CRACK REPAIR BY METAL STITCHING INSTEAD OF WELDING

Metal stitching is a technology which is over 100 years old and now very well proven and established to undertake crack repair or damage to cast components manufactured out of cast iron or aluminium alloy. In some cases, crack repair is also possible in components made of bronze.

RA Power Solutions as a repair company has tried the process of cast iron block repair by metal stitching, metal locking and welding. We have observed that the repair of damage casting and repair cracks by metal stitching, metal lock and metal surgery is most successful in comparison to welding.

The following are the advantages of the welding process of repair:

• The metal stitching and metal locking is a cold repair of the crack, no stresses are developed as no heat is generated.
• In most of the cases, no dismantling of equipment is required.
• In normal situations, access to the pneumatic tools is only required.
• Metal lock/Metal stitching being a cold method, no loss of alignment or profile is observed, hence in most of the cases, no machining is required.
• The repaired area by metal lock and metal stitching process is liquid and gas tight.
• With time, it has proved to be almost a permanent repair.

The brief process of metal stitching/metal locking for crack repair in aluminium, bronze, and cast iron components is as follows:

To make the crack repair or repair of damage casting successful by metal stitching and metal lock process, it is important that the damaged area is thoroughly checked for the length, location, and number of cracks, preferably by MPI equipment.

We suggest that a minimum of level two or level three qualified technicians should undertake the crack detection inspection by MPI process. In case of non-availability of MPI equipment, the crack detection test by dye penetrant test can also be undertaken. It is of utmost importance that no crack should go unidentified, which in case left without metal stitching and metal lock can elaborate further and can cause serious damage to the component and the equipment in totality.

The cracks and the damaged portion should be identified and marked clearly.

The cracked metal is replaced with special metal stitching pins, which are placed by drilling and tapping.

To pull the sides of the crack together, insertion of specially allowed metal stitching pins results in the continuous formation of a row of interlocking stitching pins, which in turn develops a strong and pressure-tight repair. The master locks are installed across the joint line by drilling process to give additional strength.