The Best 21-22 tutorial on |diesel engine piston

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Diesel engine piston


Diesel engine pistons are a vital and critical part of a diesel engine. They are responsible for powering the machine and providing power to the engine during combustion. Without them, the engine would be unable to produce the energy it needs to run. The piston is the part that surrounds the combustion chamber.

A diesel engine piston consists of a metal alloy designated to resist shear. The alloy is used to make the engine piston more resistant to wear and tear. It also makes the engine piston more durable.

This blog post will help the readers to understand diesel engine pistons and how to maintain them properly. We will also look at the diesel engine pistons and their role in the engine. This blog post will cover how to replace a diesel engine piston.

In this post on diesel engine piston, I will write on the listed below topics.

  1. Piston in Engine of marine Engines.
  2.  Piston material
  3. Overhauling Process of Piston
  4.  Problems in pistons.

 I will explain the procedures in easy to understand the language for the readers. The post will be useful for the marine engineers and engineering students.

The purpose of Piston in engine

The piston is the most important unit of any Engine.

  1. The Diesel Engine Piston transmits the force of expanding gas in the cylinder via connecting rod to the crankshaft.
  2.  Piston converts the energies from one form to other. ( Chemical energy to mechanical energy)
  3.  Sealing effect between the piston and the cylinder liner is provided with the help of piston rings. Economy and efficiency of the engine is due to the contribution of piston in an engine.
  4. Small end of the connecting rod is guided by the piston, hence piston bears the side thrust.

Diesel engine piston for the marine engine

Diesel engine piston Parts identification

diesel engine piston

Top part of piston is known as piston crown. Piston crown comes in contact with the burning gasesand is heat-resisting steel.

Ring grooves on the circumference of the upper part of the piston crown accomodate the piston rings.

The part below the ring groove is the piston skirt. This part is of cast iron and the part between the ring grooves separation is the lands.

The piston pin is in the bosses of the reinforced parts.

Desired Qualities of Diesel Engine Piston

  1. The piston should withstand the forces developed by the combustion process.
  2. Design the piston to reducethe piston weight. Less piston weight will cut the inertia by reciprocating masses.
  3. Piston reduces the tendency and risk of detonation due to the excellent heat conductivity properties.
  4. Allow a higher compression ratio.
  5. Piston Material should have low expansion. The material should be able to cover various expansion rates of a Cylinder block and an aluminum piston.
  6. Under any abnormal condition the design of the piston skirt will have the uniform bearing effect

Design of diesel engine piston

Piston’s design is complex about design. A piston is in two parts as crown and piston skirts. The material of the piston crown is corrosion resistant and high strength. crown is always in contact with the combustion gases temperature.

Types of diesel engine piston fitting arrangements

Listed below are type of pistons.

  1. Crosshead Piston
  2. Trunk type piston

Cross head Piston

Crosshead Type

In the crosshead type piston, the piston connects with the crankshaft. The piston connects to the crosshead bearing through connecting rod. and to the crankshaft by piston rod and crosshead guide. with this method arrangement reduces the side thrust on the piston.

Trunk Design Piston

Trunk Type piston
Image Credit:- MAN B&W

Trunk design pistons are popularly used in four stroke medium speed engines. Skirt is long in trunk typepistons. Piston connects to the connecting rod by small end bearing. Piston pin is the axis of rotation for small end bearing

Difference in design of Cross head type and trunk design piston

Trunk type Diesel engine piston

1. There is single connecting rod in trunk design piston.

2.   Trunk design piston engines have no diaphragm.

3.  In the trunk-type engine, the small end, connects with the piston through the gudgeon pin and small end bush assembly.

4. In the trunk-type engine, no separate lube oil is used for the cylinder liner.

5. Piston skirt takes the transverse thrust

6. Cross head assembly is not required to connect the connecting rod and piston.

7. High power is produced at medium and high speed.

8. Needs less space.

9. Reduced engine manufacturing cost

10. Engine height is less as compared to the engine with same speed and power.

11. Can use low-grade oil.

Crosshead Type Engine

1. Cross head type engine use the connecting rod and piston rod

2. A diaphragm seprates Cylinder space and crankcase

3. In the crosshead type, the top part of the connecting rod connects to the crosshead consisting of the block slipper. The lower part of the piston rod supports the assembly.

4. The lubrication system for the cylinder and crankcase is different.

6. Cross head assembly connects the connecting rod and piston rod

7. Crosshead type engine develops high torque at smallest speed.

8. Need of more Height and space for maintenance.

9. Manufacturing cost is high.

Advantages of Crosshead type Piston

1.   At lower rotational speed will develop high power

2.    Lube oil contamination by combustion product is less.

3.    The lubricating oil cost is low in cross head type.

Lubrication of Trunk type pistons

 Piston for Marine Engines-Lubrication

Supply of lubricating oil from crankshaft cools the piston . The shaking effect of lubricating oil cools the crown and flows out through the centre of the joint screw. After cooling, the piston crown oil scatters on the cylinder wall. Lubricating oil flows down to the sump after cooling down the cylinder liner wall. 

