Dewar blowing off like a mother

[Splave]

Alright guys some weird ass guy (not the usual) filled my dewar this morning while I waited. He froze the whole top of the damn thing, blow off valves, handles, gauge etc like im talking half an inch of ice rofl. So the whole time one of my blowoff valves is fully blasting the whole drive to work and i figure it still is. Pressure is at 12psi and the blowoff is 10psi so that makes sense. Does this always happen? I usually drop off and pickup the next day so is this normal? The valve stops when I put my finger over it (which I did so it could thaw out a little bit) Temps are high here today too supposed to be 80s so that certainly doesnt help.

[GFDuke]

Pour some hot water on it (the blowoff valve) and tap it with a hammer. Thats what i had to do to my 160's from Airgas. Sounds like there is some ice in it.

[Chuchnit]

He coulda damaged the seal on the vacuum by freezing it. That's what my busted dewar does. It keeps too high of pressure and constantly blows off if I put the head on it.

[Splave]

are you fucking serious!
yeah duke I thawed it out real nice tapped it a couple times and it still blowing off from high pressure. There is a 15psi valve right next to the 10psi one, worse comes to worse could I seal the 10psi side?

Is it possible it always does this when it gets filled? pretty sure he left the top on to do it so I could see how it could build some serious pressure if he fucked up.

[Dentlord]

Mine does something similar to that every time, but only for a few minutes. The whole head is encased in ice after they fill it yeah. All melted off and finished venting by the time I get halfway home (20 minutes)

Like Duke said, sometimes there is ice holding it open and I have to knock it off.

[Splave]

Its sitting in the parking lot of my work lol I will go check it out and see whats going on lol I dont need it exploding on me

[ReverendMaynard]

Its sitting in the parking lot of my work lol I will go check it out and see whats going on lol I dont need it exploding on me

hopefully you don't go out and see your car surrounded by bomb squad lol.

[GFDuke]

Well if its blowing off it wont explode. Its when it dosnt blow off at all you gotta worry. lol

[Neuromancer]

12PSI is awfully low inst the air were you live at 14.7?

(Or are the rated OVER atmosphere?)

[Splave]

must be over atmosphere, and its a 10psi valve says right on it

It was barely hissing when I checked on it so I opened the vent handle for 2 seconds dropped the pressure and it cut off wanted to make sure it wasnt stuck open :) hopefully it doesnt build back up to someting stupid.

[HITandRUN]

Its sitting in the parking lot of my work lol I will go check it out and see whats going on lol I dont need it exploding on me

If its blowing off thats a good thing. Now I would not worry too much since it will take a little more that 15PSI pop the hood on a dewar. I'm sure something is froze on this thing and will be good as you start emptying it. I think this may be a product of too fast filling by the dude.

[Splave]

warm car too so thats not helping the pressure any

[MaadDaawg]

Mine only did that when the Airgas manager filled mine. He filled it through the discharge unit whereas Jose who normally fills it removes the discarge unit and fills it with the dewar open.

The time the manager did it, he left the vent valve open and I closed it about half way home. Don't remember getting all that much product out of it that time either though :(

Whe the guy removes the discharge unit he fills it all the way to the top, and since there is so little room left for air, it generates very little pressure until I start using it. The less it contains, the more pressure it seems to build ?

Hope you got enough when you went to bench Spliggitybro

[Splave]

makes perfect sense maadd thanks for the insight! just so happens the old guy that usually fills it said he usually takes the discharge unit off and this guy obviously did not.

[Buckeye]

On the side of the Dewar there should be a safety blow off valve, looks like a round plug thing sticking out the side. Is this where its coming from ?

If it is it will not hold any LN2 for very long at all

[Splave]

nope this is right where the psi gauge is and it quit once I lugged it upstairs and it cooled off a bit in my apartment. Was hot to the touch sitting in my 90 degree car lol

[Patch]

I always take my transfer device off when filling my 25L. Never had it pop off before.

[Dentlord]

I should start having them fill it without the top as well, I get the feeling I would get a lot more ln2 per fill if I did.

[Buckeye]

Thats how they fill mine. I take off the top and they just drop a hose into it and away it goes.

Like was said before, mine is a low pressure Dewar so when its full I generally have to let it sit over night before I can start getting a good flow of liquid out of it. I have seen a way to pressure the tank tho., but it requires a few fitting and a tank of LN gas to do it.

My 50L has never vented, but the 160L's low pressure Dewars I have had vented a lot. 230L high pressure one vented very little.

[Kal-EL]

You could always go back and stuff the technician into the blow off valve and see if that stops it.

[Patch]

Got a 180L today. Arrived at 150 psi. I drained 25L out of it to fill up one of my dewars so I woudn't get stuck without LN2 unexpectedly. About 7-8 hours later the thing was popping off at 350psi every 5-10 minutes.

The liquid removal port valve was stuck so I couldn't drain it (not frozen at all). I opened the vent valve and the sucker took 1/2 hour to get the pressure down to 0!

After some effort and some assistance from channel locks, I got the liquid valve to open.

Closed the vent and waiting for pressure to build up again.

Makes me nervous to have a damn bomb sitting in my garage popping off at 350psi every few minutes.......it's loud too.

Is this normal? My last 180L rental never popped off. (Of course, it was gone in a few days........was more like an 80 L rental...)

[Kal-EL]

Yikes, I'd be friggin nervous too, especially after seeing what it does to a sealed water bottle

[Neuromancer]

WTF?

I would call and complain. (after you top off another dewar ;))

[V2-V3]

Got a 180L today. Arrived at 150 psi. I drained 25L out of it to fill up one of my dewars so I woudn't get stuck without LN2 unexpectedly. About 7-8 hours later the thing was popping off at 350psi every 5-10 minutes.

