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Steel

Rolaram Actuators and Spiracon Roller Screws provide the precision linear and vertical actuation mechanisms for the de-chocking car system in the Universal Beam Mill Plant at British Steel Teesside Works.

Rolaram ® and Spiracon TM both designed and manufactured by Power Jacks were selected for their high speed, high load carrying and precise positioning capabilities, combined with their controllability and repeatability.

The de-chocking car system comprises four cars, which are operated independently and have to be controlled on three axes, all interlocked and controlled through a PLC.

The sequence of operation is as follows:

• Two Rolaram actuators precisely locate the car on its rails, parallel to and exactly on the center line of the roll/bearing assembly (the bearing assembly is known as a chock).
  
  
• Two 98mm diameter Spiracon units driven by a servo motor provide the high speed traverse drive for the lift platform, to place it under the bearing assembly.
  
  
• Four 56mm diameter Spiracon units with integral load cells raise the lift platform at 45 metres/minute, to within close proximity of the bearing assembly. At this stage, the micron accurate Spiracon screws move at “super creep” speed until the integrated load cells have sensed the 14 tonne bearing assembly, excluding the roll. At this stage, one final minute movement of 0.075mm is made, in order to locate the bearing on its radial clearance, centrally around the tapered shaft of the roll.
  
  
• The bearing assembly is removed from the roll by engaging the platform traverse drive, initially at low speed until the bearing is clear of its shaft and then at high speed to safely locate the bearing assembly on the car for transportation to the inspection area.
  
  
• Following inspection, the above procedure is reversed, in order to fit the bearing to the new refurbished roll.

Since the installation of the new de-chocking car system, the time required to prepare rolls for changing at the mill stands has been reduced by 50% of times previously achieved under the manual system and has resulted in a very significant improvement in labour utilization.

Earlier attempts using hydraulics failed to achieve these demanding performance standards of moving high loads at high speeds with a high degree of accuracy