Help...My LOX will not stop venting

[FizZle]

Just got my first 180 Dewar delivered today...since it has not stopped venting from the pressure release valve...the pressure is at 300 or so and it will not stop venting...is this normal...will it ever stop venting...is this a problem with the tank? im confused and annoyed that its basically wasting oxy...any help very appreciated...thanks in advance!

[SNYD]

Is there frost on the tank anywhere? Have you turned the economizer down?

This Thread Should Help (http://www.talkglass.com/forum/showthread.php?t=21891&highlight=liquid+oxygen&page=2)

[Mr. Wonka]

-Vent your tank below the safety valve pressure (usually 350 psi, sometimes 250)

-Pour hot water on the leaking valve until it stops leaking

-Also, you can hold a paper towel over the leaking valve while pouring water on it, and the escaping gasses will freeze it closed.

Tom

[hashmasta-kut]

mine is at 200 or so and wont stop venting. there is frost., and i tried to adjust the economizer. funny, i was thinking about posting this today too.

[Emmett's Glass]

It's not gonna stop venting untill it's below 230 lbs or whatever the vent pressure is. Get workin'
E

[hashmasta-kut]

for me i been working it many hours a day, it stays between 200 and 250 and keeps hissing. seems frozen open or sumthin, i dunno. i have had a few tanks, this is the first one to act like this at lower pressures. i vented it to 200 and it made no difference.

[LTD]

pressure building valve stuck?

[jgottlieb]

was the tank venting when it was delivered? its possible that the tank sat around for a while when it was filled so the pressure relief valve is venting, is your tank a 230 psi or a 350? whos your supplier? use the shit out of the tank and if the pressure doesnt go down to the venting pressure marked on the tank after working on it for a full day or or so than most likely you got a shitty tank -happens to me every 3 or 4 liquid tanks.

once the tank has got up to that pressure its hard to get ahead of it to make the venting stop. call your supplier and tell them that your tank is bleeding off and the pressure wont go down at all even after heavy use. if you see alot of frost or ice the next day mention that too. i have had to do this several times and gotten into arguments with the moronic airgas sales reps on the phone. every time tho after enough talking they always send someone out with a fresh tank, and so far every replacement tank has lasted over a month if not 2 and i run a phantom.

its amazing what a pain in the ass these people can be on the phone and as soon as the driver sees the defective tank he always agrees that its airgas's fault for sending a shitty tank. the last one i got had what they call a hot spot where a giant ice chunk appeared on the side of the tank when the driver was moving it- he vented the tank down for like 15mins in my driveway and told me that they have this problem quite a bit and hes sorry and its not fair to me.

as for handling the corporate dicks on the phone try to get ahold of the highest up rep that you can and speak like you know what your are talking about. mention that you know that the tanks have an economizer valve that is adjusted at the plant and that you know they can be set too high. they will most likely accuse you of messing with the pressure builder, which i have never even had to touch. the last time i had to talk to someone he tried to tell me that they dont guarantee the life of the tank even if it vents in a week. the tank i received was venting at under 200 and the venting pressure for the tank was 230psi-def a problem. i mentioned that my tanks always last over a month as long as i use them every day and that it had to be the economizer valve-then he shut the hell up and sent out a fresh tank the next day!

since its the weekend i recommend calling their emergency number and explaining it to the person on call like its a danger to have in your shop, which it can be if there is any fuel source leaking(propane,gas fumes +o2=BOOM) that way they will make it a priority and hopefully give you less bullshit. Good luck, post up how you make out and if you need anymore advice. rage that torch till you get the replacement-free gas is awesome!

[FizZle]

was the tank venting when it was delivered? its possible that the tank sat around for a while when it was filled so the pressure relief valve is venting, is your tank a 230 psi or a 350? whos your supplier? use the shit out of the tank and if the pressure doesnt go down to the venting pressure marked on the tank after working on it for a full day or or so than most likely you got a shitty tank -happens to me every 3 or 4 liquid tanks.

once the tank has got up to that pressure its hard to get ahead of it to make the venting stop. call your supplier and tell them that your tank is bleeding off and the pressure wont go down at all even after heavy use. if you see alot of frost or ice the next day mention that too. i have had to do this several times and gotten into arguments with the moronic airgas sales reps on the phone. every time tho after enough talking they always send someone out with a fresh tank, and so far every replacement tank has lasted over a month if not 2 and i run a phantom.

its amazing what a pain in the ass these people can be on the phone and as soon as the driver sees the defective tank he always agrees that its airgas's fault for sending a shitty tank. the last one i got had what they call a hot spot where a giant ice chunk appeared on the side of the tank when the driver was moving it- he vented the tank down for like 15mins in my driveway and told me that they have this problem quite a bit and hes sorry and its not fair to me.

as for handling the corporate dicks on the phone try to get ahold of the highest up rep that you can and speak like you know what your are talking about. mention that you know that the tanks have an economizer valve that is adjusted at the plant and that you know they can be set too high. they will most likely accuse you of messing with the pressure builder, which i have never even had to touch. the last time i had to talk to someone he tried to tell me that they dont guarantee the life of the tank even if it vents in a week. the tank i received was venting at under 200 and the venting pressure for the tank was 230psi-def a problem. i mentioned that my tanks always last over a month as long as i use them every day and that it had to be the economizer valve-then he shut the hell up and sent out a fresh tank the next day!

since its the weekend i recommend calling their emergency number and explaining it to the person on call like its a danger to have in your shop, which it can be if there is any fuel source leaking(propane,gas fumes +o2=BOOM) that way they will make it a priority and hopefully give you less bullshit. Good luck, post up how you make out and if you need anymore advice. rage that torch till you get the replacement-free gas is awesome!

