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Control blow off and lower the cost of compressed air

Many industries use a lot of compressed air in “blowing off”. Some of the applications include blowing off water, contaminants or cooling. We recently visited a steel industry which uses open pipe to blow off water off tubes before printing. (see picture above)

It is important to note that unregulated open blowing using tubes is extremely inefficient. The compressed air used can be reduced significantly to the tune of 50% with much better cleaning performance.

As a rule, the higher the pressure the higher the flow rate through an orifice and consequently the higher the cost of supplying compressed air. The table below shows flow rate through orifices at different discharge pressures.

Higher Pressure = Higher Flow = Higher Compressed Air Costs.

Solutions

EXAIR Nozzle: In swivel Blowoff Application

For this application the client has several options

  • Low pressure blower generated air to supply air for the blow off application. Generating air at 1.7 bar costs much less in cost per unit volume than compressed air at 6 bar. When using a blower, it is the mass of air that performs the blow off and not the thrust due to pressure.
  • Compressed Air: Air Amplifier Nozzles and Air Wipes: These nozzles/air wipes use the Coanda effect to pull in ambient air and mix it with compressed air amplifying the air available by up to 25: 1. This significantly reduces the compressed air use while generating high total flow.
Exair Air Wipe for pipe blow off

In the open blow application introduced earlier in the article we calculated the total flow at 5.5 bar as 98 l/s for the six tubes. Using an air wipe in the application would provide high quality 360-degree flow of air, drying the pipe effectively while reducing the air flow by 74 l/s to 24 l/s a 75% reduction in flow and cost.

In summary

  • Avoid open blowing using compressed air as it is very inefficient.
  • Use a low-pressure blower as it has much lower energy use per unit off air produced.
  • When using compressed air use Venturi nozzles and air wipes which reduce the compressed air use while amplifying the volume of air to the amplification up to 25 times.
  • Use the lowest pressure possible.
  • Use solenoids with sensors to only supply air when it is needed.

We are proud to be the distributors of EXAIR compressed air efficiency products in East Africa. To learn more about our Nozzles and air wipe solutions contact us.

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About the Author

Eng. Mathew Waita Mwenga is a Chemical/Mechanical Engineer with over 12 years’ experience in the industrial sector and petroleum industry. He has 6 years working for Atlas Copco Eastern Africa as a service engineer, aftermarket engineer, compressed air energy auditor and Rental manager. He has also spent 3 years working as a drilling solutions engineer in National Oilwell Varco an upstream oil and gas Equipment Company. Mathew is a Chartered engineer of the UK(Ceng) and a registered P.E of Kenya.

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