Air Compressor Pressure Settings – Air Compressor Manufacturers

Every 1 bar increase in compressor pressure costs about 7% more energy. From 7 bar to 8 bar, 7% more on the electricity bill. From 7 bar to 9 bar, 14% more.

Afraid it's not enough. Those words are worth discussing properly.

Some piece of equipment occasionally reports low air pressure. Equipment department's first reaction is bump the pressure up a bit. After adjusting, that equipment stops complaining. Problem "solved." Then it stays at that high pressure. Nobody ever thinks about whether to turn it back down.

What's wrong with this approach? Equipment stopped complaining. Production is normal. Isn't that fine?

The problem is with the word "solved." The actual cause of low air pressure was never investigated. Why was that equipment getting low pressure? Was the compressor station output insufficient, or was the loss too great getting the air there? These are two completely different things. The first genuinely needs higher pressure. The second, raising pressure just uses more electricity to compensate for losses along the way.

Industrial pressure systems — Compressed air pressure management

Pipe pressure drop is severely underestimated. Air leaves the compressor station, passes through main line, branch line, elbows, valves, tees, reducers, winds around to reach the use point. Losing pressure the entire way. Smaller pipe, more loss. Longer pipe, more loss. More elbows, more loss. Some old factory sites, original construction piping still in use decades later. Production capacity multiplied several times. Same old piping. Station outlet at 7 bar, workshop endpoint might only have just over 6 bar. Equipment complains about insufficient pressure. The source isn't the compressor.

Bump station pressure from 7 bar to 7.5 bar. Endpoint goes from 6 bar to 6.5 bar. Equipment stops complaining. Problem solved? Solved. Solved correctly? No. The extra electricity at the station is real money. The pipe pressure drop issue is still sitting there. Add a few more machines later, have to bump it up again.

This happens once or twice and it's invisible. Accumulated over five or ten years, pressure setting has crept from an original 6.5 bar up to 8 bar. Each increase had its reason at the time. Added together it's a muddled account. Equipment department KPIs count downtime. Electricity isn't their problem. Energy management watches the electricity bill and worries. But they don't manage equipment. Can't adjust the pressure. This parameter just keeps climbing. Climbing to a number nobody can explain why it's that number.

Has anyone ever done this: list the pressure requirements of every air-consuming device in the workshop. Find the one with the highest requirement. See exactly how many bar it actually needs.

Not many factories have done this. Most of the time it's a gut-feel number. Leave plenty of margin. Higher is always better than lower. Higher is indeed better than lower. Question is how much higher is enough. If 6.8 bar works, setting 7.5 bar means that 0.7 bar of headroom is doing what? Burning electricity. At the 7% rate, nearly 5% of the electricity bill is paying for the psychological comfort of "higher is always better."

The rational approach is to work backwards. Highest-pressure equipment in the workshop needs 6 bar. Estimate 0.5 bar pipe loss. Estimate 0.3 bar filter and dryer pressure drop. Compressor station output set at 6.8 bar. Not confident, set 7 bar. Anything above that is wasting money.

One scenario is tricky: vast majority of workshop equipment only needs 5 to 6 bar, but one or two specialized machines need 8 bar. Set the whole factory at 8 bar, all those 5 and 6 bar devices are along for the ride at high pressure. This is when you should consider solving for those one or two high-pressure machines separately. Either run a dedicated line with a small high-pressure compressor. Or install a booster at their inlet to step up the main network's low-pressure air. Raising the entire system by one or two bar to serve one or two machines, the math doesn't work no matter how you calculate it.

Pressure gauge calibration — Pressure system optimization

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Back to the "afraid it's not enough" mindset.

Afraid it's not enough so leave margin. The logic itself is fine. Question is how much margin and based on what. If the basis is "higher can't be wrong," that margin will keep growing. Today add 0.3 bar. Tomorrow something happens, feels still not safe enough, add 0.2 bar. Day after, new person takes over, doesn't dare touch it, maintains it. A few more years, another incident, add a bit more. The margin itself is inflating.

There's also a situation where the working pressure on equipment manuals gets misread. Nameplate says 0.4 to 0.8 MPa. Some people interpret this as must supply 0.8 MPa to work. Actually that means anywhere in this range is fine. Running at 0.5, 0.6 MPa works perfectly. No need to supply the upper limit. One or two machines misread this way, pressure requirement gets overestimated. Whole factory's pressure setting follows it up.

Leakage deserves a quick mention. Leaks everywhere in the system. Fittings, valves, hoses, cylinder seals. Accumulated leaked air volume is considerable. Enough leaks and system pressure can't hold. Operators go bump up the setting again. Raising pressure to compensate for leaks means spending more electricity to produce air that leaks away. And higher pressure means more leakage. Vicious cycle. Can't be solved by adjusting pressure. Have to find the leak points and seal them.

Pressure gauges are another easily overlooked thing. Gauge goes inaccurate. Displays 7 bar, actual might be 7.3 or 6.7. High by 0.3 bar means 2% extra electricity per year. Low by 0.3 bar means endpoint equipment is underpressured and not performing right. Bourdon tube pressure gauges drift over time. Periodic calibration is no big deal. The gauge at the station outlet is the most important. That one's off and everything downstream tracks wrong.

Air demand has peaks and valleys. Pressure fluctuates accordingly. Too much fluctuation means the receiver tank doesn't have enough buffer capacity or the compressor can't keep up with load changes. VFD machines are smoother than fixed-speed. Can continuously track the load. Fixed-speed relies on load-unload switching. Pressure curve is sawtooth-shaped.

Industrial compressor system — Compressor system pressure management

These detail problems each have their own solutions. But they share one thing in common: none of them are solved by raising compressor station output pressure. Big pipe loss, fix the piping, add a receiver tank. Too many leaks, repair and replace. Gauge inaccurate, calibrate it. Big demand swings, add VFD, add a receiver tank. Every issue has a targeted solution. Raising pressure is the easiest solution. Also the most electricity-wasting solution. Easy and efficient are usually incompatible. On this matter especially so.

Pressure optimization isn't a one-time deal. Production lines change. Equipment gets added and removed. A value that was reasonable three years ago may not be anymore. Some equipment has been retired. That high-pressure requirement no longer exists. But the pressure setting stays at that level. Nobody touches it. Re-evaluating periodically is a good habit. Avoids long-term hidden waste.

Compressors are major electricity consumers in a factory. Pressure setting is the key parameter affecting their energy consumption. The hard part isn't calculating what the right value should be. The hard part is someone being willing to spend the time to do it, instead of just cranking the pressure up with "afraid it's not enough."