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Unique Liebherr Concrete Mixing Plant for CEMEX

Liebherr's very first mixing plant for pre-cast concrete production in the UK is providing CEMEX with a dedicated and virtually continuous chute-fed ouput for their long-term customer Centrum Pile Limited. The twin Betomix 2.25 Mixing Plant, modified to both Centrum's and CEMEX's specific requirements and including a number of special and unique features, was fast-tracked throughout the planning, design, construction, installation and commissioning processes, coming into production in just over four months from the order being placed.

CEMEX has been a supplier of concrete to Centrum Pile Limited for around 15 years and, at the Centrum site near Newark in Nottinghamshire, CEMEX has been providing an average 150m on a daily basis to Centrum's reinforced concrete pile production facilities adjacent to CEMEX's batching plant, which is located on the Centrum complex. An increase in required concrete volumes for Centrum, combined with the completion of their brand new state-of-the-art automated production system, meant that CEMEX needed to source a larger and more productive mixing plant on the site.

CEMEX and Liebherr have enjoyed a long and fruitful business relationship for several years now and many CEMEX ready-mix concrete depots throughout the UK feature Liebherr mixing plants. It was a natural progression of this partnership that CEMEX should turn to Liebherr for a solution to their needs and, in turn, Centrum's own specific requirements had to be taken on board at the same time. A visit to a Centrum complex in Denmark, where a similar operation was in place, provided the project's engineering team with exactly what was required to batch and deliver self-levelling concrete via a chute system directly into the feed hopper for Centrum's automated pile production facilities.

Subsequent to the Denmark site visit, detailed discussions with Liebherr's technical personnel resulted in the design for the new plant, based on a twin Betomix 2.25 mixing plant with numerous unique adaptations specific to CEMEX and Centrum requirements.

The new plant is linked to the existing aggregate storage bins on the original old plant, from a new ground level aggregate receiving hopper with a 2m wide inclined belt feeding a 140m per hour capacity totally enclosed bucket type elevator. Additionally, an 8m long X 650mm wide cross conveyor has been installed to feed the existing tripper conveyor on top of the aggregate storage hoppers. A 26m long X 800mm wide inclined chevron belt conveyor supplies the mixing plant, where a holding hopper with diverter delivers the correct aggregate volumes into the tandem Liebherr 2.25 ring pan mixers, including one agitator, which are the heart of the Betomix batching plant. The mixing tower has a 1,500kg capacity cement weigh hopper, a 750kg water weigh hopper and a high-pressure wash system for each of the pan mixers. An admixture weighing device and pumps introduce required admixes from three bunded admixture storage containers and, additionally, the plant can be supplied with either reclaimed water from a 42,000 litres capacity agitated tank or fresh water from a 30,000 litres capacity tank. The three cement silos each have a 100 tonnes capacity and are equipped with screw conveyors. All aggregates and cements are provided from CEMEX's own resources and transported to site in the company's fleet of aggregate tipper trucks and specialist cement vehicles.

The whole batching plant is located adjacent to Centrum Pile's new production hall and has been raised above normal height on specially designed and constructed legs, so that the required level can be achieved for feeding the pre-cast pile production hall's hopper. Concrete is delivered via an inclined chute straight through an aperture in the wall and into the receiving hopper which, in turn, fills the pile moulds, complete with reinforcement cages, which pass beneath the hopper on a reversible conveying system. The chute is retractable for regular cleaning and an on-site laboratory conducts regular testing to ensure mix design consistency and optimum quality control. An additional twin chute configuration is linked to the truckmixer feed chute beneath the plant so that truck delivered ready-mixed concrete can also be produced if required.

Controls for the plant presented Liebherr engineers and IT specialists with some interesting challenges. Liebherr's own sophisticated MPS II Litronic control system ensures correct batching and a Ginco interface control was installed to allow the MPS II to "talk" to the Centrum production hall's own computer system. The resulting "dialogue" between the two systems, plus level sensors in the feed hopper, ensures that batched concrete can be called for as and when required, so that the correct feed is continuous and uninterrupted during the pre-cast reinforced pile production process.

Commenting on the new plant, Cemex's Engineering Manager Anthony Groom said "We've built up an excellent relationship with Liebherr, are impressed with their build quality and our past experience with Liebherr has only ever been extremely positive. Their specialist knowledge was invaluable in assisting us to develop this very special plant", he continued, "and the modular yet versatile construction of the Betomix plant allowed us to stick to the very tight manufacturing schedule, in spite of the numerous modifications from standard required to accommodate the demands of our valued customer Centrum Pile Limited."

Liebherr "turnkeyed" the entire project from design to commissioning, including all civil engineering works, water system, compressed air systems and electrical installation.