CYLINDER LINERS

Liners at stages of reconditioning

 Finished liner Various liners

DMI specialise in the porous hard chromium plating of new and worn diesel engine cylinder liners used in Rail, Marine, Power Generation and other Industries. Liners processed by DMI (UK) range from 70 mm to 400 mm diameter bore. Using a combination of hard chromium and engineering nickel electroplating together with associated grinding, honing and machining, DMI are able to surface treat new and to recondition worn cylinder liners from diesel engines, pumps, compressors and gas engines and return them to original size.
Every year, DMI recondition thousands of cylinder liners in this way.
DMI Porous Hard Chromium has a range of characteristics that make it an ideal choice for the surface coating of liner bores:
A hardness of 67 - 70HRC
Controlled surface finishes (intermediate porous hard chromium)
Corrosion resistance
A very low coefficient of friction
Thermal stability
Can be applied to steel and cast iron liners with equal success
The ability to be removed and reapplied at intervals without effecting the base material
Reduced maintenance
DMI porous chrome is 3 to 4 times harder than cast iron and has a much higher resistance to abrasion, wear and corrosion.  Intervals between overhauls can be greatly increased. The combination of the chrome properties result in lower piston ring groove wear, lower piston ring wear and reduced instances of sticking and breaking of piston rings.
Porous Hard Chromium
High wear rates of conventional, cast iron liners result in inconsistent and high lube oil consumption. Controlled surface finishes of the hard chromium in the liner bore (intermediate porous chromium) provide for more controlled running in and for more predictable, controlled and reduced lube oil consumption. Different finishes can be produced for different applications.		 Porosity Porosity
Wear and corrosion resistance
Chromium provides exceptional wear resistance. It resists abrasion and scoring from sand, grit, dust or lubricant contamination. It stands up against corrosive by-products and acid build up in crankcase oil and severely corrosive vapours and liquids. Its high thermal conductivity and low coefficient of friction aid in maintaining low temperatures on bearing or friction surfaces. The porosity in the chrome surface does not extend through the chrome to the base material, resulting in excellent corrosion resistance.
Service Life
Porous hard chrome plating in the liner bore will outlast conventional cast iron bores by four to five times. The reconditioning process can be repeated many times. The service life of the liner can therefore be increased by a substantial amount. The liners can be removed from the engine and re-chromed back to original size, thus eliminating the need for oversize piston rings, for time consuming and expensive maintenance and the need for the fitting of new liners.
Nickel plated o/d's Nickel plated seal areas

Outside diameters and sealing areas
Outside areas can be reconditioned by a combination of nickel and hard chromium to build up eroded, corroded or damaged flanges, seal areas and 'O' ring grooves and return them to original dimensions. The nickel and hard chromium layers provide exceptional corrosion and erosion resistance.
Cheaper piston rings
Plain cast iron rings are compatible with DMI porous chrome liners and give long life at low cost.
Chromed rings must not be used with chrome plated liners.

The same processes are used for the surface treatment of new and the reconditioning of worn cylinder liners for sludge, sewage, cement, mud and tar pumps, hydraulic cylinders and pistons, rolls for the textile industry and components for the offshore, mining, food processing and packaging industries.

For further information
E mail: DMI (UK) or DMI Europe B.V.


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