Effect of Transient Operations on the Reliability of Hydraulic Systems

Abstract

Hydraulic systems, including those for water or fuel distribution, are often designed on the basis of steady state operating conditions. During transient operations, however, pressures much higher than steady state values can develop. Transient operating conditions can result from a number of causes, including pumps stopping or starting, valves opening or closing, and system startup or shutdown. Some systems, such as aircraft fueling systems and fire protection sprinkler systems, always operate in the transient condition. Operation of check valves and air release/vacuum break valves can cause large pressure surges. Burst pressures may be exceeded or fatigue limits may be reached as the result of transient operations. This paper presents three case studies in which transient operating conditions are substantially more severe than those indicated by a steady state hydraulic analysis. These case studies are based on field data and experience with existing operating systems, and on systems for which preliminary designs are being developed. In some cases the pipes failed. In other cases surge control devices were required or operating procedures to reduce pressure surges had to be developed. The results of computer analyses of the various cases will be shown and, where possible, compared with field data.