• Home
  • News
  • Videos
  • Marine Tech
    • Air Compressor
    • Ship Generator
    • Oily Water Separator
    • Ship Stabilizer
    • Boiler
  • Navigation
    • Mooring
    • Watchkeeping
    • Maneuvering
    • Anchoring
    • Equipment
  • Maritime Law
  • More
    • Case Studies
    • Life At Sea
    • Maritime Knowledge
    • Marine Careers
    • Naval Arch
    • Ship Safety
    • Shipboard Guidelines
    • Forums
    • Types of Ships
    • Financial Planning
    • Photos
    • Apps
  • Premium E-Books
  • Free E-Books
  • Home
  • News
  • Videos
  • Marine Tech
    • Air Compressor
    • Ship Generator
    • Oily Water Separator
    • Ship Stabilizer
    • Boiler
  • Navigation
    • Mooring
    • Watchkeeping
    • Maneuvering
    • Anchoring
    • Equipment
  • Maritime Law
  • More
    • Case Studies
    • Life At Sea
    • Maritime Knowledge
    • Marine Careers
    • Naval Arch
    • Ship Safety
    • Shipboard Guidelines
    • Forums
    • Types of Ships
    • Financial Planning
    • Photos
    • Apps
  • Premium E-Books
  • Free E-Books

Marine Insight

The Maritime Industry Guide

You are here: Home › Marine Technology › How are Piston Rings Made?

How are Piston Rings Made?

By Ritbik K | In: Marine Technology | Last Updated on June 17, 2021

TwitterFacebookLinkedInPinterestBuffer

Table of Contents

  • What are piston rings?
  • Why are Piston rings needed?
  • Main uses of a piston ring
  • Thermally Tensioned Ring
  • Oval Pot Cam Turning Method
  • Material and Piston Designing Consideration
  • Piston Rings Design and Arrangement Consideration
  • Types of Piston Ring Gap
  • Design Consideration as Per Piston Ring Types
  • Ring Pack Design as Per Engines
  • Plating of piston rings
  • Plasma coating
  • Other platings that can be added- Molybdenum, Copper, Nickel 

What are piston rings?

A piston is a cylindrical component of an engine that slides back and forth in the cylinder out of the forces aroused by the combustion process.

The piston consists of the piston head, piston pin bore, piston pin, skirt, ring grooves, ring lands, and piston rings.

A piston ring is an expandable split metallic ring that is attached to the outer diameter of a piston in an internal combustion engine or steam engine usually used to provide a seal between the piston and the cylinder wall.

Piston rings of marine engines are made with the help of pot casting method. In this method, a short cylinder of an oval cross-section is made and the piston rings are then cut and machined from the cylinder.

With this method, a homogeneous and balanced casting is formed around the entire circumference of the ring.

how are piston rings made

Why are Piston rings needed?

Pistons are usually equipped with piston rings that fit into ring grooves in the piston wall and they assure a snug fit of the piston into the cylinder.

Piston rings are the essential components in the modern internal combustion engine in their optimum tribological performance which have a controlling influence in minimizing frictional power loss, fuel consumption, oil consumption, blow-by, and harmful exhaust emissions.

Main uses of a piston ring

Maintenance of Compressed Gas Between the Piston and the Cylinder Wall– The basic function of the piston ring pack- the collective name for the three or more rings mounted on the piston- is to seal the cylinder in such a way that the combustion gas generated at the time of ignition does not leak from between the piston and the cylinder.

The efficiency of the marine diesel engine depends upon the effective sealing between the piston and liners. Leakage would result in an insufficient power supply. Moreover, it would result in more fuel consumption hampering the efficiency thereafter.

Make Necessary Optimum Lubricating Oil film to Prevent Scuffing– The piston goes up and down innumerable times. A small amount of lubricating oil is poured over the pistons for smooth functioning and avoiding friction arising from metal to metal contact. The piston rings adjust and maintain the proper amount of lubricating oil and provide the necessary lubricating film to prevent scuffing.

Improve Heat Transfer from the Piston to the Cylinder Wall– The temperature inside the piston goes as high as 300 degrees Celsius during ignition. The heat build-up can damage the piston. The piston rings furnish heat transfer from the piston to the cylinder wall and help the excessive heat to escape.

Piston rings also prevent the piston from knocking on the cylinder wall by supporting the piston in the cylinder. Rings act as a barrier that prevents frictional force and eventually engine failure.

Sticky piston

The piston rings should have tension properties with which sealing effect is produced.

In olden days, the tension in the engine room was produced by hammering around the circumference of the circular ring.

