Contrec were recently approached by one of Aberdeen’s largest engineering companies who were involved in the contract to lay 14km of under sea pipeline off the North West Australian shelf. The engineering company were required to do the pre-commissioning flooding, pigging and water treatment. Part of the contract required an automated system with an additive controller to control the injection of corrosion Inhibitor at 500ppm and Dye at 50ppm with some specific alarms and other integration to their main pumping system. There wasn’t a system already suited to their specific needs or one that could handle the difficult nature of pulsating dosing pumps and so they approached Contrec, who worked together with their R&D team to develop the AI01 Additive Controller.
Based on the existing Contrec 515’s hardware platform and existing flow measurement and control modules Contrec Systems Australia provided the control system, fit out and wiring in the stainless steel enclosures and worked with Power Systems Australia to build and design the skid and additive lines.
FAT tests were held with representatives from both companies, main flow was simulated and water used as the additive mediums. While direct pulse would have been the preferred control of the dosing pumps, the nature of the pumps specified required 4-20mA control which introduced more inherent variability in the system. However, with use of flexible parameters, the change in fluid dynamics and inherent delays were catered for and the system tracked the target ratio within a few PPM. Error conditions were simulated and the appropriate alarms and exceptions were raised.
The skid shipped to Perth where it will be part of a more comprehensive setup so that it can be trialed and tuned to the main pump and pigging system. Although a pulsation dampener has been included in the additive lines to great effect, a four or five point non-linear curve will be implemented for the Trimec Oval Gear flowmeters to further tune the system for its variable flow range.
Summary
- Volumetric pulse input from flowmeters
- Wide injection ratio’s (10-10,000 PPM)
- Ability to handle pulsating dosing pumps
- Permissive input to reduce alarms whilst system is settling
- Alarms for deviation, no additive, high mainline flow
- Pulse or analogue output for dosing pump control
- Modbus RTU output
- Explosion Proof Option
