A piston ring is a split metal ring in reciprocating or internal combustion engines that is placed around the piston head’s outer diameter. The piston rings can be made either out of iron or steel. A single piston head has more than one ring each serving a specific function. Basically there are three types of piston rings that is; compression/ pressure ring, intermediate/ scraper ring, oil control ring. Their functions are as discussed below:
Compression/ pressure rings
The compression ring is usually placed on the top of the piston head that is the side of the combustion chamber. Its main function
Intermediate/ scraper rings
Scraper rings are placed second after the compression rings. Their main function is to wipe off oil left behind by the oil rings. They also smear the oil on the cylinder walls ensuring the compression rings are properly lubricated. The scraper rings also assist the compression rings to seal off combustion gases
Oil control rings
These rings are placed at the bottom of the piston from, from the crank case side. The main function of oil rings is to control the amount and economy of lubricating oil used in engines. They ensure oil is evenly spread on the cylinder walls and scrap excess oil off the walls and send it to the crank case.
Some engine designs may only have compression rings and oil rings only. In such engines the compression rings are referred to as; the top compression ring and the second compression ring. The second compression ring will double as the scraper ring in such engines.
For efficiency, the compression rings and scraper rings are made differently according to application. The cross-sectional faces of the rings are made into varying shapes from rectangular to taper faced rings. Since invention, piston rings have reduced friction in engines thus increasing cylinder life longevity. The reduction in friction and gas leakages has also seen increase power efficiency engines.