Procedure for Inspection of Diesel engine piston

Overhauling Process of Piston

Pre-overhauling preparation

1. Close and lock the air starting system

2. Open the indicator cock

3. Cool down the engine.

4. Disconnect fuel and cooling water.

5. All the measuring and inspection tools should be ready with calibration, and working conditions 

6. Check the availability, workability, and validity of lifting and strops and shackles.

7. Personnel involved in the maintenance should have the adequate knowledge of working procedures.

8. Place the safety symbols as per the manufacturer’s recommendations in the vicinity of the maintenance area.

9. Confirm the availability of spares.

10. Check the workability of hydraulic tools.

11. Ensure the mobilization permission.

12. Undertake the risk assessment.

13. Carry out the ventilation of the crankcase with permission to undertake the job.

14. Rope off the working vicinity.

Overhaul Procedure of Diesel engine piston

Carry out the below procedure for the liners with flame mounting (design of piston)

1. Clean the cylinder liner top of coking as the piston may stick in the deposits

  • Turn the piston to BDC
  • Remove the flame ring after Inserting and mounting  the tool above the piston.
  •  Put an old discarded piston ring above the flame ring removal tool.
  • Install the liner holding tool on one of the cylinder head nut.
  • Turn the engine slowly to push out the flame ring.

Important procedures for Diesel engine piston

2. Dismount the crankcase cover for the cylinder section in question to dismount the platform to help access

3. Mount the supporting device on the crankcase cover frame.

supporting device

4. Place the mandrel in the guide sleeve and push forward to rest the shoulder of mandrel in correct postion.

5. Turn the crankshaft till the center of the connecting rod screw is on a level to mandrel top

Piston for Marine Engines- mandrel

6. Bring the crank throw is in a position to loosen the both upper and lower connecting rod screw .

Lossening CR bolts

7. Install the piston lifting device after cleaning the threaded hole.

Piston lifting device

8. Mount the pipe for retaining of the cylinder liner

Liner retainer

9. Grab the tackle in the lifting tool for the piston and tighten.

Before turning the crankshaft, loosen the rope.

Re-tighten the rope to suit the new position.

2nd Part of dismanteling procedures

10. Pull out the mandrel of the guide sleeve and dismount the supporting tool

11. Rotate the supporting tool to turn the position of torque exrension wrench.

supporting tool

12. Mount the supporting tool

Mounting of supporting tool

13. Loosen and dismantle one of the upper connecting rod screws.

14. Fit the guiding pin in the threaded holeand tighten hard with tool

guide pin

15. Mount the holding-up tool on the cover frame of the crank housing on the opposite side of the engine

holding tool

16. Press the forked rod tool against the connecting rod and lock it in this position with the locking screw on the tool

17. Dismantle the remaining screws and the bearing cap.


Note: Guide pin is fitted to ensure the protection of any damage to the crank journal, joint faces and bearing surface.

18. Loosen the locking screw and release the forked rod tool, see fig. 8 for the connecting rod to swing free of the crank-pin for the proper dismanteling .

19Dismount the upper bearing shell with care.

Dismounting bearing

20. Pull out the piston and the connecting rod throughout the cylinder liner and out of the engine.

21.Guide The connecting rod with care in order not to damage the cylinder liner skirt

Dismounting piston

Separation of Piston from connecting rod – Piston in Engine

1. Place the piston and connecting rod with care on wooden supports to avoid damage to the piston and rings

Piton placement

2. Mount the bearing cap with the screws forthe protection of threads in assembly.

3. Take out the shackle and piston lifting tool from the piston

4. Rest the connecting rod and piston in upright position with top face of the piston.

5 Arrest the connecting rod with wooden wedges for the swinging movement

Con rod lifting

7. Remove the securing ring, push out the piston gudgeon pin and lift away the con rod.

Removal of the Piston Ring ( Piston in Engine)

  1. Take out the piston rings with the help of piston ring expender tool
Ring Removing tool

2.Clean and inspect the rings to ascertain for the acceptance of re-use.

3. Clean both sides of piston.

4. Carry out the inspection of piston ring grooves..

Important checks on Piston for Piston in Engine

2. Piston crown side wall and ring grooves for any wear marks

3. The top part of the piston for cracking caused due by the thermal ad mechanical stress

4. Entire piston for high-temperature corrosion. 5. for hot corrosion at the upper surface and acid (cold)corrosion at the lower part.

Piston Ring Grooves and Piston Rings ( Piston in Engine)

1. Make the piston rings free in the ring groove.

2. But clearance and radial clearance

3. Any wear, stepping, and scuffing at grooves.

Piston Skirt/ Sidewalls

Inspect the piston skirt for

1. Any rubbing marks

2. Wear of wear rings

Cooling Water section

1. Scaling by poor water quality

2. High-temperature congestion.

Condition for change of Piston for Marine Engines ( Piston in Engine

Abnormal conditions to change the piston.

