7/16/2015 3:53:27 PM

Compressed Air Audit

The first step in controlling compressed air costs is finding out what you have and how much it costs.

1.    What exactly is the compressed air audit?

Compressed air audit is the method of studying the whole compressed air system including compressors & user side.

2.    Why the audit should be conducted?

“Air is free but compressed air is not” It is necessary to know the exact scenario of the whole compressed air network i.e. whether the compressors are working efficiently or there are line losses or there are any leakages, etc. also to know what is exactly required to run the plant in stoichiometric conditions so as to save the energy.

3.    What are the activities for air audit?

•    Compressor efficiency testing.
•    Pressure profiling.
•    Power profiling.
•    Flow profiling.
•    Analysis of auxiliary equipment.
•    Analysis of the network & piping design.
•    Leakage detection & tagging.

Scope of the Air Audit

4.    How the compressor efficiency is tested?

At the outlet of compressor a flow meter is installed through tapping and the flow is measured & compared to rated flow.

5.    Audit methodology steps

6.    What provision is required from the customer’s side?

Tapping’s at the outlet of the compressor at the specific distance which will be provided. One Mechanical engineer, one Electrical engineer & one fitter to be deputed with the auditor.

7.    Is it required to shut down the whole plant for the tapping?

For tapping at the outlet of compressor only that specific compressor needs to be shut down. For the flow analysis of the demand side then only the specific line needs to be shut down at a time.

7/16/2015 3:45:43 PM

FAD Meter

1.    What is FAD Meter?

The FAD Meter is vortex flowmeter custom designed to monitor the efficiency of the compressors. It is the only flowmeter that integrates pressure and temperature compensation and gives an accurate information of the compressor’s true output, its Free Air Delivery (FAD)

2.    What is FAD?

Free Air Delivery: It is the amount of Atmospheric Air (Free Air) that is sucked in by the Compressor at inlet (Suction Side) in order to produce a given amount of compressed air, under conditions like:
•    Atmospheric Pressure at 1 atmosphere.
•    Atmospheric Temperature at 20°C/15°C.
•    Relative Humidity at 0% (100% Dry Air) &
•    The motor RPM at 100% of its rated value

3.    Why is it important to use the FAD Meter?

The efficiency of compressors is affected by factors such as altitude of location, temperature, dust, humidity etc. This means that the output of the same compressor will vary from location to location. For example, a compressors will produce 7% more FAD in Pune than at Chennai (due to altitude difference). By measuring the FAD, we can monitor the efficiency of compressor in real time, and then compare it against the rated output given by the manufacturer

4.    How FAD Meter works?

Forbes Marshall FAD Meter is a mass flow meter which works on the Karman Vortex Street principle of flow measurement. Compressed air passing through the flowmeter body create vortices, and an piezo-electric sensor then measure the frequency of vortice formation, and calculates the flowrate as per that. The integrated pressure and temperature sensor then help calibrate the output of the flowmeter to make it more accurate.

5.    Where it should be installed?

The FAD Meter is installed on the outlet of the compressor. A straight length of 20D  (flowmeter inlet) and 10 D (at the flowmeter outlet) is to be maintained in order to get accurate readings.

6.    What are the advantages of Forbes Marshall FAD Meter over other air flowmeters?

a)    The integrated pressure and temperature compensation of the FAD meter ensure a best ever accuracy. No other flow meter offers this feature.
b)    Lesser energy consumption - Orifice type, DP flow meters induce a pressure drop in order to measure flow. In order to compensate for this the compressors have to generate higher pressure pressure, causing higher energy consumption. The FAD meter causes only very marginal pressure drop.
c)    The FAD meter has no moving parts. This ensures a long life and better performance.

