Thinking Differently Ensures Integrity of Fire Water Network

Abstract

With focus on enhancing Integrity and efficiency, ADNOC Gas Processing identified an opportunity for optimization of existing FRP firewater system in Ruwais. A comprehensive study of complete firewater network and review of operating and control philosophy performed in order to optimize the system performance and mitigate pressure surge problems. This paper presents measures that ADNOC Gas Processing have adopted to achieve improved system efficiency and lower operating cost. A study was undertaken by GASCO to review issues with existing Fire Water network (FWN) at Ruwais to enhance overall performance of system in terms of design, operation and control. Initiative was to identify problems, evaluate root cause and think of optimization including some cost saving solutions. Study explored various operating configurations of existing 4-working+ 4-standby pumps with active involvement of operation personnel followed by hydraulic and surge analysis with different operating scenarios. Study revealed reduction in flow, head and pressure to mitigate fire water piping surge problems. Study also engaged pump vendors to establish feasibility of modifying the existing pumps. The study identified that each existing fire water pump is suitable to deliver 1400 m3/hr against required flow of 1000 m3/hr. Additional flow may create pressure spikes and surges in FWN. Hydraulic analysis found that pressure was above minimum requirement of 7bar (g) at the most remote point in network. Simulation indicated that fluid velocity was above 3.5 m/s at specific sections on the ring main. Increase in pipe sizes is required to arrest velocity within recommended limit in these areas. Option of lowering the operating pressure of main fire water pumps without the fire water network pressure falling below 7bar (g) at the most hydraulically remote point in the network was studied. Also the option of 3W+3S and 4W+4S [working (W) and standby(S)] pumping configuration was studied so as to establish that system can work with less number of pumps. Hydraulic study concluded that rated pressure should be reduced along with shut-off pressure. The maximum worst case fire water demand is 3200 m3/hr. The demand is found to be achieved with three Fire Water Pumps. During study pump vendors were engaged to arrive at the conclusion that 3W+3S configurations are hydraulically acceptable with pump / impeller modifications and de-staging options.