Spiral Pipe Maximum Vacuum

[mrkhubert]

I am looking for imformation on the maximum allowable vaccum on a 24 inch diameter 22 gauge stainless steel spiral pipe. SMACNA only gives lengths up for pressures up to 10". I am looking to calculate higher vacuum pressures.

 

[KenRad]

mrkhubert,

Contact a manufacturer of stainless steel spiral duct, like Lindab (

http://www.lindab.com).

They can tell you.

---KenRad

 

[CountOlaf]

It addition to SMACNA's "HVAC Duct Construction Standards-Metal & Flexible", they also publish "Round Industrial Duct Construction Standards". This second publication takes you up to -30" wg. Trouble is it doesn't include the spiral duct types which can presumably handle more pressure.

At any rate, one thing that has to be established first is the material handling class of the duct. This is comprised of 4 classifications ranging from non-abrasive applications to highly abrasive. Per United McGill's literature (and this seems in agreement with SMACNA's lit.), you need 20 ga min. for 24" spiral duct up to -10"; 18 ga. for -10 to -20", etc. for just the least severe classification. There are other iterations depending on the level and type of additional reinforcing, so it's not like there is one exact answer.

Unstiffened, you shouldn't really go past -2" wg for a 24" diam spiral seam duct (this is shown in the "HVAC Duct Construction Standards-Metal & Flexible"--presumably the one you already have).