The benefits of monitoring compressed air

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Courtesy of Contrec Europe Limited

Compressed air is used in many manufacturing processes for many different reasons, from the actuation and control of pneumatic valves and cylinders to the operation of process machinery and tooling. It can also be used as a transport medium for bulk materials or as a purge gas. For all its uses it is nonetheless expensive. This is why, through detailed monitoring, a business can enjoy the financial, environmental and operational benefits of an efficient and effective compressed air system.

Typically compressed air uses more electricity than any other type of equipment in a production plant. It can account for 20% of a company’s overall energy costs. This is not surprising considering the myriad of uses it has in many manufacturing processes and the number of compressors that may be used in a large compressor system. By measuring compressed air consumption leaks can be identified and dealt with immediately, it can ensure the correctly sized compressors are being used in the best places, at the right times, and it can reduce the overall plant consumption. This could reduce overall energy usage, lower a company’s carbon footprint and save thousands of pounds a month in large industrial plants.

With faster and more accurate pressure controls it is possible to maintain a lower average pressure in the whole system as it is no longer necessary to keep a higher pressure in order to maintain the minimum level required. Fluctuations are smaller, the control range narrower and the overall consumption reduced. Narrower variations in power also make it possible to avoid negative effects on production quality control.

But of course very few air systems operate at full-load all of the time. It is therefore essential to have the ability to implement a strategy of part-load performance, through system-wide and individual compressor controls, to suit the requirements of the plant. These can take the form of start/stop, load/unload, modulating, multi-step or variable frequency drives for individual compressors. For system controls these can include single master, sequencing controls; multi-master, network, controls; flow controllers; or air storage.

In addition to maintaining the optimum pressure level in all parts of the system it is also crucial to ensure the quality of the compressed air itself. Compressed air contains moisture. If this is not controlled it may cause damage to the process, the product or even the components of the air distribution system. To reduce the moisture content refrigerant dryers are used to cool the air in a heat exchanger. When the temperature is just above the freezing point of water the moisture in the air will condense to a liquid, which can be drained off. Maintaining good temperature control is critical for the efficient operation of the dryer as too low, below 320F, ice will form instead of water. An accurate temperature gauge is needed to make sure the dryer is functioning correctly.

There are a number of different Contrec instruments, which can be used to monitor compressed air depending on the specific flowmeter used. For example, Contrec’s 515 GC01 application is ideal as it measures the volume, corrected volume and mass of a general gas. The instrument uses a frequency volume flow input and analog temperature and pressure sensor inputs. It is compatible with a wide range of flowmeter frequency outputs. Millivolt signals, reed switches, Namur proximity switches or pulse trains can be selected via its smart front-panel programming.

The properties of a gas are calculated using common industry standard equations of state: Ideal Gas, Redlich-Kwong, Soave-Redlich-Kwong and Peng-Robinson. These equations use a simplified set of parameters to quickly and accurately determine the value of compressibility and actual quantity of gas. A variety of calculations are available to suit the nature of the gas and the measurement conditions.

Its many features include its ability to allow quadrative flow input for ISO6551 level B pulse security and its non-linear correction capability. The front panel display shows the current values of the input variables and the results of the calculations. It can be supplied with a real-time clock for data logging of over 1000 entries of the variables as displayed on the main menu.

There are two communication ports available: RS-232 port (standard) and RS-485 port (advanced option). The ports are available for remote data reading, printouts and for initial application loading of the instrument.

As with many Contrec instruments the 515 GC01 application offers a wide range of options, which can be further tailored to suit specific application needs, including units of measurement, custom tags, second language or access levels.

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