Northwest Dive Club

Waynne Fowler wrote:You dove the tank and your SPG worked ON THAT TANK on the dive right?
You get out shut off your air, turn it back on and it reads zero.
hubby hooks up his reg's and the SPG reads zero.

you put your regs on another tank and it reads appropriately
hubby puts his regs on same tank and it reads appropriately

back to original tank and both reg's read zero.

Is that right?
------------------------------------------------

If it is...
Sorry but I'll bet you a beer the tanks empty. I drink Root beer BTW!!

An obstruction of the HP port will not typically impede the LP side of the reg.

your cobra can IIRC be set to have a higher threshold than 200 psi... I could be mistaken. It's been a long time since I owned one.

but let us know what you find out Cera... this is most interesting.

If this is the case, answer a question for me. How did the tank go from 2930 psi to 0-200 psi during a surface interval between dives without anybody noticing? A small leak that's barely audible would take a very long time to drain a tank--more than your typical 1-2 hr surface interval. Anything substancial like a free flow, larger leak of some kind, or simply cranking the tank open to drain it would be obviously noticeable to those around. Any thoughts on how that much air escaped from a tank between dives without anybody noticing? It just seems all the theories posted so far don't take into consideration all of the facts outlined by Cera. She has indicated quite positively that she ended her dive with 2930 psi as noted on her computer. Just curious....thoughts?

Yes Wayne. Correct. We even opened the tank valve and let it run for over 30 seconds and it was still giving air. Turned it off, turned it back on, still giving air. Under 200 psi would not have given air that long. As soon as I get the tank I will hook an analog gague up to it, but I don't have it right now, someone else hauled it home for us... however, we can assume since it wasn't even pressurizing the line for the computer, that it will read 0 as well. (I will confim this ASAP) I am also going to hook an analog gauge up to the LP ports ASAP. I really posted this to see if it had ever happened to anyone else.

What type of first stage do you have?

here's a crazy off the wall scenario, maybe there was junk in the valve, when you turned it off the junk settled and blocked the hole enough to only let <200 psi through the tank valve...though I figured at some point it would build up to the full amount you didn't give it enough time to do so Out of excitement.

just an idea, Doubt its true from technical stand point.

enchantmentdivi wrote: If this is the case, answer a question for me. How did the tank go from 2930 psi to 0-200 psi during a surface interval between dives without anybody noticing?

A few possibilities:
Gauge was misread.
Gauge malfunctioned (electronic) possibly reset between uses and now working.
Tank was mistaken for one visually identical.

airsix wrote:

enchantmentdivi wrote: If this is the case, answer a question for me. How did the tank go from 2930 psi to 0-200 psi during a surface interval between dives without anybody noticing?

A few possibilities:
Gauge was misread.
Gauge malfunctioned (electronic) possibly reset between uses and now working.
Tank was mistaken for one visually identical.

It's pretty hard to misread a blinking 0..0..0
Especially twice, with two seperate computers.
I had the tank in my hand the whole time when it wasn't on my gear (I didn't remove any gear after first dive)... so... I don't think I'm that stupid. lol
When you look at all the facts it has to be the tank valve.

You may have a obstruction in the HP port on the valve that is letting just enough gas though to allow the LP side to work somewhat. sounds odd but I have seen similar on tanks that had foam peanuts inside that did not get all the why cleaned out from shipping or heavy corrosion. I also had a valve that I had to replace as it was not machined enough or they put too much chrome on it so that when you screwed in the DIN on your regulator the clearance to the back of the valve was so tight that barley any gas gets buy. You could breath on it but it took for ever for the SPG to charge up.

If you have checked the regs and they are good it has to be the valve. that is the only other thing in the system.

Cera wrote:

airsix wrote:

enchantmentdivi wrote: If this is the case, answer a question for me. How did the tank go from 2930 psi to 0-200 psi during a surface interval between dives without anybody noticing?

A few possibilities:
Gauge was misread.
Gauge malfunctioned (electronic) possibly reset between uses and now working.
Tank was mistaken for one visually identical.

It's pretty hard to misread a blinking 0..0..0
Especially twice, with two seperate computers.
I had the tank in my hand the whole time when it wasn't on my gear (I didn't remove any gear after first dive)... so... I don't think I'm that stupid. lol
When you look at all the facts it has to be the tank valve.

