Crankshaft Heat Treatment | Crankshaft Annealing - RA Power Solutions

RA Power Solutions undertakes on site repair of crankshaft having diameter ranging from 30 mm to 700 mm. The crankshaft repair services are offered through our experienced technicians and customised onsite crankshaft grinding machines. We have experience of more than 40 years in successful repair of crankshafts of main engine, auxiliary engine and crankshaft used for various applications. We have successfully executed repair of more than 10,000 crankshafts during our extending services to the industry for the last four decades.

Reason for Crankshaft Heat Treatment and Crankshaft Annealing

RA Power Solutions has experienced that due to oil starvation the oil film between the crankshaft , crank pin/crank journal and bearing get damaged resulting to the movement of bearing shell on the crankpin journal without presence of any lubricating oil. The rubbing of bearings steel casing with the crankpin journal increases the temperature substantially in certain cases extending 900°C. When the crankshaft after the seizure of bearing comes to the stand still it rapidly cools and the metallurgical composition and micro structure of the crank pin journal is badly affected .

It is generally observed that in case of such kind of failure the hardening takes place which results in the development of hard spots and hard areas even to the scale of 700 HB next to the soft areas . The extraordinary increase in the hardness of the crankpin journal of the crankshaft is not desirable as per the manufacturer’s specifications and crankshaft heat treatment and annealing is done.

In order to reduce the hardness and bring it to the limits specified by the manufacturers, RA Power Solutions has undertaken the annealing process in-house and have also availed the services of leading well known European companies offering annealing services. It is our experience that in most of the cases after onsite heat treatment and annealing, the crankshaft either immediately failed or have failed after few hours of operation. The reason for failure after annealing are many and few of them are listed below to caution Engine users.

Onsite Crankshaft Grinding on Board a Vessel		Onsite Crankshaft Repair & Polishing Services

Reason for Failure After Crankshaft Heat Treatment and Crankshaft Annealing

I) Prior to the start of annealing process, it is important that exact metallurgical composition of  shaft is known. It is not possible to get the exact metallurgical composition as some times it is not known to the manufacturer, model of engine is obsolete, manufacturer doesn't want to share the information to the user, etc.

In absence of the exact metallurgical composition, annealing process can not be planned properly and results to the failure of crankshaft.

II) For the purpose of annealing of the crankshaft, it is important that the original hardening and tempering temperatures are known which were maintained at the time of heat treatment. It is our experience that it is impossible to get the data from the crankshaft manufacturers.

III) For successful onsite annealing of the crankshaft it is important to maintain the temperature of the journal which is to be heated, the rate of heating, the soak time, the time crankpin needs to maintain the maximum temperature and the rate of cooling to the ambient temperature.

It is not possible to maintain these parameters onsite. The annealing process for reducing of crankshaft hardness is to be done in a controlled environment which is not possible on the board the vessel or in the power plant where the engine are installed.

IV) It is commonly observed that after annealing of the crankshaft the loss of alignment of crankshaft takes place due to development of stresses. Sometimes it become mandatory to straightened the crankshaft in order to maintain the runout.

V) The companies known for repair of crankshaft for years based in Europe and other countries have failed in undertaking onsite heat treatment and onsite annealing of the crankshaft.

Onsite Crankshaft Grinding in a Power Plant		Crankpin After Repair by Crankshaft Grinding Machine

Suggestions:

RA Power Solutions feel that heat treatment and annealing of the crankshaft onsite should be avoided.

This blog written by Mr. Raj Shahani (Managing Director of RA Power Solutions) having more than forty years of experience to caution the client and to advise them not to get carried away by the false promises of reduction hardness by the companies as the results are not satisfactory and successful in most of the cases.

For more information, please email us at rajshahani@rapowersolutions.com, info@rapowersolutions.com, or call us at +91 9582647131 or +91 9810012383.

Damaged Crankpin Before Repair		Crankpin After Grinding by Onsite Crankshaft Grinding Machine