It’s not very often a block plant manufacturer receives an enquiry with all the technical drawings already included. When project manager Mr. Erik de Graaff sent out the enquiry for a new block machine in Amsterdam he had all the technical, product and installation specifications already in place. The goal was to ensure that the existing production line would not be at a standstill for longer than necessary. HESS GROUP replaced the complete wet side of the concrete block production line and designed each component of the project individually for this purpose.
Struyk Verwo Infra (SVI) is part of the CRH group and has several production units in the Netherlands. One of the productions units is SVI Amsterdam, located in the industrial zone “Westelijk havengebied”, focusing on making kerbstones in all varieties, with the ability to make block paving as well. SVI Amsterdam is known for the very wide production range of kerbstones, up to 5000 different products, with a large proportion of these directly available from stock. Bespoke products or specials are custom made and available on short notice, very important for a company that is working nation-wide. When the decision was taken to replace the existing block machine, the machine had done its time and a lot of love and care was necessary to keep it in production.
HESS GROUP was awarded the order to replace the complete wet side of the block plant, consisting of the block machine, washing station and elevator system. The complete project for SVI was large, including changes to the existing board buffer, changes to the finger car system controls, modifications in the batching plant and the work on the building.
The beating heart of the new plant: the RH 1500-4 MVA by HESS GROUP
The core of the new plant is a concrete block and paver machine RH 1500-4 MVA supplied by HESS GROUP with a production board size 1.500 x 1.100 mm with the capability of a maximum product height of 500 mm, although the highest product is a 400 mm high kerbstone. Concrete is delivered to the block machine by an overhead skip system, coming from a batching plant that is serving several other users. The HESS concrete plant is consuming the highest volume of concrete between these users, so the RH 1500-4 MVA block machine can hold a high volume of concrete by using an additional silo extension for the hoppers. For the face mix section is an extraction belt used to ensure that loose concrete is dosed in the filler box, instead of pre-compacted concrete.
Side view of the concrete block machine RH 1500-4 MVA
Quality of the product is vital, during the production cycle the quality of the product is monitored in many ways. The first steps are taken in the batching and mixing plant to have equal quality concrete, batch after batch. Within the block machine different kinds of monitors are available. Every production board is lifted twice out of the conveyor for weighing, first without product and then with products. The difference in weight is an exact indication of the overall product weight. The height is also measured exactly, first through the system functions and later by a R&W laser height measurement system.
MAC-8 block machine control
The block machine is a M-version machine, so every hydraulic function in the block machine has a linear encoder which feeds back the exact position of the (hydraulic) movement. A separate PLC is controlling the length of the stroke with extreme high accuracy. Before a movement starts, the PLC knows the starting and stopping point, with that it calculates the optimal acceleration, highest possible speed and smoothest deceleration for this movement. With the highest possible speed, minimal use of energy and no operator influence, every hydraulic movement in the block machine is spot on.
Additional quality inspection in special testing area
For additional quality tests, a production board can be taken out of the walking beam conveyor in a specifically designed testing area. Several conveyors are used to lift a production board out of the walking beam conveyor into the quality inspection area, leafing a gap on walking beam conveyor. This gap is filled one position later, with the previous board which was taken out for quality control testing. On the quality control position all the necessary quality tests can be done without interruption to the production process. When the quality inspection is complete, the quality manager confirms this by pushing a release button. The board moves one position closer to the walking beam conveyor into a waiting position and is ready to fill the gap on the walking beam conveyor when the next board is removed from the walking beam conveyor for quality inspection.
Quality inspection of freshly produced concrete pavers
Training Academy and commissioning
A week before the plant produced for the first time, intensive training took place at SVI's premises as part of the HESS GROUP Training Academy. This training week was specially organized for the unusual circumstances the world had to cope with. All the operators, mechanical and electrical engineers were trained according to the training programme developed by the experts of HESS GROUP. The aim was to especially help the operators to cross the technology bridge of almost 30 years between the old machine and the new one. Within a week the operators were already familiar with the machine controls, the mechanical principles and the theory behind it. Although every start-up of a new plant has its highs and lows, the team managed to make quality products on the first day of the commissioning.
Thanks to SVI's carefully prepared specifications and the creative and adaptable team, the customer's expectations were met: a perfectly adapted plant, optimally integrated into the existing building, combining high performance and safety standards with innovative design. With the new, high-quality products of the modern plant, SVI is ideally positioned for the future.
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BWI International 3/21