Seawater systems are essential to the offshore industry as they provide water to the injection wells, cooling water and also drinking water. The control of flow to the various users is often through control valves and hence there is the potential for interaction between the different controllers. This needs to be considered in any design study.
As with firewater systems on platforms, drained seawater pump risers are often used in conjunction with an air release valve (or an overboard dump valve) for submerged seawater pumps. The flow through the pump can build quickly as the air is vented, and this high flowrate is then stopped when the air valve (or dump valve) closes, leading to a large surge pressure rise. We have studied several systems where significant damage to piping and supports has been sustained. Our software can accurately model this flow build-up, taking account of the air compression and evacuation, and assist in correctly sizing the air valve, or to find other means of preventing unacceptable conditions.
The start-up of seawater systems often necessitates the use of a priming or jockey pump together with overboard dump valves at the filters. This complicates the start-up logic and our mathematical model can be used to consider the behaviour of the system under steady and transient conditions, to determine control valve settings and pump start or stop sequencing to ensure that the system may be operated safely under all conditions.