Importance Of Piston Rings

What are Piston Rings?

Every combustion engine has a reciprocating part called a piston which executes To & Fro motion in the cylinder bore led by the forces that are produced due to the combustion processes. Piston features include Rings. Piston rings are extensible split rings that endues a perfect seal between the walls of the cylinder and the piston. The rings are retained on the grooves localized on the circumference of the piston, called ring grooves. Usually, the piston rings are manufactured of cast iron as it has the property to retain their original shape under immense heat and load. Piston rings are placed closest to the piston head. Piston rings help in the effective working of an engine.

Assembly of piston rings with important piston parts are shown.

Piston Ring Functions

  • Sealing – Piston ring seals the cylinder in such a way that the combustion gas does not leak through the opening between the piston and the cylinder, which is produced at the time of ignition.
  • Lubrication – Piston rings help in proper lubrication between piston and cylinder in order to reduce wear and tear. Lubricating oil is poured and the piston ring makes a thin film of lubricating oil between the two surfaces and, excess oil is removed by the rings.
  • Heat Conduction – The temperature inside a piston goes up to 573K when the gas ignition occurs, if this heat is accumulated inside then the engine will get damaged. To avoid this, piston rings come into action, piston rings transfer the heat from the piston crown to the cylinder.
  • Piston Support – Piston rings guide the piston in the bore for smooth reciprocating motion and prevents direct knocking of the piston on the cylinder wall which can damage the engine and can result in engine failure.
  • Engine Oil Regulation – Piston rings scrap the excess oil from the cylinder wall back to the sump and prevents overconsumption of engine oil.

Types of Piston Rings

  • Compression Ring – The ring placed in the groove closest to the piston head for the sake of sealing the combustion chamber from any leakage during combustion.
  • Wiper Ring – The piston ring with a tapered face placed in between the compression ring and oil ring, which offers further sealing to the combustion chamber and wipe the cylinder wall clean of excess oil.
  • Oil Ring – This ring is fitted in the groove closest to the crankcase. It maintains a uniform thin layer of oil on the cylinder during piston movement and wipes off the excess oil and returns it to the oil reservoir in the engine block through ring-opening.

Piston Ring Material

The primary material for the piston ring is cast iron, steel, some alloys, and coating are also added which vary according to the type and functionality of the ring. Cast iron is chosen because it contains graphite in lamellar form, which itself is a lubricant that reduces friction and avoids wear during the sliding motion of the piston. Different alloys are used such as silicon, manganese, molybdenum, vanadium, titanium, nickel, chromium, copper, etc. An alloy of silicon and manganese is added as it increases heat and wears quality. Also, as we know cast iron is a brittle material so to improve its elasticity alloy of silicon and manganese is preferred.
Piston rings are made harder than the cylinder liner in order to improve its span and better functioning of the engine.

Ring Gap

A gap is to be cut at the ends of the ring so that it can be expanded in order to fit over the piston head. This gap also ensures circumference wise expansion of the piston ring at higher temperatures.
The ideal ring gap is 0.30mm to 0.35mm.
These ring gaps are further classified as-

  1. Square cut
  2. Angle cut
  3. Step cut
  4. Title joint
  5. Hook step
  6. Mitre step
  7. Seal cut
Parts of a piston rings are shown in detail.

Manufacturing of Piston Rings

Cast iron and steel piston rings are made through different processes varying according to their type and also the manufacturer. Some manufacturers cast piston rings as individual rings in a non-circular shape, some others cut the individual rings from pots and cuffs. The piston rings are generally forged in the desired shape and size by the process of double cam turning.
In the case of steel piston rings, they are manufactured from a profiled wire. In this process, first, the rings are coiled into a circular shape and then the ring gap is cut out. Heat treatment is done in order to acquire the prerequisite shape for the rings.
The piston ring for a marine engine should be harder than the liner material for this purpose some additional coatings of different materials are added in order to provide additional strength. Different materials used for coating are chromium, molybdenum, vanadium, titanium, nickel, copper, etc.
Chrome plating is the most common for surface treatment. Chromium is highly worn resistant, corrosion-resistant and it has a lower coefficient of friction that is why it offers less friction.
Nowadays, the plasma coating method is also used for this purpose. Plasma coating provides better properties than chrome plating. Nickel, copper, and molybdenum plating can also be added.

GOETZE Piston Rings

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GOETZE is a world-class company with a wide range of products related to combustion engines such as GOETZE pistons, GOETZE piston rings, cylinder liners, etc for two wheelers, cars, tractors, commercial locomotives, etc.
GOETZE Piston Rings are one of the finest piston rings. The company focuses more on quality and research for greater efficiency. In 2005 GOETZE introduced the FO-PISTON RING design (Form Optimized) and LKZ (Laufsteg, Konisch, Zylindrisch) oil ring for low oil consumption and low friction.
For greater efficiency and better quality, GOETZE Piston Ring are one of the best as they are modified for better performance. For more details about GOETZE piston rings visit www.goetzeparts.in

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