Operational failure analysis of a hydro-pneumatic system in a hospital facility

Introduction- This paper presents the study of the operational failure of a hydro-pneumatic system for the supply of water to a hospital facility. Objective- Determine the cause or causes for the interruption of the water supply of the hydro-pneumatic system to the building. Methodology- The hydraulic characteristic of the pipe system was drawn and compared with the hydraulic characteristic of the hydro-pneumatic system, verifying that it fully satisfied the load and flow requests demanded by the building. Given the presence of noises and vibrations in the suction pipe, the comparison of the required NPSH vs. the available NPSH determined that the current design of the suction pipe is the cause for the hydro-pneumatic system failure. Results- Three variants for the modification of the design of the suction pipe in order to eliminate the phenomenon of cavitation are proposed. This avoids putting into operation an auxiliary pump that increases energy consumption by 8,760 kWh/year with a cost of 1,839.6 $/year and the insecurity in the water service. Conclusions- The selected hydro-pneumatic equipment satisfactorily meets the requirements of the installation, except for the design of the suction pipe where the available NPSH is lower than the NPSH required at flow rates higher than 900 l/min, hence, producing the cavitation phenomenon and causing the output of system's service.