New two-stroke piston ring coating gets provisional approval

Scott Rhodes Scott Rhodes

NOVEMBER 10, 2016 — Chesterfield, U.K., based piston ring manufacturer Precision Products (UK) Ltd. (PPUK) has received provisional approval for its ground-breaking new "CM2" (ceramic metal) advanced coating technology from MAN Diesel & Turbo, the world's largest supplier of two-stroke marine engines.

The new coating process combines a reformulated material matrix with the very latest application technology resulting in greater hardness, improved temperature performance and enhanced durability.

The provisional approval from MAN Diesel and Turbo comes after well over a year of ocean trials on board container vessels featuring MAN B&W main engines and envisages further shipboard tests, paving the way for the widespread adoption of CM2 piston ring technology for a range two-stroke marine engine applications.

"This is a key development for PPUK," commented Managing Director Scott Rhodes. "It is an important milestone in our ongoing R&D program which we undertake jointly with key partners, including MAN Diesel & Turbo. Our research has focused on CM2 which incorporates a more complex matrix of materials in its new formulation and is combined with an effective high velocity oxy-fuel (HVOF) application process. This complements the material itself in providing improved hardness, temperature performance, ductility and longevity.

"The provisional approval reflects the exceptional results we've seen when comparing a lengthy period of CM2 piston ring performance with CM1 in the same two-stroke engine. CM1 coatings are applied using plasma-spraying technology, whereas the latest HVOF application allows the coating powder to be applied using a mixture of gaseous fuel and oxygen at more than one thousand metres per second. This provides a more compact, harder coating with improved overall adhesion and durability."

Moves to increase piston ring time between overhauls (TBO) are a welcome development because opening up large marine diesel engines can be time-consuming, expensive and, in some cases, disruptive to future engine performance.

Mr. Rhodes said provisional approval of CM2, and its likely full approval, will open up a significant new after-sales market in piston ring maintenance and replacement. Development of the new technology is also an important step in its continuing strategy of developing closer and wider relationships with licensees, particularly in Asia, he said.

PPUK's ambitious R&D program is continuing, with a focus on key challenges including moves to limit the impact of sulfuric acid corrosion on piston rings, and new ceramic coating application technologies to supersede the existing ceramic chrome application process which is potentially hazardous to human health and damaging to the environment.

"Together with our partners, we will be announcing the next stage of our R&D program within the next few weeks," Mr. Rhodes said,

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