Can Support Directly Weld to Pressure Piping?

Every job is executed as per the design drawing provided by the client. Are you designing this piping? If yes, then you should spend some more time as an apprentice & hone your skills. In the meantime follow the clients instructions.

I would normally avoid welding to a pressure pipe because of possible differential movement such as vibration, expansion and contraction. The only time I would weld directly is within a pressure vessel as between bulkheads in a submarine and then I would use the encircling member as reinforcing for the pipe.

Yelettew,

The answer to your basic question "Can I weld a shoe direct to pipe?" is yes.

Go here: http://www.pipingtech.com/products/ptpcat/pipeshoes/withfw/index.html

you will see many examples.

SMYS, Specified Minimum Yield Strength.. you can look that up for the pipe you are proposing to use.

Whether or not you exceed 20% of that value will depend on what you are supplying it with....pretty basic starting point design info.

How to consider localised stress and thermal displacement? Localised stresses are things like the weight of attachments, vibration of attachments, weight and action of the pipe itself...thermal displacement is the pipe changing length with varying temperatures and so on......sounds like you need someone there to guide you.

Thank you for your well worded and easily understood question.

For this forum, it is certainly a rare treat to have, in English, a properly posed question.

First, it is important to note that integral welded attachments should be discouraged in pipe support design. They cause design and installaton problems that can usually be avoided through use of other support types on the system.

Secondly, in my opinion, the only types of welded attachment that the p[iping system designer may be "forced" into using are welded lugs (usually on a vertical riser support) or trunions on a elbow, just beneath a riser.

All other circumstances can be "designed away" through the use of competent piping designers and good piping stress analysis software ( eg CAESAR-II).

There are ASME methods available to evaluate the localized stress in riser lugs, which are loaded mostly in simple shear. Make sure that the ASME materials selected for these lugs are the same as those of the piping.

Similarly, there are established methods available to evaluate the local stresses on trunions.

I cannot answer your 20% SMYS question