It was venting when it was delivered...Its 350...and its from Airgas...thanks everyone for your quick replies its very much appreciated :)

[FizZle]

Is there frost on the tank anywhere? Have you turned the economizer down?

This Thread Should Help (http://www.talkglass.com/forum/showthread.php?t=21891&highlight=liquid+oxygen&page=2)

there is some frost buiding...and dunno bout the economizer...the pressure builder is not on...can you inform me please about the economizer? thank you very appreciated

[jes]

What kinda torch are you runn'n? I think making lotsa stuff for hours on end should help bring down that pressure...

I keep track of all the tanks that come through my studio, and have for years!

Its easy, Just have a piece of paper on a clipboard and when you get a new tank write down the date and serial # for the tank then when you get another new one write the date next to the date on the last tank

and another new and the date and s#. I grade each one too, A B C D
Below shows a good tank and bad tank the bad one graded with a d because it only lasted 2 weeks and leave and explanation too, like it leaks or valve leaks or wont build pressure... with these facts you can then give better customer feedback as well as make sure your tank is always accounted for... If you dont write these things down then its really really difficult to know if that tank was a problematic one or the best one... by looking to see if youve had the tank before and what kind of grade it got, you can tell the delivery driver before they take off if the tank has had problems because here it is documented on the clipbord!


didnt mean to be so wordy but I figured out a solution... Directly below is the ultra simple system I use, and like I said add a little foot note if the tank has a specific problem, the store prolly wants to know if their tank aint up to par...

New 7-30-10
S# DL43ut7
Returned 8-17-10 D-F

New 8-17-10
S#GH9523J54
Returned 9-20-10 A

9-20-10 new
S# BF359S1

S# where just random made up numbers for the example.
I have a delta and these good tanks seem to last me a month exactly no matter what I am making....

please let me know if any ? anyone!

[Chris Juedemann]

Does the LOX tank like gladiator movies?

[Dom]

Fizzle and Kut, your tank is not supposed to do that. Call up airgas and tell them you have a tank with a defective pressure relief valve.

They will try to tell you its normal blah blah blah, assure them youve had good tank in the past and would like one now as well.

On my most recent tank, I got the 200lt 500 psi, thing has not vented a singel time, nor has it hissed once, Ive had it for close to 6 weeks now.

[hashmasta-kut]

ya i thought it was fucked up, they are good guys, if i am short a week or two on my regular use-age i'm gonna whine about it and they will give me a deal. my sister got one a couple times when she got shitty tanks.

[Julian]

Call your welding company and tell them they have failed at their alloted duties in life.

Tanks should not be venting when they are new - I've had my sleep interrupted and thus received free 02 for the weekend from this before. Thanks SW Airgas in ABQ!

[Greymatter Glass]

... when you first get them if they are venting from the relief valve it's ok. Vent them to like 20 psi and time how long it takes to regenerate and vent. If it's more than a few minutes you just have a really full tank. If it takes under 5 minutes there might be a problem. under 1 minute and it's deff a bad tank.

See, when that inner tank is full there's very little space for gas to build up. You can't really compress liquid oxygen any further. A small space will build pressure very quickly.

As you use the oxygen you'll create more space for gas (head space) and it will build pressure slower.

If you supplier saturation fills then it will almost always vent within a half hour of being filled. If they fill be weight and leave the proper head space it will be slower.

Venting a new tank is always a good idea if you're not going to use it right away. Drop it down 100 psi or so below the vent pressure (or lower for longer periods).

Also, you may need to thaw the relief valve, they can and often to freeze open. But you'll notice that, because the pressure will still be venting 50-100 psi below the rating. You can also try tapping it lightly with a lighter or something... lightly = just hard enough... start slow.

[n3rd]

bang on that valve once with something metal and it should stop, sounds like it's stuck open, mine do that often.

[Dom]

... when you first get them if they are venting from the relief valve it's ok. .

I completely disagree, this is a telltale sign that you are getting bent over.

A good tank should never vent, perioud. Unless you dont use it for a week or longer.

[Chris Juedemann]

I completely disagree, this is a telltale sign that you are getting bent over.

A good tank should never vent, period. Unless you donut use it for a week or longer.

This is fact. Good tanks don't sound like a jet passing over your house every 15 minutes. Oxy companies know glass folks, and most are slackers, and they try to scam us.