This tension is achieved by two methods:-

1) Thermally Tensioned Ring
2) Oval Pot Cam Turning Method

Thermally Tensioned Ring

The thermally tensioned ring is one of the cheapest methods to induce tension in the piston rings but is restricted to smaller engines. In this method, the piston ring is machined from the circular pot to the required cylinder diameter.

After making the ring, a gap is cut and a metal piece is inserted in the gap which expands the ring and induces tension in the ring.

After expanding, the ring and the distance piece is placed inside the oven to relieve any stresses induced during the process. The major disadvantage of this process is that the ring loses its tension because of the heat of the engine.

marine engine piston ring

Oval Pot Cam Turning Method

The oval pot cam turning method is expensive but the rings produced from this method retain their tension while working in heat of the engine.

The rings are machined in a cam turning lathe. By changing the cam shape and the oval form, the pressure distribution around the ring is changed and tension is induced.

Video On How Piston Rings Are Made?

Material and Piston Designing Consideration

Piston rings should be made up of material that possesses these properties:

1. Low Friction Coefficient– This property enables the marine piston rings to slide along the cylinder’s surface and make them capable to withstand high pressures at various temperatures under limited lubrication conditions.

2. High Modulus of Elasticity- This property of material enables marine piston rings to provide the required specific pressure upon a cylinder’s surface. Further, it avoids the seizure of piston rings when they are moving in contact with a cylinder.

3. High Yield Strength and Hardness Grey modified cast iron possesses the above properties. Therefore, piston rings are generally made up of cast iron or steel. Moreover, the properties depend on the structure formed during the casting process.

A small amount of chrome, copper, Molybdenum, RIAS, and tin additives are used for plating which enhances the properties.

importance of piston rings

Piston Rings Design and Arrangement Consideration

The design of the piston rings and the arrangement of rings vary as per the engine type, size, and typical piston assemblies.

Ring Gap

A gap needs to be cut at the ends so that it can be expanded, slip over the piston head, and can be released while releasing it into the piston groove.

This also ensures circumference- wise expansion of the ring at higher temperatures.

The gap is cut with precision because excessive gap results in blow-by and scuffing of rings while lesser gap causes piston rings to butt at higher temperatures which leads to excessive and non-uniform pressure on the cylinder walls and causes excessive wear.

Ideal Gap – 0.30 mm to 0.35 mm

Types of Piston Ring Gap

A. Square Cut
B. Angle Cut
C. Step Cut
D. Title Joint
E. Hook Step
F. Mitre Step
G. Seal Cut

Design Consideration as Per Piston Ring Types

1. Compression Rings – These usually have a rectangular or keystone shaped cross-section. Upper compression rings have a barrel profile for the periphery, while the lower compression rings usually have a taper napier facing.

2. Oil control rings- Made from a single piece of cast iron, multiple pieces of steel, or steel/iron with a helical spring backing that have two scraping lands of various detailed form.

Ring Pack Design as Per Engines

1. 2 Stroke Petrol Engines – 2 Plain Cast Iron Rings

2. 4 Stroke Diesel Engines – Chrome-plated top ring 2 taper faced iron rings 2 scraper rings

3. 4 Stroke Petrol Engines – Plain iron top ring Taper faced iron ring Scraper ring

4. Large 2 Stroke Diesel Engines – 5 plain iron rings

Detailed design of the piston rings depends upon the required elastic pressure, the ring to piston fitting stress, and the ring to cylinder fitting stress.

Plating of piston rings

The piston rings used in the marine engines should be harder than the liner material in which they are used. To provide additional strength to the piston rings, some materials like chromium, molybdenum, vanadium, titanium, nickel and copper are added.

Chrome plating is one of the most common methods of surface treatment. It is generally used on the running surface of the piston rings and on the landing surfaces i.e. in ring grooves.

Chromium has the advantage of high wear resistance, low friction and corrosion resistance properties. The coating done should be of high quality and be able to operate under all conditions inside the engine without damaging or peeling off or breaking.

Plasma coating

It is also one of the methods used for plating the rings. In this method, a gas mixture is passed through an arc generated between the tungsten electrode and a water-cooled copper tube.

A very high temperature is thus generated and the gas molecules start to disintegrate. The plasma state-level carbides and ceramic are sprayed as a fine powder which melts and coats the ring surface.

This plasma coating provides better properties than those provided by the chrome plating.

The disadvantage of chrome and plasma coating is that the thickness of the coating and the bonding to parent metal is limited.

