Manufacturers of high capacity diesel engines are maintaining close tolerances in terms of taper and ovality of crankpin and main journal diameter of the crankshaft. The maintenance of close tolerances and high surface finish results in the generation of more power, longer life of crankshaft and bearing, less noise level, low vibration, friction, and better fuel efficiency. RA Power solutions have been working on crankshafts of marine engines and engines used for various applications with the diameter ranging from 30 mm to 700 mm.
In general following close tolerance of crankpin and main journal are observed:
I) Taper and ovality of crankpin and the main journal are maintained between 0.02 mm to 0.05 mm depending on the diameter of crankpin and main journal.
II) The surface finish of less than 0.25 RA value is maintained.
RA Power solutions have observed that sometimes due to an emergency, to put back the engine into operation, the crankshaft crankpin and main journal are hand polished by emery paper, nylon rope and other means. This has serious consequences on CR pin and main journal. Few of them are as follows:
I) Bearing line marks, pitting marks are observed on crankpin and main journal of crankshaft cannot be removed by hand polishing.
II) It is our experience that in case of development of taper and ovality, it can never be reduced and controlled by hand polishing. On the contrary ovality and taper increases.
III) The surface finish of the crankpin and main journal is of great importance.
IV) It is observed that by hand polishing the marks can never be removed fully. Thus the desired surface finish as per the manual cannot be maintained.
RA Power solutions, during their work on high capacity engines installed with clients spread all over the world, have observed that in most of the cases hand polishing rather deteriorates the condition of crank pin and main journal and in some cases results in the rejection of crankshaft.
Recently one of our client having 3 generators of MAN B&W 8L 23/30 had a problem in all crankpins having a standard diameter of 185mm. Bearing line marks and the rough surface was observed. All the crankpins were hand polished by nylon wire and new bearings were used. The crankshaft failed within 20 minutes of the operation of the engines. Few photographs are given below:
Introduction of Portable Crankshaft Grinding Machine by RA Power Solutions
RA Power solutions have introduced portable, lightweight onsite crankshaft grinding and polishing machine which is capable of grinding and polishing the diameter ranging from 30 mm to 700mm. The onsite crankshaft grinding machine is revolutionary portable equipment which can be inserted from the inspection window of the engine block. There is no requirement of removal of crankshaft from the engine block.
On site crankshaft grinding and polishing machine is easy to operate and we also extend training to the buyer’s technicians. Inviting companies for polishing of crankshaft is no more required as it can be undertaken by your technicians with the portable onsite crankshaft grinding machine. You can save on the exorbitant amounts charged by European companies, which was their monopoly till the last few years.
More than 70 machines have been sold all over the world and are operating successfully.
The author is Mr. Raj Shahani, Managing Director of RA Power Solutions Pvt. Ltd. He has 40 years of experience in working on large crankshafts and Diesel Engines.He is on the board of directors of reputed shipping companies and companies having a large number of Diesel power plants.
The crankshaft grinding and polishing machine has been developed through a consistent and focused R&D with field trials undertaken in different conditions.
For more information, please email us on email@example.com
Manufacturers of high capacity diesel engines are maintaining close tolerances in terms of taper and ovality of crankpin and main journal diameter of the crankshaft. The maintenance of close tolerances and high surface finish results in the generation of more power, longer life of crankshaft and bearing, less noise level, low vibration, friction, and better … Continue reading “Consequences of Hand Polishing of Crankshaft & Benefits of Onsite Polishing Machine- RA Power Solutions”