Oh, Godfather, what can I do? What can I do!? SMACK! You can act like a man!

[hashmasta-kut]

bang on that valve once with something metal and it should stop, sounds like it's stuck open, mine do that often.

mines venting from the little thing attached to the gauge, not the actual vent release..

[p.j.]

mines venting from the little thing attached to the gauge, not the actual vent release..

that thing after the gauge is the pressure relief valve

[hashmasta-kut]

but when the last tank vented, it would just vent right out the vent exit, which is a different thing isnt it? i',m not surprised if you are right of course, i just dont understand fully yet.

[Shatner]

pressure building valve stuck?

Probably frozen open, like others have said.

Get a pot of hot water and slowly pour it over the pressurepressure relief valve- Not the "vent" with a knob on it.

The more you work, the less it'll vent. Scared the shit outta me on my first liquid.

Edit: Which way do you turn the economizer screw to slow things down?

[hashmasta-kut]

i believe they say screw it out. i did pretty far. my tank was froze over, but its finally melted off, still a slight hiss, pressure at about 210. last time i was out there chipping ice off, it made it vent way louder and the pressure go up to 250 from 230 so i vented it to 200, but it makes me leery of banging on the pressure relief valve now cuz like i said last time i tapped on itnear the valve, it seemed to be detrimental to the pressure somehow. i guess i gotta risk it tho, wherebaouts to tap? one end the gauge attachement it leaks out of, the other end points down and doesnt leak.

[Shatner]

i believe they say screw it out. i did pretty far. my tank was froze over, but its finally melted off, still a slight hiss, pressure at about 210. last time i was out there chipping ice off, it made it vent way louder and the pressure go up to 250 from 230 so i vented it to 200, but it makes me leery of banging on the pressure relief valve now cuz like i said last time i tapped on itnear the valve, it seemed to be detrimental to the pressure somehow. i guess i gotta risk it tho, wherebaouts to tap? one end the gauge attachement it leaks out of, the other end points down and doesnt leak.

That's what I thought, just wanted to make sure.

Sounds like you got a screwy tank, kut. Tapping on the relief valve usually helps. :shrug:

[hashmasta-kut]

ya i just tapped it a bunch seems no help. i dont wanna hit it too hard.

[Shatner]

Try some hot water. Just pour it on there slowly. That will unstick a stuck vent 99% of the time for me. Can't hurt to try. You can also tap at the same time. Don't hit it too hard, though.

[Greymatter Glass]

So you guys are saying it's a FACT that you can pressurize liquids, a fact that a small space will not build pressure than a larger space, or what?

It is perfectly common (and normal) for a tank that is saturation filled then left sitting on a dock for 10-20 hours before being delivered to be venting by the time it's delivered. I've seen my tank build to 150 psi on the trip from the dock to the shop which is like 5 minutes tops. I have a 500psi vent, so it doesn't vent, but if it were a 350 and I let it sit for an hour I know it would be venting.

There are two ways to fill a tank. By weight and saturation.

To fill by weight they put the tank on a scale and add exactly 450 lbs of oxygen to a 180L tank, that's about 178-179L of liquid oxygen. The tank then has it's built in headspace and it will take many, MANY hours to fill to the blow off pressure... still they often fill them 10-20 hours before they go out for delivery, so by the time you get it it will be venting. Vent off the pressure to at least 100 psi below the vent pressure and wait and see if that doesn't fix the problem. If it's venting 15 minutes later you have a problem... but check and make sure the pressure builder is closed and the economizer screw is backed out to a pressure lower than the vent pressure. Suppliers have been known to turn these screws in on all their tanks to cause them to vent so they can sell more gas. There is no good reason to have the economizer set above the vent pressure marked on the tank.

Saturation filling is where they connect a transfer hose to the liquid port and open the vent port and fill until liquid is spewing out the vent port. You get a few extra liters of liquid this way (varies, about 3-5L more) Since the vent port opens to the top of the head space (internally it extend about 1/2" or so into the head space to keep liquid out of the manifold... but its minimal) they have effectively filled every void in the tank with liquid, and there is very little space for gas to accumulate. It takes maybe 15-20 minutes to build up to 250psi and start venting. And it will keep venting every 5-10 minutes until you use or vent some product. As the tank gets emptier it takes longer for the natural pressure build up to reach the blow-off pressure. Once you've used a few liters it should get better. Again, check the pressure builder and the economizer and make sure the PB is closed and the economizer is backed out to below the vent pressure.


Now there's something to be said about how long and how loud tank vents. Typically a tank that has proper head space shouldn't vent for more than 2 or 3 minutes MAX before it shuts off, and then it will pop off every so often depending on the valve and how it's set. It shouldn't sound like a truck horn (unless it's a 500psi vent, they are loud no matter what) but it SHOULD sound like a very loud hissing sound. Crack the vent valve a turn or two - it should sound about like that. If it's very quiet that means it's not properly seating and is leaking. A light tap might help. If it's frozen then pour a gallon or two of warm (tap hot) water over it and see if that thaws it. If it sounds like a fog horn it's loose and vibrating in a bad way and likely to get stuck open.


