Shop air line pressure?

[Graham08]

What do you guys set your line pressure at? The reason I ask is I'm about to hook up my new compressor, which is a two stage and the pressure switch is factory set to come on at 140 psi and kick off at 175. Most of my air tools are labeled for input pressures between 100 and 120 psi.

I'm thinking about putting a regulator at the compressor set at 120 psi, and adjusting the switch so it runs between 120 and 155 psi.

Any thoughts?

 

[kwb]

Depends on the lines but if you are 3/4 copper or 1/2 iron the odds of you getting line losses that are too high are pretty low until you start trying to run a rivet buster.

Leave the compressor alone - the higher pressure in the tank equates to more reserve volume. (equal to bigger tank at lower pressure).

Put a regulator on the feeder to the shop and set it to about 125psi.

 

[GeorgiaHybrid]

I leave the airlines at tank pressure and regulate each drop as required.

 

[GarageEnvy]

My compressor is 2 stage and also 175psi. I have a regulator off the tank set at 90 (sometimes up to 110) and then regulate down as needed at each drop with individual filter/regulators. It's just a hobby garage. Mostly I'm running inflator, impact, plasma or air shear. I'm not doing any sandblasting or DA sanding.

 

[Graham08]

I leave the airlines at tank pressure and regulate each drop as required.

What tools are you running at full tank pressure, and what gets regulated?

My compressor is 2 stage and also 175psi. I have a regulator off the tank set at 90 (sometimes up to 110) and then regulate down as needed at each drop with individual filter/regulators. It's just a hobby garage. Mostly I'm running inflator, impact, plasma or air shear. I'm not doing any sandblasting or DA sanding.

I think I'm in about the same situation. My tool with the largest air consumption is the air over hydraulic pump for my tube bender (rated for max input of 120 psi).

Sounds like a good gameplan is to leave the compressor settings alone, and just put a regulator in-line.

 

[ptschram]

Your tools were probably rated at maximum output at 90 PSI. Any more than that is abusing the tool for marginal benefit.

 

[MoonRise]

Check the pressure rating of your airlines.

If OK, then run output from the compressor at the full 175 psi into the airlines. Do not change the pressure switch on the compressor to a lower pressure, leave as-is.

Put a few end-of-line / point-of-use regulators where you use the tools. Check flow-rate ratings of the regulators to make sure you aren't starving the tool(s) of air flow.

Done.

Advantages: no messing with the compressor cut-in / cut-out switch, compressor and tank run where they were designed to run from the factory, full air pressure in the air lines (minimizes pressure drop through the lines when the tool is using air), setting the 'output' pressure according to the tool in use close to the point-of-use (again, minimizes pressure drop effects at the tool).

Disadvantages: Have to buy a few pressure regulators.

 

[djjsr]

150 in the tank and 100 in the lines. I have a portable regulator that I plug in if I need it any lower.

 

[Steevo]

My tank pressure is set at 150psi.
The output line has one hose disconnect fitting on it, just before the regulator, allowing me a place to tap in for full pressure, should I ever need to.
The regulator is set for 90psi, and the entire piping system, all drops and hose reels are running at 90psi.

 

[bob15]

What tools are you running at full tank pressure, and what gets regulated?

He is referring to leaving the tank pressure alone and at each drop or wherever there is a tee & a hose, there is a regulator.

Personally, I would leave the tank alone and run a regulator set between 90-100 psi. I would also add a couple water separator/filters as well. I would also make sure these are drip legs in the system as well, with a ball valve on the end.

bob

 

[Graham08]

He is referring to leaving the tank pressure alone and at each drop or wherever there is a tee & a hose, there is a regulator.

Personally, I would leave the tank alone and run a regulator set between 90-100 psi. I would also add a couple water separator/filters as well. I would also make sure these are drip legs in the system as well, with a ball valve on the end.

bob

Gotcha.

I think that's the plan. Regulator first in line, then everything else. I am planning on the drip legs, ball valves, etc. as part of the system.

 

[thightower]

I like at least 150 psi. Makes a 1/2" gun thats rated for 90 psi really sing.

