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What O-ring is this?

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Gary Wooding12/11/2021 11:19:49
968 forum posts
253 photos

My ancient Sievert blow torch gave me a fright today - it burst into flames as I was using it. I was able to blow them out and I wasn't burned, but it was rather scary. The flames originated around the valve, so I dismantled the handle and reckon I need a new o-ring. I've got a box of o-rings, but none of them fit.

Does anybody know which one I need? The photos show the torch handle and valve with the o-ring separated. Sorry about the focus, I blame it on my phone.

Sievert o-ring.jpg

Sievert torch handle.jpg

J Hancock12/11/2021 11:51:02
832 forum posts

Looks like the 'gas' has swollen the O -Ring , whatever size you choose , do make sure it is compatible for

use with the gas you are using.

Jouke van der Veen12/11/2021 11:59:27
171 forum posts
17 photos

It seems to be a “square”-ring, not an “o”-ring.

Why this shape is applied, I do not know.

Does this ring constantly see gas, also when you do not use the equipment?

Gary Wooding12/11/2021 12:14:41
968 forum posts
253 photos

It's actually rather difficult to see, but it looks like the ring only sees the gas when the valve is open.

Jeff Dayman12/11/2021 12:31:16
2223 forum posts
47 photos

I'd ask a Sievert dealer first about a replacement, but if they don't have them, o-ring suppliers will. If it is actually intended as a square section o-ring, they are available, see link below.

However it may have started out as a normal round section ring and has just compression set to the square groove shape, In that case, I suggest going to an o-ring firm or industrial supply, and test fit a few to get a good fit. If that isn't possible you can buy an assortment of o-rings quite cheap from Ama Zone or E you know and find one. If you get one rated for hydrocarbon / oil service it will be OK with gas. Depending on how hot it gets in the torch, you may want a high heat one. Good luck.

Michael Gilligan12/11/2021 12:50:45
20097 forum posts
1042 photos

Probably worth grabbing this catalogue whilst it is still available: **LINK**

Several O-rings identified therein.


Oldiron12/11/2021 12:59:47
963 forum posts
40 photos

Sievert probably still stock spares for that gun Gary.

Are we banned from saying AMAZON & EBAY. ???????

As far as I recall we are allowed to mention these two huge companies in this forum. Why do ppl faff around when it is easier to type the actual name than think of a pseudonim ?


Gary Wooding12/11/2021 16:34:11
968 forum posts
253 photos

Neither eBay nor Amazon helped much, and TheOringStore are outrageously expensive - it's cheaper to replace the torch. A semi-retired guy at Rothemberger (Sievert) thinks he may have one in a dusty drawer somewhere. He'll let me know next week. Maybe I'll get lucky.

Les Jones 112/11/2021 17:47:18
2255 forum posts
156 photos

As you have not given any dimensions of your O ring I estimate from your picture that it is about 6mm ID and about 2mm cross section.
If this is a correct estimate then this is one possible source.



Phil H112/11/2021 18:11:23
458 forum posts
60 photos


I am really interested in the answer because I think I have the same or at least a similar torch. Does yours have the economiser trigger? Mine too is ancient but is still an excellent torch. I haven't used mine since the mid 1980s and even then it was ancient.

Phil H

bernard towers12/11/2021 20:37:02
574 forum posts
109 photos

Bearing companies, hydraulic companies and pneumatic companies all use ‘o’ rings drop into one with your torch you’ll be surprised how helpful people can be when you are actually in front of them.

Gary Wooding13/11/2021 07:39:12
968 forum posts
253 photos


It actually measures 6.2x2.5, do you suppose a 6x2 would do the job?

Nicholas Farr13/11/2021 08:21:13
3317 forum posts
1530 photos

Hi Gary, looks like it is an imperial size of 1/4" x 3/32" and by the looks of the age of your torch is very likely. LPG will leak out of the smallest gaps it can find, so I would try and find one that is much closer to the one you want to replace.

Regards Nick.

Les Jones 113/11/2021 09:17:52
2255 forum posts
156 photos

This is one source from ebay. (But you will probably find more as I only spent a few minutes searching.)


Nitrile seems to be a good choice for propane or butane.


Circlip13/11/2021 10:54:47
1500 forum posts

Not forced to be a "Standard". Only place to get o-rings for carb on my bike was from carb spares supplier. Similar problem with the one the water governor on boiler.

Regards Ian.

Edited By Circlip on 13/11/2021 10:55:23

Gary Wooding13/11/2021 11:31:30
968 forum posts
253 photos

Thanks Les,

The link you supplied looks promising, I'll give it a try.

Brian Morehen14/11/2021 12:31:01
189 forum posts
11 photos

Morning Garry , Took my Torch to pieces this morning am certain that this is round at the top mine is quite visible , The next question is this a Metric Size or Imperial Size as both are available.

Regards Bee.m

Gary Wooding14/11/2021 13:39:45
968 forum posts
253 photos

Hi Brian,

Nick's observations that my measured dimensions (6.2mm x 2.4mm) are very close to 1/4"x3/32" (6.35mmx2.38mm), and I couldn't find any metric sizes that were closer leads me to think they are Imperial. That's what I'm going for.

Gary Wooding28/11/2021 14:31:08
968 forum posts
253 photos

I opted for the 1/4"x3/32" size (had to buy 5) but it turned out to be a mite too big - the valve actually went in, but was far too tight. I probable something closer to 1/4"x1/16" will be OK.

duncan webster28/11/2021 16:41:27
3928 forum posts
61 photos


Edited By duncan webster on 28/11/2021 16:42:04

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