A new method of laser hardening treatment is also done. This produces a wear-resistant layer which is several times thicker than that of the conventional coatings.

Sometimes, copper is plated directly over the chrome layer of the ring. The plating thickness is very thin and the life of this is long enough to cater for running in period. Plasma coated rings are graphite coated to cater to the running-in periods.

Other platings that can be added- Molybdenum, Copper, Nickel 

Copper – Copper plating is done either directly on the base metal or on the chromium plating. Tufftriding and phosphating of cast iron also help to ease scuffing problems during running-in. A thin final surface layer of the copper plate is applied thereafter.

Flamesprayed Molybednum– Flamespray is used to deposit molybdenum on the peripheral surface of a piston ring, the resultant coating contains a mixture of molybdenum and oxides of molybdenum.

This coating offers more resistance and is harder than wrought molybdenum which does not contain oxides or porosity. This is considered as the best coating for scuff resistance but tends to oxidize and break up in long-life applications.

Nickel Plating– Nickel ceramic plating is done by conventional electroplating. It was found that Ni–P–BN has better self-lubricating properties than Ni–P–SiC or Ni–P–Si3N4 coatings and exhibits low wear when slid against cast iron and aluminium liner. Ni-P-BN coating is done by screen printing or spray process.

If you liked this article, you may also like to read:

  • A Guide to stroke marine engine components
  • Types of Piston ring and maintenance.
  • Piston Skirt, Piston Rod and Trunk Piston
  • How is Marine Engine Repair Done Onboard a Ship?
  • Reason for cylinder liner wear and how to measure it?

Disclaimer: The authors’ views expressed in this article do not necessarily reflect the views of Marine Insight. Data and charts, if used, in the article have been sourced from available information and have not been authenticated by any statutory authority. The author and Marine Insight do not claim it to be accurate nor accept any responsibility for the same. The views constitute only the opinions and do not constitute any guidelines or recommendation on any course of action to be followed by the reader.

The article or images cannot be reproduced, copied, shared or used in any form without the permission of the author and Marine Insight. 

Report an Error

Related Posts

Understanding Indicator Diagram and Different Types of Indicator Diagram Deficiencies
Understanding Indicator Diagram and Different Types of Indicator Diagram Deficiencies
Everything You Ever Wanted to Know About Scavenge Fires
Everything You Ever Wanted to Know About Scavenge Fires
Types of Piston Rings
Types of Piston Rings and Piston Ring Maintenance
marine engine
Piston Skirt, Piston Rod and Trunk Piston

Tags: piston rings

Want to share your tips and advice? Got questions? Visit the community forum to ask questions, get answers, meet people, and share your tips!

About Ritbik K

Ritbik is a student of Marine Engineering at IMU Kolkata and has research interests include Maritime Technology and Subsea Structures. He is an avid reader and writer and has been indulged in technical and creative writing for a long time.

Leave a Reply

Your email address will not be published. Required fields are marked *

Popular Now

all women crew vessel

Photos: All-Women Crew Embarks On An Expedition – International Day For Women In Maritime

autonomous vessel AI identification

Watch: Autonomous Vessel Avoids Collisions, Completes 800Km Voyage Without Human Assistance

Seafarers win commitment to mandatory internet access in international law

Seafarers Win Commitment To Mandatory Internet Access In International Law

navy vessel

Pirate Attack On Cargo Vessel Prevented By Iranian Navy In Gulf Of Aden

AbujaReady

Abuja MoU: Harmonizing Port State Control And Flag State Implementation

Marine Engineering

  • Marine engine
  • Air compressor
  • Marine boiler
  • Oily water separator
  • Marine Electrical
  • Ship Generator
  • Oily water separator

Nautical Science

  • Mooring
  • Bridge Watchkeeping
  • Ship Manoeuvring
  • Nautical Charts
  • Anchoring
  • Nautical Equipment
  • Shipboard Guidelines

Explore

  • Free Maritime eBooks
  • Premium Maritime eBooks
  • Marine Safety
  • Financial Planning
  • Marine Careers
  • Maritime Law
  • Ship Dry Dock

More

  • Shipping News
  • Maritime Reports
  • Videos
  • Maritime Piracy
  • Offshore
  • Safety Of Life At Sea (SOLAS)
  • MARPOL
  Privacy Policy   |   Refund Policy   |   Contact Us  |   Disclaimer   |   About Us   |   Team   |   Advertise  |   Send Us News

Copyright © 2010 - 2022 Marine Insight — All Rights Reserved | Made with ♥ in India DMCA.com Protection Status

This website uses cookies to ensure you get the best experience on our website