7.    Benefits of FAD Meter

  • Accuracy of +/- 1% of measured value
  • Optimum process reliability thanks to Flodoc Intelligent Signal Processing stable readings, free of external disturbances
  • Reconcile generation with consumption and losses
  • Reduce downtime through preventive maintenance
  • Avoid periodical overhauls, When not necessary
  • Better process control resulting in enhanced product quality


Very simple to compute the Monthly Bill of compressor:

Example: Your’s is a 2,340 cfm (Free Air) Compressor,
        Then your Monthly Electricity Bill is,
(In Rupees)    = 2,340 × 0.95 × 60 × 24 × 30 / 100
           [1 cubic feet of Air (Free Air) costs approx 0.95 paise.]
= Rs 9,36,000/-    
= Rs 1,15,24,000 /- per Year
= approx Rs 1 Crore 15 Lacs per year

An Investment of close to 1% of this 1 Crore 15 Lacs is worth investing to monitor this 1 Crore 15 Lacs!
7/16/2015 3:37:13 PM


1)    What is exactly CountAir?

CountAir is a comprehensive monitoring system for compressed air networks. It keeps track of compressed air from generation to consumption. It gives, at a glance, data on performance of key parameters, and helps identify areas for attention and improvement in performance.


2)    How it will inform about leakages in compressed air n/w?

The CountAIR continuously monitors the total generation of compressed air and the actual consumption of air in the various user lines. By doing this it keeps track of the gap between demand and supply. Moreoever, it identifies the trends of consumtion in all the lines and based on that is able to identify the leakage in the user lines.

3)    What are the different parameters that the CountAIR can monitor?

The CountAIR monitors the key parameters of the compressed air network such as Flow, Pressure,  Temperature and Power.  Monitoring these parameters gives  you a precise understanding of the system’s performance.

4)    Is the CountAir compatible with existing flowmeters and instruments of other makes?

Yes, CountAir can integrate inputs from most makes of flowmeters and field instruments.

5)    What are the key features of CountAir?

a)    Historical trends of each unit/area with graphical representation
b)    Benchmark for the system
c)    Alarms when demand spikes in any area
d)    Real time, user selectable alarms   
e)    Intelligent or user defined benchmarks for generation and consumption
f)    Real time compressor efficiency monitoring
g)    Linking with existing DCS or SCADA

6)    What are the benefits of CountAir?

a.    Comprehensive, Real-time plant monitoring online
b.    Round the clock updates on compressed air system performance
c.    Pressure profiling and analysis of usage patterns
d.    Monitoring of compressor performance and efficiency
e.    Acts as an Early Warning System
        i.    Reduces response time to system problems such as leakages, compressor tripping etc
        ii.    Helps reduce downtime of system components
f.    Identify areas of energy wastage
g.    Identification of pressure drops across the system

7/16/2015 3:38:42 PM


1)    What is an AirMon?

⇒    The AirMon is a cost-effective, budget-friendly vortex flowmeter with integrated online pressure & temperature compensation, specifically designed for measuring compressed air consumption on distribution lines. 
2)    If not installed, what we are losing? Or Why it is needed?

⇒    Without accurate metering of your compressed air distribution lines, it is practically impossible the real consumption of your plant. Most plants usually meter their compressed air at the compressor outlets only. In such a scenario the assumed consumption also includes wastages, leakage, artificial demand etc. Therefore to know the real plant demand, flowmetering at user sides is essential. The AirMon provides a much higher accuracy and technology as compared to other low-cost options and thus get the exact measure of demand.

3)    Can it be monitored centrally? How?

⇒    The AirMon can communicate with any central monitoring system, BMS or SCADA. It provides a 4-20 mAmp signal, and can be integrated into any existing or new system. It comes along with a flow totaliser that also offer MODBUS communication.  

4)    Does it need any straight length?

Yes. General upstream & downstream straight lengths to be maintained are 20 D & 10 D.       

