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Gear talk: O-rings- check ’em!

Many of us will have managed to fit in a few weeks of backpacking this year and some gear might have been having a rough time of it. Beside cleaning, re-proofing and condition checking, think about including an inspection of the O-rings fitted to gas and multi-fuel stoves.

O-ring in Kovea Spider connector
O-ring in Kovea Spider connector

Gas stoves are screwed onto a gas canister valve. An O-ring is incorporated into a groove in the stove’s connector and is compressed when the stove is attached to a gas canister to form a seal and prevent gas escaping from the join. It isn’t often that an O-ring fails and most hikers may never experience it. However they can perish, harden, split or simply be damaged. What is more likely to occur is that they are unseated when the stove is being removed from the canister, then to be potentially dropped and lost. Three Points of the Compass tries to always make a point of checking the O-ring when the stove is unscrewed from a canister, it has not been unusual for me to have to push it back down into its grooved seat. Particular stoves have been more prone to this than others. Some users will put a little silicone grease on the O-ring so that it remains ‘stuck’ to its seat however I do not like to do this as I think it attracts dust and debris, which brings it’s own sealing problems. I recently fitted a new O-ring to my Kovea Spider so took time out to check my other stoves.

O-rings fitted to Jetboil Flash and MRS Windburner. I have had the o-rings work their way out of both of these connectors. A gentle push back and re-seating by screwing a canister on is all that is required. If lost, the stoves could not have been safely used
O-rings fitted in Jetboil Flash and MRS Windburner. I have had the O-rings work their way out of both of these connectors on a couple of occasions. A gentle push back and re-seating by screwing on a canister is all that is required. If the O-ring had been lost, the stove could not have been safely used

A damaged O-ring will not form a good seal and this can manifest itself in an audible continued hiss of escaping gas, with obvious potential for catastrophe. In freezing temperatures O-rings can stiffen and potentially leak fuel. A brief hiss and smell of a little released gas when connecting and disconnecting is normal and to be expected. My Soto Windmaster has two O-rings and gas pressure can build between the two, released with an audible pop when unscrewed/disconnected from the canister, this is normal.

It doesn’t take long to have a quick check of the O-rings fitted to a stove and check for obvious signs of damage. If an O-ring does appear damaged, or possibly the stove is quite old, take the opportunity now to order a replacement. It is a sensible precaution to order a spare or two anyway. Not only do stoves fall out of production and spares become progressively more difficult to source, but a spare can be slipped into a ditty bag ready to replace one damaged or lost while actually on trail. To lose the opportunity to heat water or meals because of the loss of such a simple, small, light, cheap component would-not-be-good!

Two o-rings are fitted to the Soto Windmaster
Two O-rings are fitted to the Soto Windmaster. BS011 and the larger- 20.5mm ID, 24.5mm OD, 2.00mm CS ring
Primus Omnifuel 3289
Primus Omnifuel 3289 has two O-rings. There is one on the pump as well as the connector
Service kit for Primus Omnifuel 3289 includes a single o-ring
Service kit for Primus Omnifuel 3289 includes a single O-ring

Annoyingly, manufacturers are poor in including such basic information as the size and specification of O-rings fitted to their stoves on the packaging, in information leaflets, or even on their website. There is poor reason for the latter not to be easily available. Complicated stoves, such as the multi-fuel offerings, have many components and dedicated service kits are sold for these that will include replacement O-rings. These stoves by their very nature are well-made, intended to cross time-zones and be used in extreme conditions and can last many years. Some components will definitely require changing in the stove’s lifetime. Dedicated service kits can remain on sale for some time after a stove has fallen out of production, but not for ever. Again, it makes sense to buy a service kit that includes small and difficult to source spares now rather than ten or twenty years down the road. MSR supplied the response below regarding third-party parts, however it does not address the problem of stoves being withdrawn and a paucity of spares there-on:

“we do not advertise O-ring sizes because we cannot guarantee the quality or materials used in ‘off the shelf’ parts. Some O-rings found in hardware or auto-parts stores use a different grade of elastomer; some are poorly made and have defects on their sealing surfaces that could allow dangerous fuel leaks; some are mislabeled or beyond their shelf life. Safety is always our number one priority, and an incorrect or low-quality O-ring could compromise the safety of your stove; for this reason all replacement stove parts should be purchased from Cascade Designs or from a qualified dealer of MSR products and parts”

