Repair of hydraulic pump shafts

Hydraulic Pumps (UK) Ltd are a Rotherham based South Yorkshire SME specializing in the supply of new and the repair of damaged hydraulic equipment for a wide range of industries and applications.

The general condition of the types of units which are being presented for repair is often very poor. This is caused principally by the arduous conditions in which they operate, for example in mines and quarries, which can lead to severe wear and damage being present in many of the internal components. Additionally, some of the hydraulic units are obsolete and it has become impossible to purchase spare parts. Even in those cases where spare parts are available, lead time and costs are excessive.

On attending a RAMP open day and seminar at the TWI Technology Centre on the Advanced Manufacturing Park in South Yorkshire, Nick Marshall and Steve Cliff of Hydraulic Pumps (UK) Ltd were shown the laser deposition process. After discussions, it was thought that in some cases, this process could enable some of the damaged parts that are currently being scrapped, to be repaired using laser deposition. Conventional weld repair techniques are often not suitable to repair the type of highly alloyed carbon steel used to originally produce the hydraulic pump components. This is because the amount of heat needed to undertake the conventional repair could be detrimental to the material properties of the component. This could leave the material brittle and liable to premature failure and could also cause distortion of the part such that it could not be re-used.

However, the laser deposition process involves adding an inherently low heat input onto the component surface and produces a very small heat affected zone into the material. It can, therefore, successfully deposit material with similar properties to the original metal and can complete the repair without affecting the strength of the part and without the likelihood of significant distortion.

The deposit is produced by creating a small melt pool on the surface of the part using the laser beam and then delivering a precise amount of metal powder into the melt pool using a powder delivery system. The powder then melts and fuses to the surface to create the necessary deposit. By moving both the laser beam and the supply of metal powder in a very precise fashion, a very accurate and consistent continuous deposit can be created.

It was agreed between Hydraulic Pumps (UK) and TWI that a damaged hydraulic pump shaft would be an ideal component to test the effectiveness of the process. Consequently a number of these shafts were prepared for laser deposition by machining away the damaged areas to leave a good clean surface finish. The shafts were delivered to TWI and, following metallurgical tests, new metal was deposited over the prepared areas using the Trumpf DMD 505 laser deposition machine. These were then returned to Hydraulic Pumps (UK) Ltd where the deposited material was machined back to original size and tolerance.

The repaired parts were then fitted back into their original casings and subjected to a range of tests before being dispatched to customers for extended use. The success of the procedure was demonstrated by the ongoing reliability of the units following repair.

As a result of intervention by the RAMP project funded by Yorkshire Forward and Objective 1, Hydraulic Pumps (UK) Ltd have been able to both maintain a tight control on costs without compromising quality, and reduce leadtimes for their repaired units.

This has allowed Hydraulic Pumps to safeguard sales of around £26k and create further sales of around £84k in a 12 month period. It has also helped to create 1 additional job and safeguarded 8 existing ones.

The support provided was made possible through the Rapid Manufacturing Capacity Building Programme (RAMP), funded by Yorkshire Forward and the European Union through the Objective 1 Programme.

For further information read about Laser Processing at TWI or email contactus@twi.co.uk.

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Repair of hydraulic pump shafts

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