Compressor question

[rbahr]

Hi All,

I have a new to me Saylor-Beall 5hp compressor. I fired it up and saw that the pressure cut-off switch is set for ~125psi. seems a bit low. My previous compressor would shut off ~155psi.

What is considered typical?

Thanks

Ray

 

[Barn5]

What is the use case for this compressor?

 

[rbahr]

It is a model 503 - 80 gallon tank.

It will drive air tool, media blast cabinet etc. I have regulators at the outlets

and BTW it was a $300 score at an auction...

Thanks

Ray

 

[bsaint]

Its whatever the design of the machine is.

 

[rbahr]

The compressor & tank can easily support 175psi, just want to understand what ideal should be.

Thanks

Ray

 

[larry_g]

Hi All,

I have a new to me Saylor-Beall 5hp compressor. I fired it up and saw that the pressure cut-off switch is set for ~125psi. seems a bit low. My previous compressor would shut off ~155psi.

What is considered typical?

Thanks

Ray

The following assumes that you have a single stage compressor;

Years ago the single stage compressors were 125-130 psi machines. Modern machines seem to be rated to 150 psi. A worn compressor will struggle to make 150 psi. I would suggest that you run a test. Time the machine as it pumps from 110 to 120 psi. Then time it from 120 to 130 psi and again from 130 to 140psi and 140 to 150psi. You will see that each increment takes a longer time to get there. How long do you want to let the compressor struggle for that last 10 psi increase? The higher the cutout the less efficient the compressor becomes, the more heat it builds, and the more electricity it uses. If you keep raising the cutout you will find a point that the compressor cannot reach. That is not where you want to be.

If your compressor is two stage then keep running the test to 175 psi or whatever you want.

Run the test and make the choice from the data you get.

lg
no neat sig line

 

[sberry]

There is a huge amount of difference between 125 and 175. The reason one wants a 175 is this headroom for running air tools. The unit can basically always provide 130 or so to the in of a regulator. Running a large 1/2 air guy can incur losses near 1 # a foot on new 3/8 hose, to get 90 at the tool we need 135 or so in to the regulator. A single stage only provides full power at the top of the cycle when its fully pumped, the 2 stage is cutting in where the single is cutting out.
A 3 hp 2 stage mechanics comp used to be common. Was sized for 60A service and made for tire and mechanics shops, for air tools and truck tires. The advent of more competitive manufacturing, the small cost difference and more common 100A or larger service gave rise to the popularity of 5 hp which is more suitable for body work or even multiple mechanics.

 

[rbahr]

I think this compressor was used to provide an air source for light duty stuff, I am using this for a media blast cabinet and/or air tools. I also thing the pump comes back on ~75psi.

Ducksface: The label describes maximums not typical.

Ray

 

[larry_g]

It is a model 503 - 80 gallon tank.

It will drive air tool, media blast cabinet etc. I have regulators at the outlets

and BTW it was a $300 score at an auction...

Thanks

Ray

Doing a few searches I can find no model 503 SB compressors. Can you confirm the model number and a link to its information? If you can't can you confirm to the members if it is a single or two stage compressor?

lg
no neat sig line

 

[rbahr]

Hi,

I had it wrong - brain cramp!

It's a model 705 Saylor-Beall, 5hp, 2 stage - http://www.saylor-beall.com/manuals/

Ray

 

[Niteman9]

Hi,

I had it wrong - brain cramp!

It's a model 705 Saylor-Beall, 5hp, 2 stage - http://www.saylor-beall.com/manuals/

Ray

175

Sent from my SM-N960U using Tapatalk

 

[md21722]

Hi,

I had it wrong - brain cramp!

It's a model 705 Saylor-Beall, 5hp, 2 stage - http://www.saylor-beall.com/manuals/

Ray

705 is a 2-stage pump rated for 175 PSI.

Normal cycling would be for it to cut in at 140 and cut out at 175.

It's possible that the pressure switch died and was replaced with one meant for a single stage air compressor.

Air tools are really great running on 2-stage compressors because of the air drop across the filters, air line regulators, couplers, and hoses as others mentioned. I have my air line regulator set around 115 PSI and I only use a 25 foot hose. This ensures my tools see 90 PSI when running.

 

[bts]

I cannot agree with the need for 175 psi. Two stage compressors are not common here. Single is what most use.

To run my 1/2" kukon, regulator is set at 115 psi gives 90 psi at the gun on a 10mm hose, 5 m (30') long. That's with 2 x 10 cfm (measured at 90 psi) compressors cutting out at 120-125 psi. Also have 2 x 12 lines joined at a couple of places running the length of the garage. This makes sure of minimum line loses getting to the regulators.

Common problem I came across while involved with pneumatics was people running to long a distance on too small a line with to small a compressor.

Something to keep in mind is that when testing an impact gun the usual standard is for a 3m (10') line 3/8" or 1/2" depending on size and manufacture of the gun. So pressure readings at the regulator is not a true indication of what the gun is getting. Readings should be made at the gun.

Sorry for going on a bit.

Tony

 

[AntonLargiader]

x2 there is a huge difference between 125 and 175. At 175, every gallon (or whatever unit you want to use) of the tank has ~40% more air mass available to expand to your working pressure. The reserve difference is substantial.

You need the reserve in cases where your demand outstrips your ability to compress. If your compressor can keep up with the blast cabinet, you don't need a big reserve. In that case, you can just run it so that you keep your minimum working pressure available at all times, which is probably something like 120~140. That keeps 90 at the air guns and is probably more than enough for the cabinet (I run my cabinet no higher than 40).

Running higher pressure will cycle the compressor fewer times, but it will get a bit hotter at the end of the cycle. It's designed for it; probably not a big difference either way. There are a few factors involved in calculating efficiency but I'm pretty comfortable saying it's less efficient to run higher pressures.

 

[md21722]

I cannot agree with the need for 175 psi. Two stage compressors are not common here. Single is what most use.

To run my 1/2" kukon, regulator is set at 115 psi gives 90 psi at the gun on a 10mm hose, 5 m (30') long. That's with 2 x 10 cfm (measured at 90 psi) compressors cutting out at 120-125 psi. Also have 2 x 12 lines joined at a couple of places running the length of the garage. This makes sure of minimum line loses getting to the regulators.

Common problem I came across while involved with pneumatics was people running to long a distance on too small a line with to small a compressor.

Something to keep in mind is that when testing an impact gun the usual standard is for a 3m (10') line 3/8" or 1/2" depending on size and manufacture of the gun. So pressure readings at the regulator is not a true indication of what the gun is getting. Readings should be made at the gun.

Sorry for going on a bit.

Tony

That's when the tank is full. Does your compressor cut in at 115 PSI? Folks with single stage air compressors that cycle on at 90 PSI would only be getting 65 PSI at the tool using your example. Dual stage compressors eliminate the single-stage problem of tools not having full power as the compressor gets closer to cycling on.