Piston Ring Types - Scraper Ring

Expandable split rings are attached to the outer diameter of a piston in an internal combustion engine and are used to provide a seal to maintain gas compression between the piston an the cylinder wall.

The top two rings — known as compression rings — are designed to seal the combustion chamber. The bottom ring is known as the oil control or scraper ring and controls the amount of lubricating oil passing up or down the cylinder walls. Oil control rings are designed with a step recessed into the bottom outface and scrap the oil off the cylinder walls, prevent its entrance into the combustion chamber and send back it to the crankcase.

Oil control rings are designed with a step recessed into the bottom outer face to aid oil scraping. The step allows oil to be stored and can be varied in size. Due to the undercut step, when the ring twists the scraping edge scrapes the oil from the outer edge into the reservoir preventing it from clogging the scraping edge.

Scraper Ring Types

Napier Ring:

The Napier ring (or ‘Hook’) is installed in the second groove and is used in compressors of air brake systems. However the Napier ring has be superseded by the Taper Faced Napier Ring.

Taper Faced Napier Ring:

More commonly used – the Taper Faced Napier Ring provides a more efficient edge to improve running-in which aides oil control.

Taper Faced Closed Gap Scraper Ring:

This ring is designed without an undercut – the step runs out at the gap and seals better than the Napier and Taper Faced Napier Rings.

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