ASK THE EXPERT


ASK THE


EXPERT


Paul Kendrick, welding applications specialist at Air Products, offers some advice about how to choose the right gas product and mode of supply for laser cutting applications.


WW: The manufacturer of my laser cutting system recommends that three separate pure cylinder gases – Carbon Dioxide, Helium and Nitrogen – are used as resonator gases. Why is this?


PK: Certain manufacturers specify the use of separate pure cylinder gases which are mixed internally by the machine to produce the correct resonating environment. It should be possible to select these gases, according to the grade required, from your gas supplier. As a guide, Air Products’ premier grade CO2


provides 4.5 grade


(99.995%) purity and BIP Helium and Nitrogen achieve Ultra High Purity (UHP) grades of 5.7 (99.9997%) purity. High quality UHP gases are required in a high quality environment.


WW: What mode of supply would you recommend for gases used to assist in metal removal?


PK: Oxygen is generally used to assist with the removal of mild steels. Copper and nitrogen is generally used to remove stainless steels and for aluminium cutting. In both cases, for low volume manufacture, it is usually best to use manifold cylinder packs (MCPs). Combinations of cylinders manifolded in quantities of 12, 16, 17 or 18 can be the answer to small-scale niche production where regular changes from Oxygen to Nitrogen are required and there is limited space for gas supply. Oxygen flow rates tend to be low (3-10 Nm3


/hr)


therefore oxygen MCPs are a good option. In the case of Nitrogen, which is used with a 6Kw machine, flow rates can vary from 50-120 Nm2


/hr, therefore requiring


multiple changeovers. Where larger volumes are needed, CryoEase liquid


supply is a more suitable option. A 2,000L high pressure mini-tank contains approximately 1,250Nm3


of


gaseous Nitrogen in liquid form. Regularly filled at its 30% remaining content limit, it enables uninterrupted Nitrogen cutting.


28


WW: When would I need to consider bulk gas supply for my laser cutting installation?


PK: For 24/7 facilities, a continuous gas supply is essential and therefore bulk liquid tank supply is recommended. Depending on the tonnage of gases required, medium–large high pressure tanks are positioned on-site and filled by large liquid road tankers. Filling intervals and gas usage are typically monitored using telemetry to ensure consistency of supply. Nitrogen cutting will almost certainly require a high pressure bulk tank. Air Products uses a specially-designed fleet of high pressure delivery tankers with the ability to deliver and fill at 28 bar pressure. This very efficient mode of supply is also available for some of the larger mini-tank installations. ●


FURTHER INFORMATION To find out more about Air Products’ welding


experts, visit www.airproducts.co.uk/expert. For a fuller version of this ‘Ask the Expert’ column as well as past columns, please visit www.airproducts.co.uk/weldingexpert. If you would like to Ask the Expert a specific question, to be answered in the next issue of AWD’s Welding World, please email expert@airproducts.com.


Oxygen cutting using lower flow rates enables use of


smaller, lower pressure tanks – for example, 180L mini-tanks or 950L mini-tanks. This mode of supply is ideal for laser jobbing shops where a range of materials and thicknesses are cut to demand. Generally speaking, a typical CryoEase installation with


pipeline would have a similar cost to an MCP installation and require a similar footprint outside the facility. However, it would require no pack changeovers, no ordering and low maintenance.


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32