Compressor Load

Not in themselves. Adding users onto the system will increase the proportion of time that the compressors run, though.

What is the economic driver driving this proposal, please?

Only, if they were to be installed, it will take more time for the system to come up to pressure at start-up and to recover operating pressure following a sudden compressed air usage event.

I was to answer that if you have more kids you will have to cook more. This increases the load in the kitchen.

But if you add enough receivers the overall pressure in the system might drop to a lower level which in a sense decreases the "load" in the system.

More will need more.

If the "receivers" dont use air at all the load stays the same!

Buy a bigger air compressore and check if your distribution system (pipes) is up to the task.

^{I can see more questions coming our way . . .}

Not.

Never.

Nee
Arangkwa
Poyeda
Poi-e
Bee ya
Nahin
Naheen

Not knowing the design of your system, it's hard to provide a specific response. But, one method of reducing the frequency that your compressor needs to run under load, without changing a lot of your system is to add a pressure reducing valve just after your receiving tanks and increasing the PSI threshold that your compressors shut off. This is only of benefit if your compressors and receiver tanks are capable of higher pressures than your system pressure is currently set at.

For example, here a standard operating pressure is 80 PSI for components (cylinders, valves, etc.) It is typical that the overall system is pressured between 100 and 125 PSI (compressor turns on at 100 PSI system pressure and turns off at 125 PSI system pressure.) And Pressure Reducing Valves are located near the components that reduce the system pressure to an operating pressure 100/125 PSI down to 80 PSI.

But, if your receiver tanks are located right after your compressors (typical installation) and they are capable of higher pressures (example 175 PSI) then install an additional Pressure Reducing Valve right after the receiver tanks that will keep your system pressure around 125 PSI but allow you to store up to 175 PSI in your receivers, thus increasing their capacity and reducing the frequency of your compressor load cycle. Be careful here though as you could easily make a bomb. Your maximum pressure output capability of your compressor should never exceed the pressure capacity of your receiver tanks and piping system. If your compressor can generate up to 175 PSI but your receivers are only rated up to 150 PSI, you need to change them out, now.

Otherwise, to answer your question basically, you need to produce what you consume and your system design is impacted more by how you consume rather than how much you consume. Do you consume 45 cubic feet per minute steadily for 10 hours (45*60*10=27,000) or do you consume 9 cubic feet per second for 10 seconds, once every two minutes for 10 hours (9*10*30*10=27,000). At the end of 10 hours you consumed the same amount of air but in drastically different fashions. Where you put receiver tanks and how large they are is derived through technical analysis of your system.

Good Luck,

JavaHead

Only if they are used, or if they are leaky.

If air receiver is meant to be an air receiving tank:

Question is why are you asking about increasing the amount of air receivers. Is there more users in the system? And why not looking at it from a point of increasing the volume in the system?

In general if the air usage in the system is the same the compressor will have to provide the same amount of compressed air - regardless how much volume is in the system - but only in in longer intervals.

If the increased volume means that the system can be kept at a lower pressure the work from the compressor might indeed be less. It all depends on the system and what is required.

Back to you or was this a rhetorical question?

P.Nithin Kumar-

The present load on the compressor will not change (be lowered). You are still using the same amount of compressed air but are storing it in receivers closer to its use. The load going out at the user locations is what determines the load going in and the compressor's total run time. The only thing that will change is a longer time to bring the system up to pressure because of the increased volume of the receivers vs. without the receivers.

Even operating the compressor at a higher maximum pressure and reducing it at the use point will not change the load. The pressure regulators will reduce the line pressure but the user points still use the same amount of air at their operating pressure. Higher compressor pressures will make the compressor work harder to achieve the higher pressure and cause the components of it and the piping to fail more frequently. The higher pressure would permit you to use smaller piping but the compressor load is determined by the volume and pressure of the air used.

Good Luck, Old Salt

We are having 3 compressors (1000 CFM) in which 2 compressors ( Reciprocating Compressor )will be in line ( 1 Compressor is standby). Our System req 100 PSI pressure and we had set :

Compressor # 1 - 94 loading & 100 Unloading

Compressor # 2 - 96 loading & 102 Unloading

and compressor will get load within 60 sec and for almost 2 min.It doesn't mean that 2000 Cubic feet of volume is consumed. But due to minute consumption of air with 100 psi creating the pressure drop in the main line resulting loading of air compressor.

My opinion is if we provide additional receiver , pressure drop in the system is less when low volume of air is consumed with 100 psi.By this there will be a mintue variation in loading & unloading further minimizing the Power.

Pl suggest

Nithin

Essentially, you're correct. And, from your description it sounds like you do not have any receivers currently; adding them will help. And the higher pressure you charge them to the more benefit they will provide.

P. Nithin,

Sure....Nitin, ... Sure....

The load on the compressors is reduced for every air receiver added to the system !

In fact, some plants add so many air receivers to their system that the compressors never run at all !

Hope that this helps !

That's a good one!

Not really what it will do is make the compressors work more to maintain the pressure, since you will have more volume stored.

Of course the load will depend heavily on the actual air consumption more than the number of volume bottles.

The only advantage you would have is that the system will be emptied in a longer period of time.

Advantages to having more receivers for us include:

air where you need it, at the pressure you need it

fewer start/stops on your compressor motor (or load/unload all the time and the compressor never shuts off)

We have rotary screw compressors and condensate builds up in the oil. If the compressor is only run for a few minutes at a time the oil doesn't get hot enough to "release" the water back into the air stream to be removed by condensate traps and driers down the line.

We even have ejectors that use a lot of air in a 5 second blast every 10 minutes , so the receivers near them have their air supply from the compressors metered (choked down) so that only one compressor loads and slowly fills them instead of two or three compressors turning on to quickly refill (when we don't need that air for ten more minutes).

