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Extended Life Power Piston Rings

Dual Coated for Large Bore Integral Engines
Cooper Machinery Services Emerging Legends Series Logo

DUAL COATED FOR DURABILITY & Environmental friendliness

As part of our Emerging Legends™ series of new products and services, Cooper is excited to introduce plasma-sprayed power piston rings, dual coated with molybdenum and nickel graphite (Mo2), for large bore integral engines. Offered as an upgrade to traditional ferrox coated rings, the Mo2 coating technology was first introduced to large bore diesel engines in the marine industry many years ago and has been applied with great success around the world. Cooper is launching Mo2 coated rings to reduce risk of start-up and break-in failures, and to allow extended time between ring replacements. In addition, the new coating allows Cooper to further eliminate chrome from our manufacturing processes. The Mo2 coated rings are available for large bore, slow-speed engine brands such as Cooper-Bessemer, Clark, Ingersoll Rand, and Worthington.

Cooper is the only engine O.E.M. that manufactures engine power piston rings. These world-class Mo2 rings are produced and stocked in our Houston, Texas manufacturing and distribution center.

Mo2 Coating (hexavalent Chrome Free!)

Piston rings are critical to engine performance. The rings must create an effective seal against the bore and ring groove while operating in a hostile environment of hot, and sometimes corrosive, gases with limited lubrication. A premature failure can be costly, which is why quality piston rings make good sense. By applying a coating on the ring, the wear properties are greatly improved.

The Mo2 coating has two layers: a base layer of molybdenum composite material and a top layer of nickel graphite. Both coatings are applied through thermal (plasma) spraying. Molybdenum-based coatings provide low wear rates and prevent scuffing. Nickel graphite material has the ability to wear in and conform without causing wear or damage to the counter surface. Best of all, there is no hexavalent chrome in our ring manufacturing coatings.

The nickel graphite top layer will remain for the first several thousand hours of run time. When this layer wears off, a second coating layer of molybdenum is exposed, providing excellent wear and scuffing resistance for extended engine life. The coating is applied to a barrel-faced ring for optimal seating-in and lubrication performance.

Mo2 advantages

m02 power piston ring faqs

Why should I choose a High-Performance (Mo2) kit instead of a standard kit?The main benefit is a lowered risk of ring scuffing during the critical start-up period as well as for the remaining life of the ring. In addition, the ring will last longer thanks to the excellent wear resistance of the molybdenum layer.
Is it compatible with all cylinders?Yes. We have installed it in cast iron, hard iron, nitrided, chrome-plated, and Thermalloy® coated cylinders without issues.
How long will the coating last on the ring?The nickle-graphite (break-in) layer lasts 5,000-10,000 hours. The second layer of molybdenum has a much higher wear resistance that should extend the life of the ring kit significantly. More important, the ring will have much better scuffing resistance all through its life cycle including the critical start-up process.
Since it is a new coating, how can we be sure it is works? We don’t want to be a test site.The coating has been used in integral gas engines in the US since 2017, accumulating hundreds of thousands of cylinder hours. It has also been used in marine diesel engines for over 30 years.
Are the new rings dimensionally the same as traditional rings? Yes. They are designed to fit the same ring grooves. End gap clearances and side gap clearances (required only for Cooper Bessemer rings) are on the kit build sheet.
Why aren't all rings the same material (top ones only are MO2; the others are uncoated)?The top rings handle the combustion pressure. The 2nd ring doesn't need to be coated, but we do it to add a safety factor. The remaining rings serve other purposes (primarily oil control) and don’t require the coating.
These rings look different, and the surface looks very rough. Will it damage the cylinder?While the surface appears rough, it is also much softer than the cylinder surface so it will not scratch or wear the cylinder. The rough and porous nickle-graphite in the topcoat can retain oil, and the low hardness/strength allows it to break in and seat much quicker than other rings.
Cooper’s new extended life power piston rings are an inaugural member of the Emerging Legends™ Series, our portfolio of new products and services that advance the industry and transform Cooper’s traditional way of doing business. Emerging Legends™ serves as a testament to the Cooper commitment of optimizing performance of legacy engines and compressors, helping our customers extend the life of their equipment, and bringing environmentally sustainable solutions to the market.

coating comparison

Types of CoatingBreak-InWear Resistance
Uncoated Ring
Hard Coating
(i.e. Chrome, Molybdenum)
Soft Coating
(i.e. Ferrox, Nickel Graphite)

in-house manufacturing — Genuine O.E.M.-Quality power piston rings

Cooper has spent decades providing technology and engineering services for AJAX engine and compressor upgrades. With our advanced technologies, expertise, and project management experience, we offer AJAX upgrades to reduce engine emissions, increase horsepower, improve efficiencies and reliability of your equipment, and reduce maintenance costs.

To further strengthen our upgrade portfolio for AJAX engines, Cooper acquired HOERBIGER’s Engines Services (HES) division in 2019. Cooper now offers even more upgrade technologies including the HyperLogic™ and ePCC™. The Engine Services team has been offering engine emissions reduction and efficiency improvement upgrades, applicable to all types of AJAX integral engines.  

expedited delivery

Our Mo2 power piston rings are produced and stocked in our Houston, Texas manufacturing and distribution center for all Cooper O.E.M. and non-Cooper slow-speed engines, assuring the power piston rings you need are available when you need them. Our goal is to have same day or next day delivery service to our customers.

Contact your Cooper sales representative to learn more about Mo2 coated rings and place an order.