In-house solution produces answer to gas supply inconsistencies

Having invested in state-of-the-art laser equipment that would allow faster production turnaround, 24-hour operation, and a variable system for future capacity, Oldham based laser cutter  ABi Laser found that the equipment’s full potential was hampered by the supply, specification, and costs of delivered nitrogen. 

Laser-cutting metal relies on a continuous supply of nitrogen gas to prevent burning during the process. Purity of the gas is an important factor in overcoming the tendency for discolouration of laser-cut edges and to provide a high-quality finish. As well as these critical process requirements, it was important for ABi’s production management to achieve savings on the cost of delivered bottled nitrogen supplies. 

ABi managing director Arran Reader determined that installing on-site nitrogen generation was the answer. It would deliver significant cost savings, maintain supply independence, and ensure a continuous, reliable source of high purity nitrogen.

Atlas Copco was contracted to install an all-in-one nitrogen generation assembly HPN2 Skid 7 on a trial basis which convinced Reader with its performance and helped to establish the appropriate nitrogen purity level for ABi’s application. 

The compact skid package came with a GA VSD+ FF full-feature, rotary screw compressor, an NGP+ nitrogen generator, air and nitrogen receivers, plus a booster, dryers and filters integrated into one pre-commissioned unit. Atlas Copco’s local distributor Pennine Pneumatic Services  carried out the installation, ensuring minimum risk of pressure drop in the system by linking the unit to the production area with a full AIRnet modular alloy pipework system. 

The trial confirmed the need for bulk nitrogen deliveries could be eliminated, with corresponding savings, while the installation was flexible enough to allow for downsizing the system in case of fluctuating demand. 

Delivery rate of 99.99% purity nitrogen generation from the unit was established as 19 Nm3/hr at 300 bar(g) to charge the onboard 16 bottle manifold cylinder pack (MCP) thereby producing 408 Nm3 over a 12-hour period. When running flat out, that equates to 57 MCPs a month – 30% more in comparison to the nearest competitive offering (limited to a maximum output of 44 MCPs). 

The unit’s energy-efficient components, including VSD+ permanent motor drive and NGP+ generator, offer more than 50% cost savings in comparison to conventional on-site generation solutions, asserts Atlas Copco. 

Average cost of ABi’s high pressure nitrogen supply now produced on site by the HPN2 skid is £0.09 per m3, compared to the previous figure of £0.68 per m3 for delivered gas. 

The NGP+ generator’s low-volume, high quality absorbent medium provides optimum capacity to produce the nitrogen. Whereas other competitive systems require six volumes of air to produce one volume of nitrogen, Atlas Copco’s generator design requires a ratio of only four parts of air to one part of nitrogen.

An additional bonus is savings on energy costs of other operations that can now utilise the unlimited on-site nitrogen supply; the company employs lasers for tube cutting and engraving, as part of its other metal fabrication services such as folding, tapping and plasma. 

Eliminating the expense of delivered supplies contributes to reduction in the total cost of ownership. This in turn ensures an early payback on the company’s capital investment and an estimated ROI within two to three years. 

Commenting on the nitrogen project, Arran Reader said: “We are saving on the cost of nitrogen, saving on energy consumption, and now have more capacity and a variable system for future developments”.