The company employs almost 2300 people and reported an annual turnover of 391 mill. pounds (GBP) in 2018. Clay bricks have been manufactured at the Dorket Head site near Nottingham since the 1860s. Following modernization, the production capacity here is around 95 mill. bricks per year.
Higher output required
Originally, the Dorket Head plant used liquid ring vacuum pumps for extrusion moulding. But when the output was to be increased, more suction power was required. This could only have been achieved with much larger machines based on liquid ring vacuum pumps. However, as these run very hot, which was undesirable for the process environment, the manufacturer was looking for an alternative vacuum source to achieve the desired increase in productivity.
Screw vacuum pumps with plug-and-play concept
The company evaluated various vacuum technologies available on the market, including rotary vane and dry-running claw pumps, before choosing Atlas Copco‘s oil-injected GHS screw vacuum pumps. They look similar in appearance to Atlas Copco‘s proven screw compressors and are designed according to the same plug-and-play concept. However, they offer considerably more performance than conventional rotary vane vacuum pumps. In addition, they run significantly quieter, do not get so hot and require far less maintenance.
Variable speed and pressure setpoint control save a lot of energy
The GHS vacuum pumps are also available in a version with frequency converter (VSD: “Variable Speed Drive“), so that the generated vacuum quantity can be exactly adjusted to the process requirements.
Ibstock decided to install two plug-and-play GHS 350 VSD+ vacuum pumps, each with 5.5 kW power, one for main operation and one as a standby machine. Each has a pumping speed of 390 m³/h and delivers an ultimate vacuum of up to 0.35 mbar (absolute). The installation was completed with condensate separators and particle filters. Ibstock has signed a full-service contract with Atlas Copco for all units.
The speed of the vacuum pumps is intelligently controlled by an Elektronikon control system. In addition, the so-called pressure setpoint control ensures that the pump always generates the lowest possible volume flow rate with which the required vacuum can be maintained. In this way – unlike with the full-load idling control systems of other vacuum technologies – no energy is wasted. This drastically reduces operating costs. The low maintenance requirements also keep lifecycle costs low: there are no rotary valves that need to be replaced, and the screw element used is maintenance-free for many years. In addition, inlet filters and oil separator elements can be replaced without having to dismantle any piping.
No problem when handling humid media
Dealing with the moisture contained in the clay was an essential prerequisite for modernization. Ibstock purchased the humid versions of the GHS VSD+ pumps, which, with their electronically controlled gas ballast and temperature regulation, allow adaptation to the plant-specific process. 100 % water vapour is no problem at pressures above 30 mbar (absolute): The gas ballast is automatically switched on as required and the purging cycles before and after emptying are automatically controlled by the machine. The machine is also automatically heated to operating temperature before the system is started (“pre purge“). Before the system stops, the machine switches to an oil regeneration phase (“post purge“).
For Ibstock engineer Daryl Leivers and his company, the new installation has met all the criteria: “I am impressed with the performance of the Atlas Copco pumps. They have allowed us to increase productivity while maintaining the same vacuum level and consistent quality. The machines are also quieter and take up a footprint the size of a pallet. And the pumps enable us to reduce our energy consumption for the process by up to 60 %.”
Atlas Copco Kompressoren und Drucklufttechnik GmbH