I meant it was possible it was misread at the end of the dive or was giving you a bad reading at the end of the dive. I believe that it is now reporting/being read correctly (i.e., the tank is almost empty). I hope I'm not coming across as argumentative, I just like puzzles. This is a logic puzzle and I feel 99% of the possible explanations can be eliminated with some deductive reasoning. Wayne's post sums it up. The gauges show pressure on another tank, but don't on your tank. Opening the valve allows gas to escape from your tank. Therefore, it stands to reason that the pressure reported is to be believed. You can breath off your regulator and operate your inflators, therefore the valve is functioning and the regulator is being pressurized to equilibrium with the internal pressure of the tank. The only logical conclusion is that tank pressure is high enough to operate the regulators/inflators but too low to report a pressure on the SPG. Regardless of end-of-dive pressure readings you can't explain around your more recent observations.

I don't buy the HP port blockage for a second. If the port was blocked in the regulator it would not function on the other tank. If the valve was malfunctioning it would not release gas when operated without an attached regulator. If it was a valve/regulator interface problem there wouldn't be enough flow to breath off of and yet still not pressurize the SPG. Those theories just don't add up for me.

This discussion reminds me of that scene from Sling Blade where the guys are trying to start a lawn mower. They check the plug and the magneto and the air cleaner, but just can't seem to find the problem... The slow guy walks up and asks if there's any gas in the tank. I think Billy Bob had it right. There's no gas in your tank.

enchantmentdivi wrote:

Waynne Fowler wrote:You dove the tank and your SPG worked ON THAT TANK on the dive right?
You get out shut off your air, turn it back on and it reads zero.
hubby hooks up his reg's and the SPG reads zero.

you put your regs on another tank and it reads appropriately
hubby puts his regs on same tank and it reads appropriately

back to original tank and both reg's read zero.

Is that right?
------------------------------------------------

If it is...
Sorry but I'll bet you a beer the tanks empty. I drink Root beer BTW!!

An obstruction of the HP port will not typically impede the LP side of the reg.

your cobra can IIRC be set to have a higher threshold than 200 psi... I could be mistaken. It's been a long time since I owned one.

but let us know what you find out Cera... this is most interesting.

If this is the case, answer a question for me. How did the tank go from 2930 psi to 0-200 psi during a surface interval between dives without anybody noticing? A small leak that's barely audible would take a very long time to drain a tank--more than your typical 1-2 hr surface interval. Anything substancial like a free flow, larger leak of some kind, or simply cranking the tank open to drain it would be obviously noticeable to those around. Any thoughts on how that much air escaped from a tank between dives without anybody noticing? It just seems all the theories posted so far don't take into consideration all of the facts outlined by Cera. She has indicated quite positively that she ended her dive with 2930 psi as noted on her computer. Just curious....thoughts?

nope I got nuthin for that... however I read in the OP it was 2500... 2500/2930 who cares it's still odd and I'm really all the more curious with each post. I can't even phatom a way two regs get clogged, and both of them blow it out before being put on another tank only to have both clog again dbl checking the original tank AND THEN both regs blow the chunk out when checked at the diveship?????? too many WTF's?.
could it happen... statistically I'm gonna guess yes... but I think I'd have better odd's of tripping with a coffee can full of old metal parts in my hands and having a Rolex put itself together in the drop... LOL...

I hope Cera post what she find's out though cuz I'm scratchin my head over here and it's starting to hurt a bit.

If you started your dive at 3500 psi and spent 20 minutes at 40 feet, assuming a RMV of 0.7 you would have used 32.2 cubic feet of air and your tank pressure should have been around 2300 PSI. I don't know your air consumption rate but 0.7 cu ft/minute is usually what I use for my own gas planning and I have seen people use more that twice that. By itsself it doesn't mean much but as Ben said it does bring up the question of wether you you either misremembered your air pressure or you gauge was reading incorrectly at the end of the first dive.

Ok even if my usage was at .7 it would still be 2300 or 1300 or 500psi left, it should still read.. Mine is around .4.
If we agree to state that there IS air in the tank, there in lies the problem. (Can we just continue with an argument from this stand point please?) I just hooked up an analog gauge and it didn't even register. HOWEVER, air still comes out of the LP ports... and I can turn the tank on (STILL) and get air coming out.
You can't tell me that it was at an unreadable pressure on saturday, then I have hooked up 2 regs, let the tank air run(without regs on), hooked up another reg set, let the tank run more AND it's still giving me air that the tank was empty.
I wish I could post a video so you could believe me, but really, there is air in the tank...

I downloaded my computer, it said there was 2930 when I turned the air off at the end of the first dive.

Leave it regs on there for an hour and then try reading it.