As for calling the supplier... yes, if you've diagnosed a bad tank and are certain it's bad, then call them and give them the info you have. Keep notes of good tanks, and use a sharpie marker or scribe to make a small mark on the tank somewhere so you'll know it again if you see it. Don't blatantly deface it. But on the other hand, if you really don't KNOW how these tanks work, and just think you do, and fly off the handle and make accusations and bitch someone out for something that probably isn't even their fault you're not only going to piss off your supplier you're also giving lampworkers in general a bad name.

All that said, I know there are a lot of bad tanks in service out there. The biggest users of them are steel scrappers, and they can go through a tank a day, so they don't care and often wont say anything if a tank is venting, they're gonna use it all long before they lose much to venting. Letting your supplier know when there's a problem can help them somewhat, but chances are they're not going to fix the tank or replace it or take it out of service, they'll just give it to a scrapper. The best way to get better tanks is to be civil with them. Go over and bring the plant manager a case of cheap beer, introduce yourself, let them know what you're doing, and that it's important you get decent tanks. The plant managers know which are good and which are crap. The desk guys probably don't. Then TIP YOUR DRIVER. These dudes have good paying jobs with benefits usually, but no one bitches about beer money or whatever. They have a CDL so they don't (shouldn't) smoke, but they're always happy to get marbles for their kids, or a paper weight, or a goblet or something. Let them know you've got their back and they will get yours. Before I owned my own tank I would get crap ones, then I started tipping the driver and not only would I get better tanks, but i would be first on his route, and sometimes even get same-day deliveries if a driver had the time. Worth the $10 a tank or so.

Anyways.... slow day at work, but that's all I got.

-Doug

[FizZle]

Thanks for all the information Doug...my situation is still the same...i have been using the tank 8 hrs a day for the last 2 days...it still blows off no more than 15 min after its been shut off...the pressure builder is off...tried tapping...just makes it hiss more...tried water...doesnt do anything but get water everywere and continues to hiss...i have a 350..at what pressure will it start to vent off at...and how long should it vent...after last nights work session it vented all night...and was still venting in the morning...worked all day today and it stopped hissing after bout 4 hrs of work...no more than 10 min after it was turned off it was hissing again and is still hissing...WTF is this normal never seen a tank like this and i have been around a bunch of diff tanks...

[Chris Juedemann]

Thanks for all the information Doug...my situation is still the same...i have been using the tank 8 hrs a day for the last 2 days...it still blows off no more than 15 min after its been shut off...the pressure builder is off...tried tapping...just makes it hiss more...tried water...doesnt do anything but get water everywere and continues to hiss...i have a 350..at what pressure will it start to vent off at...and how long should it vent...after last nights work session it vented all night...and was still venting in the morning...worked all day today and it stopped hissing after bout 4 hrs of work...no more than 10 min after it was turned off it was hissing again and is still hissing...WTF is this normal never seen a tank like this and i have been around a bunch of diff tanks...

It's the oxy suppliers deal. Call them and say "this shit is venting way too much, I am not paying for it, come replace it". Or am I missing something?

[FizZle]

My oxy nazis are Airgas...and they are closed till Monday...Here is a shitty video of what its doing...this is kinda lighter than it has been hissing but its been as steady if not worse for 48 hrs now...again thanks you everyone for your input...it is very much appreciated...

http://i480.photobucket.com/albums/rr166/EuphonicArts/th_0925102132a.jpg (http://s480.photobucket.com/albums/rr166/EuphonicArts/?action=view&current=0925102132a.mp4)

[jes]

IS THE TANK in newer condition or is it looking like its been through alot?

I would mark the tank with sharpy if I wasnt going to keep a list of bad tanks serial numbers.

I would copy its serial # on a list in your studio along with the problem and put a tag or note attached upon returning the tank saying (bad tank) for the air company to see and know. (good customer feedback)

On monday 15 minutes after they open go in and explain the situation, they can come look at it to verify its condition if explaining it isnt good enough to get satisfactory results. Just keep cool and hopefully they will treat you cool too, that has been my experience with Northern Airgas and am still with them...

everybody prolly has different advice, hearing from everyone can help, hope I have helped too...

:- j

PS
I keep a list of every tank good or bad, its one of the easiest thing in the world to do. just write the serial # and grade it A-F and the date... it takes literally a couple minutes and can help save $, time and frustration and more $ too...

much
peace

[Chris Juedemann]

IS THE TANK in newer condition or is it looking like its been through alot?

There is a video of it being whacked.

[Greymatter Glass]

Thanks for all the information Doug...my situation is still the same...i have been using the tank 8 hrs a day for the last 2 days...it still blows off no more than 15 min after its been shut off...the pressure builder is off...tried tapping...just makes it hiss more...tried water...doesnt do anything but get water everywere and continues to hiss...i have a 350..at what pressure will it start to vent off at...and how long should it vent...after last nights work session it vented all night...and was still venting in the morning...worked all day today and it stopped hissing after bout 4 hrs of work...no more than 10 min after it was turned off it was hissing again and is still hissing...WTF is this normal never seen a tank like this and i have been around a bunch of diff tanks...


