Home blending

[stevechesh]

Following on from another thread about O2 prices..........If i were to start from scratch doing my own blending at home, what equipment would i need to start and what sort of costs would be involved.

for example: whips and adaptors - suppliers/costs/recommendations?
gas prices and suppliers : has already been covered in a previous post.

My theoretical plan to start with would be to decant O2 and/or He as required and then use the LDS to air top the cylinder (The LDS don't do Nitrox). The main reason is i don't have a compressor yet, but i do have 90 mile round trip every time i want nitrox or trimix, so at the moment, homeblending would seem to be conveniant and less time consuming.

Also, with regard to obtaining the gases, do they sell to 'private' individuals or do you have to have a registered company?

I'm sure there is loads i've not put down, so any top tips would be appreciated.......

regards

Steve

[Dave_S]

Originally Posted by stevechesh

My theoretical plan to start with would be to decant O2 and/or He as required and then use the LDS to air top the cylinder (The LDS don't do Nitrox). The main reason is i don't have a compressor yet, but i do have 90 mile round trip every time i want nitrox or trimix, so at the moment, homeblending would seem to be conveniant and less time consuming.

I'd also be interested in that, as i have a similar round trip the issue seems to be whether your LDS provides "clean air" if not you have to provide an in line filter which they may or may not be willing to use.

Dave

[warmwaterdiver]

whips; start at around £200 unto over £300 depending upon make, SAP are good

blending course; optional but advisable if you don't know what your doing

gas; J of each and your away

Woz will be along in a bit, he'll explain more!

[stevechesh]

A blending course is on the cards this year anyway,

So, would i be right in assuming the following:

1. Get a J, and a whip,
2. Decant 'X' bar of gas into my cylinders (dependant on mix req'd)
3. Air top the rest from a compressor and hey presto, i have a mix of whatever.....

can Joe bloggs off the street just go and buy O2 or He?

Steve

PS, i did have a look at Woz's garage pictures. Would i need car ramps and a dodgy looking fire extinguisher as well!!

[Okeanos]

The Sub-Aqua Products O2 whip is the best one, it's nearly £400 but well worth it. It has a large gauge and a one way valve.

All you need the is a good blending program. Look for Nigel Hewitt's Van Der Vaals program, it's free and will do the job.

[Okeanos]

Originally Posted by stevechesh

can Joe bloggs off the street just go and buy O2 or He?

It depends on the supplier.

[stevechesh]

Originally Posted by Okeanos

It depends on the supplier.

Well, i am in the fortunate position that i have my own company, so that might be a way round it....?

[BobK]

Originally Posted by stevechesh

My theoretical plan to start with would be to decant O2 and/or He as required and then use the LDS to air top the cylinder (The LDS don't do Nitrox).

Steve

Had similar problems, a few years ago. Many LDS will not top up for you, for various reasons. As an absolute minimum you will need a 'one way valve' so that O2 will not feed back into their system.

Does your LDS know what you are planning to do ??

[stevechesh]

Originally Posted by BobK

Had similar problems, a few years ago. Many LDS will not top up for you, for various reasons. As an absolute minimum you will need a 'one way valve' so that O2 will not feed back into their system.

Does your LDS know what you are planning to do ??

i've not spoken to him about home blending, BUT, when i have had an air top in the past, i've always told him the cylinder contents contain 'X'% of He or O2 and it's not been a problem.....

He won't get Nitrox in because the costs outweigh the demand.......

Steve

[Woz]

Hello.

Right. You need the gas (of course) and a way of getting it out of the cylinders. Currently IMHO the cheapest and most idiot proof way of doing this is to buy an AP Valves O2 decanting hose with gauge (AP8K), the AP56D200 DIN adpater for it (not needed for blending but handy) and a Keller 0-300 bar Eco1 gauge from Omni Instruments (get the rubber boot too). All this will cost you less than £200 for a digital blending setup. If you are feeling keen then go for the SAP digital blending doofer for about £400 which is a very nice bit of kit.

Next- buy a copy of the Oxygen Hackers Companion from Airspeed Press and read it. Twice.

For blending software, Geekoid Nigel has some freeware you can download or I use JDeco on my phone which has blending and topping programs. Very useful (as well as VPM and GF deco too).

So- you've decanted your O2 nice and slowly (I use 6 bar/min just cos the digits on the digital gauge tick off at 0.1 per second which makes it really easy to track). The O2 will be a bit hot at this point (by hot I mean a teeny bit over ambient) so you need to decant a little more than the blending programs say to get it accurate.

Next you need to top off with air. Ideally a compressor you can use yourself cos if you turn up at a shop with a cylinder with neat O2 in it and ask them for an air top they may get a bit shirty.

Finally leave your cyls lying down for a bit as O2 is heavier than air then analyse after a while.

If you are mixing trimix then you need to analyse after you have blown in the He and O2. Not that I have done this, you understand. GIT somewhere in DIR world has a good trimix blending sequence.

Oh and last thing- get a roll of silver gaffer tape and after each analysis stage, write down the mix, the date and your name and stick it to the cylinder. And keep a notebook with this information in it too as you are blending as it's really easy to forget how much of what you have poked into where. After not that much practice you should be able to blend to +/- 0.5% reasonably easily. Which is fine as analysers are nowhere near that accurate.