When hydraulic cylinders show signs of wear after a long period of running or because of permanent extraordinary stress, an overhaul and repair is often the most cost-effective alternative, in order that they can continue to fulfil their tasks reliably.
Montanhydraulik Repair and Service takes on this task and provides a worldwide repair service for its own and for third-party cylinders. The range of services extends from diagnosis, to repair or sample manufacture, to punctual delivery.
Andreas Schade
Managing Director
Stephan Böhnke
Sales Manager
Anthony Libhart
Sales Manager
Pierre Morin
Field and Technical Service Manager
Carolin Scherbarth
Sales Manager Spare Parts
Andreas Schade
Managing Director
Stephan Böhnke
Sales Manager
Anthony Libhart
Sales Manager
Pierre Morin
Field & Technical Service Manager
Carolin Scherbarth
Sales Manager Spare Parts
On a production area of 6,300 m2 we use modern machinery to repair and overhaul hydraulic cylinders up to a weight of 40 t and a length of 20 m. We are able to provide full service on this basis, and this extends beyond our factory gates, because our service technicians are also in action for you directly onsite.
We analyse your problem and develop solution proposals which are optimally adapted to your local conditions:
We dismantle your repair cylinders and create a detailed report of findings, as well as a repair proposal with fixed delivery schedule and description of the scope of work.
After installation, your repaired cylinders are pressure and function tested. We generate a test protocol for each cylinder.
After dismantling, all individual parts are tested and, where necessary, reworked or replaced. Grooved cylinder bores are honed. Grooved or damaged piston rods are polished and recoated if necessary.
We supply the following coatings:
Individual parts are manufactured new according to sample or drawing. Seals are also renewed according to sample or parts list.
Welding tasks (MAG, WIG, E-Hand) are performed exclusively by experienced professional welders.
Every cylinder is tested before despatch:
The documentation consists of an archived test protocol for each cylinder. You therefore always have the security of proven quality.
Our service technicians are in action for you all the time and all around the world. As far as possible, they perform repairs, analyse your cylinder problem, or perform monitoring functions during extensive renovation projects.
The Bucyrus DBT Europe company from Lünen engaged Montanhydraulik Repair and Service with the repair of a test cylinder which is an important component of a test machine for hydraulic rams for mining.
The results of the dismantling and analysis were that the cylinder’s rod guide was seized in the guide bushing. To correct this problem, the rod guide was rebuilt as hard fabric guide rings. In addition, the rod was completely remanufactured. Delivery took place in 2009.
Hydraulic cylinder:
It was the first repair of the steering cylinder since the BG 285 bucket wheel excavator was built in 1975. Wear, combined with enormous impact forces, had completely destroyed the piston sealing system and the sealing material. The axial holding rings for the piston seal had come away from the piston and were jammed in the cylinder bore. Because of the serious leakage through the disintegrated piston sealing system, the forces required to move the steering shaft could no longer be applied. The digger could not be manoeuvred.
Because Montanhydraulik Repair and Service had already successfully repaired two similar cylinders in the past, the repair company was also engaged to repair this steering cylinder. For this, the greatest challenge was the piston rod head. Initially shrunk onto the rod through heating and cooling, in order to transfer tensile forces of 10,000 kN, it had to be removed in the same way, so as to be able to dismantle the cylinder weighing 45 t. In fact three attempts were necessary, requiring ten hours of patience and a certain amount of technical creativity, until the six ton rod head could be loosened with the aid of hydraulic pressure and by heating the rod head to 300 ºC
Good collaboration with Montanhydraulik in Holzwickede
It was then clear that the 610 mm length and 500 mm fitting diameter of the two parts were heavily grooved, and that there were numerous deep seizure marks. However, through the support of Montanhydraulik in Holzwickede, the repair lasted only one day longer than planned. For the necessary turning tasks, the technicians first built a steady-rest which was freely adjustable on the piston rod, and reduced the diameter of the rod by 4 mm. They then welded the reduced diameter up to size using submerged arc welding, and machined it again to the true diameter. The rod head was machined to +0.5 mm. The work required the greatest precision, because the press fit had to be created as per the original pattern, so that the tensile forces could again be fully transferred without any problems.
Vertical cylinder installation
The final obstacle was to shrink the rod head back onto the piston rod in such a way that the press fit could be used to its full extent and that the repaired steering cylinder would guarantee the problem-free operation of the bucket wheel excavator. For the installation of the cylinder, the piston rod with piston and cylinder head were suspended from a 300 t mobile crane hook lowered through the opened roof of the manufacturing hall. Beneath this was the vertically aligned rod head, mounted in a steel frame; this was again heated to 300 ºC, while the fitting diameter of the rod was cooled to –150 ºC using liquid nitrogen. The piston rod was then lowered little by little into the rod head. After successful function and pressure testing, as well as filling with 3,500 litres of hydraulic oil, the steering cylinder was finally transported back to the customer on a special low-loader – punctually and maintained to be as good as new.
