DEARS,

It is understood that designers use some precalculated span/guide charts for planning the location of pipe supports in model. But, whether it is economical to check the results of stress analysis with the same span chart ? If maximum sag limitation & codal sustained,occasional & expansion stress conformances are met through careful piping stress analysis, even with lesser number of supports & guides than provided before starting stress analysis, is it good or bad to the end user?

regards,

sambhu

The support span/guide charts are typically for rack systems where in most cases a formal stress analysis is not required. The rest support spans are based on arthmetic mean of fixed end and simply supported beams.These are conservative.

But all these span charts have their limitations , in the sense , they are not to be used for Dynamic loading like Water Hammer, seismic etc.So these are to be used on systems which are simple and not subjected to dynamic loads. For such cases use of these charts are definitely good ways to reduce stress man -hours.

Since they are conservative , they come out with shorter spans. If you do a formal stress analysis, you may find that a larger support span is acceptable. In such cases formal stress analysis has its advantage.

To summarize: Use charts for non critical systems but if a formal stress analysis can come out with lesser no. of support requirement,particularly where supports are costly like SS shoes,go in for stress analysis.

One important point: these charts are typically based on standard wall thickness. For Stainless Steel pipes where use of schedule 10S is very common, these charts should not be used.

Regards

Anindya Bhattacharya