It's really starting to sound like you got a bunk tank, and I would call Airgas and explain it to them and see if they want to take a look first and if they will replace the tank or give you a credit on it and let you use it all up. They can't easily transfer the liquid back to their bulk tank, so if they're cool they will let you use what you can and credit you for the next tank. Even venting you should be able to get a few days use off it. I've been in that situation and a venting tank lasted almost a week.

Likely a bad relief valve than a bad vacuum on the tank.... it doesn't sound all that loud in the video. A proper vent will be much louder than a normal TV volume or talking voice, that sounds much quieter.

A couple more questions/answers:

What kind of torch(es) are you using (I'll re-read to see if you say... but humor me). When I ran a small torch (Nortel minor, then a midrange) my tanks would be venting pretty much constantly even running a torch for 8-10 hours a day. I could never seem to catch up with the natural evaporation rate of the tank... it doesn't mean you have a bad tank, just that you aren't (can't) using it fast enough.

What does the tank pressure gauge read? have you tried venting it down to 125 psi and see if it stops venting for at least a couple hours? If you get it down to 100 psi and it's still venting it's a bad valve and it's an easy fix. If it stops venting but the vents again 15 minutes later the vacuum on the tank is failed, and should be taken out of service.

Are there any ice spots on the wall of the tank? not on the top or along the bottom, but like anywhere else?

A 350 pressure relief valve should vent right around 350 +/- 5 psi. They will usually blow off no more than 10psi then shut off.


... as for the life span of a fill....liquid oxygen IS perishable, it's use it or lose it. With a small torch and not letting it vent often you can get 30-45 days on a good tank.

If you don't use it, you're still gonna get about 30 days out of it before it vents empty. The higher the pressure the faster it will evaporate also. Pressure = friction = heat = evaporation. So using it and keeping it lower is actually better in some cases than letting it sit...probably...I haven't done the math tho, so I don't know if it's just theoretical or actually a practical matter.

With heavy use you can drain a 180L in a day. A shop full of Cobras and Vipers will last hours, not days.


Anyways, when you call Airgas be honest in your experience level, let them guide you. They're not going to lie to you, but they might try to make you eat it. Ask them "what would you do in my situation?" that question often gets more things done faster than anything else I've used.

As a new customer don't be surprised if they blow you off a little, but do invite their plant manager to come by and check out your set up and check the tank on site if that would help them determine what's up.

Ultimately, if it IS a bad tank you're really not responsible for the whole thing. 9 times out of 10 they will credit or replace the tank. Sometimes they will credit you back like half the tank, it's all up to them. Whatever they decide if the tank is in a safe location and not venting too loud (bothering neighbors, keeping you up at night, etc.) see if you can keep that tank till it's empty and use what you can out of it. Worst case you use as much as you can of what you're paying for. best case, free oxygen!

Make sure whatever space it's venting into is ventilated. Even a couple percent increase in oxygen saturation can lower the combustion temps of some things to a dangerously low level. Ideally you would use a proper sized vinyl or tygon tube and a hose clamp to vent the pressure relief outside through a wall or something.

... if the tank is in an enclosed space you should get it outside or into a well ventilated space pronto!

anyways... use what you can!

Good luck

-Doug

[FizZle]

I am running a Phanom myself...and my brother is running a lynx...there is no other frost than on the top...the pressure reads somewere round 310 or so...just a lil past 300...we ran the pressure down to 180 or so yesterday and it wasnt venting for atleast 1/2 hr...but it was venting again in the morning...not venting very loud but it is in my garage which contains 2 cars and my studio...which is an attached garage to my house...for now i have the ventilation running for my studio...so hope that will be enough to keep it from building up to much oxy...thanks again

[Greymatter Glass]

...hrm... it MIGHT be ok then....

Hard to say really. If it stops venting while you work and the tank is below 300 psi then you're probably ok. Liquid tanks DO vent if you don't use it fast enough.

I would keep an eye on it. Call monday and talk to them, see what they say.

When you say it wasn't venting for at least a half hour...how long before you noticed it was venting? building from 180 to 350 over night isn't a big deal... especially if the tank is still fairly full.

At this point I wouldn't worry too much, keep an eye one it.... if it will stop venting the chances are you've just got a really full tank and aren't able to use it fast enough to outpace the natural evaporation rate. vent it down to 125psi or so with the vent valve right before you start working. If it starts venting withn an hour or two of workinf you're probably owed a new tank. If it doesn't vent as long as you're working you're fine... I like Jes's idea.. I'd rate the tank a C.

As you get more experience with these tanks you'll learn to spot bad ones. For now, inform Airgas that you MIGHT have a bad tank. If it's empty by the end of the week it was deff a bad tank.

[Dom]

.. building from 180 to 350 over night isn't a big deal... especially if the tank is still fairly full.
.

