Single plc controls expanding tank farm site

A Mitsubishi Electric Automation Systems product story

Edited by the Processingtalk editorial team Jun 24, 2008

Mitsubishi plc-based control system ensures optimum materials management at Kingspan Building Products - an ancient application story passed on from Buildingtalk!

Kingspan Building Products is securing production of its insulating panels by more than doubling its raw materials holding capacity at its manufacturing plant in Pembridge, Herefordshire.

To do this it has added 11 new chemical storage tanks to the eight existing ones and installed a state of the art Mitsubishi control system to ensure optimum materials management.

Demand for insulating panels was increasing in 2005 as Building Regulations placed more and more emphasis on thermal efficiency and as builders developed new construction techniques to reduce dependency on time consuming wet trades such as plastering.

Kingspan's objective was to be able to store enough materials on site for one or two weeks' production so that delivery problems never translate into production stoppages.

Kingspan run production as a continuous process five and a half days a week, with maintenance scheduled for the Saturday shutdown.

The finished panels consist of expanded and set foam sandwiched between aluminium-based foil sheets.

The foam is laid down as a liquid and sets or goes off when the panel is passed through an oven section.

Once solidified the panels are cut to length, usually 7m, and dispatched to the ever-hungry builders' merchants.

The base chemical from which the foam is made is MDI and this is mixed with one or more polyoils, the precise 'recipe' dictating the chemical reaction and therefore the final performance characteristics of the foam.

This mixture is held in a relatively small 'day tank' which holds enough material for several hours production.

The main storage tanks are all 50 tonne capacity and 8m tall and are supplied directly by the road tankers which bring the powders from the chemical manufacturers.

Kingspan brought in the expertise of local systems integrators Wildgoose and Davis to design, install and maintain the control system.

Partner Graham Wildgoose recalls: "There was a history of using Mitsubishi control equipment on site, and we were happy to continue this because we could see that the new system requirements could be handled very elegantly by one Mitsubishi Q-series PLC (programmable logic controller) fitted with a Q-02 CPU (central processor unit)".

Each tank is fitted with a load cell to monitor its material content, and also with a temperature probe installed as a backstop to indicate if there has been any untoward chemical reaction in the tank.

Such a reaction is highly unlikely, but could have a significant effect on production if one were not spotted promptly.

The load cells constantly feed real time data to the PLC which is running Mitsubishi's MX4 SCADA (supervisory control and data acquisition) package as its main control platform.

This audits materials, usage, pipe routes and operations to provide the plant operators with up to the minute process data and information.

"The SCADA communicates with the PLC via Ethernet.

The PLC also hosts three ASI (Actuator-Sensor Interface) masters, as we have three separate ASI networks running around the site," says Wildgoose.

Every field device on site, including the load cells, pumps and valves, is fitted with an ASI interface and feeds into one of the networks, as it was one of the systems design objectives to reduce the amount of wiring compared to that used for the original eight-tank system.

"The Q-series is designed specifically for this sort of architecture; its modular flexibility means we can easily extend the system at a later date if necessary.

It also means we can switch over to a standby PLC in seconds should there be a need to do so".

In fact there is a back-up PLC already fitted in the main control rack and tests have shown that a complete change over can be accomplished in a matter of minutes.

The system also includes a Mitsubishi E900 HMI (human-machine interface) which provides the operators with highly sophisticated graphic representations of the tank farm and production processes.

In fact the whole plant can be run using just the PLC, HMI or SCADA.

"This level of redundancy means we are unlikely to ever lose production, and also provides a very high level of safety," says Wildgoose.

Kingspan was founded as a small family firm barely 30 years ago, but now is a global organisation whose 3000 employees turn over GBP800m a year.

Thermal panels is one of its fastest developing product lines, with growth expected to continue for many years to come.