Best Way to Use Air Recievers

If your statements are accurate, and the modifications have already been installed, then the obvious answer would be to test the different conformations of valve openings and closings, recording the settings and the pertinent results, such as various pressure readings, equipment function, etc.; and making a decision based on that data. Normally an analysis of air flow in the system would be done before the modifications. If you were getting "pressure drops" before the modifications, then the flow rates are outside expected values, and it is possible that the modifications will not be effective.

An economic analysis of the "slightly lower pressure" energy savings would be of interest.

Hello,

Yes, the vessels have been installed, so we could do some measurements to see which solution is best. The problem is that it is extremely difficult to establish by measurement which is the best solution. Consumption is changing so frequently that any variations could be attributed to the machines' demand at the moment, rather than to plumbing changes. The scope of my question was to see if by theoretical reasoning one could see which is the best way.

No, it will make no difference. If your CFM supplied by the compressor does not exceed the requirement of the tools, no amount of receivers will improve the situation. However, since you have installed the system, I would also add a couple of non return valves to prevent the air in receivers being available to the entire system. As it is now you have only increased your total receiver capacity. By installing non returns to isolate each "tool branch" you will have the accumulated air available only to the relevant branch. This way the total receiver volume will always be available to that branch. By the way, it also makes no difference from which end of the receiver you feed the tool. See it like a balloon, the air will be available to the tool from the "t".

Will not make any difference as you will be using the the same volume of air. Will not change the amount of work the compressor needs to preform. Cost saving will be if you are able to drop the system pressure.

Was the pressure drop noted after or before dropping the system pressure?

You may not see any cost savings at all. You have already mentioned a loss of pressure to these machines. That loss if compensated for by the additional receivers will mean that the compressor is working longer to refill them.

The air accumulators that you have installed will only work if the air consuming devices that you are trying to feed have periods when their demand is reduced long enough for the air pressure in the accumulators to equalize with the pressure in the main pipe line.

In either case OZZB is right that the amount of work needed to perform the operation will remain teh same.

I do think, however, that the best solution would be to leave the 4" line open to the tool and keep the 2" lines open to the tank. The overall pressure loss through the piping should be less.

Think about it like an electrical circuit. The resistance through the 4" pipe, for a given flow, will always be less than it will for that same flow through a 2" pipe. The accumulator will be there, no mater what you do, provided it is relatively clsoe to the line, to provide supplemental volume to maintain the pressure in the line (assuming of course that you have idle periods that allow th accumulator to recharge.) If you close the 4" pipe, you force the air flow through two additional resistors in series, resistors that offer more resistance than the 4" pipe.

Our tools consume air at intermittent periods and in variable quantities, so that there will be time for the recievers to be replenished with air pressure.

This is how we could justify the addition of the receivers: Let's say that our tools require a minimum of 6 bar to work. Without the receivers we had to provide a pressure of 7 bar to the main line to ensure that when pressure drops occur the machines do not fail with low air pressure. With the addition of the recievers we could lower the supply pressure to 6.4 bar while still maintaining all machines in operation.

Just a tweak to what MrGeneRall said: we have a 2" branch coming off the 4" main, feeding a number of tools. The Tees and valve are connected to the 2" branch, not the 4" line. MrGeneRall could still be right, though when stating that the resistance is less when the air is allowed to passes straight to the tools -- at least this quantity of air will avoid the number of bends fitted to the receiver plumbing. Only the portion of the air needed to maintain pressure will need to flow from the receivers.

Are there any different opinions?

This leads to something that I have been thinking about. In my application, I have a number of machines with a high instantaneous demand but a short duty cycle. I have provided these machines with accumulators, but at times a hungrier machine will pirate the air in the accumulator. I have been thinking about installing check valves at the input of each accumulator to prevent this back feeding. (Of course, I would fit each accumulator with its own pressure relief valve.)

I have more than adequate compressor capacity, but some parts of my facility have inadequate supply lines; a situation that I am trying to correct.

Is this approach viable and useful in your situation?

The check valves will help stabilize the system pressure.You are trying to remove"ripple" in the pressure.The accumulator acts like a capacitor in an electrical circuit.With the check valve, the receiver will charge to the maximum pressure available, and discharge when pressure downstream is less than supply, therby reducing ripple.The check valve must be between the receiver and the supply, as close as practical to the demand point.

HTRN

Several years ago, I took a similar approach for a client. However, I calculated the actual air pressure required by the equipment in each area and sized the storage tank to be able to support those loads at peak usage, using a PRV from the HP storage tank. Each tank was fed continuously from the main- using branches sized for the average flow required at each tank.

The central compressor fed the minimum pressure needed (which was higher than MOST devices required) and each piece of equipment was fed with the pressure it required.

Note- that was one feed line per tank, sized for the average flow and a larger pipe leaving the tank (and PRV) sized for the peak flow at the reduced pressure.

Hi everyone.

First let me say that I agree with all that was said in terms of efficiency of air flow through friction in the pipes and providing adequate flow to the equipment, the accumulator is needed to prevent that drop in pressure to keep machinery working. Calculations must be made to ensure that the compressor can provide the necessary air flow at peak demands.

"My question is this: what is the most energy-saving way of using this system" . So are you looking at the most efficient type of compressor for your air consumption requirements. Is it better to have a compressor running all the time or a bigger unit that cycles less. Next do your thermodynamic calculations to find out how much pressure is lost through the cooling of the compressed air sitting for longer periods in your accumulator. You should look into insulating all the delivery lines as well as the tank(s) to prevent this cooling pressure loss.

1. Put a swing check (Low cracking pressure) on the inlet of each reciever to keep the higher pressure air from back flowing into the main line.

2. Put a Non Relieving Regulator on the outlet of the reciever set for pressure slightly below desired operation pressure.

The receiver will capture and hold the highest pressure at any time. When the operating pressure drops below the desired level to the pressure set by the regulator the stored air above that pressure will flow into the main air.

MUCH BETTER THAN A RECEIVER

Receivers do not make pressure and are seldom the soluion. Measure the pressure at your compressor and again at your machines. If you are losing 10% or more double your main header and main branch lines to each machine. [I know double a 4" main is 8"] This will cut your pressure drop to approximately 2% (if you keep all the parasitic crap out of the line). Filter the air one time with a generously oversized filter (Not to exceed 1 PSID at full flow) at the compressor. No regulators (except immediately prior to any machine as required) but if necessary big is beautiful and pilot operated is best. No lubricators except on a bypass line that will injest lubricant and not cause a pressure drop.

Now you picked up enough pressure to run your system and save electrical energy at the compressor with room to grow.