Mountain Safety Research
Replacement O-rings can be located from many outlets. Don't go for the cheapest suspect quality, look for well-made products to the correct specification
If it proves impossible to obtain ‘official’ replacements, O-rings can be sourced from many alternative outlets. Don’t go for the cheapest suspect quality, instead, look for well-made products to the correct specification. Nitrile should be a minimum standard, Viton rings are usually better

O-rings are used in many types of machinery and equipment and are not special ‘back-packing gas stove O-rings’. That said, beside their dimensions, they will be made to a particular specification. Pure rubber becomes brittle with extreme temperature variations, so synthetic rubber is used. Different materials are used for the manufacture of O-rings, such as nitrile, Viton, neoprene and EPDM (ethylene propylene diene monomer). Note that EPDM is not suitable for use with petroleum based fuels so is not used on any multi-fuel or gas stove. Viton (a brand name) rubber O-rings are normally a good choice of replacement but sell at a premium. Standard Viton O-rings do not handle temperatures below -20°C well while standard nitrile O-rings will operate successfully at -35°C.

MSR Pocket Rocket 2. The stove on the left has been used a dozen times, the one on the right more than six hundred. Neither O-ring looks in any way damaged
BRS 3000-T
BRS 3000-T
Fire Maple Hornet
Fire Maple Hornet- FMS-300T

Because the lindal valves on gas canisters are standard, certified to EN 417, O-rings found on many gas stoves are frequently also standard. Most common is the BS011 O-ring though Primus have used the similar but thicker in diameter BS108 O-ring on some of their stoves. My MSR Pocket Rocket 2, Soto Windmaster, Kovea Spider and almost all of very small stoves such as the BRS 3000-T , Fire Maple Hornet and clones are fitted with the same size BS011 O-ring, no doubt there are exceptions amongst the hundreds of other stove models out there. I show the Fire Maple Hornet here but this stove is effectively the same as the Alpkit Kraku, Robens Fire Midge and Olicamp Ion.

Primus Gravity 3279 gas stove
Primus Gravity 3279 gas stove O-ring is thicker than that found on many other stoves

With larger or more complicated stoves, such as the multi-fuel stoves, there are numerous different O-ring requirements so I have only listed the most common sizes here, relevant to my needs. Already mentioned is the Windmaster with two sizes of O-ring. Many Primus stoves also have two sizes of O-ring. Not only that but the dimensions of the pair of O-rings fitted to Primus stoves has changed over the years.

ReferenceInside diameter (ID)Outside diameter (OD)Cross section (CS)
BS 0062.90mm6.46mm1.78mm
BS 1086.02mm11.26mm2.62mm
BS 0117.65mm11.21mm1.78mm
Soto Windmaster- large ring20.5mm24.5mm2.00mm
Picks
Picks

O-rings can be easily removed with a metal or plastic pick but be careful not to damage the ring if intending to replace it. A wood cocktail stick or toothpick may suffice if need be. I use a titanium toothpick dedicated to the job that does just fine. The thick blunt end on the handle end is just right for easing a new O-ring into a connector head, past the threads. There is absolutely no need to pack this along on trail, it is strictly for home stove maintenance. Once a new O-ring is fitted in a connector and pushed down, spin on a gas canister to make sure that it is firmly seated.

Titanium toothpick for removing O-rings from gas stove connectors
Titanium toothpick
It is not just the O-rings in stoves that should periodically be checked. This gasket seal in a propane canister adapter is working loose in it’s seat
Propane gas cylinder adapter. There is no need to replace an unseated seal unless damaged, eased back into place this continues to work perfectly
Propane gas cylinder adapter. There is no need to replace an unseated seal unless damaged. Eased back into place, this gasket continues to work perfectly
Three Points of the Compass contacted Soto directly for replacement o-rings for his Windmaster stove. A package direct from China was promptly dispatched, however it might have been a little large for the contents
Packaging for O-rings for Soto Windmaster. The package sent from Japan containing my replacement O-rings was very generously sized…

Most stove manufacturers and their regional dealers are more than prepared to sell you the appropriate O-rings, or the larger (and more expensive) service kits for their present range of stoves stoves and some more recently discontinued products too. If an O-ring has failed it may be possible to persuade a manufacturer to supply a replacement under warranty. That doesn’t help you brew a pint of tea and heat a meal halfway up a hill in the middle of a storm however. It might be best to check the condition of a stove prior to it failing on a trip.

