SA-6 Compressor Balanced Stage Pressures and Temperatures With Other Considerations

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There is more to it than that. the rpm and bpr sets the sweet spot of sorts. the compressor is designed to run ballanced at a certain rpm and BP stetting. I am not sure what the rpm may do for it but the BPR sets the pressure for the last stage to match the force ( psi and area of the piston) of he other cylinders. At that pressure the compressor runs smooth and does not vibrate. below or above that pressure the compressor will vibrate. It is best to have that sweet spot n the upper 2000's so that at the top off of the tank the final stage does not have the larger force on it. The compressor will last longer if it is designed with a ballanced bp at say 2800 rather than 1500. The bpr has little to do with the final stage floating piston chattering as it will chatter until the BP gets to maybe (like my SA6) 50-100 psi and is good after that. Any bpr immediately after the final stage is good for that. However they are not normally put there. They are put after the first external moisture separator to pull the water out. In that use,,,,, the higher the BP the better,, as it mechanically removes the water and not chemically in the filter stack. Compressor rpm ,,, as I have seen determines the output of 3 or 6 cuft/min. I think that on that SA6 the BPR is right after the internal final moisture separator,,,,, however that separator is a very small volumn so the clatter stops after a couple of seconds. The larger the separator the longer the chatter if your first BPR is placed after it.

Now I really like this, way off topic I know but such an important consideration.
But I have again one question as I'm not sure if we are all talking about the same thing or if the Anglofiles on the forum understand the term "sweet spot" or you lot understand what us lot think of balancing a compressor

I have heard before on the forum this term "balancing" or the compressor being "balanced" and never got around to asking before I'm just not sure what we all mean by the term "balanced" or if we even fully understand the term
Maybe we should use the term balancing just for describing mechanical vibration reduction
and the term "Pressure Balancing" for what your describing above the "Sweet Spot"

If so the "Pressure balancing" on your SA-6 design is 3000psig or 207 bar.

But the mechanical balancing is adustable by the counter weight length at the front end (fan side)
and at the back end (driven pulley) by adjusting the PCD position of the three 19mm weight balancing holes
Or by using a standard industrial SPZ twin groove pulley and adding another counter weight at the back end
in the opposing face to the front one (upside down) The crankshaft has a drilling at the back end pulley side for this purpose.
 
There is a price for every solution, and I am not sure you will get the desired end you want. you may as well put a clutch like device on the compressor to allow motor start and then compresssor engagement. I think the RIX manual said 1900 for BPR and the worked for me with my LP tanks.
 
There is a price for every solution, and I am not sure you will get the desired end you want. you may as well put a clutch like device on the compressor to allow motor start and then compresssor engagement. I think the RIX manual said 1900 for BPR and the worked for me with my LP tanks.

Agree for marine use over here in Europe we tend to go down the route of using the PTO shaft from the marine engine and as the SA-6 runs at 1500 RPM it matches fully with the PTO shaft rotation speed. Hence the upside down positioning of the compressor above the clutch shaft in the engine compartment.

For a clutch option we use the Anderson clutch design

Anderton Clutch Manufacturers, Anderton PTO Unit Suppliers

But I dare say you guys have fancier systems.
Then again we get no sunshine and I just fancy the idea of working the summer fitting solar power compressors in the south of France
 
Now I really like this, way off topic I know but such an important consideration.
But I have again one question as I'm not sure if we are all talking about the same thing or if the Anglofiles on the forum understand the term "sweet spot" or you lot understand what us lot think of balancing a compressor

I have heard before on the forum this term "balancing" or the compressor being "balanced" and never got around to asking before I'm just not sure what we all mean by the term "balanced" or if we even fully understand the term
Maybe we should use the term balancing just for describing mechanical vibration reduction
and the term "Pressure Balancing" for what your describing above the "Sweet Spot"

If so the "Pressure balancing" on your SA-6 design is 3000psig or 207 bar.

But the mechanical balancing is adustable by the counter weight length at the front end (fan side)
and at the back end (driven pulley) by adjusting the PCD position of the three 19mm weight balancing holes
Or by using a standard industrial SPZ twin groove pulley and adding another counter weight at the back end
in the opposing face to the front one (upside down) The crankshaft has a drilling at the back end pulley side for this purpose

SWEET SPOT

Ballancing the compressor is having the same force on each stage. at the start on a 3 stage compressor, atage 1 and 2 come up to full piston force while eh 3rd is significantly lower. it runs like a wheel/tire with a flat side. you adjust teh BPR so that on start up you have the same force on each stage. the only time it them does out of ballance is when you are pumping to a tank with higher pressure in it than the BPR is set for. It is much like having a 3 sided see saw allwith different length legs,,, with the weights sized and placed such that 2 of the legs have with same leverage force. the weight being the piston pressure IE stage one 70 psi stage two 700 and stage 3 the output psi. the whole thing is only ballanced at one output pressure. You use a BPR to simulate the compressor seeing a tank as the psi needed to make its see saw leverage equal to the other two stages. If that psi is 2200. then the compressor runs ballanced up to the point of 2200 psi and theen it starts becoming more unballanced as the output psi rises above 2200. If youare going to fill hp tanks your compressor willnot laset as long as filling lp tanks because of the time running unballanced above the designated ballancing psi.

for the example i gave using the 3 legged see saw

leg length weight or psi allprovides a leverage of 100 foot pounds on each leg

stage 1 leg one 10 ft 10#

stage two leg two 5 ft 20 #

stage 3 final leg three 2 ft BPR set to 50#


with out the bpr it would be like having stage 3 having a 1# weight on it leaving a 100/100/2 loading making it unballanced.

put wheel weights on your tire each the same size 120 degrees apart and it drives fine reove one of the weights and it is a rough ride.
 
