Piston rings are made of which of the following?

Question

Question

This question was previously asked in

RRB ALP Mechanic Diesel 21 Jan 2019 Official Paper (Shift 1)

Answer 1

Explanation:
Piston ring:

A piston ring is a metallic split ring that is attached to the outer diameter of a piston in an internal combustion engine or steam engine.

The main functions of piston rings in engines are:

Sealing the combustion chamber so that there is minimal loss of gases to the crankcase.
Improving heat transfer from the piston to the cylinder wall.
Maintaining the proper quantity of oil between the piston and the cylinder wall.
Regulating engine oil consumption by scraping oil from the cylinder walls back to the sump

Materials:

Piston rings are made of high-grade cast iron, centrifugally cast and ground.
This provides good elasticity and minimizes vibration.
In some cases, steel- chromium-plated rings are also used in cast iron cylinders.
Chromium-plated rings are only used in the top groove.
These rings have less friction, less wear, and longer life.

Piston rings Types:

Compression rings:

These rings effectively seal the compression pressure and the leakage of the combustion gases.
These are fitted in the top grooves.
They also transfer heat from the piston to the cylinder walls.
These rings vary in their cross-section.

Oil control rings:

The main purpose of an oil ring is to scrape the excess oil from the liner and drain it back to the oil sump during the downward movement of the piston.
It prevents the oil from reaching the combustion chamber.
One or two oil control rings are used in a piston.
If two rings are used, one is fitted above and the other is fitted below the gudgeon pin in the piston.