When an urgent repair to a cracked piece of metal machinery occurs onboard, welding is often the go-to solution, but alternatives exist, explains Andre Mortimer, president of Metalock International Association
Although the Metalock process is a well-established, permanent in-situ repair for cracked metal machinery, many chief engineers trained in the last 30 years are unfamiliar with the technique. Instead, the turn to the technology they do know: welding. In many cases this is the wrong tool, at best a sticking plaster. Where welding is completely impossible, removal and replacement are frequently seen as the only remaining solution, again the Metalock process is an overlooked option.
The metal stitching technique, codified and certified continually by the Metalock International Association (MIA) since 1953, delivers permanent repairs, in-situ, requiring neither the removal of machinery or hot work.
Although chiefly applied to cast iron machinery, the process is also applicable to other metals, including steel and aluminium. Metalock technicians are trained to recognise the best approach for the circumstances and will recommend the most appropriate action, including welding.
The Metalock approach
Welding Vs. Metalock
In certain cases, welding may have significant drawbacks, including inherent weakness along the line of fracture. It is often necessary to dismantle machinery before repair and in the case of ship-board repairs, welding requires considerable adjustment to the surrounding area to remove potential flammable or explosive materials.
Consequently, welding of machinery on board a ship may be impractical, not just because the repair fracture is in a confined environment, but also because of the stresses and brittleness that welding may introduce. A welded repair increases permanent distortion and brittleness of the parent metal, so when machinery is back under normal operation there is a greater risk of it cracking again.
The Metalock process, known as metal stitching, is a unique, rapid and permanent repair method for cracks or for joining pieces of broken cast metal components without welding. These cold casting repairs carried out by MIA members, are superior to welding in the case of crack-sensitive metal. The repairs can take place in otherwise hazardous conditions and cause minimal disruption to vessel operation; in certain circumstances they can even be performed whilst the vessel is actually sailing.
Each repair only requires equipment that can be carried by hand and is generally completed in a matter of days. The repair can typically restore the strength of the equipment, so that it will continue to operate to full specification.
Metalock repairs are accepted by the major classification societies, and since the 1940s the number of ships sailing on for years with stitched repairs runs well into the hundreds.
Carried out by specifically trained technicians, the Metalock process offers a variety benefits, including:
• performed in-situ, major dismantling is not required;
• permanent repairs completed in days;
• does not require hot work, can be performed in any area of a vessel;
• can be used to repair cast iron and other metals;
• almost always cheaper than replacement;
• is accessible via a worldwide network of trained technicians;
• does not require heavy machinery or equipment to carry out repair;
• causes minimal disruption to vessel; and
• reduces vessel downtime.