FEATURE COMPRESSED AIR
Compressed air accounts for 10% of an industrial company’s electricity bill and for some can be far more. Knowing the system’s actual cost will help you justify targeted action to make your system more efficient says Marion Beaver, technical officer at BCAS
nvesting in servicing and maintenance to reduce compressed air waste will save
energy and costs and improve the reliability and productivity of the system. This argument is made even stronger if you can outline exactly how much a system costs a business and therefore the likely savings that are possible. While the largest energy consuming
component in the system is the air compressor(s), it is the demand by users, the overall design and how well the system is maintained that determines the demand placed on the compressor to supply the system and therefore its energy consumption. But first let’s calculate the costs and provide you with the facts that you can present to justify investment in maintenance and service.
CALCULATING THE SYSTEM’S ANNUAL COSTS There are four ways that allow you to calculate the electrical energy consumption of a compressor: Option 1: the simplest way to get the
actual electrical consumption of the compressor(s) in kilowatt hours (kWh) can be obtained by sub-metering the compressor house. Option 2: a quicker temporary solution is
to install a data logging system over a period of at least seven days. This will determine both the demand
profile and the off load running time when there is no demand for air. To get even more information to help build a usage picture you could incorporate flow monitoring into the system.
Option 3: if no metering is in place you
can estimate the energy consumption of each compressor as illustrated below: Let’s say that you have a 75kW
compressor operating at 7 bar pressure that is on load for 65% of the time and works for 2,000 hours per year and assume that the motor is 90% efficient. Energy consumption of the compressor while on load = (75 ÷ 0.9) x 0.65 x 2000 = 108,333kWh/year. You need to factor in the energy
consumption from the offload running so PLUG-ON DISPLAYS PROVIDE REAL TIME DATA
Many production and treatment processes can only be run efficiently if real time data is available on site. Without this information it is impossible to closely monitor the quality of applications and processes and take swift action if the need arises. The METPOINT UD01 and UD02 plug-on displays
make measuring data available directly at the transducer where you need it. You are then in a position to evaluate the quality of your processes in real time right at the plant, enabling you to intervene quickly should it be necessary. Simply mount the device on your transducer. Apart from displaying the current process
parameters, the plug-on displays allow for the transfer of the measurements to a data logger such
as the METPOINT BDL or to a master control system. The UD02 plug-on display comes with two integrated alarm contacts that enable you to implement visual and acoustic alarm signals.
Advantages of the METPOINT UD01/UD02 include: Flexible integration Intuitive configuration Integrated diagnostics system Safe on-site display User-friendly display Easy and quick to install
BEKO TECHNOLOGIES T: 01527 575778
www.beko-technologies.co.uk
Illustrating the cost of a compresssed air system is a useful exercise but just the first step in reducing its energy
assume that for a rotary compressor part- loaded running draws 25% of the full load power then it will be: (75 ÷ 0.9) x 0.35 x 0.25 x 2,000 = 14,583 kWh/year. The total energy consumption of the compressor over the year will be: 108,333kWh/year + 14,583 kWh/year = 122,916 kWh. If a unit of electricity costs £0.12/kWh
then the annual energy cost for this example is: £14,750. If the production time is 6,000 hours per year then this figure increases to £44,250/year. Note that for older or less efficient
compressors the offload draw power could be nearer 70% rather than the 25% used in this example. Option 4: a further option is to use the
maximum rated package power which should be available from the manufacturer. Illustrating the cost of a compressed air
system is a useful exercise but it is just the first step in reducing its energy consumption.
It does however help justify
action as Peter Drucker once said: “What gets measured gets improved.” To find out how to reduce the energy
consumption of your compressed air system download BCAS latest whitepaper.
BCAS
www.bcas.org.uk
8 MARCH 2017 | FACTORY EQUIPMENT
MEASURE TO IMPROVE EFFICIENCY I
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