The Old Design
The grate drive shafts at Bolton ERF are driven by hydraulic rams connected to a drive lever which is clamped on the 6” shaft by four 7/8” high tensile bolts and uses a 2” key to drive the shafts.
The key and keyway were prone to damage and the bolts needed regular inspection. After a site operation review and a meeting with Gary Ashworth, managing Director of ITEC Engineering, it was decided to modify the drive system by fitting a 150 mm Ringfeder torque bush. To achieve this the shafts were machined from 6”dia to 150mm dia. This was achieved whilst the shafts were in a stationary position and in-situ… this in itself was a big problem solved. Itec were able to achieve the machining tolerance required using special hydraulic turning equipment.
Gary commented “we needed to reduce the shaft sizes to 150mm to enable us to supply equipment ‘off-the-shelf’ rather than supply a totally ‘none standard part’ In case any of the torque bushes were damaged it wasn’t going to be a problem to replace.”
Rather than using a split design casing for the arm we were able to manufacture a unit out of solid steel. This gives a far stronger drive arm plus increases the amount of Nm of torque the bush transmits. There are also no weak spots.
By using this type of design we are able to stop fretting of the drive key and increase the torque around the shaft itself. No longer do we have to rely on the bolts to hold it in position (which previously could have been over-tightened by the operator or service engineer) which could cause the bolts to shear or fracture.
After machining the shafts the drive levers were redesigned into a solid arm rather than a split unit for added strength and less maintenance.
The couplings and arms were then aligned on the shafts at the correct position.
For ease of maintenance the arms can be taken on and off by using a series of caphead bolts around the circumference. The bolts must be tightened correctly.
Even after extreme temperatures it is easy to remove the arms,
The New Design
The outer bearings then had to be modified to the same diameter (150 mm) as the shafts. Itec Manufactured 2 x split phosphor bronze liners, which were fitted into the original casings.
Each arm was set-up using a torque wrench and then tested accordingly.
To date, the modification has performed very well and has not caused any issues.
Viridor would like to thank Itec for their continued support and an idea which should prove very successful in the future.
This modification will reduce the amount of wear and tear on the shafts and reduce the amount of inspections and maintenance on the drive levers and bolts.