Plasma cutting provides five times higher cutting

Reports show that the Arab Shipbuilding and Repair Yard Company (ASRY)'s $188 million expansion programme in Bahrain is bearing fruit. Work on a 1.38km repair quay wall is well under way with Nass Contracting carrying out the work under an $800 million contract.

Shipyards worldwide almost exclusively use plasma cutting to cut shipbuilding plate in the thickness range, 8-20mm. Plasma cutting provides five-times higher cutting speed than oxyfuel cutting, and thermal deformation is much lower, guaranteeing better dimensional accuracy of cut parts.
In the hunt for increased speeds in plasma cutting, plasma cutting with oxygen has consistently been developed, because it guarantees the best results with regard to the quality of the bevel and the absence of slag. Currents as high as 400A have now achieved that results in a considerable increase in cutting speed.

However, with a higher current at the cutting nozzle, heat input also increases, resulting in a more oblique cutting edge. A possible remedy is to use a torch with bevel units, which position the torches at a slight incline. Naturally, cuts for weld edge preparation are carried out with these machines; V and Y bevels with plasma torches, additionally K bevels using oxyfuel torches.

In plasma cutting, the consumption of wear parts (electrodes and tubes) is a cost factor, which should not be underestimated. Nowadays, considerable life cycles have been achieved by consistent research and development. For example, the life cycle with oxygen cutting used to be considerably shorter than with nitrogen cutting, at the initial development stage. New developments, i.e., a silver coating on the hafnium electrodes, have considerably increased the life cycle of wear parts. Modern electronics have also brought about considerable progress, i.e. a controlled increase and decrease of welding current at the start and the end of the cutting sequence, respectively. Today, the life cycle of modern electrodes can exceed four hours arc time.

It is well-known that plasma cutting generates airborne particles, such as dust; IR and UV light, as well as high noise levels. For this reason, in Europe, it was mostly  performed under water. Water muffles the noise, binds dust, and protects sufficiently from radiation. There are disadvantages, however. Filling the water tables takes time, in comparison with dry tables. In addition, wet plates cannot be welded without loss of quality. Rust may occur on the bevel edge faces, and cutting particles must be cleaned from cut parts after water drainage. This is carried out with high-pressure water pumps, installed on the cutting machine.

There is a tendency, in Europe, for users to return to dry cutting, as this technique offers considerable advantages for productivity, cut quality, charging, discharging. However, noise level is a major problem. Noise protection cabins are provided for operating personnel and, sometimes, machines are encapsulated (modern cutting machines can operate fully automatically).

The heavy machinery and vehicles industry in the last two years has reflected many of the changes and fluctuations taking place in the construction market generally. Leading suppliers in the Middle East have altered their business outlook in line with the changing project landscape and are trying to adapt to the new realities.

For a manufacturer that sells heavy machinery components to companies in the construction or even in the agricultural industries, high productivity, manufacturing precision and safety are of utmost importance.

Plasma cutting systems

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