hi all this may seem a bit dense but i would like something explained to me,i have read over and over again that the srv shouldn't be touched as it's set to a certain release pressure. i have taken apart a srv and replaced the nitrile pip and the cap works.but i can see no means of any adjustment of the pressure release, to me it seems to work on the same principle as an nrv,we have all come across nrv's that are frozen solid and need to be released usually by pouring some paraffin into the pump tube and using the hydraulic pressure to force the nrv loose,bearing this in mind is it not fair to assume that if an nrv can freeze then a srv can do the same? and if so surely it is safer to replace the srv pip than to use the stove with a possible frozen srv ? how do you adjust the pressure release ? is it a matter of stretching the spring? or a different thickness pip ? as for the pressure that is needed in the tank for the cap to "blow" has anyone got a psi figure to work on as i intend to make a cap tester any help gratefully received but could you keep the explanation simple so a fool like me has a chance understanding it as i don't at the moment
Hi Parra. Good questions. I think the main concern is that if you get a stove with, say, a non-sealing pressure relief valve, you might suspect that the valve had done its job, and released fuel pressure as a result of tank over-pressurisation. If the stove to which it was fitted was petrol-fuelled, it is quite likely that such a release would have been accompanied by flames! In most cases the valve will automatically re-close after the tank gets below the pre-set pressure. If the valve is stuck open, it obviously hasn't and needs to be dismantled, repaired and re-set, or simply replaced. Most users do not have the skills or equipment to repair and re-calibrate such a safety-critical piece of kit. It is therefore probably safer to advise them to buy a new cap. The person who has done a lot of work on checking, and calibrating, pressure-relief safety caps is Robert from Vermont. He has not been on CCS for some time but you could check previous posts if you have plenty of time to spare....he is(was) a prolific poster. Best Regards, Kerophile.
Hi George thanks for the reply i will do a few (a lot) of searches on Roberts posts and see what i can find,the bit that got me when i took the cap apart was that there seemed no obvious means of adjustment it was virtually the same as an nrv,and after getting more than my fair share of stuck nrv's i started to worry that the same could be happening to the srv's and if they where stuck then i could be cooking on a potential petrol bomb, i have an idea on making a tester but am not sure how well it would work,i'll run my idea through here and let you all tell me what you think but keep it polite as i'm running away with my self here the idea is to alter a pump cap to accept a tubeless push bike valve that i can rig up to a compressor/tyre inflator this would enable me to pressurise the tank on a 111 to test the nrv as well as the srv,i thought that if i remove the nrv and shut the stove off i can then apply pressure till the cap blows this will test the cap ,then if i replace the nrv i can pressurise the tank to a few psi less than the cap takes to blow,if i then release the pressure from the tyre valve emptying the pump tube of air the nrv will hold the pressure in the tank after 24 hours i can recheck and see if there is any pressure in the pump tube if so i will know that the nrv is not seated/sealing properly,also i thought that if i want to clear a semi blocked burner then i could remove the nrv and jet/cleaning needle and blow air through the tank while heating the burner head up to nearly cherry (i intend using a small aquarium pump and a loop of pipe with holes to water cool the tank so that the soldering won't melt) i want to try it with air instead of heat and quench as i feel that it would be less likely to bugger up a good burner (as i have trashed 2 already ),and after seeing the one in the ref gal that used a stirrup pump it seemed a good way of doing it. comments good or bad welcome
Hi Bill, Someone else might correct me, but I have always assumed the adjustment on the SRV is via how much you compress the spring. E.G. You have the nitrile pip that sits within a carrier. On the carrier is a spring, and then the spring is compressed by screwing the threaded insert into the cap. Therefore how far you screw in the insert determines how compressed the spring is and therefore you have some adjustment. In my own mind I must admit I question exactly how critical this adjustment is though. It would be interesting to see the actual difference in pressures between the limits of adjustment. Given aging of the spring, potential erosion of the spring (the tool hole in the insert in the top of the cap is exposed if used in wet conditions) plus any fat or other foodstuffs that might get split on the cap and "glue" it up (if your cooking's anything like mine), it's my opinion that the exact adjustment is not critical. In support of my opinion I would also point to the claims of stove makers that there stoves have "been up Everest". Typically when we pump up stoves we pump them up to between one and two atmospheres. This will be relative to the outside ambient pressure. Therefore if you climb 18,000ft the ambient pressure is only half an atmosphere compared to one atmosphere at sea level. Therefore a stove tank is likely to run at a higher relative pressure at higher altitudes. Therefore the SRV has to cope with this, and I suspect has far less criticality to the adjustment than might be assumed. Just my opinion, and usual disclaimers apply around trying stuff at your own peril Finally, just on the aquarium pump. As an owner of a few of these (I keep tropical marines) I'd question whether one would really have the grunt for the burner cleaning application. Compared to a stirrup pump they would generate very little pressure. Something like a 12 volt car tyre inflator might be a better choice.
hi bbbb the aquarium pump was only to pump water through a cooling tube with holes in it so the tank remains cold (like a sprinkler) to stop the solder melting i would use a 12v compressor for pressurising the tank,i can't see that it's that critical either but i agree that if you mess with it (srv) you'd better err on the side of caution,and that it's at your own risk
Hi Idiots way to test safety release valve on 111. Fill tank to the brim with paraffin replace cap and pump up stove. Don't put your face anywhere near the cap coz if its OK it will emit paraffin rather rapidly. I'm sure this isn't how it's supposed to be done but it works.
