Empty Tanks???

[Pavao]

I have never used lube on the tank valves, and I never have any problem getting them off the next year. Easy as pie.

I think it has to do with what you wrote earlier, about proper installation.

My belief is that if a dab of lube were applied in the threads and this retailer did nothing different, there would be no problem removing those valves.

Or they could apply a different technique installing the valves.

Anyway, every time I encounter cylinders from them, it is impossible to remove the valves, has happened several times.

 

[Tracy]

They don't need to be lubed. I have never lubed valve threads and I service many hundreds of them every year.

 

[Tracy]

I think it has to do with what you wrote earlier, about proper installation.

My belief is that if a dab of lube were applied in the threads and this retailer did nothing different, there would be no problem removing those valves.

Or they could apply a different technique installing the valves.

Anyway, every time I encounter cylinders from them, it is impossible to remove the valves, has happened several times.

Sounds like an installation issue, not a lube issue.
Many people see the torque information and misundertsand it.
Minimum torque required for seal and not to exceed 100 ft pounds.
I see a lot of shops read that as, I need to torque this to 100 foot pounds.
Hand tight and a slight push with a wrench to make sure it doesn't spin free when empty is all it takes.

 

[Still Kicking]

The idea of the lube is to provide a barrier between the dissimilar metals of the valve and the tank threads. It's only an issue in the extremely unlikely event that water gets inside the tank but I have come across seized threads due to galvanic corrosion.

 

[Tanks A Lot]

Sounds like an installation issue, not a lube issue.
....
Hand tight and a slight push with a wrench to make sure it doesn't spin free when empty is all it takes.

I'm so with you on this!

Unfortunately the agencies that set forth these standards still publish very high torque values. Especially for parallel threads I just can't see the point.

If you take BS EN ISO 13341-2010 + A1 2015 as an example:

Steel:

Thread	Minimum Torque (Nm)	Maximum Torque (Nm)
17E	120	150
25E	200	300
M18	100	130
M25	100	130

Aluminium:

Thread	Minimum Torque (Nm)	Maximum Torque (Nm)
17E	75	95 (140 with neck ring)
25E	95	110 (180 with neck ring)
M18	85	100
M25	95	130

These values are insanely high, but a technician working according to standards should abide by them. It is one of those things where I deviate from the standards in my work and do so deliberately.

Lube on valve threads is a terrible idea. All that you achieve by putting lube on threads is trapping moisture between the valve threads and the cylinder threads. Granted, that moisture has to find it's way inside first, but if it does, a lubed thread is where it quite often does the most damage.
Often dive centres get complacent, make a late filter change, or the compressor operator sleeps and doesn't drain the cyclone separators, or whatever they achieve this time to get their cylinders wet (Dive centres seem to be very adapt and inventive at finding new ways to do this!). They got some cylinders moist, but pretty quickly get them dry again after filling properly and getting on track with filters / compressor service. With lube in place, moisture often has no way to drain back out of the thread area. It effectively traps moisture at this point.
Telltale signs are pits in the thread area of the cylinder. Often this leads to the failure of the cylinder. Catalina for example would like you to throw the cylinder out, if the corrosion hits two threads. Even if those two threads are below the 9th thread...

Rejection Criteria:
Corrosion is unacceptable if:
• it interrupts the required minimum number of complete threads, or
• it interrupts two complete threads, or
• it causes loss of contents of the cylinder.
An eddy current thread inspection device can detect corrosion in the threads of a cylinder.

Incidentally, BS EN ISO 13341-2010 + A1 2015, got the part about lube correct in my opinion:

6.2 No lubricant, sealant or tape shall be applied to the threads.

 

[Tracy]

I'm so with you on this!

Unfortunately the agencies that set forth these standards still publish very high torque values. Especially for parallel threads I just can't see the point.

I have noted ISO cylinder list a min torque spec. Most DOT cylinders specify "minimum torque required for seal not to exceed XX."
So there is no minimum, whatever seats the Oring is acceptable.

 

[OMyMyOHellYes]

I have noted ISO cylinder list a min torque spec. Most DOT cylinders specify "minimum torque required for seal not to exceed XX."
So there is no minimum, whatever seats the Oring is acceptable.

That'd pretty much be hand tightened to where you can't turn the valve any more.

 

[Pavao]

Sounds like an installation issue, not a lube issue.
Many people see the torque information and misundertsand it.
Minimum torque required for seal and not to exceed 100 ft pounds.
I see a lot of shops read that as, I need to torque this to 100 foot pounds.
Hand tight and a slight push with a wrench to make sure it doesn't spin free when empty is all it takes.

Right, see third paragraph I wrote from the post you quoted me.

 

[Caversluis]

Put it on a scale and check the weight. The weight of the empty cylinder should be embossed on the cylinder itself. A full cylinder is heavier; as an example, a 230 bar 10 liter cylinder will weigh 2,9 kg more.

 

[iointerrupt]

The Thermo Valve Service Manual lists the "Valve Into Cylinder" torque as 50 ft/lb/68 Nm. Which seems pretty reasonable.

My quick skim of it doesn't show any official mention of lubricating the valve thread.