A gas loss non-emergency

[Akimbo]

Agreed. Too many dive shops think that cylinder valves only need to be a little more than hand-tight and LP hoses need to be tightened by leaning hard on a 12" wrench... go figure.

It takes a lot of force to over-torque a cylinder valve — if you define over-torque as stressing the valve body near the point of failure. There is a huge margin between over and under torqued on a cylinder valve. Not that much difference between a LP hose unscrewing under normal handling and stress-cracking the fitting.

---------- Post added May 5th, 2014 at 05:27 PM ----------

Here is a video that will give you a better idea what “little-girl snug” looks like:

How to Assemble Scuba Regulators - [url]www.simplyscuba.com - YouTube[/url]

 

[Hatul]

See postings above... but here's the overview.

Given the orings are the correct specs for the job at hand -- size and harness -- tighten using a torque wrench set at the manufacturer's suggested setting in either inch pounds or milli-Newtons. When in doubt, tighten just enough to make it very hard to loosen the fitting by hand.

I have a torque wrench, but every torque wrench I've seen is made to work with sockets. I've never seen one that works with open spanners, so I don't see how you can use a torque wrench to tighten hoses.

 

[Otter]

Torque Wrench for open ended tools

Not sure about a tool specific for reg hoses ( I just do mine by feel), but in other applications, the open wrench has a square hole in it like this one for the socket wrench to fit into.

 

[Doppler]

Also pretty common if your "tank commander" doesn't mate the cylinder and manifold properly after a VIP...

View attachment 183468

That is a classic, mate!

 

[KeithG]

I have a torque wrench, but every torque wrench I've seen is made to work with sockets. I've never seen one that works with open spanners, so I don't see how you can use a torque wrench to tighten hoses.

Sears.com

 

[Doppler]

I have a torque wrench, but every torque wrench I've seen is made to work with sockets. I've never seen one that works with open spanners, so I don't see how you can use a torque wrench to tighten hoses.

I have a torque wrench that has a fitting for open-ended "spanners." It cost me around $100. Not sure how accurate it is, and frankly the last time I used it on hoses was when I put one of my rebreathers together... I usually do hoses by feel, but you asked for the correct way.

 

[nimoh]

Torque wrenches are calibrated to their specific length. If you change the length, as with adding a crowfoot, there is a simple formula to convert the torque for the new wrench length:

 

[flots am]

I have a torque wrench, but every torque wrench I've seen is made to work with sockets. I've never seen one that works with open spanners, so I don't see how you can use a torque wrench to tighten hoses.

I have one right here on the end of my hand. I tighten LP hoses with one finger on an open end wrench, about 3" from the fitting. It's "just tight enough"

 

[Hatul]

I use a crowfoot on my torque wrench for tightening hoses. It doesn't change the accuracy or precision of your wrench by any measurable amount, but you do have to account for the extra length the crowfoot adds to the wrench using a simple formula. I tighten my hoses to 40 inch pounds, and set my wrench for 36 inch pounds.

Yes these would work, and as you say you have to subtract the distance from the middle of the square hole to the axis of the hose to compensate for the extra length of the lever arm. Do you use metric or SAE wrenches for scuba hoses?

What I've been doing is holding the wrench close to the axis to limit the torque and hand tighten with steady firm pressure until the wrench stops and more. Then I test to see if I can undo the hose by hand.

 

[Akimbo]

…What I've been doing is holding the wrench close to the axis to limit the torque and hand tighten with steady firm pressure until the wrench stops and more. Then I test to see if I can undo the hose by hand.

Are you saying that you can unscrew the hose by hand after tightening with a wrench? IMHO, that is not tight enough unless your fingers are like Vice-Grips. It is probably tight enough to prevent an LP O-ring from extruding or blowing out but not secure enough to prevent the hose from accidently unscrewing a little under normal use. At that point the O-ring can blow out.

It should be noted that the hose is far less likely to unscrew under pressure due to the added torque resistance imparted by the O-ring under pressure. The risk is in handing the hoses, probably setting up your gear before opening the cylinder valve.

The risk of an O-ring extrusion is much greater on the HP hose, though the flow is so restricted it is actually much less of a hazard. The article and chart shows illustrates the relative risk between HP and LP hose failure. However, blowing an LP hose O-ring would “probably” flow slower than a free-flowing second stage.

Life Ending Seconds, 3000 to Zero in 72 Seconds