The concept of the hydraulic control block enjoys clear advantages over the more conventional method where each hydraulic control element is piped individually.
A block has a small footprint, and the risk of leaks is low. The screw-in valve technology is easy to maintain, and both standard valves and tailored valve solutions can be used. Energy and flow optimised systems can be implemented using the block concept.
Ruppel Hydraulik, which specialises in the design and manufacture of hydraulic drive systems and controllers, recently developed a control block with more than 50 valves for the control console of an item of construction machinery and which can be connected up within a single day by a fitter. In contrast, pipework design for a control console of this size would require around two person-weeks for completion.
“The issue of assembly time plays an important role in our developments,” explains Gerhard Ruppel, founder and owner of Ruppel Hydraulik. “A circuit has to be of optimum design from both a technical and economic point of view, as well as in terms of energy. Our block concept is the best guarantee against downtimes a customer can have. There is also the added benefit of massively reduced assembly times.”
While the control block approach is not suitable for all hydraulic installations, it is for a wide range of applications from presses, through construction machinery to deep-sea drilling rigs.
So, for instance, the hydraulic safety system of a cement mill needed to be of robust design with quick reaction times. The particular problem here was that if a very large lump of rock has to be processed, the gap in the crushing gear has to be enlarged in a very small space of time. This is the only way to prevent the rock material damaging the crushing rollers and/or their drive. Using conventional pressure limiting valves as shock valves does not work, as they will not react quickly enough. Instead a control block was developed incorporating a pressure limiting valve from the Sun Hydraulics range which has a particularly fast reaction time.
Thanks to this valve, the adjustment drive is able to react very quickly. Within 300msec, the system flow increases from 100l/min to 1000 l/min without any pressure spikes.
All the functions required by the machine manufacturer have been incorporated in a compact, application-specific block which is also reliable under the harsh environmental conditions prevailing in the production of cement. The hydraulics are therefore instrumental in achieving practical implementation of an innovative, highly energy-saving concept in the production of building materials.
As well as extensive knowledge of and experience in control technology and applications engineering, flexible production options are needed if customer-specific control blocks of this type are to be developed and manufactured economically. The use of pre-existing partial solutions in the modular system is important in ensuring short lead times, both in larger production runs and on single batches.