@iain/hsm what is your ideal BPR setting for the filters and third stage? I have a pair of SA6's that I'm building now. One is going to have a 1.5hp motor run off of a VFD for travel use, the other will have a 3hp motor for stationary use. Went with the 3hp 220v for noise, but also from the Rix engineers recommending to run considerably slower for better life. Compressor will be filling 6x 4500psi banks, but rather infrequently and most of its life will be running 3000-4500psi refilling the banks.
@KWS no need you can't put a pair of BPR's in. One set low to let the compressor come up to pressure quickly, then the other for the filters
1. The ideal BPR pressure setting for normal use using mains power with an oil free SA-6 with a standard 18 inch filter tower its 1000 psig minimum to 1500 psi maximum anything more and its a diminishing return as far as extending the filter life is concerned.
Now by contrast those with the oil lubricated Bauer compressors you will need it much higher at 200 bar 2900 psi
as per the Bauer Junior II example we have on the post because you really need to extend the filter chemical as much as possible because of the oil mist carry over you get off small oil lubricated compressors.
Further using oil in the compressor the filters are compromised by having to remove the oil smell using Charcoal
and even then that chemical needs to be kept dry at all time or else the collected or what is called adsorbed oil
can be desorbed released back out in one lump when the filter water vapour chemical (the zeolite) is saturated.
By contrast with your SA-6 there is no charcoal so you have more water removing chemical, you have additional cooling because your not trying to cool the cup full of hot oil in the block
2. For your 3rd stage on the SA-6 you have three choices, A. use a single standard BPR after the final stage and use either a 500 -1500psi back pressure setting, or a reduced pressure say 20 bar as in this position you are using it only to reduce the free floating (knocking) time before the line pressure builds up.
B. Or fit a single BPR after the chemical filter to increase the "dwell time" of the water vapour across the adsorbing zone in the chemical tower and for this 1500 psi woud be as much as you need to remove the water vapour dewpoint The only issure not covered using this method is the increase in time to initially fill the tower with pressure increased the knocking time before the back pressure is sufficiant to hold the floating piston on the rod hence the free flow knocking time is increased charging the tower each time the filter is changed.
C. Use the single BPR after the filter use a check valve before the filter and presure prime the 3rd stage from the 2nd stage filter tower blank plug. Now what you need to understand is you must prime from the 2nd stage up into the 3rd stage inlet valve. Not directly into the 3rd stage head or the 3rd stage discharge valve will stop any pressure from loading the 3rd stage piston. Clear as mud I guess.
Also from the Rix engineers recommending to run considerably slower for better life
The Rix enngineer is wrong. Running slower doesnt give a better life...... First off define better.
It's another messed up piece of junk advice, not deliberate I'm sure but a 'Better Life"
This is a term better used for those of us who believe in a better life to follow if you catch my drift.
By implication you are made to think its a longer life and if so we are back to the sort of understanding made by Michael about the 17 year old Bauer.
And in the same vein as the 17 year old Bauer if you run your Rix at half speed for twice as long
you no better off than I am filling twice as much in half the time.
Running slower you do because you need to and if you need to fit a smaller motor.
Incidentally halving the pressure to 1500 psi in the scuba tank also works and that really does increase the comoressor life but no one wants to hear that as a suitable solution now do they.
Now your problem will be your required 4500 psi pressure and to explain that we are going further off topic