Marine piston rings are an important part of the compression system in a 2 stroke or a 4 stroke engine. To ensure that the piston rings will perform thoroughly, it is important to know the required properties and types of piston rings used for specific purposes.


Compression piston rings for two stroke large engines seal the chamber to prevent high-temperature combustion gases from escaping whilst distributing the oil on the liner surface.


Apart from ensuring that the piston rings have a similar thermal expansion to that of the cylinder liner, listed below are some of the major mechanical properties of piston rings that maintain their optimum clearances:

  • Low Friction and Self Lubricating
  • Load Bearing
  • Corrosion Resistant
  • Good Heat Transfer
  • Innate Hardness for Wear Resistance


Ring clearances are essential to allow movements and thermal expansion. Here are two kinds of clearances you should know about:

  • Vertical Clearance

This clearance is important for free movement during operation and must be kept to a minimum to avoid ring hammering and ring groove wear. However, when the vertical clearance is insufficient, it may cause rings to stick in the groove or break as they come up to operating temperature.

  • Gap Clearance

Whilst gap clearance should never close completely, it must be as small as possible and should be maintained within a range of 0.4 – 0.5 per cent of a cylinder bore. The ring may break due to the restriction on its thermal expansion when coming up to working temperature if the ring gap is too small. Keep in mind that too small a gap may cause an increase in liner wear or lead to liner scuffing due to the oil film breaking down.

Based in Chesterfield, UK, Precision Products UK specialises in the design and production of piston rings and metallic seals that are all manufactured here in the UK. We supply expert products and services to customers from different industries worldwide. Click here to know how you can order or contact us via +44 1246 261621 for more information.