5)    Benefits of AirMon

a)    Specialized solution for utility metering of compressed air
b)    High accuracy
c)    Cost Effective solution
d)    Maintenace-free sensor design
e)    ROI (Return on Investment) for AirMon is within 6 to 9 months


    Assuming at 6 bar of pressure the specific power consumption is 0.2 Kw/CFM and considering out of total 1000 CFM, 100 CFM as a loss/wastage then –
    Power for 100 CFM = 100*0.2 = 20 Kw
    Hence, yearly power loss = 20 Kw*24 hr*350 days = 168000 KWh
    Annual cost of losses = 168000 KWh*6.5 Rs/KWh = 10,92,000 Rs.

Thus, just monitoring the compressed air network with AirMon & FAD meters, we can get the huge savings. Also prevent the loss of power & conserve the energy.
7/14/2015 12:25:21 PM

Master Air Control (MAC)

1)    What is the Master Air Control?
⇒    Master Air Control (MAC) is an energy saving demand control system that helps to balance the fluctuations in demand.

2)    Why is the MAC needed?
⇒    As demand fluctuates, the pressure in the lines keep varying, and this impacts deliver of pressure to the plant. To take care of this varying demand the compressors have to work at higher pressure set points and keep cycling frequently between loading and unloading conditions. This results in a significantly higher energy consumption by the compressors. The delivers the constant pressure to demand side irrespective of the demand fluctuations and hence separates the compressor from demand side. This not only helps save energy, but also has a positive impact on the life of compressors.

3)    How does the MAC work?
⇒    It eliminates the artificial demand & ensure the steady delivery to demand side.
It introduces the differential pressure between the receiver and itself and hence creates the useful storage. The sensor inbuilt in MAC senses the demand pressure & then depending upon the pressure required at demand side, it delivers the exact required amount of pressure.

4)    What is Artificial Demand
Artificial demand includes the
•    Excess pressure delivered and consumed
•    leakages, unwanted usages,
•    air utilization for cleaning/washing etc.

5)    What is difference between MAC & PRV/VFD?
⇒    MAC offers a more precise and reliable controlling than any PRV, since it has intelligent control logics to ensure the steady delivery of pressure at sudden peak loads. Reaction time of MAC is considerably faster than that of a PRV because of its control logic.
MAC & VFD perform a similar function when installed at the generation side (compressors or the main header). However the MAC scores over a VFD in two aspects.
1.    To install a VFD the motor should get changed to variable speed & it is not always feasible to replace the motor. The MAC on the other hand is relatively hassle-free and doesn’t involve any costly modifications of the existing setup.
2.    In cases where there is varying demand at different user sides with different pressures to be supplied, the VFD is not suitable. However, installation of MAC at these individual user sides will help deliver better savings.

6)    Suitable for which type of compressors?
⇒    The MAC is suitable for any type of a compressor since it is a demand control system and doesn’t control the compressors whatsoever. It delivers on energy savings by smoothening out the pressure delivery for a fluctuating demand.

7)    What should be the minimum CFM required to install MAC?
⇒    For ideal payback of one year it is preferable to have a minimum running demand of 600 CFM.

8)    Where it is installed - location of installation?
⇒    The MAC is always installed in a compressed air line after a receiver. Proximity to a receiver helps it control the demand more effectively.

9)    Is the MAC still required if the compressor’s pressure band is kept very narrow?
⇒    Yes. Frequent fluctuations in demand may cause the compressors to load-unload with high frequency in case the pressure band is narrow. This may result in damage to the compressor and is therefore unadvisable. The MAC will help increase the time spent between these cycles and therefore not only reduce the energy consumption, but also help protect the compressors from such damage.

10)    How is the potential savings through MAC calculated?
⇒    To determine the potential energy savings by installing a MAC on the compressed air network is done by studying the loading & unloading pattern of compressors and the demand pattern of the user sides. It is important to identify the base demand of each user area, after which we can determine the potential to achieve energy savings. 
This is usually done by the means of a data logging study, which Forbes Marshall can conduct for you.
Example: Savings Calculations