 

[Trey T]

There's no right or wrong way of doing it, placing the regulator at the compressor or at each drop.

The reason why one would have regulator at each drop because the compressor is far away or not reachable. Another reason is that their tool, operates at under 90psi, does not have a dedicated regulator. Other than that, I don't see any reason why you would need a regulator at each drop. Feel free to enlighten me.

 

[HIRISC]

My compressor is 2 stage and also 175psi. I have a regulator off the tank set at 90 (sometimes up to 110) and then regulate down as needed at each drop with individual filter/regulators. It's just a hobby garage. Mostly I'm running inflator, impact, plasma or air shear. I'm not doing any sandblasting or DA sanding.

Me too.. 175psi dialed down to 100psi for my tools - grinder, jig, drill.

I use this:

 

[Charles (in GA)]

I keep my regulator set to about 110 psi and figure the line loss in the hose will reduce it to 90-100 psi which is about what I want.

Charles

 

[AndyA]

Having a regulator at each drop lets you keep the line pressure higher. Having the line at higher pressure results in less loss for a given flow. See the table at http://www.engineeringtoolbox.com/compressed-air-pressure-loss-d_1014.html

A regulator at each drop makes the pressure at the drop relatively stable when other drops are being used.

None of this probably matters much for garage use. I regulate my line down to 125psi simply because that's the input pressue my filters are rated for and I don't relish the idea of exploding filters.

 

[Falcon67]

My lines go with the tank pressure - 95 kick in, 135 shut off. If I had a higher pressure compressor, I'd probably regulate the lines at 100. I use portable regulator/filters at the drops. I don't run the tools over 90 psi. I recently used my nice 16 gage nail gun at 110ish because I was too lazy to walk across the shop and get the regulator. Just needed a couple of shots in a quickie shelf, can't hurt. Lazy cost me $125 for another nailer when the main aluminum power cylinder in the gun split down the side. And that part of the gun is not serviced or supplied as a spare. Oops.

 

[Greatbear]

All my lines are at tank pressure (175psi), with filter, regulator and the occasional coalescing filter at each drop. Flawless operation since '95.

 

[78Bird]

I'm in a small garage so I regulate at the end of the line, just to let the air cool as much as possible so the filter/regulator works better at trapping any remaining moisture.

 

[KCarGuy]

I have a Main Regulator coming off my Compressor that is set at 120 PSI...Then at each drop around the Garage (there is 4) I have it split into 2 Milton Quik Connects.
One is Regulated to 80 PSI and One is not, so it is 120 PSI.
I like having the choice, for Air Tools or A Blow Gun or Whatever...without having to readjust the Main Regulator.
Each Drop has a Drip Leg. Each Regulator has an Auto Drain, plus I have a 120 VAC Auto Drain on my Compressor Tank.
So, its nice Dry Air!

 

[sberry]

I really dont care if it wears down the tools or not, I use hi pressure mains with a regs connected to general area, tapped,plumbed to secondary mainfold, hose reels. I have 4 regs in the shop but 90% is done with 2 or 3, 50% by 1,

These pics are old but this one reg feeds 2 whips on the hoist and 2 hose reels and a circuit with reel for paint guns that is regulated filtered again. There is a line between adequate service and adding on extra stuff that isnt used or needed. Good placement of hose reel rids the place of air hydrants in every imagineable place, piped to the general area, hooked it up as needed, used it, came back as needed and re- pipe,,,, pretty much at any time untill we did the most with the least.

A safety engineer type was here, a big thing he noticed was the air, served by whips and reels, NO hooking unhooking hoses to hot hydrants. All the connections done at the end of the circuit at a tool, whips are fixed in place. In pic below you can see a couple quicks but they are not end user connections.

Great thing about piping,,, a big reason I like steel on the end,, contrary to a lot of popular belief you can shut the feed valve off and change it. It doesnt have to stay a way forever.

 

[GeorgiaHybrid]

What tools are you running at full tank pressure, and what gets regulated?.....