  1. The wear limit on the testing mandrel has exceeded
 Piston for Marine Engines-piston groove

2. Piston ring and piston groove clearance out of tolerance.

 Piston for Marine Engines-Ring clearance

Conclusion on Piston in Engine

Hope the post ondes Piston in Engine have been useful to the engineers and engineering students.

Good Luck!!

Frequently Asked Questions

Chemical treatment is required, High thermal stress in piston and Piston of more complicated design

Deposit in cooling spaces, Impingement of fuel due to faulty injection, and insufficient piston cooling oil flow.

Not to be allowed to fall below manufacturer recommended value

Difficulty in formation of the oil wedge

Books on Marine Diesel Engines

Product ImageTitleBuying Option
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Handbook of Diesel Engines

Handbook of Diesel Engines

“This English translation … provides a good overview of the state of the art of modern diesel technology, manufacturing, and practice. … The 60 chapter contributors, almost all from German industries, provide good coverage of supercharging, fuel, injection systems, bearings, pistons, cooling, materials, lubrication, and emissions. … The handbook is a welcome addition to the existing resources on diesel engines and will be helpful to advanced students and practitioners in the field. Summing Up: Recommended. Mechanical engineering collections serving graduate students and above.” (A. M. Strauss, Choice, Vol. 48 (7), March, 2011)

Fundamentals of Medium/Heavy Duty Diesel Engines

Fundamentals of Medium Heavy Duty Diesel Engines

Based on the 2014 National Automotive Technicians Education Foundation (NATEF) Medium/Heavy Truck Tasks Lists and ASE Certification Test Series for truck and bus specialists, Fundamentals of Medium/Heavy Duty Diesel Engines is designed to address these and other international training standards. The text offers comprehensive coverage of every NATEF task with clarity and precision in a concise format that ensures student comprehension and encourages critical thinking. Fundamentals of Medium/Heavy Duty Diesel Engines describes safe and effective diagnostic, repair, and maintenance procedures for today’s medium and heavy vehicle diesel engines, including the most current, relevant, and practical coverage of: • HD-OBD emission diagnostics • Common rail injection systems

Pounder’s Marine Diesel Engines and Gas Turbines

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Pounder’s Marine Diesel Engines has served seagoing engineers, students of the Certificates of Competency examinations and the marine engineering industry throughout the world.

Now in its ninth edition, Pounder’s retains the directness of approach and attention to essential detail that characterized its predecessors. There are new chapters on monitoring control and HiMSEN engines as well as information on developments in electronic-controlled fuel injection. It is fully updated to cover new legislation including that on emissions and provides details on enhancing overall efficiency and cutting CO2 emissions.
After experience as a seagoing engineer with the British India Steam Navigation Company, Doug Woodyard held editorial positions with the Institution of Mechanical Engineers and the Institute of Marine Engineer

* Helps engineers to understand the latest changes to marine diesel engineers
* Careful organisation of the new edition enables readers to access the information they require
* Brand new chapters focus on monitoring control systems and HiMSEN engines.
* Over 270 high quality, clearly labelled illustrations and figures to aid understanding and help engineers quickly identify what they need to know.

Lamb’s Questions and Answers on the Marine Diesel Engine

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The book is comprehensive and includes almost all topics needed to understand marine diesel engines. The book explains the role of heat in engineering science, the principles behind internal combustion engines, the role of fuels and lubricants, the cooling systems, the lubricating systems and the heat exchangers.

The book also explains the various parts of the marine engines and their functions. Air-storage tanks and air compressors are also dealt with in the book. Information on balancing and vibration, various instrumentation and control methods, along with the safety measures are covered in the book.

Lamb’s Questions and Answers on the Marine Diesel Engine was published by Butterworth-Heinemann in 1990. The eighth revised edition is available in hardcover.

A Pocket Book of Marine Engineering: Questions and Answers

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A Pocket Book of Marine Engineering: Questions and Answers is a book that covers the topic of air filter for engine in great detail. This book is a great resource for anyone who wants to learn more about this topic. The author, John Myatt, is a world-renowned expert on marine engineering. In this book, he covers everything from the basics of how these engines work to more advanced topics like choosing the right air filter for your engine. If you’re looking for a comprehensive guide to air filter for engine, this is the book for you.

This handy pocket-sized guide is filled with hundreds of questions and answers on marine engineering, covering all the basics from engines and propulsion to steering and safety. It’s perfect for anyone who wants to learn more about this fascinating subject, whether they’re studying for a qualification or just interested in how boats work. With clear explanations and plenty of diagrams, this book is an essential reference for anyone with an interest in maritime engineering.

Blog Conclusion

We hope that you enjoyed our blog about Diesel engine piston. Diesel engine piston is a vital component for the function of a diesel engine. The diesel piston is a rotating component that is connected to a crankshaft and is at the heart of the reciprocating motion. Our blog post is designed to help the readers understand the components and the function of the piston. We would love to hear from you. Please contact us anytime if you have any questions or comments at

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