A Stitch In Time... Metal Stitching Technology Helps To Cut Costs, Keeps Vessels Sailing
Up in the bridge the first mate is in charge as the container ship Archangel is setting a course towards Seattle. The gauges indicate that the engine is losing pressure. A call goes down to the captain who is catching up on sleep and the drill begins. The inspection confirms the fears of the ship's engineer - the Archangel has thrown a conrod in one of its engines.
After the captain radios the owners, they conclude the ship will be in for hundreds of thousands of dollars of repairs and months in dry dock as the Archangel limps towards port at half speed. An hour later, the office radios in they have contacted an outside vendor and have possible good news, "from what we know about the damage, we think we can get the casting stitched." Metal surgery, not a widely known repair approach, is practiced by just a few companies across the country. It is intended to save time and money, as a part that may need to be replaced with weeks or months of down time can be repaired in just hours to days.
The process allows broken cast iron or dissimilar metals to be repaired either on-site or in-house.
For example, if the conrod housing on the Archangel had been remedied with a replacement part, the ship would have faced many months in the repair berth. Instead, a technician was flown in to meet the ship at its home port in Vladivostok to engineer the repair process.
Repaired at a Fraction of the Cost The ship took on a load and headed back across the Pacific under half speed to its destination. An insert was machined at the Metal Surgery facility in Milwaukee for the lower bore liner and the cracks in the housing were stitched back to the original surface alignment. The repair took place in a very difficult to access portion of the engine. In 76 days the housing was back in shape with the engine providing full power to the Archangel. Cost of the repair was roughly $120,000 - significantly less than the estimated six million dollars to disassemble and totally repair the engine. Upon inspection, ABS concluded that the operation was an excellent repair.
For castings that suffer cracks or breaks, stitching can restore part casting strength to equal or better than their original shock load capabilities by creating an even stronger structure along the course of the pattern. High-strength locks in the stitched and repaired areas absorb shock loads up to or greater than the original design is able to sustain.