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Air Consumption

11/17/2011 8:50 AM

In Our Plant 2 nos 1000 CFM Compressors are running, I don't know how much air consumption in the plant due to vast usage, I want to stop one compressor or to reduce the loading time of compressor to save energy.

For this if I keep 1 air Receiver of 3 Cu mt Capacity would acheive my purpose?

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#1

Re: Air Consumption

11/17/2011 9:16 AM

Most compressors work off pressure switches. They stop and start to maintain the pressure at some minimum and maximum threshold. If both compressors run continuously it maybe you air consumption never allows the system to reach max pressure.

Reduction of receiver capacity will do nothing to reduce energy.

Other areas to save energy is reduction of the system pressure. Soft starters on the motors if they cycle on and off.

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#12
In reply to #1

Re: Air Consumption

11/19/2011 4:16 AM

Not with compressors of this size, they reach the set pressure then Unload the pistons so they aren't under load, To stop & start a machine of that size takes time & energy, a 1000cfm compressor is a big piece of kit.

Bazzer

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#2

Re: Air Consumption

11/17/2011 10:02 AM

Have you gone through and repaired all of the leaky connections?

Do you have records of how long the compressors are running?

You need to establish a baseline of current conditions, before any repairs, in order to know what effects the repairs or other changes make.

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#3

Re: Air Consumption

11/17/2011 11:38 AM

Hi P.Nithin Kumar,

An air receiver, is only really a help if you have a varying demand, as it will help to smooth out the peaks and troughs.

As already stated, check for leaks, because unless you have a first class system in place where you are constantly monitoring them, and fixing them, they are likely to be costing you a great deal of your air (and money), it could be that half of the output of one of your compressors is being wasted.

Air leaks of 25% of the system output are not uncommon.

Best regards,

John

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#4

Re: Air Consumption

11/17/2011 4:19 PM

A larger reservoir can help in some situations where usage is high but variable. It can help reduce cycle times. However, unless you have identified all the leaks, and fixed them, this would be secondary.

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#5

Re: Air Consumption

11/17/2011 10:57 PM

where you are useing the compressed air ?

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#6

Re: Air Consumption

11/18/2011 12:28 AM

If you are not having any reciever, please have one immediately. Start with 3 cu.m capacity. It will even out short peaks.

Please find out how long the compressors run on "No-Load". This is the period when compressor runs but no air is delivered. You can find out from the ammeter reading itself.

On off day, run a compressor and move round the plant with ears open.All hissing sound be investigated and taken care off.

You can also know the air leakage by just finding out how long it takes the pressure gauge to come from peak to around 50 psig on non-working day.

If your peak pressure is 100 psig, reduce it to 95.And see if anyone complaining. If no one complains then do similar excercise to find who is the first one to complain. Lower pressure will also reduce power consumption.

Study your distribution line and see what is the peak pressure difference from compressor end and this point.This will give you an indication of pressure drop due to incorrect sizing of pipe lines.

Try these and report back.If you do not have ammeter,pressure gauges etc please put these first. There are much more on reducing energy, but the same can be advised post above simple checks and actions.

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#7

Re: Air Consumption

11/18/2011 12:34 AM

Hi kumar,

1.If your compressors are reciprocating type they should not run continuously.

2.You do not mention whether the discharge pressure & pressure at using points is almost same(considering the line loss) or not.If delivery pressure is higher you will be benefitted by installing an air reservoir(say for half an hour storage).In that case one compressor will run & the other is on stand-by mode.The stand-by compressor will run after getting signal from the reservoir pressure.The set pressure should be selected in such a way that the using points are not disturbed.There should be a higher set point where the stand-by compressor will stop. The two set points & the storage tank capacity are to be chosen so that the stand by unit should not run frequently.

thanks

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#8

Re: Air Consumption

11/18/2011 5:26 AM

I used to work with four 1000cfm vee triple stage broom-wade compressors,and to turn one off & on again is not advised, the start up loading is more expensive than to leave it "unloaded", To answer your question on receiver capacity is impossible without knowing the consumption of the plant,I would think that to find that consumption would'nt be that difficult,If your useing two 1000cfm compressors my gess is that your running a few machines that are the same,so you only have to workout one & multiply,in most cases the maufactures hand book will tell you the consumption, I know it will be time consuming but you may find that you need a bigger or aditional receivers, with the four units we were running we had four receivers,4ft dia x12ft tall,and these were placed close to where the machines were so each area that had a high consentration of consumption had it's own storage tank.

