Metal Stitching/Cast Iron Repairs
On-site Metal stitching is often the only reasonable method to repair cast iron cracks and salvage what is otherwise a condemned component or major piece of machinery. Traditional welding methods are not effective for repairing cast iron and other cast metals and in many cases can result in more damage to the piece being welded.
Goltens stations around the world maintain an expertise in metal stitching repairs. Utilizing metal stitching, Goltens solves these major problems for customers, minimizing asset downtime and saving them significant sums in the avoidance of unnecessary equipment replacement.
Metal stitching to repair cast metal damage has a variety of benefits:
- It provides a permanent crack repair without the introduction of heat associated with welding.
- It can be performed on-site avoiding the high costs associated with disassembly and transport.
- The repaired area is restored to its original strength with a watertight and gas tight repair.
- On-site machining and milling restores the surface of the repaired area to original dimensions
The applications for the process are many and cover a broad range:
- Cracked Engine Block Repairs (sidewalls, liner bores)
- Damaged Engine Bedplate repairs
- Steam turbine repairs
- Repairing damage to heavy industrial machinery
- Metal crack repairs for mining equipment and large earth moving machinery
- Damaged pump casings, gear boxes and gears
When completed correctly and coupled with Goltens’ in-place machining capability to restore the surface of the repair, the surface will be largely indistinguishable from the rest of the component and as strong as the day it was cast.
How does metal stitching work to repair damaged cast metal?
The image above shows damage to an MaK 12M282 diesel engine block resulting from a connecting rod failure. Without metal stitching to repair the cast metal damage, the block would be condemned
After performing extensive crack tests to ensure that all damage is captured, the damaged area is cropped out of the engine block leaving a clean surface to metal stitch a replacement piece into place.
A replacement cast iron insert section matching the original casting is then shaped to the exact dimensions of the cropped section of the block in preparation for repairing the block.
This cast metal insert is then fit into the hole in the damaged engine block, checking for fit and grinding the insert as necessary to unsure the mating surfaces have perfect contact before beginning stitching.
Once the insert is fit, holes for the metal stitching pins are drilled and tapped along the mated seam between the block and the insert.
Stitching pins are then screwed into place along the entire seam between the engine block and the cast metal insert. The stitching pins draw metal on both sides of the seam together when they are tightened.
Once the seam is completely stitched, the heads of the stitching pins are removed in preparation for insertion of the locks.
Prior to lock insertion, the surface of the stitched seam is machined using portable machining tools and stress relieved and checked to ensure that there are no cracks or irregularities.
Using a drilling template, a precision hole pattern matching the dimensions of the metal locks are made at various points along the stitched seam.
Locks are then driven into the hole patterns along the seam drawing the repaired seam even closer together.
Once the locks are installed along the seam, the surface is machined clean and the repair is checked to ensure it is crack free resulting in a watertight and gas tight repair using a dye penetrant or other NDT method.