Abstract

Large water pipeline systems are crucial components in oil sand production. These water systems include, hot process water, raw water recycling, closed loop cooling water, gland water, and fire water systems that supply water with high flow rates at required pressure to multiple units such as ore preparation, mine slurry handling, oil extraction, and utility, etc. Hydraulic surge analysis is important in the design and operation of these systems to assure economic and safe, reliable water supply.

Common pipeline surge studies focus on transient scenarios caused by pump trip, valve closure, and power loss. For simple systems with few sources or deliveries surge is often easily explained. For instance, when a valve closes a hammer will be originated at the valve and travel upstream through the pipeline. A simple comparison with the Joukowsky equation can show the expected surge in this case. For large pipeline networks with many branches, various equipment, and controls however, the surge effects can often be widespread and unpredictable. The resulting surge shockwave may travel through the system to locations where surge is never considered a risk. When pumps trip the flow behavior becomes dictated by gravity. The gravity flow due to loss of pressure can cause slack flow and/or column separation/collapse in unexpected areas. Improper pump selection can also result in overpressure during operation, particularly if the pump operates at a shut-off head pressure that exceeds the design limit of the system. When a pipeline closes, there may be a delay in pump shut down that continues to push the flow into a closed loop to over pressure the pipe section. Surge events that do not immediately occur at the upset location may require unique attention and solutions. The influence of air entrainment and entrapment is another unique issue that needs to be addressed in water pipeline systems.

This paper summarizes the transient modeling strategy and identifies common causes and solutions to surge or low pressure issues in the system. This paper also illustrates the consideration and modeling technique in entrapped air effects on the fire water system surge using single phase pipeline hydraulics software.

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