Opinions requested on EAN/Tank issue

[Uncle Pug]

roakey once bubbled...
And as long as I’m getting in trouble, I’ll take on UP for his use of terms.

Ah Roaky... you can't get in trouble with me for something like this.

All collies are dogs... but not all dogs are collies.
All O2 serviced tanks are O2 clean... but not all O2 cleaned tanks are O2 serviced.

So the point doesn't get muddled by semantics:

If an O2 serviced tank is used with non-compatible air it only needs cleaning again to restore O2 service.

 

[MikeFerrara]

An issue we ponder all the time. I prepare a tank for a customer by cleaning and installing O2 compatable components. The diver then has a tank I am willing to blend in. But..I may not always be the one filling the tank. Most fill station at dive sites (around here) have membrane systems. This gas is not garanteed to beet modified grade E standards. Will I bllend in this tank after it is filled there or does the poor diver have his tank cleaned onece a month? We take our chances. Even small amounts of contaminants collect over time but if it is clean enough your OK (fingers crossed here). Most compressors pump air that will meet modified grade E (I know mine does) However, If their is a problem and performance degrades there is no way to know. The hyper filter is supposed to provide modified grade E even if the compressor output is not so good.

There is a calculated risk every time we pump pure O2. Some blenders will assume more risk than others. Heck we don't prep this equipment in a clean room so is it ever "clean"? We hope that it is clean enough. There are some that will not PP blend in any tank that they don't own and there are others that don't use hyper filters or even care if the tank has been O2 cleaned. And...there are more incedences than we hear about. Global gets alot of calls about burned out seats in valves and other (usually minor) O2 fires.

 

[Uncle Pug]

I know of a shop that gets all the local non-O2 clean tank business in town when it comes to Nitrox... even from the other shops.

Any guess as to what their blending set up is...

Several safe roads find the same destination. ;-)

 

[MikeFerrara]

Continuous ?

 

[Uncle Pug]

with a RIX SA-6.

 

[padiscubapro]

MikeFerrara once bubbled...
An issue we ponder all the time. I prepare a tank for a customer by cleaning and installing O2 compatable components. The diver then has a tank I am willing to blend in. But..I may not always be the one filling the tank. Most fill station at dive sites (around here) have membrane systems. This gas is not garanteed to beet modified grade E standards. Will I bllend in this tank after it is filled there or does the poor diver have his tank cleaned onece a month? We take our chances. Even small amounts of contaminants collect over time but if it is clean enough your OK (fingers crossed here). Most compressors pump air that will meet modified grade E (I know mine does) However, If their is a problem and performance degrades there is no way to know. The hyper filter is supposed to provide modified grade E even if the compressor output is not so good.

There is a calculated risk every time we pump pure O2. Some blenders will assume more risk than others. Heck we don't prep this equipment in a clean room so is it ever "clean"? We hope that it is clean enough. There are some that will not PP blend in any tank that they don't own and there are others that don't use hyper filters or even care if the tank has been O2 cleaned. And...there are more incedences than we hear about. Global gets alot of calls about burned out seats in valves and other (usually minor) O2 fires.

Not knowning where people get fills can be dangerous.. I know most shops in my area don't pump gas thats clean enough in my opinion.. When I blend my own banks (I bank 32%, 50% and a 21/40 trimix - ) I use 100% oxygen (LOX or gas I banked from LOX).. I usually blend all other mixes using my 50% bank (approx 4000 cu ft) and air to reduce the risk. (the only real exception is for people I know well that may need a cylinder adjusted for a different % with an 02 top off)

 

[pescador775]

I don't buy the definitions used by Roakey and Gorji, regardless of source. 'Blending' is a continuous process involving active mixing, control and monitoring of the individual gases as they are pumped or decanted. This involves a device called a blender and is not a partial pressure process. It is based on flow volume and concentrations. Percentages can be checked later with a separate analyzer to verify original flow settings. This is blending.

Partial pressure mixing involves no blending. Rather, individual gases are sequentially added to and mixed in a container (tank). The amounts of gases are controlled by calculating partial pressures prior to filling and reading corresponding pressures during separate stages of filling. The subsequent mixing is entirely passive and must be verified after the fact. Percentages of gases verify PP calculations and effectiveness of mixing. This is partial pressure mixing.

 

[roakey]

pescador775 once bubbled...
I don't buy the definitions used by Roakey and Gorji, regardless of source.

American Heritage Dictionary. Take it up with them, not us.

Roak

 

[MikeFerrara]

I have gas blender cards from two different agencies and all I have ever done is PP MIXing?

 

[pescador775]

The dictionary wordsmiths (?) are not divers. Every sport and/or profession has its own definitions and jargon. It's past time that the 'experts' like the folks who write Nitrox manuals think about what they are saying with an eye to making their descriptions unequivocal. The present state of affairs is a good example. People may be associating blending with pure oxygen fills. It could lead them to think that an O2 clean tank with O2 clean valve and rings are necessary to get filled from a shop who furnishes blended gas.