Largest and quietest 12CFM FAD @ 7 bar single phase compressor?

[flanajb]

I have a requirement for a single phase compressor that will be suitable for an air tool with the spec

"Gas or electric air compressor, with 15 to 30 gallon (60-114 liter) air tank using 12 cfm @ 100 psi (340 liter@ 7 bar) "

But as quiet as possible. The neighbours are in close proximity to us and a compressor running at 80db in the garage might cause issues.

What options do I have?

 

[normspanners]

A big compressor pump turning slowly, better getting double the size pump 25ish cfm and drop speed ie halve the motor pulley size.And then you can use a 240v 1ph motor. IMO
that makes it quiet and reliable. Also a timed solenoid unloader to stop heavy load at start up.

 

[flanajb]

That sounds interesting. So could I do the above with something like this one?

https://www.machinemart.co.uk/shop/product/details/se29d270-ol-air-compressor

 

[brightspark]

u cant half the pulley size on the motor. any smaller than the one fitted and the belt would slip .there on the borderline with the ones fitted as standard . there isnt a quiet compressor . belt drive slow running compressors are quieter than a fast running one and a direct drive though

 

[dannyp]

compressors dont allways slow down well, big piston compressor often need some inertia to get ver the compressions run them slower and they may stall. if quietness is an absolute must and budget allows its got to be a hydrovane

 

[Maker]

if quietness is an absolute must and budget allows its got to be a hydrovane

Or a Bambi; Hydrovane quote 62-73 dB which is like a conversation outside, Bambi quote 40 dB which is like a quiet whisper.

 

[flanajb]

I was looking at the hydrovane compressors, but could not see a single phase option that provided the required CFM

 

[normspanners]

u cant half the pulley size on the motor. any smaller than the one fitted and the belt would slip .there on the borderline with the ones fitted as standard . there isnt a quiet compressor . belt drive slow running compressors are quieter than a fast running one and a direct drive though

How do 3 kw single phase car lifts work with their 50mm pulleys then ?
A standard compressor pulley is 200mm, as long as the pulleys have the correct maths applied ie size and number of belts and wrap etc to cope with the load applied there should be no problem.

compressors dont allways slow down well, big piston compressor often need some inertia to get ver the compressions run them slower and they may stall.

most compresors have a speed range to work within and that can vary greatly.

My petrol one for instance runs with a much smaller pulley and still produces air right down to idle just doesnt pump as much cfm but is obviously a lot quieter.
petrol / electric hp is hp. If I need more air I just rev it up.

 

[Gareth J]

most compresors have a speed range to work within and that can vary greatly.

I think the amount you can slow it down will be restricted by the oil system. I'm trying to do just this with a big compressor and a 4hp single phase motor. Have found the quoted rpm range is between 460 and 750. Presumably if it drops too far below the lower end, the oil system suffers.

Smaller compressors won't have a fully pumped oil system but will still want enough speed to effectively slap it about.

What's a safe limit? 2/3 normal speed? 1/2 normal speed? Hard to say

 

[normspanners]

If it is a twin cyl and has unloaders on both cyl like the broomwade you can basically shut one cyl down so that it reduces the load when it gets to a predetermined pressure /load on the motor so that you can utilize the the lower current required to pump up to that pressure.
So with a clamp on feed just watch as the motor comes to the max amps then adjust mechanical unloader to off load the cyl furthest away from the flywheel, so to then let the pump carry on up to high pressure without overloading the motor.
That means the motor is allways at max work load.
the old broomwades had oil rings that dipped into the oil carried it round then into the centre of the crank then centrifical force threw it out to the big ends.

 

[dannyp]

I didn't say you chouldn't slow all compressors down, some really don't like it tho.

i put a 3 hp singel phase motor in place of a 5 hp and droped the revs accordingly, that didn't work. at the lower speed there wasent enough inertia in the flywheel so the motor would struggel each compression causeing lights to flicker, then it would stall. solve the inertia problem by robbing the flywheel off another T30 and double it up. problem solved

more of a problem on slow running pumps with big pots

 

[normspanners]

solve the inertia problem by robbing the flywheel off another T30 and double it up.

how did you double up the flywheel ?

 

[dannyp]

on the t30 the fylwheel just clamp onto the cranck with a pinch bolt, so got both flywheels off, stacked them ontop of each other, clamped them together and drilled through them in 6 places, taped the one m10 drilled the other for clearance on an m10. bolted them together and mounted them as a pair as close to the pump as possible so there was at least some of the cranck n the 2nd flywheel.

 

[normspanners]

That cured your problem completely ?

Did running it slower make it a lot quieter

 

[normspanners]

An epicyclic gear train on the crank would be the answer ------- less start up inertia but loads of energy stored. HUM----------------

 

[dannyp]

i wouldn't say competly cured it, if you data log ( with the posh multimeter ) the current drawn by the motor there is still a fair rippel there and the frequency of peacks is same as the compressions on the pump but i would say it's accseptable, no flickering lights, it sounds happy and has run like it now for some time.

i wouldn't say it's made that compressor much quiter it's a littel quiters and dosent run at that speed where the vibrations from it seem to make everything want to resonate, i origanly did it use the compressor on singel phase noise wasent so much of an issue but it is a lot quieter than other belt driven compressors makeing the same cfm but with smaller cyinders running faster most of the noise from it comes from the intake so chould easly be quietend down quite a lot if needed