• Technically advanced metal stitching casting repairs

• Double the strength of other known metal stitching procedure

• Superior sealing properties compared to other metal stitching systems in use today

A TYPICAL IN-SITU METAL STITCHING & MACHINING REPAIR

In-Situ Machining Solutions (UK) Ltd conducted a Metal Stitching repair to a large V12 diesel engine at a power station in Southern Europe.

Due to previous work successfully carried out at this site, the customer had no hesitation in calling upon the services of ISM (UK) Ltd to repair the severely damaged engine.

The damage, it transpired was due to one of the balance weights on the crankshaft had become loose which led to the subsequent detachment of the balance weight breaking through the 25mm thick wall of the cylinder block and bedplate causing extensive breaks and fractures to major internal and external parts of the engine.

Ideally the obvious solution to the problem was to replace the damaged parts with new or second hand, but after extensive searches for replacement parts, these were not available and the repair procedure adopted.

In conjunction with the engine manufacturers and after a detailed on-site assessment/survey, a repair procedure was established with the OEM and agreed with our customer before the repair work taking place.

Parts of the engine that were refurbished are as follows:

Crankshaft balance weight locating face repair

Due to prolonged oscillation of the balance weight prior to it’s detachment from the crankshaft, fretting damage occurred to the balance weight face as too damage to the weight fixing holes.

The balance weight faces were machined and finally ground using portable milling and grinding machines, manufactured by ISM (UK) Ltd, to remove the minimum amount of material (0.5mm approx.) to render the surface flat and square to the axis of the crankshaft. In addition to which the tapped holes and dowel locating bores used to secure and locate the balance weight were modified to eliminate the damage sustained during the weight’s detachment.

The photographs below illustrate the work being undertaken.

Milling of balance weight locating face of crankshaft	Grinding of face
Engineer’s bluing of the face after grinding to ensure flatness	Modification to the balance weight securing holes in crankshaft
Metal Stitching of major engine parts Severe breakage to the inspection doors of the crank bay and cam shaft space necessitated that new parts had to be cast and stitched in place, as too, internal intercostals areas of the engine. On-Site machine tools were deployed to form the cutouts and contours to enable the new cast parts to be closely fitted into the engine prior to metal stitching.
Inspection window aperture in the process of being machined prior to fitting of the cast part	Picture shows the machined aperture
Cast/Machined part closely fitted into engine before the metal stitching process	Metal stitching work in progress
Newly fitted cast iron insert fitted showing the metal stitching and locking system	Internal view of the repair showing the cast & dressed form
Damage to internal areas of the engine included broken ribbing, ‘A’ frame, channelling, column bore and several impact cracks and fractures. The following pictures give an indication of the internal repairs undertaken.
Column bore ribbing repair showing cast insert	Damaged column bore ribbing with fitted stitching screws & locks
‘A’ frame ribbing repair in progress	‘A’ frame repair completed
Repair to column base channelling	Channelling repair completed
Machining and Alignment Techniques  During the progression of the engine refurbishment work, various machining and alignment procedures were undertaken to satisfy the integrity of the total repair.
In addition to the laser alignment system, an optical telescope and target technique was utilized to check the alignment of the cam bore line. Due to the damage caused by the balance weight detachment there was a possibility that an out of line situation may have occurred. A line of sight indeed indicate that the cambore adjacent to the catastrophe was misaligned by 0.008” as a result of impact stressing. This figure was reduced significantly to within OEM limits as a result of cutting out the damage to the adjacent cambox inspection window thus relieving this stressed up area. After the subsequent metal stitching of the cast iron insert into the cambox area, an alignment of the cambores indicated that the line of cambores were with the manufacturers tolerances and accepted. The total repair was very successfully completed in 40 days. On-site repairs such as this saves customers unnecessary down time and loss of production and is an alternative to purchasing new parts. This V12 engine has been running continuously on high load for over a year.

