Piston ring Position: Home >Piston ring
1. Definition
A metallic circular spring with a high relative outward expanding strain . It fits into an annular groove that fits its section. The reciprocating and/or rotating piston ring seals against a pressure differential of a gases or liquids between the ring face and cylinder bore and one side of the ring and groove.

2. Field of application
Piston ring is widely used on power machines, such as steam engine, diesel engine, gasoline engine, compressor and hydropress, etc. Generally, it is installed in piston groove, and works in the chamber which makes up of components such as piston, cylinder jacket and head, etc.

3. Function
Piston ring contains four functions, that is, sealing combustion gas, regulating oil consumption, heat transfer and Supporting.
(1)Sealing combustion gas: Piston ring can prevent gas in chamber from escaping outside to the crankcase. Moreover, it will control gas leakage, which can not only decline the engine power but also deteriorate oil, at the minimum volume and increase thermal efficiency of the engine.
(2)Regulating oil consumption:Piston ring can scrape spare oil film the cylinder wall, and form a thin oil layer on the inner, this guarantees a lubrication state among the cylinder, piston and the ring. Engines of modern high speed attach great importance to control ability that piston ring effects on the oil film.
(3)Supporting: Piston ring can hold piston inside the cylinder, protect it from direct contacting with cylinder wall and keep its motion smooth-going. As a result, this will reduce friction between piston and cylinder wall and avoid cylinder knocking.
(4)Heat transfer: Piston ring can transmit combustion heat inside piston to cylinder liner, and keep piston inner a cooling state. Generally, 70%~80% of combustion heat on piston top will dissipate by transmitting through piston ring to cylinder wall.

4. Product classification
(1) Separated by structure
A、Single-piece ring, a ring formed from only one part which is intended for installation in a single ring groove.
B、Multi-piece ring , a ring comprising two or more component parts which are intended for installation in a single ring groove.
C、Compressor ring, a ring intended primarily to prevent the leakage of gas past the piston.
D、Oil ring, a ring having oil return slots or an equivalent and intended to scrape oil from the cylinder wall.
E、Slotted oil control ring, an oil control ring with parallel sides, two contact lands and oil return slots.
F、Coil spring loaded slotted oil control ring, a slotted oil control ring with a cylindrical coil spring inside. This spring increases radial pressure and acts equally in all directions against the inside of the ring, common in diesel engine
G、Expander/segment oil control ring, a three-piece oil control ring comprised of an expander-spacer and two segments. Expander-spacer design will vary with manufacture, common in gasoline engine.
(2) Separated by cross-section configuration
There are piston rings such as barrel-faced ring, taper-faced ring, internal bevel twist ring, half keystone ring, keystone ring, napier ring (undercut step), scraper ring (stepped), expander/segment oil control ring, bevelled –edge oil control ring, double-bevelled oil control ring, cast iron coil spring loaded slotted oil control ring.
(3) Separated by material
(4) Separated by surface treatment
Gas nitriding ring: It exhibits good wear and corrosion resistant, with hardness above 950HV and brittle level 1th.
Chroming ring: With highly densified interconnected network of micro-cracks, the plating layer hardness is above 850HV. In addition, the micro-cracks will provide an area lubricating oil can be stored in, thus greatly improving wear resistance.
Phosphating ring: Using chemical treatment that can generate phosphate coating on the surface of piston ring. This coating can effectively prevent piston ring from rusting and improve its initial running-in ability.
Oxidation ring: Effected by high temperature and strong oxidant agents, steel material surface will generate a layer of oxide film.This flm keeps piston ring a good capacity of corrosion resistance and improves its anti-attrition performance as well as good appearance.

5. Marking of piston rings
According to GB/T 1149.1—94, all rings requiring orientation shall be marked to indicate the top side only, that is, the side nearest to the combustion chamber.
Marking of the top side applies to the following type of ring: taper-faced ring, internally bevelled, scraper ring, nippier ring, half keystone ring and directional oil control ring. Our have markings of top side like “DY”、“NDY”、“DA”、“3N” and “D”.