Refilling Oxygen Cylinders

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Gbro

Forum Lieutenant
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I will start,
Our service has refilled the D size cylinders from 2 M size cylinders. This is done by cascadeing, (series of consecutive cylinders) labeled as 1st(CYL 1) and 2nd. (CYL 2)
The cylinder to be refilled(CYL 3) is attached to the 1st M size cyl(CYL 1), and the valve is very slowly opened on the CYL 1 to get a gauge reading from that cyl. then the valve is closed. (the pressure should hold steady. If so, then the D cylinder(cyl. 3) valve is slowly opened and the gauge is monitored. if the pressure decreases, Cyl 3 pressure is less therefore we will charge cyl. 3 with Cyl 1. This process "MUST" be done at a very slow rate. A high rate of refill will create heat, and this could very well result in a rupture of the Thermal relive valve (lead reinforced copper blowout disc).
When the both cylinder pressures are balanced, both valves are closed. The pressure in the connection fittings is released, and cyl 3 is then ready to be placed back into service if the pressure is 2000psi or more, or is then connected to cyl 2 (M size) and again cyl. 2 valve is slowly opened, then closed, holding the pressure (if pressure drops in tis stage, the connection between the cylinders need to be addresses(seal condition, tightness, index pin alignment, etc). Cyl 3 valve is slowly opened, and the gauge is checked for pressure (lower means cyl 3 need, pressure rises, Cyl 3 is already higher than cyl 2, pressure stays same(cyl 2 & 3 are equal).
The refilled cylinder must be assessed for heat, as a cyl may take several minuets to stabilize after filling(heat), If done properly, the cylinder temp, should rise very much. Any cylinder that heats to a point where its to hot to handle is improperly filled, and could be a danger to anyone or anything in close proximity.
This happened year ago with our Fire Department. A "D" cylinder was refilled(to fast) and put into the spare rack. aprox. 5 min after it was filled the thermal relive plug ruptured and the cylinder left the rack and spun around the fire hall, with about 10 firefighters dodging out of the way. It was a terrible racket and it hit the tires on several vehicles, but nobody was injured.
Upon inspection of the spare cylinders one more was found with lead protruding about 1/8 th inch out of the plugs release holes. (that cylinder was filled to fast before also).

Many services have discontinued this refill practice and elect to have a vendor service preform this need for them.
 

Ridryder911

EMS Guru
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Don't mess with gasses. Only on the bird did I use the cascade service. I'll leave this open to Vent for possible further discussion.

R/r 911
 

Flight-LP

Forum Deputy Chief
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Bad idea, let the gas companies mess with refilling O2. Without proper training, it is a disaster waiting to happen........................
 

VentMedic

Forum Chief
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I haven't refilled my own oxygen tanks in EMS since around 1988. It can be very dangerous in the wrong hands with little quality control.

Hospitals may still have large O2 cascade tank banks to pressurize the system.

HBO centers may have air and some O2 cascade systems for pressure maintenance. This may depend on the center's location and zoning. Alternative commercial systems may be required and highly recommended.

Fire departments may also keep their own Air cascade systems for SCBA refill .

Dive shops do air and some do NITROX (approx 33% O2 with Nitrogen) mixing This also can be dangerous as noted with the dive shop explosions with a few deaths noted from those accidents.
 

JPINFV

Gadfly
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4 tank cascading system for the portable tanks [hook up tank to be refilled and open. Open tank one till pressure is equal, close tank, rinse, wash, repeat till tank 4. Close both tanks and open relief valve to drain pressure. Close drain valve and disconect tank]. Main unit tank refilled professionally. Quality control was definately lacking and it was common to see people over tighten tanks on purpose (i.e. use O2 wrench to get leverage on the screw used to tighten the regulator to the tank. Also seen people use a non-O2 wrench with slots slightly too large for the valve and seriously tweak the valve to the point that O2 wrenches wouldn't fit anymore. Of course the company saw nothing wrong with those tanks half the time).

Probably the scariest part was when I witnessed a crew almost hook up a medical air (yellow tank) instead of an oxygen tank. They said that it was "close enough to not matter" (the dedicated children's hospital units have a medical air system. 99% of the time there aren't any yellow tanks in the bay anyways).
 
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JPINFV

Gadfly
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JPINFV,

Is this the ambulance service or hospital that is utilizing the cascade system?