When Three Points of the Compass contacted Soto directly regarding replacement O-rings for my Soto Windmaster, an email was received the same day from the US distributer, also copying in the international supplys department in Japan. The latter despatched a package to me within hours and I received it two days later in the UK. My set of replacement O-rings, plus a spare set, were sent gratis. This is excellent service.

Reciept for replacement O-rings for Kovea Spider
Replacement O-rings for Kovea Spider- 25 pence each

It is preferable to buy ‘officially approved’ O-rings from the stove manufacturer. There may be a premium to pay for these, but not always. Replacement ‘official’ O-rings for my Kovea Spider were a grand total of 25 pence each, plus postage. Sourcing official replacements ensures you are getting manufacturer specification, in good condition. Others may choose to simply source their spare or replacement O-rings from a secondary supplier. Manufacturers may also cease to provide spares for withdrawn models of stove and alternative suppliers have to be found and used. Particularly old or rarer stoves can prove problematic in obtaining spares for, though thankfully there remain just a few suppliers for small replacement parts, but these will get progressively harder to source.

Using titanium pick to carefully remove O-ring from Kovea Spider connector
Using titanium pick to carefully remove O-ring from Kovea Spider connector
Pushing replacement O-ring past first few threads of connector
Pushing replacement O-ring past first few threads of connector, This is a size BS 011
Gently easing replacement O-ring in to its seat with blunt end of pick
Gently easing replacement O-ring in to it’s seat with blunt end of pick
Check replacement O-ring is seated correctly with no damage, then screw on canister to firmly seat home and ensure a seal is maintained
Check replacement O-ring is seated correctly with no damage, then screw on canister to firmly seat home and ensure a seal is being maintained

Three Points of the Compass includes spare O-rings in the ditty bag carried on trail. The three O-rings taken are two BS011 (one nitrile, one Viton) that will fit almost all small stoves, such as the Kovea Spider, Soto Windmaster, BRS 3000-T, as well as the Fire Maple Hornet when using a heat exchanger pot set-up. Also included is the larger size O-ring for the Soto Windmaster. These three O-rings stay in the ditty bag regardless of what stove is being carried, even if using a meths/alcohol stove on trail. I prefer to leave them there rather than take them out and forget to return them, that way I know they will be there should I require one.

Ditty bag carried by Three Points of the Compass on trail contains replacement O-rings. For simplicity, these remain in here regardless of the stove being carried
Ditty bag carried by Three Points of the Compass on trail contains replacement O-rings. For simplicity and certainty, these remain in here regardless of the stove being carried. Also handy to help out a fellow hiker in dire straits

It doesn’t end with gas stoves. O-rings are found on other items too, fuel bottles and water filters come to mind. Each with their own vital but vulnerable component.

For those people who say that they have never had need to replace an O-ring, have never had one come loose, have never had a problem. I would simply say that my house has never burnt down, but I still have insurance for it.

Writing this blog, Three Points of the Compass was reminded to unearth the old Trangia burner last used almost twenty years ago. This too, contains an O-ring in the lid. Note that there are two sizes of Trangia O-ring
Writing this blog, Three Points of the Compass was reminded to unearth his old Trangia burner, last used almost twenty years ago. Beside requiring a bit of a clean up, this has a 4mm CS x 48mm ID nitrile O-ring in the lid. Note that there are two sizes of Trangia O-ring and the right one has to be installed. The Swedish Army burner has a larger O-ring than the civilian version. The Trangia gas and multi-fuel stoves, needless to say, also have O-rings. All of these are readily available from the manufacturer

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