Tarmac Builds Modern Manufacturing Production Facility with Velotic

Tarmac, part of the CRH Group, is the largest manufacturer of lime products in the UK. Tunstead Quarry, which was opened in the 1920s, and Old Moor Quarry, its more recently established neighbor, is one of the biggest mining operations of its type in the UK. The two quarries extend to over 840 acres, and their combined extraction output is up to six million tons of limestone a year. Tunstead was established to provide a consistent supply of high purity industrial limestone for use within the chemical and other industries.

Tarmac’s operation uses computer-aided techniques to dislodge around 30,000 tons of stone per blast, which is then loaded onto tipper trucks and carried to the primary crusher in 100 ton batches. The crusher processes up to 30 truckloads of stone per hour. Conveyor belts then transport the rock to a secondary unit, which crushes the stone down to a range of sizes, from 125mm to dust. The Tunstead site also produces aggregates for the construction industry.

The rocks and stones are fed into 10 huge hoppers, which hold various grades of stone that range from fine dust to big rocks. The final makeup of the bagged and dispatched products depends on the applications.

Tarmac called upon the services of Astec Solutions to make an upgrade to its MES software, which was obsolescent, in order to improve reliability and consistency of its output.

"The system the company was using had been in place since the 1990s. Handling of the material as it was mixed had been by a manual system; the operator would type in the percentages required and then set things going.”

Managing Director, Astec Solutions

The human involvement inevitably meant that consistency between batches was not totally reliable. The time taken to manually input data also affected output and productivity.”

The site was using out-of-date Mitsubishi PLCs and an MX32 SCADA system, which was also obsolete. Although the site is physically large, the control systems are not and so the cost of replacing the PLCs was not as much of a hurdle as could have been the case.

“Tarmac had the appetite to upgrade to the latest Mitsubishi PLCs, which offer improved performance and better availability of spares,” said Andy “The company has the in-house capability to undertake the electrical work, including control panel and code changes.” However, while the PLCs could be upgraded the MX32 system was more problematic, as there was no continuity available in that form. Astec’s solution was to implement a ‘ground-up upgrade’.

“We were able to take certain things from the existing MX32, including the I/O scheme, the equipment list and the way the equipment was visualised,” Andy explained. The system was migrated from MX32 to Velotic’s iFIX; Astec Solutions is one of Velotic’s partners in the UK. “We created a virtually new MES system and recipe and used a modified SCADA system to provide plant visualization and operation.” A big difference to the previous setup was that Astec implemented SCADA within the IT system itself.

"Lifting the solution and leveraging within the IT world gave more functionality. We took that route in order to get all the functionality required with as little custom code as possible – we kept it as close to standard as could be."

Such an approach would have consequent benefits during the system’s lifetime. Velotic’s best-in-class software provides a solution that is supportable, extendable and adaptable to meet Tarmac’s future demands.

“We used MS SharePoint to provide the product specification and recipe package and we were able to do so using completely standard SharePoint methods,” he said. “This provided Tarmac with a recipe management system that has version control, workflow, validation and security, with a familiar and easy to use Intranet web-based interface.”

Because all the significant elements of the system were essentially off-the-shelf, so implementation was comparatively low cost. Off-the-shelf makes it easy to support and extend, and is also more flexible than the system it replaced. Production lists, recipes, and specifications can be maintained and accessed from anywhere within the Intranet—from an office or a completely different location.

The production list will respond to the market. Customer demand will drive through to logistics, planning and scheduling, which will in turn drive production. The SCADA system will read the data store; production operators will select the required product and quantity.

“The operator simply identifies the desired product from the list, selects the required quantity and then presses ‘go’. Room for error is greatly reduced,” Andy explained. The possibility of errors was further cut by the fact that Tarmac now had a database-driven application.

Andy continued “The company now has full ‘track and trace’ and, consequently, vastly improved quality control. The system can store all loading data for reporting and the operators and management have full access to information on the volume and recipe version each truck was loaded with.”

The site had a number plate recognition system and the system had the capacity to connect the stone filling, loading bay and station data together.

It is possible for the system to be updated to completely automate the process. Individual trucks would be recognised and directed to the right bay for filling with the correct formula - and recipes are protected as well. Access to version control is secure; any amendments to recipes or formulae have to receive approval before they will be actioned.

Andy Tripp is proud of how the upgrade and migration was achieved, the system that is now in place and the speedy delivery of the entire project.

"After the client completed their responsibilities, the project was turned around in three months. That’s a pretty impressive timescale for a major change."

Tarmac’s Tunstead Quarry complex now has a modern, scalable, adaptable, visible and controllable production and execution system. It is transparent, secure and relievers greatly improved quality control, efficiency and consistency. The system is fully supportable, as it has been implemented largely with standard, out-of-the-box commercial software and provides improved visibility through Intranet interface and access, including access from off-site. It is also more reliable, being based on modern PLCs, for which spares are widely, easily and much less expensively available. Quality control and product specification have also greatly improved due to a database of approved recipes that require authorization for any amendments.