ScubaLawyer wrote: ↑
Sun Apr 08, 2018 4:21 am
I'm still on my quest to try to learn all I can about compressors. A friend of a friend got a brand new Alkin W31 and filter system and I was invited over to see him set it up. In addition to the separator(s) and the attached short filter tower that come with the compressor, he also had three 36 inch filter towers affixed to the wall. In each of those towers he had a Lawrence Factor three media filter. He said he needed the extra filters to get "medical grade" air which he uses in his nitrox, helox, trimix and other assorted Voodoo death gases he mixes in his garage. Looked like overkill, but what do I know.
What interested me was that he had the standard back pressure (PMV) valve that came with the compressor which was located just after the first short built in filter tower (that the fill whip usually attaches to), and then he installed a second back pressure valve after the three wall mounted towers.
Is that normal? All the other systems I've seen and really looked at (only a few) just have one back pressure valve at the end of the entire system, post filter array and just before the fill whip.
Again, I'm fairly ignorant here but have all confidence this compressor stuff isn't rocket science. Mark
Overkill? Probably. He likely could get O2 compatible air with one tall filter added to his original one, but it would have to be tested to confirm. That's a relatively low volume compressor to run through so many filters, but it sure doesn't hurt anything but his pocketbook. Would still need testing, but less often. Added safety factor is certainly comforting when playing with Oxygen and diving the way he probably does. Three filters on a trailered 15 cfm compressor always gave me amazingly pure air for blending, and the slower air flow of the smaller Alkin compressor makes the filtration even more efficient.
The first back pressure valve was original and he just left it in place. You are right that it is not really required, but it would add to the efficiency of the original first tower since it would reach a higher pressure sooner than if he was filling all four towers. Result of that would be dryer air reaching the subsequent towers sooner, and in my opinion an increase in efficiency. Also, if that Alkin has a floating final piston like some others do, the sooner the pressure on that piston increased the sooner the floating piston would be held firmly against the drive piston, reducing wear and tear and noise. Better for those two pistons, bearings, rods, etc., and conceivably increasing machine life.
BTW, you mentioned that compressor stuff is not like Rocket Science, but I do know of a couple of instances where compressor stuff did become "Rocket Science
". One when the top cover "launched" from an old Worthington compressor separator, up through my friend's porch awning. It did not reach orbit, but the concussion did blow a nearby kitchen window into the house, and his wife was somewhat displeased. The separator top was found in the yard several houses away, and no one was injured, with the exception of some hearing loss. He called me over to see the damage that same day. In a decision reached in a heated consultation with his wife, (where he sustained the hearing impairment
) he retired from filling tanks.
In a similar Rocket experiment a dive shop owner at Lake Whitney was very lucky just to get a broken arm due to his proximity to the launch pad. His aircraft surplus hydraulic accumulator lid was not latched firmly in place by its retaining ring after he changed the filter media. Upon almost reaching full pressure there was a lift-off that spawned a new nickname for his shop.... "Cape Whitney". The escape velocity was slowed only a little by his roof, but he was injured and the shop was a mess. Legal action ensued, and the supplier of the compressor system had to fork over a little $ in spite of the fact that the shop owner admitted he must have erred in his installation of the retainer.
I'll save some other grisly stories from the past 6 decades for later.