Bazzer

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#9

Re: Air Consumption

11/18/2011 7:55 AM

Assuming they are reciprocating compressors they will pump 1,000 cfm while on-load and nothing when off-load (where off-load means the compressors are running but not pumping).

Pick the busiest time of the day and with a stop-watch time each compressor for on-load and off-load. A simple example will show that if one comp runs for 6 mins on-load and 4 minutes off-load means the comp is delivering 1000 cfm for 6 minutes out of the 10, thus an average of 6/10 x 1000 = 600 cfm. The second compressor might be running for 3 mins on and 9 mins off, thus 3/12 x 1000 = 250 cfm.

The total average demand is 850 cfm so you could shut one comp down. If the average is over 1000 cfm then the second comp will have to run - but this could be arranged by a suitable stop-start pressure switch set to come in when the pressure drops too low (with a run-on timer to prevent too many starts per hour).

Then add a change-over switch to allow each compressor to take turns (a week on and a week off) in meeting the base load.

....after you have fixed all the leaks and made sure that the air supplies to machines not in use is are switched off. The latter load could be estimated by timing the compressors again when it is known the machines are not in use.

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#10

Re: Air Consumption

11/18/2011 7:57 AM

Power consumption in unload condition is between 25 to 30%. It is better to switch off motor will need Soft Starting unit.

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#11

Re: Air Consumption

11/19/2011 12:19 AM

Before any modification in your air system you have to do lot of home work. You have to have answers to questions like

1) what is the required pressure of air system at your works and how much vaiation is acceptable

2) How much of the air is really required for productive work and how much is used for other works (cleaning etc.)

3) What is the present loading/unloading running hours of the compressors

4) Do you require same pressure at all the time

5) What is the condition of air system network (Piping, hoses, valve, traps etc.)

6) What is the controlling system of usage of air.

7) In present system where is the pressure switch installed for unloading of the compressor, if receiver is there, what is the capacity.

8) Leakages in the air net work and dirty suction filters of the compressors shall be checked frequently to get the efficiency,

9) Is it possible to store compressed air at high pressure and release to plant usage after let down to required pressure

After audit of your system, you can very well decide for the instalation of the capacity receiver.

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#13

Re: Air Consumption

11/29/2011 9:35 AM

1)what is the required pressure of air system at your works and how much vaiation is acceptable

Required Pressure ( Spec) is 95 psi 5 Psi Variation is allowable

2) How much of the air is really required for productive work and how much is used for other works (cleaning etc.)

Cant Measurable Because of Huge Usage with Very Large and Small Pneumatic Equipment

3) What is the present loading/unloading running hours of the compressors

Loading at 95 psi and Unloading at 102 psi

4) Do you require same pressure at all the time

Spec is for only 4 RAM Cylinders , Other than these We dont Need Same Pressure

5) What is the condition of air system network (Piping, hoses, valve, traps etc.)

6) What is the controlling system of usage of air.

We Had Regulators at Few Areas Where We Dont need Full Pressure

7) In present system where is the pressure switch installed for unloading of the compressor, if receiver is there, what is the capacity.

We Had 3 Compressors in which 2 are Running , for Each Compressor we had 3 Cu mt Capacity air Receiver

8) Leakages in the air net work and dirty suction filters of the compressors shall be checked frequently to get the efficiency,

Already we Have Checked all Leakages and Corrected., and we are Cleaning Suction Filter Every Day

9) Is it possible to store compressed air at high pressure and release to plant usage after let down to required pressure.

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#16
In reply to #13

Re: Air Consumption

11/29/2011 10:26 AM

It is not clear how much air RAM cylinders are taking, but if this is key high pressure component, it is better to isolate this with another compressor of high pressure and use low pressure for other areas. 5 psi variation is too less. In some case an intensifier can help. Only for RAM cylinder high pressure can be created from a low pressure supply. This is good if RAM cylinder consumption is comparatively lower and difference of pressure with other consuming points is high.

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#17
In reply to #16

Re: Air Consumption

11/29/2011 10:44 AM

We have 4 Ram Cylinders for 4 Machines in which Ram Cylinders have Different Capacity

1 ) 24 "dia , 57.5" Stroke - 1 no

2 ) 22" dia , 57" Stroke - 3 nos

  • Ram Cylinder Pressure tolerance is 5 psi , Spec Give by Technical Dept From Our Plant Which Cant be Changed ( if Tolerance Changed it effects the Quality of the Product)
  • We Cant Place High Pressure Compressor Separetly for ram Cylinder because total Pipe Lines in the Plant has to e Changed.
  • Major Consumption takes place in the Ram Cylinders it self

Best Regards

Nithin

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#18
In reply to #17

Re: Air Consumption

11/29/2011 11:31 AM

How often do the RAM Cylinders operate and do they work at the same time or is their operation staggered also how fast do they operate (time to out-stroke and in-stroke and is there a delay between the two movements)?

