an expansion loop is necessary alludes to the oft, over-reliance on flexibility to provide unnecessary solutions. When considering thermal expansion and secondary stresses there are three routes a) if permissible, let the equipment simply accept the load, b) provide additional flexibility to reduce the load, c) provide additional stiffness to transfer the load to supports, civils or structures. The last would invariably include correctly placed anchors and stops, and heavier support structures.

Not being aware of the equipment, it could be assumed that the expansion joint was originally installed to alleviate all loading on the nozzle. If this were the case even additional flexibility i.e. a loop or offset would only reduce the level of loading

I would suggest that you may consider four, rather general, guiding principles when analysing brownfield piping modifications:

1. Don’t tear down a farm fence until you know why it was put up and who put it up in the first place.
2. If it's not for NASA and you’re designing necessarily to 3 decimal places, in practice it aint going to work.
3. Any new component in a piping run, however trivial, equals a new system entirely i.e. the piping's personality changes.
4. Keep the centroid (center of area) of your piping arrangement as far away (offset) from the line drawn between your nozzles

Hopes this helps

2M
.