Nice to know | piston ring

Piston rings from BARIKIT are available as rectangular rings, trapezoidal rings and L-rings, made of cast iron, steel and steel with a chrome coating. The different materials and geometries all have advantages and disadvantages. In this blog post we have summarized the most important facts for you.


Piston rings have to fulfill the following tasks:

  • sealing the combustion chamber to maintain combustion gas pressure; Avoidance of blow-by
  • Dissipation of the heat occurring in the piston to the cylinder surface
  • Centering of the piston in the cylinder barrel.

1. Piston ring: Compression of the gas mixture and absorption of the gas pressure in the working cycle. Dissipation of the heat generated.

2nd piston ring: absorption of the remaining gas pressure as a result of blow-by. Control of the pressure conditions in the ring section and dissipation of heat in the ring section.


The following requirements apply to piston rings:

  • good running ability
  • elastic behavior
  • Mechanic solidity
  • high heat resistance
  • high thermal conductivity

forces and stress

Piston rings are subject to high mechanical, thermal and tribological stress. They have to fulfill their tasks at high combustion temperatures and combustion pressures of up to 120 bar. Up to 20% of the heat absorbed by the piston is transferred to the cylinder wall through the piston ring.


As mentioned above, BARIKIT piston rings are made of cast iron, steel and chrome-plated steel. Piston rings made of cast iron have proven themselves for many years. Due to the high proportion of graphite in the cast iron, the rings have good emergency running properties. The demands on the engines have increased over the years, which is why the more brittle piston rings made of cast iron have been replaced by rings made of steel. Steel rings are nitrided to increase surface hardness. The rings can be plated with chrome to reduce friction.

The selection of the piston ring geometry and the material depend on several factors. L-rings have an increased contact pressure resulting from the gas pressure. However, these are exposed to large thermal loads. Trapezoidal rings have the property of preventing the ring groove from coking. The increased run-in clearance results in increased running noise. Cast rings have good running properties, but the mechanical properties are limited.

When selecting the rings, it is important that the material pairing between the rings and the cylinder running surfaces is not identical, otherwise galling will occur.

Due to the many possibilities, piston rings are therefore individually adapted to each engine characteristic.

If you have any questions or would like individual advice, please give us a call or send us an email or WhatsApp. We are glad to help you.

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