Multi-purpose press

Steel and rolling mills supply their customers, for example power plants, with building components made from heavy plates that they cannot manufacture themselves. In this category fall machine-worked pieces, spherical segments and single or multi-part container bases and pressed parts. The latter are reshaped with the aid of multi-purpose presses or so-called hydraulic floor presses.

A multi-purpose press at the Dillinger Hütte with a total push force of 2,500 tons had seen its last overhaul in the 1990s; so over recent months wear-and-tear started to increase. After an impressive runtime of more than 20 years in multiple shift operation the piston rods finally showed the strain with heavy scoring, while the seals were clearly worn out.

Since repair works could not take longer than two weeks, Dillinger Hütte awarded the contract to Montanhydraulik Reparatur und Service from Dortmund, Germany, who have the technical know-how for cylinders of this size and the manufacturing technology to deal with such weights and dimensions.

The following requirements were successfully fulfilled:

  • cutting/machining and hardening of the central plunger cylinder’s piston rod
  • coating of the clamping cylinder with SuperCoat
  • hard-chrome plating of the piston rods for the plate holder and hold-down cylinders
  • honing of all cylinder barrels
  • renewal of all bronze guide bushings
  • replacing seals for rods and pistons
  • modification of piston guiding and piston seals to a slide seal system from Merkel
  • machining of the leading outer diameter of the central plunger cylinder`s barrel
  • producing new guide bushings with a diameter of 1,250 mm, adjusted to the cut and machined outer diameter of the central plunger cylinder
  • vertical assembly and hydraulic pressure and function testing in a purpose-made retaining jig
  • returning the central plunger cylinder with special transportation requiring special authorisation

Type and quantity of repaired cylinders:

  • 1 central plunger cylinder with 2,500 t push force
  • 4 clamping cylinders
  • 8 hold-down and plate holder cylinders with 500 t push force each

Technical data of central ram cylinder:

  • piston diameter: 870 mm
  • rod diameter: 710 mm
  • leading outer diameter of the cylinder barrel: 1,200 mm
  • stroke: 3.500 mm
  • weight: approx. 36 t
  • operating pressure: 250 bar