What do you feel about using Teflon tape on Gas Cutting Equipments?

I am not sure--Some materials will seal without foreign material like teflon introduced--steel is hard and porous and will not seal by engaging the threads alone and requires teflon--Brass is soft and will seal with some pressure and teflon will hinder the joint from sealing or at least, is unnecessary.

There are two potential problems with Teflon tape:

(1) It cuts easily on the threads and can allow a leakage path;

(2) Small pieces can dislodge and migrate to places you really don't want them.

There is a "better" type of Teflon tape - it's yellow rather than white - for natural gas service.

The teflon is there to act as a dry lubricant for the threads, I understood, enabling you to get the best effect from tightening the connection. The tape does not seal, that job is done by the mating surfaces. Any tape around these is a bad idea in my opinion. But others will disagree I am sure.

A quick question. Do the joints in question get hot or are they away from the heat? I have kinda assumed they are cool, but if they do get hot there is a possibility of Teflon giving off toxins. Just one possibility to think about.

-Doug

The reason you should not use Teflon tape at the fittings of your gas torch is they are designed for a metal to metal seal and the teflon just makes a mess and can go places where it should not go, also if the fittings are improperly tightened they could come loose later on or strip threads if over tightened due to the low friction effect.

NPT threads are OK for Teflon tape or better still use the correct grade of Loctite.

I agree. Don't do it. The problem with leaking oxy-acetalene systems is that the fittings get over-tightened and this causes the threads to roll, so they don't seal. The connections should be snugged with a wrench, about 1/4 turn beyond hand tightened. Also, bleeding down the system is very important to ensure that, should you have a leak, gases don't accumulate and create a potentially fatal situation. We use quick connect fittings and this keeps the threaded fittings from undergoing constant wear and premature failure, it also saves an incredible amout of time in assembly. Non-sparking wrenches are a good idea but they are not necessary because the system shouldn't be charged until it's assembled unless there are other considerations.

The Teflon don't has significant resilience neither elasticity (in constant movements it will not perform); it has nearly pure plastic properties (if it's subjected to a defromation it doesn't return to original shape), it's permeable. So, it seems that it can't be a good sealant. I think that normally Teflon tape is not pure ptfe so, the charges and impurities can be dangerous in contact with Oxigen.

'Teflon Tape' is used for preventing the leakage arising out irregularities of threading. The irregularities could be mocroporosity and gaps between the crust & valley of mating threads.

It is observed that at times the 'Teflon Tape' can not adequately plug the irregularities mentioned above. Further, while working on a LPG related project, I learnt that threaded joints actually cut through the 'Teflon Tape' , due to the sharpness of threads and also due to improper wrapping of 'Teflon Tape' over the threads.Once the tape is cut, it can not prevent leakage. Hence , many experts discourage or even disallow the usage of 'Teflon Tape' while working with threaded joints.However , quite a few experts / institutes allow the usage of 'Teflon Tape' , although with a condition on the minimum thickness that is acceptable for use with threaded joints.As such the views on the usage of Teflon Tape for threaded joints is divided.

Referring to any research institute (eg,LPRI, Bangalore) , India working on LPG handling methods could be useful.

As regards for effectively preventing leaks from taking place , you may consider other options as well.

Anaerobic Compounds, preferably having a thinner viscosity for enhancing a better flow to ensure plugging of microporosity and even filling up of tiny voids, gaps between crust & valley of mating threads are also used for such applications.

Teflon filled 'Anaerobic Compounds' are available, and also recommended by many research institutes, consultants etc for use on threaded joints. You may access www.pidilite.com, www.loctite.com etc for more more information on these products.

Anaerobics cure to a film when confined between two metals in absence of oxygen,and may not deliver desired result due to process parameters beyond the conditions required for producing an effective seal.

In such a situation other sealant such as Silicon or PU based sealant may be worth trying.

Process temperature should also be considerd before selecting the correct sealant.

Well guys.

Does anyone have any incident or past experience whereby it leaks when using teflon on gas cutting equipments and that resulted in fire or explosion?

It'll be really great if I can have some of those case studies or info sharing so that I can actually use them to educate the workforce.

There is no place for use of teflon tape on the actual gas cutting torch so the problem should never arise. You are in more danger of a flashback due to incorrect operation of the cutting torch, also it would be highly unlikely for low pressure oxygen to start a fire on teflon tape. The exception being oil or grease contaminated tape used on the high pressure oxygen regulator fittings. Clean tape is not a problem and is a recommended method of sealing regulator taper thread fittings, though I prefer anaerobic sealant. Teflon is often used in the internal mechanisms of regulators for seals and seats without any problems.

I have seen a high pressure oxygen ball valve with teflon seats burn itself out due to oil contamination and heat build up during the operation of cracking the valve so cleanliness is paramount in the assembly of this equipment.

Some people think teflon tape will cure all leaks and use it indiscriminately any place there is a threaded part I have seen it wrapped around the high pressure cylinder valve fitting where it is useless and dangerous.

My motto is if you do not understand high pressure gasses and the fittings used with them leave well alone

Do you have any concerns about using steel pipe on oxygen pipework? We've always used copper for oxygen as it it won't burn in the presence of oxygen. Mind you, you have to have the fire first for the steel to be a problem but it doesn't take much for stuff to fire up in pure oxygen, hence the efforts to keep little bits of teflon out of the pipe work. It won't burn but who knows what mischief it might get up to in company!

Nutwood, I never had a problem using steel pipe with oxygen. The systems I built were temporary distribution systems in industrial construction jobs. It wasn't one of the "pure" systems such as in hospitals. I would think that copper pipe put together with silver soldier would work fine though. I did run some oxygen pipe in 304 stainless once because the project manager was afraid that the rust and scale in the carbon steel pipe would cause a problem with the torches getting stopped up. This was not a problem in my opinion and a complete waste of money but I still did it the way the boss wanted it.

pipewelder

Interesting. I see your point about the temporary nature of the installs. I'd imagine that the pipe sizing would be quite adequate in that sort of application, where you're looking as much at strength and robustness, as flow. Probably your boss should have been worrying more about high speed particles as a safety item rather than torch blockers. The scenario is that if you have a restriction, where the velocity can increase, fast travelling particles can become ignition sources, once you have an ignition source, any tiny protrusion on the steel pipe can light up and away you go. Still, I'd imagine in your industry, you'd be very aware of what burning steel does when you add oxygen.

The other one to watch for is copper pipe on acetylene. The two react. very nasty! My recommendation for a reticulated system, in a factory or similar, is copper on the oxygen and steel for the acetylene. That changed on the last job to stainless for the acetylene. Steel pipe's getting expensive!

I don't have a strong dislike for teflon tape, as long as it's oil free. It's a good product, used correctly but then I've seen some pretty good messes created with the various other thread sealants. The type that come in tubes.