Having a regulator at each drop lets you keep the line pressure higher. Having the line at higher pressure results in less loss for a given flow. See the table at http://www.engineeringtoolbox.com/compressed-air-pressure-loss-d_1014.html

A regulator at each drop makes the pressure at the drop relatively stable when other drops are being used.

None of this probably matters much for garage use. I regulate my line down to 125psi simply because that's the input pressue my filters are rated for and I don't relish the idea of exploding filters.

I like being able to regulate the pressure at each drop depending on what I need. There are times when I will kick the pressure up to 110 psi +/- with an impact gun and less with others (blow gun, etc). It does help regulate the airflow when I'm blasting and someone uses an impact at the other end of the shop. I also have a bunch of regulator/filters (8) from a buddy closing his shop so the cost was minimal. All of the filters that I am using are rated for my tank pressure (160 psi) and I have never had a problem with them.

 

[NUTTSGT]

This is interesting as I was considering this when I replumb my lines. I currently have a couple of CH regulators with quick connects so I can move them from drop to drop. I wanted to get away from these as I don't think they are the greatest regulators. I know they also regulate via a small bleed hole, which will make the compressor run even with out air being used. What are you guys using for regulators ?





EDIT I just did a quick check on the internet. Those regulators I have are made for up to 150 PSI. My compressor is set for 175. hmmmm, maybe that's the problem. I guess I'll be buying new ones for the replumb.

 

[Shocker]

When I plumb my lines, I will go with full air compressor pressure and regulate at the drop.

 

[fluid power]

Depends on the lines but if you are 3/4 copper or 1/2 iron the odds of you getting line losses that are too high are pretty low until you start trying to run a rivet buster.

Leave the compressor alone - the higher pressure in the tank equates to more reserve volume. (equal to bigger tank at lower pressure).

Put a regulator on the feeder to the shop and set it to about 125psi.

This is not correct.

This is against Boyles law, which states: the absolute pressure and volume of a given mass of confined gas are inversely proportional. Think of this the next time you need to remember pressure and volume. Would you rather fill a swimming pool with a fire hose or a power washer? A power washer gives you a ton of pressure, with little volume. A fire hose on the other hand, tons of volume and not near as much pressure.

Darren

 

[rodm1]

I leave the airlines at tank pressure and regulate each drop as required.

 

[cnc-me]

I keep my regulator set to about 110 psi and figure the line loss in the hose will reduce it to 90-100 psi which is about what I want.

Charles

Same here, besides if you have any small leaks they are amplified
when running higher pressures.

 

[Kevin C]

For an industrial applications I have always run the lowest compressor pressure that would deliver sufficient pressure at the regulator to run the air tool.

If the tool needs 90 psi and the filter/regulator has a 10 PSI drop at the tools max flow rate, 110 PSI would be a workable compressor cut in pressure.

Yes you have less reserve capacity in the tank with the lower pressure. But assuming you have sufficient compressor CFM this wont be an issue. What it will get you is less wasted energy and less compressor wear.

Running 175 PSI when you don't need it is a lot harder on a compressor than the extra start cycles you get from a lower pressure.

This may not be a big issue for a home shop, but when your running 40 hp and larger compressors 24- 7 the energy savings are pretty significant.

Compressed Air Systems: Reduce Pressure Settings


Overview
Most industrial compressors are designed to compress air to between 100 psig and 125 psig. Both the efficiency and capacity of air compressors decline as pressure increases; thus decreasing the discharge pressure reduces compressor energy use. A common rule of thumb is that compressor efficiency improves by 1% for every 2 psig reduction in discharge pressure. Lower air pressure also reduces the amount of air lost to leaks and extends the life of the air compressor and the pneumatic equipment in the plant. Close inspection of the figure below shows the increased electricity use required as the pressure increases to the upper bound of a load/unload cycle.





Estimating Savings From Reducing Pressure Set Points
From an energy balance, the work required to compress air from an entering temperature of T1 to an exit temperature of T2 is:

W = m cp (T2 - T1)

For polytropic expansion:

T2 = T1 (P2/P1)k where k = 0.2857 for isentropic expansion of air

Thus, compressor work can be calculated as

W = m cp T1 [(P2/P1)k -1]

The cost penalty for operating at a high system pressure is found using fractional savings.