Yes. :sad:

To clarify about the med air tank. They weren't refilling it, but putting it in their ambulance for use.
 

piranah

Forum Captain
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well at my ambulance service we use the 4 tank refilling for the portable but for the large in-house tanks we just replace the whole tank....
 

mikie

Forum Lurker
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well at my ambulance service we use the 4 tank refilling for the portable but for the large in-house tanks we just replace the whole tank....

Same. I'm on an FD and for our ambulance, we use the cascade and once the big tanks are empty/too low, I believe they're replaced either by us or a company. And for the ambulance O2, we would just replace the entire tank.

I've only used it once. I kinda forgot to close the valve on tank 1 when switching to tank 2...thus equalizing the two tanks. It wasn't an issue (except a mistake on my part, which I have learned from!) with the dept, as the tanks were low as is. However, our cascade system for the SCBAs is similar, but if you equalize the tanks, it's not a big deal because it's just the air we breathe (...filtered though) and can be easily refilled.

But I do agree with many poster's above in saying it's dangerous. Gas=pressure. Too much pressure=bad=it go boom! :ph34r:
 

KEVD18

Forum Deputy Chief
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worked at two ambulance services that used cascades. one three tank plus the empty system and one two tank plus the empty. neither company has ever had one single accident. ive also seen it done opening the m tank valves very quickly without a problem on a regular basis.

you can even fill the main 02 tanks in the truck off the cascade. you dont get much in em but when you work for the cheapest private on the planet, sometimes you struggle to meet par requirments.
 

eggshen

Forum Lieutenant
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BITD used a cascade system in the privates. We also had a drunk midget that was the mechanic for the ambulances.....got on scene one time and found out the banging noise under the hood was a cordless drill. I have about a weeks worth of stories like that. So there you have it. Cascade bad, never did feel right about that bit.

Egg

p.s.
KEV, I'll box you any day over the cheapest private on the planet.
 
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Ops Paramedic

Forum Captain
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The good old cascade systems, those tings make my hair stand up. I am not to fond of them, but some services still use them out this side.

It was best mentioned by some else who said to leave it to the proffesionals (Then again, i have been to a few calls where the so called proffesionals blow it up!!), at least it won't be me.

At our service (PVT), we get our cylinders already filled from the gas company. We mainly use two sizes. The first one is a relitavely new type, constructed from aluminum and carbon fibre. Its capacity is 0,94kg (Portable), double that of the old type, but the same size and half the weight. The big advantage is that these cylinders are provided with built in regulator in a fairly rugged casing, so it breaks for what ever reason, the gas company picks up the tab...

The second size is what we refer as our mainlines. It has a 1.84kg capacity, but we have to supply the regulator. There is a medium size inbetween these two, which we call a "Slim Jim", and also has the regulator built in.
 

Jon

Administrator
Community Leader
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Both volunteer squad's I've been involved with have oxygen cascades... and I've never had an issue. At the high-volume squad, we've got lots of spare bottles, and we almost always have spare bottles.

At the per-diem company, the national policy is that the company DOES NOT ALLOW cascading or trans-filling of bottles... we contract with a supplier for medical oxygen (and air for the Children's Hospital trucks).

At the new full-time job, we use a D-cylinder with a integrated regulator/handle assembly on the top, with 1 DISS port and a port that looks like a CGA 570 for filling. The per-diem job just starting getting these tanks too... it is great to not have to worry about regulators or anything else.
 

KEVD18

Forum Deputy Chief
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rmellish

Forum Captain
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Wow, I just sorta figured everyone cascaded their own tanks. Gotta love being a private I suppose. We cascade our Ds, Es, and our on boards...
 

hitechredneckemt

Forum Crew Member
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At the private company i work for we cascade our D bottles. my vollie dept. they are all filled by a service.
 

eggshen

Forum Lieutenant
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deal. but i get to wear the black and gold trunks

Can I wear those groovy ones that "Macho" Camacho used to wear?

Egg
 

Outbac1

Forum Asst. Chief
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Cascade systems!! I thought they had gone the way of the dodo bird. I hadn't heard of them in a decade or more. Ours are all filled by a professional service.
 

SwissEMT

Forum Lieutenant
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We run a cascade system. I literally cringe with every opening of a valve. I keep worrying that I'll be blown to pieces with shrapnel.
I hate cascade systems.
 

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