Laser cutting firm saves £30k annually using on-site nitrogen generation

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Metal cutting service provider LaserMaster, based in Cornwall, UK, has generated savings of up to £30,000 a year by investing in a high-pressure nitrogen generation container unit.

The firm switched from having its nitrogen delivered in bulk to ensure it had a continual, unlimited supply of high-purity nitrogen, all while saving itself £2,500 a month. 

LaserMaster offers metal cutting services from two fibre laser machines, as well as CNC folding and bending operations, to industries ranging from private customers to local, national, and international manufacturing companies.

Laser cutting relies on a continuous supply of nitrogen gas as a blanket 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.

For the past seven years, LaserMaster has had a bulk nitrogen supply agreement in place and was renting an on-site storage tank. The perceived benefits of this approach were: a large storage facility with the required nitrogen quality; a scheme cheaper to run than delivered bottled gas; no large capital outlay was involved; and there were regular deliveries from the supplier.

However, despite these advantages, there were evident drawbacks to the scheme. Rental costs were in the order of £8,000 per annum and long contracts with 12 months’ minimum notice were the norm. Other negative aspects comprised the company’s dependence on on-site deliveries, the percentage of tank losses, environmental carbon footprint issues, and, ultimately, the total cost of a nitrogen supply, which was in the region of 35-40p per Nm3.

The alternative option of on-site generation had been considered for some while, but the decision had been put off by the apparent prospect of dealing with several separate companies in the supply of the equipment, the installation on site, and the subsequent servicing programme.

Related: Oxygen shortage hits laser cutting units in Aurangabad, India

After having its current supplied usage figures reviewed, it was recommended to LaserMaster to invest in an on-site, high-pressure nitrogen generation containerised package. 

The package in question was an ‘Atlas Copco HPN2 skid 8’, which was to be rented for an initial three-month period in order to compare performance and costs against the current supply facility. The package came complete with a GA VSD+ FF full-feature, rotary screw compressor, an NGP100+ nitrogen generator, air and nitrogen receivers, plus a booster, dryers, and filters, all fully integrated into one pre-commissioned unit. The generator’s low-volume, high quality absorbent medium provided the firm with optimum capacity to produce the nitrogen. It requires a ratio of four parts of air to produce one part of nitrogen.

The nitrogen generator operates using Pressure Swing Adsorption (PSA). The system separates nitrogen and oxygen molecules within the compressed air stream feeding the unit, with the PSA trapping the oxygen using adsorption techniques. Adsorption takes place when oxygen molecules attach to a carbon molecular sieve allowing the smaller nitrogen molecules to pass through.

A successful trial

The trial unit is now a permanent installation, providing nitrogen for the two fibre laser cutting machines. It delivers 42Nm3/h of nitrogen and 480Nm3 of storage at 99.99% purity. The quality of the delivered nitrogen is as per the contents of the original site tank. This gives LaserMaster the option of reducing the quality of nitrogen relative to the material being cut, thereby increasing flow and reducing generation costs.

The container unit was installed at the rear of the company’s main building together with a power supply to an isolator. The production area’s nitrogen supply pipework was connected to the container with a flow valve to enable the use of the current tank option if required. An additional bottle bank has also been positioned adjacent to the container to provide even more storage capacity and creates an opportunity to expand output in the future.

Related: Nitrogen gas generators now supplied by Bystronic for fibre laser cutting machines

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