Control system replaces manual manufacturing process

Mersen Scotland Holytown Ltd is described as a market leader in the supply of premium carbon-based thermal insulation and precursor materials. The company's products are used in a wide range of high-tech industries including electronics, aerospace, automotive, special castings, vacuum and high-pressure sintering, vacuum treatment and graphitising/CVD applications.

Recently Mersen, with partial funding from the Scottish Government, has invested 24million in a new 70,000sq-ft facility housing its global headquarters and extended manufacturing facility. Integral to the latter facility was the installation of a wet moulding station, and also a wastewater treatment process plant.

Burkert was asked to submit proposals for these projects; initially for providing level and flow instruments but, later, this was extended to include process valves and, finally, Burkert was asked to tender for the complete process control systems for the wet moulding station and wastewater plant. This specification included all instruments, valves, control panel - housing Burkert's innovative AirLine 8644 system that integrates solenoid valves with I/O - installation and commissioning.

The wet moulding station is a fully automated processing plant comprising large mixing tanks where carbon, water and resin are mixed. The mix is then pumped to a mould tank where, under vacuum, the required mould profile is formed. The slurry drawn down in the mould process is pumped to vacuum tanks where it is then discharged to the water treatment plant.

Level monitoring

In the mould plant, Burkert 8110 vibrating level switches provide high- and low-level monitoring in the mould tanks and resin mix tanks; Type 8175 ultrasonic level transmitters monitor levels in mix tanks and vessels that are linked to pump sets; and Type 8185 guided microwave level transmitters monitor the levels in the vacuum tanks.

In addition to level control, Burkert also provides flow monitoring. One of the company's Inline Type 8035 flow transmitters provides monitoring and batch control of water supply to the resin mix tanks, while two Type 8045 electromagnetic flow transmitters monitor the slurry flow rate and control the slurry pump speed, as well as monitoring effluent discharge to the water treatment plant.

The fully automated mould plant is controlled by a PLC-driven control panel incorporating twin HMI systems and Burkert's 8644 Airline process actuation control system. The AirLine 8644 integrates seamlessly with the Allen Bradley PLC used for overall control of the plant. Calculated to save anywhere up to 40 per cent on total system costs through the engineering efficiencies it achieves, the Type 8644 provides users with a remote field I/O network that is compact, reliable and not exclusive to any specific communication protocol. It combines digital I/O, including a full complement of solenoid pilot valve outputs, analogue I/O and Fieldbus connectivity into a single node.

Valve actuation

The AirLine 8644 system provides actuation of the Burkert process valves used in the mould plant. These include butterfly valves, which control mains water supply to the resin mix tanks, and discharge from the mould tanks to the vacuum tanks. In addition, Burkert T-ported ball valves provide a drain function on the mix tanks, and Type 330 solenoid valves control the supply of Teepol dosing, used as a wetting agent. Finally, Burkert's full-bore, actuated ball valves control the mains water supply valve to the effluent treatment plant.

Neil Saunders, Burkert UK & Ireland Sales Manager, comments: "What this project highlights is our unique ability to cover the complete control loop in process applications. Our current product range extends from solenoid valves - direct and servo-assisted - to process and analytical valves, mass flow controllers, pneumatic actuators, and one of the widest ranges of sensors for process applications. In this project we have taken a broad cross-section of these products and integrated them to provide a complete control solution - including system design, panel building and system commissioning - from a single source, and one that exactly meets our customer's needs."