Mattleycrue76 wrote:If you started your dive at 3500 psi and spent 20 minutes at 40 feet, assuming a RMV of 0.7 you would have used 32.2 cubic feet of air and your tank pressure should have been around 2300 PSI.

.7 is pretty high for most women, in my limited experience. PPants' RMV is probably half that, for example. i'm also willing to bet that Lynne clocks in about the same.

and i do believe bdub has girly lungs, too.

Air leak during SI

I swear to god, I am going to pistol whip the next person......... :angry:

So if I understand correctly, you've tested the tank in question with three different gauges and they all read zero? Either all three gauges are reading incorrectly or there is no (hardly any) air in the tank no?

Mattleycrue76 wrote:So if I understand correctly, you've tested the tank in question with three different gauges and they all read zero? Either all three gauges are reading incorrectly or there is no (hardly any) air in the tank no?

Yes, correct three gagues, where the HP hose does not receive pressure, but the LP ports do. And after every test I open the tank and there is still air coming out of the the tank AND the second stage. EVERYTIME. I can go open the tank right now and air just keeps coming out.

I guess it isn't obvious, but if I thought the tank were empty, I would not have posted this. If I had not checked the tank, MANY times to see if it were empty, I would not have posted this. Is it really so difficult to believe that a valve could fail?

and putting the same reg on a different tank the pressure is as expected.

its like you have a possessed valve only delivering LP gas...

Cera,

You are getting these replies from some very knowledgable folks, because it is indeed somewhat hard to understand how the valve would fail so that the three separate pressure gauges would read zero (not 100psi, not 150psi, not 200psi - all of which would still deliver gas via a 2nd stage) especially after it seems it was reading correctly during the dive. You asked, they have answered trying to help you out. no need to get upset with them.

the other possibility is that your pressure sensor was wonky and the tank was not as full as you thought it was during the dive. Did you have a freeflow at the end of the dive whilst getting out of the water or anything like that? what kind of tank is it (size)

when you open a tank valve, even if there is only just a few hundred psi in it, it will "seem" like it has gas in it. cracking the valve open to see how full it is, is not always a good indicator.

have you taken the tank in to get it filled at a dive shop and watched to see when they hook it up and fill it what happens? That would be a somewhat definitive answer.

valves are basically "on" and "off". the mechanics just are not there for it to identify between the high pressure and low pressure side of your 1st stage which is what it sounds like you are asking to a degree. if there was something blocking flow on the valve side, if you waited long enough, it would end up showing 'actual pressure', like dashrynn said, leave it for some time with an analog gauge on there and see if it creeps up.

air will keep coming 'out' of the tank for a while if you are just opening it a little and also as you warm the tank up by bringing it indoors considering the weather we've had as of late you can get a few hundred PSI from that alone. I've drained tanks before in the cold garage at night, only to have them still have gas in them when they 'warmed up' the next day, not a lot mind you, but enough that i would finish draining them before taking their valve off to do a VIP.

at this point take it to a shop and let them hook hook up an analog gauge and see what it says, then let them hook one of their fill whips up to it and see how 'empty' it was when they start filling it.

another really quick way to tell if its 'full' or 'empty' is to gently tap it on the floor or whap it with the palm of your hand. Full tanks will have a higher pitched 'bing bing bing' and empty tanks will be lower sounding 'bong bong bong' this works if you are comparing two tanks of the same type. other tanks will sound different so not a good indicator if you are comparing say a LP steel to HP Steel to an AL80

I'll pay for you to get the valve serviced, just to prevent any else from asking if the tank is empty.

I bet that there is an obstruction at or in the valve that is limiting the pressure coming out of the tank. Air is coming out, but perhaps not at sufficient pressure to read on a gauge.

I highly recommend a viz of the tank - I have a hunch it's not all happy in there. And a valve teardown is certainly in order.

My guess is that the tank was empty.

Your tank valve is being haunted by Betty Lou. She hated HP ports and never moved on past the J-valve. If you recorded the sound it makes when you crack the valve, tune the pitch lower and slow it down to 50% of real-time, you'd hear her dreadful warning... "Pfffffft!!" <shutter>

Damn you Koos!


Your valve could also be infected with a Scuba Transmitted Disease... which the unsuspecting first stages only learn about after they've become infected themselves. It's a shame the 1st stages are inserted into so many random valves. Try Valvtrex, and always encourage your valve to avoid random first-stage contact when experiencing an inflammation or break out.


...or your tank is near-empty.

I will guess.. Bad dive puter... Bad Bad puter... Transmittor no workie.. Now bring me fried rice and egg flower soup