Abstract
Hydraulic Power Unit (HPU) is one of the critical subsystems of a Subsea Production Control System (SPCS). HPU is designed to supply clean and regulated control fluid to remotely operate subsea valves. Failures of HPU can potentially lead to loss of control of subsea valves which are often designed to fail-safe. This automatic production shutdown disrupts normal operation with significant downtime cost. Therefore, optimising HPU's performance is critical to maximising production availability. Modelling System Failures (MSF) is a quantitative maintenance optimisation technique. It aims at determining optimum maintenance requirements by investigating equipment failure patterns. MSF helps select the most efficient and cost-effective maintenance strategy. Failure and maintenance data are collected then analysed. MSF permits the creation and simulation of a system's model to set optimum maintenance tasks.
A typical HPU was analysed using MSF methodology. Generic failure rates of HPU components were extracted from the Offshore and Onshore Reliability Data (OREDA) Handbook. HPU Reliability, Availability and Maintainability (RAM) model was designed using ReliaSoft software packages. The designed model was simulated over a period of 25 years design life of a typical HPU. Appropriate maintenance tasks were determined based on the failure characteristics of the HPU. Mean Availability increased from 97.01% to 99.56%. System uptime increased from 24.25 years (212,441.61 hours) to 24.89 years (218,036.81 hrs) and downtime decreased from 0.75 years (6,558.39 hours) to 0.11 years (963.19 hrs).