Fractional Savings = (WPhigh – WPlow) / WPhigh

Thus, the fractional savings for operating at a reduced average discharge pressure, P2low, compared to a high average discharge pressure, P2high, when the inlet air pressure is P1 is about:

Fractional Savings =

For example, the pressure ratios after reducing the average discharge pressure from 105 psig to 95 psig would be:

(P2high/Pl)0.286 = [(105 psia +14.7 psia) / 14.7 psia]0.286 = 1.822
(P2low/Pl)0.286 = [(95 psia +14.7 psia) / 14.7 psia]0.286 = 1.777

Thus, the fractional savings would be about:

(1.822 – 1.777) / (1.822 – 1) = 5.5 %

 

[kwb]

This is not correct.

This is against Boyles law, which states: the absolute pressure and volume of a given mass of confined gas are inversely proportional. Think of this the next time you need to remember pressure and volume. Would you rather fill a swimming pool with a fire hose or a power washer? A power washer gives you a ton of pressure, with little volume. A fire hose on the other hand, tons of volume and not near as much pressure.

Darren

I think you missed my point.... a 60 gallon tank at 175psi holds more cubic feet of uncompressed air than a 60 gallon tank at 125psi.

If we treat air as an Ideal Gas that 60 gallon tank at 175psi would need to be 84 gallon tank if it was at 125psi to get the same volume of air.

Assuming that we put a regulator in the system to set pressure at 110psi or so we will have more reserve volume of air if the tool we are running draws more than what the compressor can put out. Longer periods of working before you need to wait for air to build back up again or if you are lucky enough time to finish the high draw work before you need to wait.

All of this assumes that we ignore fact that compressed air is a very expensive way to run tools - if we are trying to minimize our utility bills then you need to get a compressor with more CFM and run it closer to your line pressures.

 

[pfarber]

I think you missed my point.... a 60 gallon tank at 175psi holds more cubic feet of uncompressed air than a 60 gallon tank at 125psi.

If we treat air as an Ideal Gas that 60 gallon tank at 175psi would need to be 84 gallon tank if it was at 125psi to get the same volume of air.

Assuming that we put a regulator in the system to set pressure at 110psi or so we will have more reserve volume of air if the tool we are running draws more than what the compressor can put out. Longer periods of working before you need to wait for air to build back up again or if you are lucky enough time to finish the high draw work before you need to wait.

All of this assumes that we ignore fact that compressed air is a very expensive way to run tools - if we are trying to minimize our utility bills then you need to get a compressor with more CFM and run it closer to your line pressures.

If you need MORE AIR get a higher CFM pump. When did having a compressor run become a bad thing? Its what they do. If I am sandblasting my compressor runs all the time. I get about 80PSI out of the pressure pot and my receiver will not last a full pot. If there is a PSI drop it ain't showing up on the parts I clean.

 

[kwb]

I agree a bigger pump is the best answer but once you have your equipment you have to maximize to what it can do.

If I have a 150gallon tank and a 2 stage compressor that does 175psi but only 8 SCFM then I have to make due with it.

If I have a 40 SCFM compressor at 120psi then I make differing recommendations.

 

[Gone]

This is not correct.

This is against Boyles law, which states: the absolute pressure and volume of a given mass of confined gas are inversely proportional. Think of this the next time you need to remember pressure and volume. Would you rather fill a swimming pool with a fire hose or a power washer? A power washer gives you a ton of pressure, with little volume. A fire hose on the other hand, tons of volume and not near as much pressure.

Darren

The mass is different in the two tanks. The tanks are the same volume and different pressure. This means the tank at higher pressure has a higher mass of air in it.

Mass of air is proportional to standard volume (SCFM), the volume of air at atmospheric pressure contained in the tank. Standard volume was referred to in a later post.

 

[pfarber]

I agree a bigger pump is the best answer but once you have your equipment you have to maximize to what it can do.

If I have a 150gallon tank and a 2 stage compressor that does 175psi but only 8 SCFM then I have to make due with it.

If I have a 40 SCFM compressor at 120psi then I make differing recommendations.

