Coupling plain bare end tubing for pneumatic conveying
Coupling plain bare end tubing for pneumatic conveying
(OP)
I am updating piping specifications, and haven't been able to confirm the pressure rating for compression couplings. So far a VERY frustrating search.
Morris Coupling, INC, sells these two prototypical configurations
these "lower pressure" couplings use 3 to 6 bolts to clamp the rubber sleeve to the tubing.
and this split style is used for "higher pressure".
Although Morris Coupling Inc, sales stated 15 psig some vacuum (~ 7 psi vac), they would not put the pressure limitation in writing. Similarly HP Products does not publish limits, but verbally reports 15 psig / FV. Two other manufacturers said similar things.
(a)Is there a standards organization that covers these plan bare end compression couplings?
(b)Are there other bare end tubing/piping couplings that have like UL standards proof testing, or that meet some recognized standard, similar to the ASME piping code?
(C)Is there a consensus or published manual on how to apply them, e.g., when to deviate from the first coupling and use the second &/or know how many bolts to specify on the coupling? etc.
Morris Coupling, INC, sells these two prototypical configurations
these "lower pressure" couplings use 3 to 6 bolts to clamp the rubber sleeve to the tubing.
and this split style is used for "higher pressure". Although Morris Coupling Inc, sales stated 15 psig some vacuum (~ 7 psi vac), they would not put the pressure limitation in writing. Similarly HP Products does not publish limits, but verbally reports 15 psig / FV. Two other manufacturers said similar things.
(a)Is there a standards organization that covers these plan bare end compression couplings?
(b)Are there other bare end tubing/piping couplings that have like UL standards proof testing, or that meet some recognized standard, similar to the ASME piping code?
(C)Is there a consensus or published manual on how to apply them, e.g., when to deviate from the first coupling and use the second &/or know how many bolts to specify on the coupling? etc.





RE: Coupling plain bare end tubing for pneumatic conveying
RE: Coupling plain bare end tubing for pneumatic conveying
Suggest you limit the pressure to less than 15 psi. Also, specify system responsibility for the supplier of the conveying system. This probably should not be in a piping specification, it is part of an engineered equipment package.
RE: Coupling plain bare end tubing for pneumatic conveying
donf
RE: Coupling plain bare end tubing for pneumatic conveying
RE: Coupling plain bare end tubing for pneumatic conveying
These things are just mechanical versions of wrapping gaffer tape / duck tape around a connection and are about as good in terms of pressure and axial strength.
I had a similar lack of data when trying to find mechanical couplings I could use on fibre glass pipe and just had to give up. The vendors are just not willing to provide data as they don't have enough control over the fitting, the surface preparation, the actual force on the coupling etc etc.
I don't believe there are any standards as they are designed for very low pressures (<15psi), smallish pipe sizes and shouldn't be used for anything where you need axial strength.
For a piping spec I would not use them and either specify screwed joints / couplings or weld it or use screwed couplings.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: Coupling plain bare end tubing for pneumatic conveying
Exactly. A light coating of 'dust' [from soil, dirt] on shiny stainless is amazingly slick. So a Morris cplg on galvanized steel, or squeaky clean stainless, would hold a lot of internal pressure. And on dusty stainless it would fail at a much lower pressure.