worm gear hose clamp pressure limitations.

[Tmoose]

Not much luck with Google.
Some of the name brand ones kind of dump it off against hose rating limitations.
In the smaller sizes I've seen signs of very uneven clamping.
I'm sure barv design etc enter into it too.

Before I go searching for MIL specs I figure I'd ask here.

thanks

Dan T

 

[tbuelna]

Good question. Offhand I would agree that since this type of hose clamp is primarily designed for use with internally reinforced rubber hose with modest pressure rating, then clamped connection is likely limited by the pressure rating of the hose.

Here's an MS spec for this type of hose clamp, but it does not give pressure ratings.

 

[BCjohnny]

While not directly answering the question, maybe something like this?

http://www.mikalor.com/eng/supra-heavy-duty-clamp-eng

"It's not always a case of learning more, but often of forgetting less"

 

[MikeHalloran]

Clamps with 'liners' like that to provide a pseudo- continuous inner face are strongly preferred for silicone hose, which is easily cut. Many variations exist.

The nut torque is also typically limited to 50 in-lb or less for the typical 1/4-28 t-bolt thread regardless of clamp size because even a lined clamp is capable of cutting even reinforced hose and/or distorting the underlying tube, given the mechanical advantage provided by the t-bolt thread.

In the marine exhaust trade, similar clamps are used on hot/wet/gas and water lines at pressures that rarely go above 25 psig, but they are always doubled (two adjacent with 1/2" between), and usually tripled for hoses much fatter than your arm.

Presence of a 'hose bead' on the tube is also pretty much mandatory, unless some other means is provided to prevent the hose from oozing off the tube end under pressure.

When you get to ~100 psig, you generally need a hose bead and a full circle crimped ferrule.
... Okay, it used to be common to see R12 systems with hose clamps, but the tubes had multiple barbs or multiple beads, and you had to be careful not to overtorque the clamps. ... and ~nobody does it that way anymore; full crimps and quick-connects are faster and more reliable and less skill-sensitive.







Mike Halloran
Pembroke Pines, FL, USA

 

[tbuelna]

Tmoose-

I dug out an old copy of the SAE Handbook Vol. 2 I have. Attached is the relevant section regarding screw installation torque for various types of worm gear hose clamp. There is no specific pressure rating provided. There is only a comment stating that "adequate sealing capability" should be reached at the installation torques listed. This would seem to indicate the pressure limit is based on the hose capability. As others noted there are other types of hose clamps, such as toggle bolt band clamps, that work better at higher pressures.

Hope that helps.
Terry

 

[Tmoose]

thanks all.

The SAE recommendation NOT to use an impact wrench for tightening was especially helpful in my case.

Dan T

 

[gruntguru]

Wish I'd known that earlier. Wondered where I was going wrong all those years.

Engineering is the art of creating things you need, from things you can get.