IN a typical refinery tank farm, raw materials, intermediate products and final products are stored prior to being used elsewhere in the refinery or shipped to market. Product movements between tanks, process units and input and output terminals are continually occurring as part of the normal business and process flow.
Each movement and operation has the potential for inaccuracy, for spillage, or just going missing or undetected. Inventory tracking and balancing is vitally important to the profitability of the business; losses must be both identified and kept to a minimum.
Shell’s two Australian refineries - at Geelong in Victoria and Clyde in New South Wales - used the original Oil Movements System (OMOSS), which was developed by Shell. This was initially installed in 1983 and has been subject to continuous improvement since that time.
The OMOSS system is interfaced to the refineries’ DCS control system and the process plant’s supervisory and management systems, including the refineries’ mass balance and finance system.
These improvements created a significant extra load on the system, which resulted in a marked deterioration in system response and speed.
The current system hardware is over 15 years old, and the system management is complex due to extensive local customisation and interfacing built into OMOSS. Knowledge of four different computer systems is required, as well as ability to program in a number of outdated computer languages (Fortran, Pascal and RPG).
In early 2004, Shell initiated a project to replace its locally developed OMOSS application with a third-party vendor application that would be externally supported and developed over time. Shell selected Yokogawa and its Exaquantum (process historian) and Visa (value added application) products, to be called VisaOM, as the vehicle to develop the replacement Oil Movements System (OMS) to meet Shell’s requirements.
The objective of the OMS is to record certain refinery data such as tank levels and calculated flows in a permanent database, and to provide an interpretation of this data in terms of the individual oil movements that take place in the refinery. This interpretation is model based and will provide both real- time assistance to the refinery operators as well as a permanent record of all oil movements and tank inventory.
The major objectives of Shell’s Geelong and Clyde Refineries OMS is:
• To scan and record all relevant raw process data (mainly automatically measured levels, temperatures and selected flow rates) in a long-term data historian.
• Process this data to derive additional parameters and record them similarly (e.g. derivation of volumetric flow from levels, derivation of mass flow from volumetric flow and density; aggregation of raw data over time to obtain stable values, calculation of rates of change, etc).
• Tank inventory management.
• Provide methods of defining oil movements in terms of source, destination, route, quantity, material, etc.
• Provide real-time live displays showing the progress of movements, including the tank-ranking table (tabulates key information about each tank involved in a movement, showing time to finish, current dip, end dip, movement ID, flow rate, volume remaining, dip remaining, etc.).
• Provide an alarm acknowledgement system (directed to a dedicated window) for alarms based on tanks, movements and events.
• Calculate tank compositions and other quality parameters based on movements, estimations, in-line measurements and lab data.
• Calculate and report on the stocks and net flows in and around the refinery, so as to provide information on what quantities of what materials are stored, and where they are stored, at any time. This logic is to include data on material contained in pipelines, as well as in tanks, but will exclude that held in process units.
• Provide tools to record the application and removal of batch codes to tanks.
• Provide a method of recording selected details of the route taken between tanks and other units.
• Provide reports on current and historical OMS data of all types. The reports to be produced on demand, on event or scheduled, both as built-in preformatted formats and as user-definable formats via linked external applications.
• Historise all data associated with OMS.
• Provide links to external data feeding and receiving systems.
• Log system and operator activity, including interaction with external systems.
Visa OM Tank Farm Manager combines the Yokogawa Exaquantum process historian with the Visa value-added application extensions. These are model-based and easily configurable to build up an informational model of the plant and tank farm, which can then be balanced and reconciled for accurate inventory accounting. A integrated transactional view controls and records movements of materials around the process and tank farm to indicate and record distribution and usage of material.
Shell expects many benefits from the new system, including: greater reliability and availability, reduction in product losses, reduced support costs, reduced risk of movement errors and greater environmental security.
John McGuire, Clyde and Geelong’s special projects manager, commented, “Oil movements projects have traditionally been complex and involved, with a great deal of custom engineering effort required. This new approach is a more straight-forward implementation because of the largely configurable Exaquantum and Visa applications.”
The applied system is independent of the DCS but has the capability to interact with the DCS to effect a complete oil movements supervisory solution.
The project is being developed based on guidelines in Shell’s “Early Involvement of Main Automation Contractor” program, which involves a cooperative effort by supplier and end user in developing functional design and application specifications and agreed scope and pricing. This has produced smooth business interfaces.
The project is being managed and engineered by Yokogawa Australia with technical and development support from Yokogawa Marex in the UK. Yokogawa Electric Corporation in Tokyo is providing corporate and application support.
Shell Australia has formed a project team to interface with the Yokogawa team, comprising representatives from both refineries, from Shell Australia head office, and Shell Global Solutions Incorporated in The Hague.