The 24" Bore one has a volume of approximately 30 Cubic Feet and the 3, 22" Bore ones have a volume of aproximately 76 Cubic Feet giving a total consumption of 106 Cubic Feet.

A 3 Cubic Meter air receiver has a volume of 106 Cubic Feet.

It seems that the compresser pressure of 95 to 102 psi is too close to the operating pressure of the cylinders if that is 95 psi.

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#20
In reply to #18

Re: Air Consumption

11/30/2011 4:19 AM

For 4 Ram Cylinders , we Have 4 Air Receivers each of 3 Cu mt Capacity.

And the Ram Cylinder Operation depends upon the Batch Loaded , Once Loaded its Operation Depends on the Sequence of the Batch ( Approx , it Operates for 4 Cycles(up and Downs) within 2 Min.

Delay Between 2 Strokes depends on the Sequence of the Batch

Best Regards

Nithin

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#21
In reply to #20

Re: Air Consumption

11/30/2011 4:45 AM

Hi Nithin,

What do you make at your facility?

What is the Minimum pressure you need to operate the Rams at?

The 4 cycles, is that all the Rams working at the same time?

Best regards,

John

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#14

Re: Air Consumption

11/29/2011 10:05 AM

We Have 2 Stage Double acting Reciprocating Compressor (1000 CFM Means 1000 Cu ft of Air Delivered in 1 min ) ,which load /unload according to the Pressure. Loading Pressure is 95 Psi and Unloading pressure is 102 Psi. During Loading it takes 450 Amps and in unloading it takes 280 amps ( Motor Capacity is 250 KW ).

We Have 4 Air Receiver Near Machinery ( Excluding 3 Air Receiver In Compressor Room) Each of 3 Cu mt Capacity.

Loading and Unloading Depends on the Pressure Drop Occurs in the System.

For Ex:

If the pressure drops to 95 psi then Compressor gets Loading and it Continues till 102 Psi .., if it takes 6 Min For loading ,it Doesn't Mean that 1000 * 6 Cu ft of air Delivered in 6 Min.

1000 CFM is a Volume Parameter and we Had setted Loading and Unloading of Compressor Based on Pressure..,if air Consumed for a Small Cylinder is Say 100 psi but with Very Less Volume even in this Condition also Pressure Drops and Compressor Starts Loading till Setted Pressure.

In Our Plant So many Diaphram and Piston Valves using we doesn't have Much Air Consumption but it Creates pr Drop in the Header Line. These are Located at 12 mt Level ( Second Floor, Remaining all Machines are at 6 Mt level (First Floor) ) and the Air Line Tapping Taken Directly from Main Header Line.

So Even when Small Valve Operated it Creates Pr drop directly in the Header which results Loading of Compressor.

For this case , i am Thinking to Place 3 Cu mt air receiver at 12 mt level (second Floor) ,so any air Consumed by the Valve it Wont Create Pr drop immediately on the Header Line ( Due to the Presence of Air Receiver) which Avoids the Loading of Compressor.

Pl Guide and give your Valuable Suggestion

Best Regards

Nithin

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#15

Re: Air Consumption

11/29/2011 10:17 AM

I need Small Clarification :

Case 1:

There is Air Receiver of 3 Cu mt Capacity filled with 100 psi Pressure .., I Consumed 1000 CC of air for Cylinder with 75 psi pressure.

Case :2

There is Air Receiver of 3 Cu mt Capacity filled with 100 psi Pressure.., I Consumed 1000 CC of air for Cylinder with 40 Psi Pressure.

And My Doubt is :

What would the Deficiency of air in Both Air Receivers interms of Pressure and Volume.

Here, I want Comparing the Both Air receivers intake Consumption. How We Calculate the Air Consumption from the Air Receivers, is there any Formula for Calculating.

Note :

This is related to my project - Air Consumption

Best Regards

Nithin

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#19

Re: Air Consumption

11/29/2011 11:35 PM

RAM cylinder need is too tough and since it is main consumer, you have no option but to feed it by the compressors. Since your other consumption are at much lower pressure, it is better to isolate that from RAM cylinder circuit. Reducing pressure from mainline to supply low pressure areas is not a solution. A separate Compressor at 2nd floor ( eg Screw type) closer to low pressure load will pay off handsomely. You may need some additional pipelines for this isolation. Isolation of high pressure and low pressure sections are key to your solution and will save energy too.

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