I gotta disagree again D. I have never gotten a GOOD tank that did this. Going up from 180 to 350 in two or three days WITHOUT working might be normal. But not in one day while you are working..

However bad tanks always did stuff like that. Alot of times the guy would pull up with the truck and I could hear the tank hissing already, then each time he wrestled the tank around the pressure valve would open, I dont even bother checking what is what, I just tell the guy straight up this tank is fucked up and I want a new one that is not venting tomorrow morning.

[Greymatter Glass]

*shrug*

A lot depends on how your economizer is set. If it's backed ALL the way out then yeah, it may take longer. It SHOULD be set high enough to provide working pressure and low enough to not vent. On a 350 relief I'd set it about 150 psi. Back it all the way out and yeah, it may take longer to build, but the natural rate may not be enough to provide flow to the torch. Too high and you're wasting gas.

it's also possible that the pressure builder valve is freezing up and leaking a little, as commonly happens with the liquid fill port.

venting the tank to as low as possible and letting it warm up is always a good way to diagnose a bad tank.

A venting tank, especially one that's just been filled, is not ALWAYS a bad tank. Refusing them based on that alone just runs up overhead for suppliers which they in turn pass on to the consumers as higher prices.

[Julian]

I've never seen a good tank start venting within 3 days of being delivered.

Doug, do you use SW Airgas? Their tanks were, in my experience, shit from Hell. That might explain your experiences. Or, weather makes a big difference too- it;s going to vent a lot sooner sitting in the sun for 6 hours in Albq. at 95 degrees vs. a shady 65 degree garage up here in Nordic Paradise.

[Greymatter Glass]

I'm not saying all tanks will vent right off the bat, I'm just saying that a tank that vents on the first day or two (or even when it's delivered) is not by default a "bad" tank.

There are so many factors involved that there's a very good chance a venting tank is perfectly fine.

The biggest factors being saturation filling vs. filling by weight, economizer settings, how long it sat on the dock before being delivered, and how much you use in a given day, especially the day it's delivered.

Anyways, for what it's worth, I haven't heard my tank vent in almost 3 years. We get it filled (saturated) then start using it within about 15 minutes max of it being filled. I own a tank, so I am not victim of Airgas's bad tanks, but I did see about 30 new oxygen dewers in their yard last time I was there, looks like they upgraded this year finally (they do so about every 10 years). Still, if I were to fill my tank (saturated) and let it sit unused for several hours I have no doubt it would start to vent (at 500psi). There's just no space for gas to build up and it will rise very quickly.

[FizZle]

thanks everyone...your post have been very informative...and much appreciated...the tank vented all night...already put 1.5 hrs in on it today and its still venting...i feel this tank is way bonk and its pretty annoying so im gonna try and and use as much as possible and tell airgas monday i would plz like a replacement cause this one has been venting like know ones business since it was delivered...shouldnt it stop venting itself after its relieved some pressure atleast for a little bit...its just constant...never stops

[Riley]

whenever i get these tanks i call after the first day, run it as hard as possible, and get another delivered free in the subsequent days. you really end up getting more bang for the buck, but no one likes leaky dewar. burn it

[hashmasta-kut]

mine started at low pressure when i got it, about 125, slowly rose to 2 something, and then now it hovers at 205 and hisses constantly. i tried all the tips mentioned. i worked it 6-8 hours a day, making tube pulls and using lots of oxy. i just noticed that the handle to open the pressure gauge section was turned to closed is this proper, or should that be opened to engage it? these tanks confound me, i wish i knew how the fuck they actually work, what all these things on top are for. the pressure builder is labeled, and i tried to adjust the screw out too, i dunno. looks like i'll be asking for half a tank credit or something.

[jes]

here is an old post that helps to show how one works, thanks to whoever found it!


http://www.talkglass.com/forum/showthread.php?p=510161#post510161




Whoa, IF this is Julian from up in D-minnesota area or Nordic wonderland, WOW, where and how have ya been, you where a great glassblowing role-model for me and have true awesome talents... I could not have progressed into the future the way I have without your generosity and positive guidance!

[Greymatter Glass]

THANK YOU JES!



Page 24: Troubleshooting

Problem: The cylinder builds excessive pressure or builds pressure too fast.

Problem cause 1: Low Usage
Solution 1: If daily gas usage is under 100 SCF (2.8NM3), the cylinder will build pressure. In liquid service, the cylinder should be equipped with low pressure relief valve and regulator. Normal pressure rise should not be more than 50 psi (3.4 BAR) per day.

problem cause 2: Cylinder is over filled
Solution 2: If the cylinder is filled past the vent turncock or past the DOT specified fill weight, the pressure may rise rapidly after a fill.

Problem cause 3: Pressure building regulator is set improperly or leaks
Solution 3: If the pressure builds and stays at a pressure higher than desired, adjust the pressure building regulator to a new setting.

Problem cause 4:Vacuum is deteriorating.
Solution 4:This can be accompanied by cold or frost occurring evenly over the cylinder surface. Refer to the troubleshooting section on frost.