Adding receivers to an air system increases the storage capacity and does not reduce the load demand.

Receivers are either active or passive depending on where they are located in the system.

Receivers act as accumulators in the system and increase the time between compressor loading cycles which in turn decreases the mechanical and electrical wear on/to the compressors.

If properly sized and properly placed in the system, the receiver(s) can reduce electrical power consumption by decreasing the quantity of compressor start and stop cycles therfore reducing high in-rush current events that are experienced during locked-rotor starting.

Keep in mind that the system piping also serves as a receiver/accumulator.

There are standard formulea available to apply for determining the proper sizing of recievers and there is a myriad of free information available on system design and receiver placement.

Hope this helps,

Jim

Just adding a receiver will not reduce the load. In fact it might increase the load. The load is governed by demand. The receiver supplies extra air when demand exceeds the steady output of the compressor. If an intermittent occasional demand exceeds both the receiver capacity and the compressor output, then pressure will drop (and machines might not work). The compressor, meanwhile running at this lower pressure, has less work to do.

A bigger receiver (or adding a receiver might) might provide the extra air to maintain pressure at the time, and by adding a receiver it means the compressor has to provide more air to fill it. The compressor will run longer at full pressure to recharge the receiver during periods of less demand.

In effect this increases the previous load because the compressor now runs at full pressure for more of the time.

There comes a time however when the compressor runs flat out non-stop, at which point adding receivers makes no difference.

You need to determine the amount of time your compressor(s) are loaded (making air). Such as; the compressor is loaded 58 minutes out of every hour. If this were the case then the compressor is under sized. If say the compressor is only making air 30 minutes out of every hour, then adding tanks to smooth the load might work.

You should really get someone to help you with an in plant air system analysis. This will tell you what conditions your compressor(s) are operating under and give you a true picture of what needs to be done.

P.Nithin Kumar-

With all due respect for other contributors, your question states:

"If we increase the number of air receivers in the plant , does we reduce the load on the air compressor or not ?" Nothing else, just this.

The simple answer to this is NO. It doesn't matter how many receivers you have, once the compressor starts up it will run longer to fill them and the load doesn't change, if no other additional devices are added to use more air. This additional load is compensated for with no receivers since the compressor had to run more frequently to maintain the air for the load. The longer start-up is also compensated by the use of residual air from the receivers when the compressor is shut down.

This system is similar to scooping 1 qt containers, a 5 gal pail and a 55 gal drum. In order to maintain a constant level of water for every qt taken out you must put another one in. If you are taking them out of a 5 gal bucket you only have to replace what you take out. With the 55 gal drum for you only have to replace what you take out, one qt out--> one qt in of the water. This analogy also says that it takes more water to fill up the 55 gal drum to get started but once you stop refilling it there is more water left in the drum to keep on scooping out the qt's. You get to start taking the qt's out sooner with the 5 gal pail but it will not provde as much water after the refilling has stopped. With air, water and almost everything the output used determines the input. More out ---> more in, less out--->less in. Also the ideal gas law, if utilized, will show that pv=nrt, which comes out with approx. pressure in * volume in = pressure out * volume out.

Thus your load does not change if you are using the same amount of air from the system. From a practical standpoint though, a compressed air system with many receivers will require a slightly smaller load of the compressor. Compressed air systems are usually started when they are lower than normal operating pressure and shut down when they are at operating pressure. With the receivers it takes slightly more work of the compressor to get the receivers back up to operating pressure but less initial motor start-up loads.

The only factor reducing the load, one extremely small, would be an decreased frequency of the compressor starts with the receivers. This is negligible when compared with the running power requirements.

Good Luck, Old Salt

Additional receivers are located near usage point. Selection of Receivers is based on air consumption (CFM) and distance from compressor to receivers.

To answer your question,

Power consumption of compressor will increase. Compressor will always run after cut-in pressure and stops at cut-out pressure. These pressure remains same. As you increase number of receivers, volume of air in the system increases. Compressor will have to run more time to fill in additional volume of air. This running will be at 80% to 100 % of full load.

Hop this will resolve your problem.

Let's assume your system pressure is at 100psi. Both compressors will be off-load (running, but not pumping) The air will be provided by the receiver. The system pressure will drop to 96 psi when compressor no.2 starts pumping. Assuming the load is less than 1000 cfm, then the pressure will rise to 102 psi. when No.2 cuts out.

Alternatively assume the demand is more the 1000 cfm then No.2 will not cope by itself and the system pressure will fall to 94 psi when No.1 cuts in as well.

The point to make (assuming the does not exceed 2000 cfm) the working pressure of the system could be as low as 94 psi at source. If this pressure is not enough to run your machines then you will need to increase the cut-in pressure.

However it is likely that your pressure problems are related to pressure at the machines at the point of use after it has dropped due to friction of the pipework beyond the receiver(s), but the first things to look at are the filters and dryers for blockage.

If these are OK, and there is still a pressure problem at the point of use, then this is likely to be the demand being too high for the diameter of the pipework. I this case the addition of a receiver here would help providing the demand is intermittent. If the demand here is constant then you have little choice but to increase the size of the pipe.

But to answer your original question - the addition of a receiver will not educe the load. See my previous post - 14.

In response to 18 and 19, you will probably benefit from the addition of a receiver for many reasons. But in answer to the original OP, the only way that load can be reduced is to run the compressors for less time, or at lower pressure.

This could be achieved by addition of a receiver that is large enough to meet the demand at a lower nominal system pressure. This being the case then you can run the compressors to cut-out at a lower max pressure.

Running at a lower max pressure means you will need to increase the receiver capacity to compensate.

If you really want to reduce demand then fix leaks and switch off pneumatic equipment.