The liquid removal port valve was stuck so I couldn't drain it (not frozen at all). I opened the vent valve and the sucker took 1/2 hour to get the pressure down to 0!

After some effort and some assistance from channel locks, I got the liquid valve to open.

Closed the vent and waiting for pressure to build up again.

Makes me nervous to have a damn bomb sitting in my garage popping off at 350psi every few minutes.......it's loud too.

Is this normal? My last 180L rental never popped off. (Of course, it was gone in a few days........was more like an 80 L rental...)


send it back to the supplier and dont pay for it, stress the fact that you requested (ordered) a low presser NL55 22PSI

the high pressure tanks are for gas withdraw only, you are only after the LIquid

the blow off is normal for high pressure tanks, even low pressure tanks will blow off occasionally. no danger here tho

[V2-V3]

Alright guys some weird ass guy (not the usual) filled my dewar this morning while I waited. He froze the whole top of the damn thing, blow off valves, handles, gauge etc like im talking half an inch of ice rofl. So the whole time one of my blowoff valves is fully blasting the whole drive to work and i figure it still is. Pressure is at 12psi and the blowoff is 10psi so that makes sense. Does this always happen? I usually drop off and pickup the next day so is this normal? The valve stops when I put my finger over it (which I did so it could thaw out a little bit) Temps are high here today too supposed to be 80s so that certainly doesnt help.


what is the model of your tank?

[Patch]

send it back to the supplier and dont pay for it, stress the fact that you requested (ordered) a low presser NL55 22PSI

the high pressure tanks are for gas withdraw only, you are only after the LIquid

the blow off is normal for high pressure tanks, even low pressure tanks will blow off occasionally. no danger here tho


Ahh....therein lies the problem.

I go through a mom and pop welding supply (1/3 the price of airgas and praxair in my area). I'm pretty familiar with their yard, and haven't seen any other dewars (unless the 230 L's are lower pressure). They normally have 1 to 4 LN2 tanks around. These high pressure tanks are what they fill my personal dewars with.

The 350psi is where the popoff is supposed to occur - but I got concerned with the rapid rise from 150 to 350 and the frequent loud popoffs in my garage. The last time I rented one of these, it never popped off and it hung out at 250ish psi.

Thank you sir! Methinks I'll have to go back to just bringing my dewars to fill if I can't arrange a lower pressure dewar through them. I'm skeptical about them investing in alternative equipment just to tailor to me.

[V2-V3]

Ahh....therein lies the problem.

I go through a mom and pop welding supply (1/3 the price of airgas and praxair in my area). I'm pretty familiar with their yard, and haven't seen any other dewars (unless the 230 L's are lower pressure). They normally have 1 to 4 LN2 tanks around. These high pressure tanks are what they fill my personal dewars with.

The 350psi is where the popoff is supposed to occur - but I got concerned with the rapid rise from 150 to 350 and the frequent loud popoffs in my garage. The last time I rented one of these, it never popped off and it hung out at 250ish psi.

Thank you sir! Methinks I'll have to go back to just bringing my dewars to fill if I can't arrange a lower pressure dewar through them. I'm skeptical about them investing in alternative equipment just to tailor to me.

all the tanks are the same only the regulator just needs to be dialed down (only time here) and the bleed off needs to be swapped ($15 part)

explain your situation and they should know what to do.

im betting they are getting supplied from AIRGAS any ways, in that case the tank will be swapped out as im sure they rent them :D


when you go with a low pressure tank (22PSI bleed) you will be able to withdraw much more liquid so it is by far a better deal

[DrNip]

send it back to the supplier and dont pay for it, stress the fact that you requested (ordered) a low presser NL55 22PSI

the high pressure tanks are for gas withdraw only, you are only after the LIquid

the blow off is normal for high pressure tanks, even low pressure tanks will blow off occasionally. no danger here tho

:thumbsup:

Great info.

[Kal-EL]

Filled my dewars today and the guy tells me I have the biggest dewar he's ever seen (50L) :Dizzy:

[Splave]

Yikes, I'd be friggin nervous too, especially after seeing what it does to a sealed water bottle

"Who hit the fucking mustang"
:laughing:

Brian@asus Travis and I were messing around with extra ln2 the last night. I put some in water bottle that had the spouted top and shook that bitch and the cap went flying maybe 60 yards and supposedly pinged one of the prize mustangs. Guy with a beard comes over to yell at us. :laughing:

[Buckeye]

He coulda damaged the seal on the vacuum by freezing it. That's what my busted dewar does. It keeps too high of pressure and constantly blows off if I put the head on it.

Yup sounds like what happened.

The blow off valve might be frozen and stuck open. Try what was suggested with hot water and tapping.

Frezening the Dewar like that when filling can also be bad for the vaccum seal of the main part of the Dewar.

I forget what type/size Dewar you have ?

When they fill mine I take off the pressure top and they drop the hose right into it for filling. Can yours do this ?

Gezz just wake up and only see the first post and a few comments after... must have more coffee LOL


tbh guys the big Dewars you get when renting can be total garbage. First 160L I had from Airgas was junk and was popping off all day and night. Granted it was very hot here when I had it tho. It was a low pressure Dewar and very hard to get liquid out of.

Second one I rented was a 230L and in much better shape, no venting. It was a high pressure tank.
It kept pressure at a nice steady state. The was another valve on the top that you could open which allowed pressure to build back up very fast when I was filling my 50L from it.

I don't think I will fill my 50L from these big tanks next time as I waste way to much gas when doing so.

Did they charge you for a filling hose and defuser at the end for the big tanks ?