The processing plant consists of several gas compressors which both maximise the pressure of the gas stored and the gas withdrawn from the caverns into the National Grid Transmission System. Additionally an on site drying plant removes water from the gas as it leaves the caverns. Some gas is always left in the cavern to maintain the minimum pressure required to sustain the cavern structure. The maximum pressure is carefully controlled whenever gas is injected into or withdrawn from the cavern.
The 800xA system is being supplied to Costain who are responsible for Engineering, Procurement and Construction of the plant. ABB are a ‘preferred’ supplier to Costain as part of their supply chain top level supplier initiative designed to preselect quality suppliers that add benefit to Costain business.
The ABB system will control the import of gas into the caverns for storage and export of Gas into the National grid, this includes the complex control required to handle these transfers in both free flow and compression modes.
Plant safety is critical and the TUV certified AC 800M HI controllers are used as the Safety Instrumented System to control the processing plant, associated pipelines and the well heads, which are situated up to 2 km from the processing plant.
Availability and efficiency of the plant are crucial, the AC 800M are a key part to ensure these key factors. The 800xA system also interfaces to fire and gas monitors around the plant, third party packages such as the compressor unit controls, access security and CCTV monitoring of the plant. Thereby providing integrated visibility for the operators of the process along with plant security and safety aspects.
Steve Bresnen, engineering manager at ABB in St. Neots, says: "E.ON wanted a UK supplier who could engineer, manage and build the system here. They also wanted a company with a proven record of this sort of project and we could offer our experience with other gas storage projects."
The ABB System 800xA control system supports IEC61850 allowing the controllers to link to Intelligent Electrical Devices on switchboards, motors and other electrical equipment.
E.ON also wants to use the AC 800M HI controllers to gather asset data to allow predictive maintenance and discover which instrumentation needs recalibrating etc, reducing OPEX costs and cutting total cost of ownership.