In-Situ Machining Solutions (UK) Ltd use a technically advances metal stitching system that is used in the repair of cracked. Fractured or broken castings. Metal stitching or metal locking as it is often referred to is mainly used in the repair of cast iron ranging in casting thicknesses from 6mm to anything up to 150mm. Although cast steel, bronze and aluminium can also be repaired.

This system alleviates the necessity for welding, the process is a cold repair and proves extremely effective. Major items of plant can be repaired on site with the minimum disassembly and more importantly down time, saving customers valuable production costs.

Cast Iron is probably the most difficult of cast materials to be welded due to its high carbon and silicon structure. Electric welding this material on site should be avoided at all costs as in many cases the introduction of welding leads to more cracks being produced and propagates existing cracks, breaks and fractures.

To weld cast iron successfully required the complete casting to be disassembled and preferably heat treated in an oven prior to fusion welding by a technically competent welding company. In doing this, turn around time for repair is greatly extended in addition to which the part may have to be machined after repair. Production availability is drastically reduced which ultimately leads to a fall in revenue.

Metal Stitching using the method ISM (UK) Ltd has adopted incorporates the use of a series of metal stitching pins and locks. The threaded pins are used to stitch along the full length of the crack, break or fracture using an accurate drilling jig system. Holes are drilled, tapped and stitching pins fitted.

The pins incorporate a specially designed head and a ‘snap off’ groove which enables a leak  free seal and allows each pin to be torque tightened to pre determined values.

Where pressure sealing is required each stitching pin is coated in a heat resistant sealant. The combination of these elements ensure a stress free and completely sealed repair. Where added strength is required in a repair a series of ‘locks’ are utilized, these are normally used in heavy industrial components such as diesel engine parts, compressors, large pumps, turbine parts, press tools etc.

Like the stitching pin method of insertion, a precision jig drilling system is used to form the shape of the locks to be used.. The locks come in various sizes, shapes, thicknesses and are dependant on the size of component and thickness of material to be repaired. In thick cast iron sections, locks are inserted and stacked on top of each other or laminated to give the desired repair strength. For example if a repair was conducted to a section of cast iron 25mm thick, it is usual to laminate to 66% of the crack depth of 17mm, therefore two locks 6mm deep would be hammered into the pre drilled lock profile and capped with 8mm capping lock.

The protruding 3mm of capping lock would then be ground flush and smooth to the parent surface of the casting. Implanted stitching pins and locks are coated in a heat resistant sealant for a leak free flawless and almost invisible repair.

Unlike other systems IMS (UK) Ltd use a spiral hook threading and shoulder screw system for repairs. This lends itself to pulling the crack or fracture together as opposed to spreading the crack or fracture, the inferior process used by other companies which leaves the older procedures lacking in strength sealing properties. Many industries benefit from this service, power generation, railways, gas and oil, marine and offshore, cement, steel, process plants etc. 

Customer List

Rolls Royce, MAN Diesel, Vosper Thorneycroft, A&P Group, Occidental Oil, Shell Oil, Canadian Nexen, Maersk Shipping, Stena Line, Converteam, Alstom, British Energy, Lafarge Industries, General Electric etc.

Many of the named companies above consider In-Situ Machining Solutions as their preferred on-site machining contractor.

This stitching system has been well received by our customers and head and shoulders above the competitors in terms of strength of repair and visual appearance.

Comparison tensile strength tests have been conducted by an independent testing laboratory. There findings indicated that our metal stitching method of repair proved to be more than double the strength of a rival system.

Please contact us if you have an on-site or on board machining requirement. We would be happy to quote and advise accordingly.

Barring gear repair		Barring Gearbox repair
Repairing Crushing Mill Table
Large Engine Block Repair
Large Engine Block Repair
WHY IN-SITU MACHINING SOLUTIONS FOR METAL STITCHING? The strength of the Stitching system we use has been tested by a recognised independent Insurance Company against the standard system on the market today and the results speak for themselves (Test Certificate can be submitted on request) Proven to be double the strength of other stitching methods on the market Superior sealing properties Experienced technicians Guaranteed quality results every time GENERAL APPLICATIONS All medium / heavy castings Engine Blocks Pump casings Gearboxes Crankcases