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John Gibbon & Sons LTD

Cylinder Covers PDF  | Print |  E-mail
DMI Group Cylinder Cover Reconditioning
  • Total Reconditioning System
  • Worldwide Exchange Service
  • Backed by DMI Guarantee
DMI pioneered its Total Reconditioning System for cylinder covers for large bore two stroke diesel engines more than 20 years ago.

DMI continues to lead the way in the development of cost effective reconditioning methods for the latest generation of bore cooled cylinder covers in co-operation with OEM's and shipowners.

DMI's rigorous inspection procedures and Total Reconditioning System are designed to bring components back to original dimensions tolerances to provide a long and trouble free life. DMI's Exchange Service provides an "off the shelf" service to shipping from a number of strategic locations worldwide.

TRADITIONAL DESIGN CYLINDER COVERS

Removal of the combusion chamber of a B&W K74EF cylinder cover		Traditional B&W and Sulzer cast steel covers fail due to cracking of the combustion bowl usually caused by casting defects in the water cooling space.

The DMI "Calotte" method, now widely imitated, involves complete removal of the combustion bowl and replacing with a new casting - all internal surfaces are machined and crack tested before re-assembly using sophisticated weld procedures.


B&W K74EF cover after total reconditoning		Fuel valve, air start valve and safety valve sleeves are replaced where necessary and the finished cover is fitted with accesories.
BORE COOLED CYLINDER COVERS

Sulzer approved method of total reconditioning of RTA covers by crack removal in the bore cooling holes followed by complete rewelding stress relieving and machining to original condition in all aspects condition in all aspects		Modern bore cooled cylinder covers for B&W, Sulzer and Mitsubishi engines are manufactured from forged steel with complicated cross drillings to provide cooling and although reliable in service are very costly to replace.

Failure in service can be caused by a range of problems including erosion and corrosion in air start and safety valve bores, erosion in the area adjacent to the injectors, leakage from sealing rings, cracking from the cooling bores and fretting of sealing faces and "0" ring grooves.

Reconditioning of Sulzer covers includes a number of retro modifications developed by DMI in conjunction wilh Sulzer Winterthur designed to improve long term reliability.

Standard DMI repaire procedures on B&W bore cooled cylinder covers used on GFCA engines includes replacing of sealing rings with new, repairs to landing faces and crack removal on outside diameters. Retro modifications include welding of plugged bores on the landing faces.

BORE COOLED MAN B&W CYLINDER COVERS

Completely blocked cooling water bores		Current designs of MAN B&W cylinder covers are manufactured from steel forgings and cooling is effected by passing water through a number of bores which are drilled adjacent to the combustion chamber.
Although the covers have a long life expectancy, they have predictable failure mechanisms. The bore cooling holes are completely concealed by sealing rings on the inner and outer ends of the drillings. These are shown in left picture. Removal of the sealing rings can reveal blocked cooling water holes and cracks which run into the stud holes and combustion face.
DMI's tolal reconditioning procedure automatically includes the removal by machining of both the inner and outer sealing rings to enable the complete repairs to be carried out to the bore cooling areas. Failure to remove the sealing rings and carry out a total reconditioning procedure on these cylinder covers will result in a relatively short life after repair.
All blocked bore cooling holes are drilled out, inspected using an endoscope, cracks are removed and welded using highly specialised welding techniques. All surfaces are then fully machined and crack detected. Brand new sealing rings are then welded into place and the cylinder cover is stress relieved prior to machining and classification society certification.

Finished cover

 
Cast Iron Welding Services LTD
Classification Approved Quality Assured
PIELSTICK
RUSTON
STORK
MIRRLEES
MAK
WARTSILA
ALLEN
FIAT
SULZER
DIAHATSU
YANMAR
Cylinder Head Overhaul and Repair
Upon receipt all components are given a unique identification which remains with the job during its passage throughout the works. This ensures full traceability.
Cylinder heads and inserts are pressure tested at 10 bar for a period of not less than 1 hour.
Crack detection is undertaken using Magnetic Particle Inspection. Dye penetrant is used where access is limited eg. water jackets.
Full dimensional inspection then enables a comprehensive report and fixed price quotation to be submitted to the customer.
Gas fusion welding of cast iron produces a homogeneous and stress free weld with excellent metallurgical and machining properties compared with the parent metal subject to the correct materials being used and as long as the defined pre-heating, welding and stress relieving parameters are adhered to. The following examples of welded sections with a magnification of 105 times illustrate the integrity of the welded interfaces of flake and spheroidal graphite irons.
Cast Iron Welding Services are able to provide cost effective repair of Flake and Spheroidal Graphite Casting in both gas and arc wekling processes.

Amond the items suitable for refurbishment are engine and compressor cylinder heads, pump casings, valve housing, etc.

The repair of cracked and damaged cast iron components is a highly effective process, but one which must only be carried out by carefully trained technicians operating under closely defined conditions.

Cast Iron Welding Services have developed a process for the welding of cast iron which carries approval from the major classification societies and a twelve month warranty.

Repairs are carried out by gas function welding during which the casting is pre-heated and then maintained at a controlled temperature whilst the welding process is being carried out.

The area of the casting which is to be welded is melted into a fluid pool into which a cast iron welding rod of the same grade as the parent metal is fed.

Be carrefully controlling the operating conditions the resultant weld is homogeneous and stress free. The careful selection of materials produces a weld which has improved strenght and metallurgical properties compared with the original parent casting.

Cast iron Welding Services also provide additional "in house" services which include non destructive testing, radiography, pressure testing, and machining facilities.

 
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