SWEET SPOT

Ballancing the compressor is having the same force on each stage. at the start on a 3 stage compressor, atage 1 and 2 come up to full piston force while eh 3rd is significantly lower. it runs like a wheel/tire with a flat side. you adjust teh BPR so that on start up you have the same force on each stage. the only time it them does out of ballance is when you are pumping to a tank with higher pressure in it than the BPR is set for. It is much like having a 3 sided see saw allwith different length legs,,, with the weights sized and placed such that 2 of the legs have with same leverage force. the weight being the piston pressure IE stage one 70 psi stage two 700 and stage 3 the output psi. the whole thing is only ballanced at one output pressure. You use a BPR to simulate the compressor seeing a tank as the psi needed to make its see saw leverage equal to the other two stages. If that psi is 2200. then the compressor runs ballanced up to the point of 2200 psi and theen it starts becoming more unballanced as the output psi rises above 2200. If youare going to fill hp tanks your compressor willnot laset as long as filling lp tanks because of the time running unballanced above the designated ballancing psi.

for the example i gave using the 3 legged see saw

leg length weight or psi allprovides a leverage of 100 foot pounds on each leg

stage 1 leg one 10 ft 10#

stage two leg two 5 ft 20 #

stage 3 final leg three 2 ft BPR set to 50#


with out the bpr it would be like having stage 3 having a 1# weight on it leaving a 100/100/2 loading making it unballanced.

put wheel weights on your tire each the same size 120 degrees apart and it drives fine reove one of the weights and it is a rough ride.

Ah so thats what you guys mean by sweet spot now I understand
I think we would call this rod load or rod loading, part of the initial compressor design philosophy
When the diameter of each piston is designed such that the pressure developed at each stage gives the same load to the crankshaft drive gear so that the total rod loading on the bearings is balanced out so as to reduce induced pressure pulse vibrations so that each stage is balanced weight wise as far as pressure loading.

Also to compensate for imbalance vibrations cause by the weight of each piston moving the stroke length the design engineer will also match the piston weights out and the movement of travel by the crankshaft timing angle and throw. as you would a car engine.

Compression ratio of each stage is another important consideration as is heat loading and dissipation and may take presidence in the piston diameter choice, so is blow-by losses. Also consideration in our competitive world cost reduction by using higher piston stages and valves from bigger pump designs and incorporating the same into smaller pumps to reduce design cost and parts inventory So say the 3rd stage piston diameter ring and valve assyon a 40 cfm compressor becomes the second stage on a 10 cfm

Again in the case of your SA-6 its another post.
 
@iain/hsm their argument was heat buildup when it's running full speed and recommended running around 90% or less to keep the heat in the 3rd stage down. What that means in terms of the interval between gas pumped and rebuild I'm not sure, but it is going to be a very long time before I have to rebuild these with the volume of gas that I have to pump.
We can always have the mods split the thread if they want to, but with the "sweet spot" that @KWS was referencing, what is that pressure for the SA6 in its stock build, and for someone like me who needs to run it at 4000psi regularly, what should be done to make it happier?
 
What I do to keep mine happy when filling my 4 cylinder bank to 4,500 is threefold

1 I run it in the air-conditioned indoors and set the thermostat to 70F.
2 I blow a small strong fan into the intake side of the compressor fan blade which helps keep the pesky 3rd stage substantially cooler. It is unfortunately hidden behind the block in a way that it gets the least airflow so increasing it helps.
3 I religiously lube the bearing surfaces as specified but more often than required.
 
@RayfromTX mine are actually having their fans removed. Too ineffective at that slow speed IMO. I am likely going to put a variable speed electric fan on the shroud to keep air flow maximized during slow operation. I do have thermal cutoff switches ready to put on each of the heads and set to 400f. Teflon starts degrading at 500f, so want to keep it significantly cooler than that.
Thankfully with big banks and CCR, I can let it run at 1cfm and just let it go.
 
I never see close to 400. Are you setting a timer for draining the coalescers during these very long fill times or using auto drains. I hate when people do this to me but,,,, I would let it run at it's design speed, knowing that with your minimal use you may never have to rebuild it anyway. Get the pumping over and done with when the time comes.
 
@RayfromTX power restrictions at the moment require it running slow. No benefit of going fast and as I don't have the same criteria that it had when it was run, the engineers at Rix recommended slowing it to 4-5cfm max anyway.

Autodrains are being built. Compressor isn't quite done yet
 
https://www.shearwater.com/products/peregrine/

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