Hi All,

I’m in the process of sorting out all the piping classes and material specifications. My problem is this:

Within several companies’ standard piping details (which I’ve come across)there’s always a datasheet(s) on minimum pipe spans for particular piping runs/configurations based on pipe full and pipe empty, etc.

Now, the acceptable span between pipe supports is on average 8m for laden carbon steel pipe. I stress “average” because there does not seem to be a definitive method of working out minimum pipe span. Basing the recommended span on induced stress, either for simply supported or built-in beams, yields acceptable spans considerably more than 8m, even taking into account derating for joints such as flanges, threaded joints, etc.

Therefore, designers in the past have apparently based the required spans on maximum defelection. This seems reasonable as it considers factors like drainage gradient and natural frequency better than stress-based evaluation. But what is an acceptable deflection? Data suggests that 25mm (1″) is preferred, but this seems so arbitrary!

And I’m sick of hearing “but that’s what we’ve always used”!

Any feedback would be appreciated, thanks