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Re: Chinese high pressure compressors

Posted: Sat Nov 18, 2017 2:21 pm
by AA_Fanatic
Well - as mentioned, my 4.5l bottle is less than a year old. It's rated for 300Bar (not sure what the tested saftey parameters are but I am guessing it's way above 300Bar.)

I keep an eye on all the guages whilst the pump is working and I will not exceed 300Bar. There are folks I have read about who have let it run past 300Bar and the saftey blow out disc kicks in and ruptures. I have stripped out my safety disc holder etc and made sure I've got one fitted (I've been supplied with 10 spare ones.) I have a second stage moisture filter on the line with silica in between two filter elements. At the last top up, the 2nd filter element on the end stage 'felt dry', I squeezed it in a white bit of tissue paper and I could not detect any moisture or oil. Hardly scientific, I know but even 'breathing air' from a dive shop isn't 100% free of moisture and I am told that this will vary from shop to shop depending on when last they changed out their filters and how saturated they were at the time...etc...etc..

I am not providing refilling to anyone nor advocating anyone should rush out and buy one. I am an ex fitter / machinist and am used to working on mining equipment and machinery (in a Gold mine in South Africa quite some years ago), so I guess for me I am probably willing to take more of a risk than the average individual.

I also priced up a spare con rod, piston and piston rings and incl delivery, its about £50.
Agreed - I doubt it will last 5 years but with spares cheap and available, it might be viable - who knows.

My closest dive shop is a pain in the arse to get to and deal with. If this wasn't the case, then I highly doubt I would have gone ahead with this idea.

Anyone can piss on my chips - each to his own!

Re: Chinese high pressure compressors

Posted: Sat Nov 18, 2017 10:16 pm
by gdavison
On the neck stamps you will see a PW or WP or CP (working pressure) rating and a PT or TP (Test Pressure) rating

Re: Chinese high pressure compressors

Posted: Mon Jan 08, 2018 6:14 pm
by AA_Fanatic
Hi everyone,

I have made an update to the filtration of this pump as I must admit, I have been a bit paranoid about any moisture or oil getting into my air arms rifle. So I drained my 4.5l tank upside down until empty, didn't notice anything that shouldn't have been there like any mist or vapour....etc. but that's subjective, I know.

I purchased a large 300 Bar 'Gold' filter of off Alibaba and got some 13x Molecular Sieve desiccant. This is serious heavy duty desiccant, the most efficient drying agent available and used by industry for 'general gas drying, air plant feed purification and liquid hydrocarbon and natural gas sweetening...' Much more efficient than silica gel.

So I sandwiched a quantity of these beads between 3 inches or so, between the high density cotton filters, in the 'Gold' filter.
So this is my primary, first stage filter.

Then, in the black filter, the second stage filter, I have 2 inches of high density cotton filter, with a small quantity of cobalt impregnated silica beads that turn pink when exposed to moisture, with another half inch cotton filter covering them to prevent them clogging up the line or going where they shouldn't. So this black second stage in my 'mine canary' and I figure that when these change colour, my main Gold filter is saturated and will require drying out (in an oven to re use...etc)

My 'Gold filter hack' is what I have seen others do on the interwebs, but I am using heavy duty desiccant that I had to buy from a specialist supplier (as opposed to normal silica gel). It's virtually identical to the 'Diablo dry air system' that the makers of the Omega air compresors recommend (that retail for about £1,400 but are the Rolls Royce of posh DIY airgun enthusiasts).

The 'mine canary indicator' second stage was my idea, there for convenience, as it's much easier to unscrew this and periodically check. They are all connected via 1/8 inch best fittings type connectors, so very easy to do mid filling checks etc. The Diablo system mixes the blue indicator beads with the molecular sieve beads, but that is a pain to keep having to open and check. Also - the blue silica beads are not as efficient as the molecular sieve beads so will indicate moisture saturation long before the molecular sieve beads would have reached their capacity, so what's the point of having the high end molecular sieve beads...?

Anyway - if you've not dropped off to sleep yet reading this, I filled my tank up from empty to just under 300 bar (took about an hour and 10 minutes to do, by the way.) I did a moisture check by inspecting the mine canary at 100 bar intervals and the beads were still a lovely deep cobalt blue, revealing that dry air had passed through them. The white cotton filter was still pristine, so I am pretty sure that the air in my tank is quite dry and oil free. I am much happier now and will be using this set up going forwards. All the indicator beads and the molecular sieve beads are reusable by heating in the oven. See my pics below of the set up.

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Re: Chinese high pressure compressors

Posted: Wed Jan 10, 2018 7:06 pm
by Blackbaronfish
Well I didn’t drop off to sleep :mrgreen: Very interesting really.

Him many fills have you done so far


Re: Chinese high pressure compressors

Posted: Wed Jan 10, 2018 8:46 pm
by AA_Fanatic
I've done 2 top up fills from under 200Bar to a hair under 300Bar and one fill from empty per the set up described up to 300Bar using the new improved filtration set up. Excluding fuel, (going to and from the dive shop) I have saved at least £60 so far.

Re: Chinese high pressure compressors

Posted: Wed Jan 10, 2018 10:26 pm
by TenMetrePeter
I'm lost now. What would have cost £60? My dive shop fills are £3 every 6 months.

Re: Chinese high pressure compressors

Posted: Wed Jan 31, 2018 7:18 pm
by AA_Fanatic
Apologies for the typo ....should have be 'including' NOT excluding fuel....etc.