Introduction
In the process of extending an existing power plant, the addition of a new power plant was deemed necessary. This new facility was designed around a Combined Cycle Unit (CCU), which integrated both a Gas Turbine and a Steam System. Notably, the surface condenser of this new plant was cooled using a main cooling water system fabricated from fiberglass. To ensure the robustness of this cooling water system, a surge analysis was conducted.
Analysis
The objectives of this surge analysis were multifaceted. Firstly, it aimed to delineate the maximum and minimum pressures that might arise during various upset scenarios. Additionally, it sought to identify measures necessary to safeguard the cooling water network against overpressures or vacuum conditions surpassing the tolerable limits of the pipes and equipment. Furthermore, the analysis aimed to provide pressure/flow time history plots at crucial points within the system. All of these analyses were performed utilizing the software package BOSfluids.
Results
“Several upset scenarios were identified and analyzed.”
Based on the steady-state condition, six critical upset scenarios were identified and analyzed. Across all scenarios, pressure waves rippled through the system, engendering alternating high and low-pressure zones within the piping and much of the equipment. The outcomes of these analyses were as follows:
- The used valve closing time of 30 seconds was sufficiently slow.
- All maximum pressures calculated were well below the allowable 5 barg.
- Minimum pressures at or around all vacuums occurred at several places during several scenarios. All pipes were vacuum-resistant.
- Most cavities arose during one pump operation around the surface, condenser, and heat exchanger due to column separation. Mainly around and in the upper condenser pass.
- Start-up scenarios provided no problems for the system.
- Unbalanced forces were large due to large diameter and sudden pressure change.
Based on the analysis performed above it can be concluded that the system is fit for purpose and can withstand all the cases analyzed.