Hi Parra, If you are planning to carry out tank pressurisation tests, may I suggest: 1. Make sure that your Life Insurance premiums are fully paid up. 2. Remember that stove tanks are not approved pressure vessels. If you are intending to pressurise a tank,you should first almost totally fill the tank with water, leaving only a very small air-space. Liquids are essentially non-compressible, unlike gases. Therefore the amount of stored energy in your pressurised tank will be minimised, and should the tank fail you should not suffer shrapnel wounds. 3. A foot pump might be a good idea as they often have a built-in pressure gauge. Work safely, Best Regards, Kerophile.
tanks kerophile sorry i meant thanks i'll bear in mind that the tank isn't a pressure vessel next time i go loopy pumping it by hand ,i'm really glad i asked first before just going for it,i have a stirrup pump with pressure dial on it that i use for my bike so i'll try that out,also i think i will pop down the recycle yard and see if i can pick up some laminated glass and make up a shield to work/hide behind,also i will make sure i fill the tank with water as it will better show if i have a leak or not and if you say it will be safer then i'll take your advice,as for life insurance mine really isn't worth the premium that i would have to pay if i had any
This is a great thread. In the past, any mention of the Safety Release Valve has ended quickly with, "If in doubt, replace the valve cap", because it is too dangerous. However, all of Parra's arguments make sense. How safe are 40+ year old SRVs? Surely we can come up with a safe method of servicing them?
well i am working my way through Roberts (oops56) posts and have found that the caps are usually set to blow at 75-80psi so i am now a bit further forward internal link i will keep looking to see if there is any more info,but if Optimus/Svea have "set" them to that higher pressure the tanks must be safe that high or the caps would release at a lower pressure,things are looking up 8) 75-80psi again oops's pressure jig
i have had a good rummage about and found the tubeless valves that came with my bike but i never used them as i didn't fancy punctures i couldn't fix it's to late to start messing about testing things tonight will post hopefully tomorrow on how i'm getting on edit these are the same type of valves that i had on my racing bike and that ran at 120psi so they should be well up to the job
This would be an interesting one to do a poll on. "Do you repair safety return valves in fuel caps?" I am not sure how do set up a poll but my answer is yes.
excellent topic some comments only. You were already told that the most safe way is to check tank filled with water, it is absolutely right. But in this case the volume is to small and you can jump through real opening pressure Connect second already known tank as an air buffer volume and you will get slight preassure increase good for measurments. two words about opening pressure. there are two points. stove working pressure about 2-4 bar, exceeding it doesnt lead to anything terriable tank disruption pressure 10 bar(for example). What preassure would you set on srv? for me ansfer is clear 6-7 bar, enough to excuse user for a LITLlE bit incorrect usage, and 150% reserv for incorrect srv work at the same time. Parra, valve on your last photo is fuel resistent, with good chance. expulsion of clogged burners with air is a realy good thing. Remove cleaning needles, they tend to burn. And dont do it with clear oxygen as I first time)))
I agree it is something that should be replaced. It was made to be replaced but by a "service/dealer" Good luck finding one of those now. In the case of the phoebus 625 it is easy to get to. If you have a factory repair kit it is an easy to just replace the seal and put it back. No need to touch the spring. Now I see the problem, because we have a lack of spare parts. So you have to make a new seal from a sheet to match the original seal. In the case of the optimus caps we are looking at an oring. see the attachment. Why can't we just replace the oring?... just don't touch the spring for the love of God, haha. I think if these stoves are going to last another 50 years we need to figure this out. Cheers, Jeff
Not much worries me, but after reading Para's thoughts on srv's I am getting that way. Always assumed that my life and those around me was safe in the hands of that pip of rubber and a small spring. Of course not, that valve hasn't moved since the day it was made, and as said, God knows how much crud has gone done the outlet hole. Keep up the research, this problem needs to be resolved
well the idea is sound, i have made up the tester tried two caps neither fettled yet,one went to over 100psi and still didn't blow so it must be frozen, so that one really wasn't safe to be using on a stove, the other got to just below 80psi and started to release pressure so i can assume that one is safe to use,must admit my heart was pounding while pumping.i will post some pics in a little while,the valves are online for £2.93 (very cheap to know that your safe) and it took 5 mins to sort out the tester, best bit is you don't need to modify the stoves pump cap 8)
well here's some pics in the uk you can get the valves here in the us here i cut a gasket out of 2mm nitrile for the valve and pump cap then needed to add a few washers for packing as the valve isn't threaded all the way down next fit the valve and pump cap back on the 111 tank connect pump to valve and set the pressure indicator to 80 psi (the red arrow is easier to see when stood up pumping) pump the tank up to 80psi while the tank is submerged in water so that it's easier to see when the cap blows after a minute or so the bubbles slow down as the pressure starts to drop in the tank now i suppose i ought to try it out cleaning a burner,i'll save that for later though as i have enough excitement for one day
Hi Bill Isn't it funny how people can be thinking about similar things at the same time. I had a very similar idea of fitting a car tyre valve to the pump cap of a 111b. Not to test SRV but as an experiment in making the paraffin technology NRV safe when using naptha. Being only a recreational cyclist I hadn't seen those valves before, a much better solution. Would it be possible to shorten the stem of the valve at all? Just so it would fit inside the 111 case.