If it's a freshly filled tank that is over filled, as is often the practice, it will vent until there is headspace sufficient to allow unsaturated liquid to expand at the normal rate. This is not the sign of a bad tank is is in actuality a win in your favor. You're getting as much as an extra 10-15% more liquid FOR FREE. Use it for a few days then vent the tank to 100psi or so and it should stop venting non-stop.

A bad tank, i.e. one with a blown vacuum, will vent non-stop until empty, but more importantly it will become an ice ball. If your tank doesn't frost over the entire surface then the tank is fine. At WORST you have a bad pressure relief device. that alone is reason to complain and demand a credit, but the tank itself is fine.

[Greymatter Glass]

mine started at low pressure when i got it, about 125, slowly rose to 2 something, and then now it hovers at 205 and hisses constantly. i tried all the tips mentioned. i worked it 6-8 hours a day, making tube pulls and using lots of oxy. i just noticed that the handle to open the pressure gauge section was turned to closed is this proper, or should that be opened to engage it? these tanks confound me, i wish i knew how the fuck they actually work, what all these things on top are for. the pressure builder is labeled, and i tried to adjust the screw out too, i dunno. looks like i'll be asking for half a tank credit or something.


What's the pressure rating of you tank? If it's a 250 then I'm not super surprised it vents at just over 200... PRD's aren't perfect, it's just a ball, a plate, and a spring. And they're usually cheaply made for as important as they are. But they're easy to replace, even in service. If you own the tank get a new valve, if it's the gas suppliers let them know it needs to be replaced.

You want the pressure builder valve closed unless you need more pressure. The economizer will keep things up as long as your draw isn't too high.

Depending on your tank even a delta or other medium-large torch running 6-8 hours a day may not keep it from venting. With all 6 torches running in my shop we barely lower the tank pressure in a day of heavy use.

[hashmasta-kut]

its frosting on the top, but just in the central area, not the whole top.

im not sure the rating, but its the same type of tank as they usually bring i think, its the first one to vent at around 200, continually. i havent had this issue before, it seems the float gauge is visibly going down over the week.

i'll make sure to let them know its wack , and note the number so if it comes back to me and does the same thing, i'll get it returned right away.

[Dom]

The rating is on the pressure relief valve itself next to the gauge that tells you the pressure. Its either 230, 350, or 500.

It should only vent at those pressure +/- 5 psi I would say.

So if its stuck open all the time and you cant get it closed by pouring warm water and tapping on it with a small screwdriver, then there is a problem with it.

[FizZle]

Called the Airgas Emergency weekend contact and explained the situation...said that it was not normal...and assured me that a new working tank would be delivered tomorrow morning...sooooo looks like i get to rage some free oxy for the rest of the night...sweet!

[Greymatter Glass]

right on. Sounds like it was probably a bad relief valve...if anything.

I would say if you complain too often you'll make enemies at the local AirGas. Get to know your plant manager and stay on his good side, he'll take care of you and make sure you get tanks that can last a few weeks (when/if they have one)... beer is usually a good bribe around here. My plant manager has kids too, so I made them marbles with their names in them - that was a HUGE hit.

hashmasta... The PRD manufacturers set the pop-off pressure at the factory, but some can be tampered with if someone is dumb enough to try it. Usually there is a sticker/band on the valve that gives the pressure. Common pressures are 22, 230, 350, 400, and 500, but if a customer spec'd a 200 then they would get one and have it end up in rotation... so just check it. Not likely. They're usually rated to re-set at 95% of their rated pressure, so a 230 would reset at abouf 207psi. A little tapping may re-seat the valve inside,... it might not. I have seen tapping make the valve get worse...

When in doubt vent out the tank to under 100psi and see if that stops it, and how quick it rebuilds (with the pressure builder off, and economizer reg backed off all the way)

According to the user manual for Cyl-Tec tanks it's about 50psi/24 hours. that's an ideal rate for a very high quality new tank.... if it's more than double that I would suspect some serious problem with the vacuum or some kind of leak in the PB/Econ system - that's not something we can determine, they would have to test it.

[Greymatter Glass]

Oh, and the liquid level gauge is a horrible way to measure anything. Mine will say it's full until it's down to about 20% then drop to E in the course of a day or two. They can be re-adjusted, but that's not your job... I usually tilt mine to check weight.

I'd really like a 1000# scale I can put it on and set the tare weight +10 and when it tips the scale i know I only have 10# of liquid left and to plan to get it refilled the next day or two.

[FizZle]

yeah wasnt rude or anything...just explained the situation and they said the would make it right before i even got to request a new tank...the plant assistant manager himself loaded up the new tank and delivered it...he tested the tank here and said it had a bad PB valve...the guys down at the local airgas are always good to me...def wouldnt complain for no reason...but that tank was bonk...the new one he brought has not vented 1 time and the pressure only rose around 80 in over 24hrs...