I would have to wonder the time it takes for two identical pumps, one with a set point at 125PSI and the other at 175PSI to fill the same receiver.

How much longer will it tale the pump to get that last 50PSI?

Also, do you really get 40% more CFM at 175PSI vs 125psi?

If so, why don't compressors ALL run to 175psi and bump up the CFM rating from say 14 to 19 (this is for a specific model, not a home brewed setup)

 

[hughfree]

I think you missed my point.... a 60 gallon tank at 175psi holds more cubic feet of uncompressed air than a 60 gallon tank at 125psi.

If we treat air as an Ideal Gas that 60 gallon tank at 175psi would need to be 84 gallon tank if it was at 125psi to get the same volume of air.

Assuming that we put a regulator in the system to set pressure at 110psi or so we will have more reserve volume of air if the tool we are running draws more than what the compressor can put out. Longer periods of working before you need to wait for air to build back up again or if you are lucky enough time to finish the high draw work before you need to wait.

All of this assumes that we ignore fact that compressed air is a very expensive way to run tools - if we are trying to minimize our utility bills then you need to get a compressor with more CFM and run it closer to your line pressures.

Ditto that ...

 

[Graham08]

For an industrial applications I have always run the lowest compressor pressure that would deliver sufficient pressure at the regulator to run the air tool.

If the tool needs 90 psi and the filter/regulator has a 10 PSI drop at the tools max flow rate, 110 PSI would be a workable compressor cut in pressure.

Yes you have less reserve capacity in the tank with the lower pressure. But assuming you have sufficient compressor CFM this wont be an issue. What it will get you is less wasted energy and less compressor wear.

Running 175 PSI when you don't need it is a lot harder on a compressor than the extra start cycles you get from a lower pressure.

This may not be a big issue for a home shop, but when your running 40 hp and larger compressors 24- 7 the energy savings are pretty significant.

This is the logic I was using when I initially said I would like to drop the pressure settings on my compressor. Since this is a home shop, it probably doesn't make that much difference in the long term.

FWIW, I did a little checking, and Champion rates my compressor at 15.9 cfm at 175 psi. The air/hydraulic pump for my bender uses 20 cfm at 120 psi, so I don't think the compressor will have any trouble keeping up with the bender.

For right now, I'll leave the factory settings alone on the compressor, and put a regulator in line. I'll also wind up using regulators at some of the drops to run things like my riveting hammer that only need 30-40 psi.

Thanks for all the feedback, definitely a lot to think about on this one.

 

[In My Garage]

Any thoughts?

Leave the factory set tank switch alone and install a pressure regulator.

 

[ra42mario]

My 1955 Westinghouse 80gal compressor is set at 155psi and kicks on at 145psi. I don't run a regulator except whatever is on the tank from the factory. My Coats 20/20 tire machine wants 130-150psi to do tires. I only have positive results with running my air tools over the recommended 90psi. At 90psi my impact wrench feels weak.

 

[kwb]

I only have positive results with running my air tools over the recommended 90psi. At 90psi my impact wrench feels weak.

90PSI static is not 90PSI running pressure - if your lines are at 90 and you then plug a 3/8" x 50' hose into it and take off with an impact type draw you will lose ~10psi in the hose and couplers.

You either need higher than 90psi static pressure or really f'n big lines and hoses right up to the tool if regulator pressure is set at 90psi.

It took me years of continually explaining to guys on our shop floor complaining about the tools not working right that the fact they daisy chained 3 hoses together at the end of the hose reel that was the problem and not the brand new and calibrated tool.

 

[OldTC]

Mine:

Compressor/tank: "on" @ 135 psi....."off" @ 165 psi. Pressure relief valve @ 175psi

Aprox. 200' iron pipe system: one regulator near tank for entire system set at 90 psi. One pressure relief valve in system @ 125 psi.

 

[In My Garage]

You either need higher than 90psi static pressure or really f'n big lines and hoses right up to the tool if regulator pressure is set at 90psi.

I went overboard and installed 18 mm ID Topring nylon supply lines through the house and garage. Pressure drop? What pressure drop!