These requirements were successfully fulfilled:
Technical data for hydraulic cylinder:
Technical data for bucket wheel excavator:
The opencast mines of RWE-Power AG in Hambach and Gartzweiler extract the largest amounts of brown coal in the world, around 100 million t per year. For this, the BG 290 bucket wheel excavator shifts some of the enormous amounts of overburden, and its hydraulic steering ensures that the huge piece of equipment navigates through the terrain with precision. Only one of the three tracks upon which the machine stands is controlled during travel, through the steering shaft powered by a giant hydraulic cylinder.
Because of the loosened stones which continuously fall onto the semi-extended piston rod during the operation of the excavator, at some stage the chrome surface had become littered with impact marks. Because of this, RWE appointed Montanhydraulik Repair and Service to repair the heavyweight colossus.
These requirements were successfully fulfilled:
Technical data for hydraulic cylinder:
Tunneling
Mining
Earthworks
The infeed and outfeed cylinders of a roller cement mill are in use right round the clock. That is why serious leakages occur on the piston rod sealing, even after only three or four months. Montanhydraulik Repair and Service developed a solution which contributes to quadrupling the service life of the cylinders.
Powered by a 2,000 kW electric motor, the milling drum conveys cement clinker, slag, or limestone from the neighbouring quarry under the milling roller. During the milling process, the cylinder seals must withstand short-stroke and rapid swerving motions which have high pressure peaks; these are caused by the stones in the milled material. On top of this, the various milled materials are milled at different levels of high pressure, and this results in temperatures up to 100 °C and significantly reduces the service life of the seals. In difficult operating circumstances, correspondingly high leakage rates set in after only a few weeks – a situation that the operator wanted to change.
The following steps were taken as part of the cylinder repair: Instead of steel, Montanhydraulik Repair and Service created a new seal holder bushing made of bronze, which has a smaller gap size in the triple seal system arranged in cascade-form. The fitting tolerance of the new guide bushings made of bronze was also reduced. For this, the bushing was installed into the cylinder head using a press fitting (shrunk-in using liquid nitrogen). After this, the play of the rod guide was adjusted exactly to the toleranced diameter of the rod, using finish turning.
In order to fulfil the new safety requirements of the German Federal Railway Authority, a German railway company had to install a safety circuit into its bulk material wagons in order to upgrade the existing hydraulics for actuating the wagon discharge flaps. At the same time, the manual actuation was to be converted to hydraulic actuation by means of pilot valves. The contract for the installation of two sample systems was awarded to Montanhydraulik Repair and Service in Dortmund.
Together with the development department of Montanhydraulik, the repair company developed a new control block unit for the hydraulic actuation, delivered as an installation kit, and a safety circuit which can be built into the existing system.
After certification and the successful test phase of the sample wagons, Montanhydraulik Repair and Service received the go-ahead for the conversion of the hydraulic aggregates of 136 railway wagons. The first converted systems were delivered at the start of 2011.
These requirements were successfully fulfilled:
Dillinger Hütte provides its customers, e.g. power stations, with components made of heavy plate, which they cannot manufacture themselves. The components include edge-machined plates, spherical segments, single or multi-component tank bases, as well as pressed parts. The latter are formed with the aid of multipurpose presses or so-called dish presses.
At Dillinger Hütte, after a multipurpose press having a total press force of 2,500 t had last been overhauled in the 1990s, signs of wear increased alarmingly in recent days. After a noteworthy running time exceeding 20 years of multi-shift operation, the piston rods were showing signs of grooving, and the seals were displaying signs of significant wear.
Because the repair could not take longer than two weeks, Dillinger Hütte placed the order with the Dortmund company Montanhydraulik Repair and Service, as it has the technical know-how for cylinders of this size, and in terms of manufacturing technology it is fully equipped for these weights and dimensions.
These requirements were successfully fulfilled:
Type and quantity of the repaired cylinders:
Technical data for the central ram cylinder:
After only a brief period of operation, the tipping cylinder of an electric arc furnace at Georgsmarienhütte broke down because of leakage on the piston rod. Damage analysis by the service technicians of Montanhydraulik Repair and Service resulted in the following findings: Electrostatic charges had caused functional impairments and crater-formed damage to the hard-chromed piston rod.
In addition, the hard chrome layer had been attacked by electro-chemical corrosion. Finally, the large amount of dust arising resulted in rapid abrasive wear to the rod seals.
The onsite problem analysis of the dismantled tipping cylinder resulted in conversion of the cylinder to a completely isolated piston and rod guide, continuous rod flushing, and a fused bonding coating of the piston rod. This bundle of measures extended the service life from six months to four years.
Furnace tipping cylinder:
Chipboard manufacture takes place in a press system which operates continuously. The press force is built up using hundreds of press cylinders arranged one after the other in series. During operation, deformation of the cylinder can arise, and this very often results in leakages on the static seal of the threaded clamping ring.
On the basis of the damage analysis conducted as part of the repairs, Montanhydraulik Reparatur und Service GmbH performed a conversion of the press cylinder to a flanged clamping ring, in order to transfer the position of the static seal to an area where there was less deformation.
Further benefits of the conversion measures are the guarantee of the sealing effect even during significant deformation under load, and the simple and rapid removal of the clamping ring in the event of a repair.
Press cylinder:
Railway wagon hydraulics
Forming/pressing of metal plate
Steel and smelting works
Chipboard manufacture