[hashmasta-kut]

When in doubt vent out the tank to under 100psi and see if that stops it, and how quick it rebuilds (with the pressure builder off, and economizer reg backed off all the way)

According to the user manual for Cyl-Tec tanks it's about 50psi/24 hours. that's an ideal rate for a very high quality new tank.... if it's more than double that I would suspect some serious problem with the vacuum or some kind of leak in the PB/Econ system - that's not something we can determine, they would have to test it.

i noticed on two tanks both had the handle for the pressure builder turned off, but one tank seemed to work well the other is the dud one, i dont understand why they were both shut off, should they be open?

[p.j.]

i noticed on two tanks both had the handle for the pressure builder turned off, but one tank seemed to work well the other is the dud one, i dont understand why they were both shut off, should they be open?

i just open the pressure builder for about 30 min the first time i use the tank and then shut it off, and never have to open it again, it builds the pressure each nite

[Dom]

Yup you only need to open the pressure builder valve if you want it to build pressure.

[Greymatter Glass]

i noticed on two tanks both had the handle for the pressure builder turned off, but one tank seemed to work well the other is the dud one, i dont understand why they were both shut off, should they be open?

Other than when you FIRST get a fresh tank to build up working pressure there's no reason the PB valve should be open (unless you have a good reason, of which there are only a few, and you would know them if you needed to)

But the PB valve is only half the story. The economizer regulator is the other half.

The Econ reg acts as a low-flow bypass to the pressure builder knob. If the screw is all the way in it will build more pressure than the tank can handle. If it's all the way out (i.e. off) then the tank will only build what it can naturally.

There are some economizers that are set below the vent pressure when they're turned in all the way and others that will set up to 600 psi and cause more problems than they're really worth. You can check the part number on yours to find out what style you have.

Learn to set it properly and you'll have less problems with venting.

[hashmasta-kut]

cool. i dropped teh pressure to 150 or so and the leaky valve is much quieter, but wont shut up still. its only good to about 125.

[Dom]

Ive had that alot Kut, one time I got a new tank and didnt use it for 2 or 3 days, and it was sitting at 40 psi the whole time, I though oh yea got me a nice tank this time...

Not, it turned out that the pressure relief was just leaking and you could not hear it below 50 psi, but as soon as it would build pressure it just bled it out.

So I asked nicely for a new tank.

If you could get to know your driver and maybe tip him if its customary there. They are the ones who pick out which tank is going where usually and they load them up.

[hashmasta-kut]

my driver likes me big time, so its no problem there. if he knew it was a shit tank im sure he woulda not brought it unless he had no choice. i should see him any day now, n' tell him bout da bad valve. he left the last liquid tank so i could finish it off, and said dont mention it to the shop so they wouldnt charge me extra tank rental, and he will come and grab it.

[hashmasta-kut]

whoopee, back to this thread :(

lol, my tank before last referenced in this thread i got a half credit for, the next tank was stable, and now i got a new tank with new problems :D i am not sure what the pressure builder is on this one it looks different than most pics but i think i am having a problem with it. tank history, is when i got it it was hissing, so i cracked the vent, it was at 250, then it dropped to 200 really quick, and stopped leaking. then i had a bit of pressure release valve sticking, hot water fixed it, or a tap. now, this morning after 3 days of use, its reading 260, and it seems no matter how much i vent it it just stays at 260. other days, a bit of use would bring it down to 200. no way to shut down the pressure relief leak when the tank is at 260. ran it hard on the oxy for an hour, opened the vent for like a minute super loud, and the gauge wont move :(

it seems somehow, pressure builder has stuck on? cuz when i got it the first day, cracking the vent dropped it to 200 no prob, now doing the same thing wont budge the needle at all...

[p.j.]

run your kobuki full blast for an hour see what happens. venting it shouldn't bring the pressure down that much unless you are venting it full bore for a while. can you snap a pic? maybe one of us can tell you where the economizer screw is

[hashmasta-kut]

it was pretty full blast, i made a small tube pull of starwhite then english ivy then clear, raging oxy the whole time, and three ringing it quite a bit. on a positive note, the pressure relief valve somehow seems to be holding lately, even at pressure 260 :)

i think cracking my tank vent wide open for a minute must be equal to running a torch full blast for a pretty long time. it sure is crazy loud. usually it will bring the pressure down very fast, first time i seen it where that wouldnt lower the reading. tapped teh gauge too.

[Dom]

Got yourself a bad tank there kutman. Call em up and get straightened out.

[hashmasta-kut]

they are good guys. last time i had a tank last only 3 weeks, they gave me half a tank credit. this one seems to be behaving now actually :)

[FizZle]

lol kut...im glad i started this thread for you...is that two credited tanks for u now kut...lol since i bitched about my first two tanks...and always explain that i dont want a bonk tank when ordering...i havnt (knock on wood) got a shitty tank since...

[jane clifton]

whenever i get these tanks i call after the first day, run it as hard as possible, and get another delivered free in the subsequent days. you really end up getting more bang for the buck, but no one likes leaky dewar. burn it

Had it happen to me once. I did the same thing, used the hell out of it and it was empty in a week. Called Airgas and told them I wanted another and got an extra week of oxygen for free!!! Worked great!