Double Longitudinal Seam in duct section

[Lummers1]

We have installed two pieces of SMACNA class 1 round galvanised duct 900 diameter with double longitudinal seams in each section. Please confirm if this is acceptable practice according to SMACNA and if so where I can prove this.

 

[berkshire]

If you are saying 900mm then it is an alternate method of making a long piece of duct. Stock sheets are 4x8 5x10 and 6x12 feet
so your shop would have to use two 5x 10 sheets to get you a 10 foot section. your alternative would be spiral wrap, or shorter duct sections.
B.E.

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor

 

[berkshire]

The accepted method is one seam on either side of the duct 180* apart not two seams 6" or 9" apart.
B.E.

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor