Enhancing reliability of hydraulic power units in offshore gas facilities: A novel approach of innovative design and sustained reliability

Objectives/Scope: This paper addresses the operational challenges associated with hydraulic power units (HPUs) in offshore gas facilities, focusing on their ability to deliver consistent, clean hydraulic oil for the reliable actuation of Christmas trees and high-integrity pressure system (HIPS) valves. Ensuring the sustained functionality of these systems is critical for the efficient and uninterrupted operational function of the facilities.

Methods, Procedures, and Processes: To mitigate common operational risks, a novel approach is proposed that incorporates an integrated hydraulic oil flushing recirculation system coupled with an online hydraulic oil monitoring framework. This new setup aims to prevent elastomer seal failures in valves due to hydraulic oil contamination by recirculating the hydraulic oil for specified intervals. This is adjustable based on the oil cleanliness target, and typically maintains oil purity levels between NAS 3 and NAS 6, in alignment with the valve manufacturers’ recommendations.

Results, Observations, and Conclusions: The introduction of this design modification—centralizing the HPU to serve multiple hydraulic- operated valves—addresses the high-risk nature of single-point component failures that could lead to complete production halts. This integrated design will result in significant reliability improvements in unmanned offshore gas facilities, generating major cost avoidance over the life cycle of the field due to the elimination of the high cost of HIPS repairs, minimizing production downtime, and lowering overall maintenance costs.

Novel Information: This paper demonstrates the applicability of the redesigned HPU setup across a broad range of oil and gas facilities, particularly those using electro-hydraulic operating systems to operate critical valves. The approach significantly reduces maintenance demands and life-cycle costs, offering a robust solution for enhancing system reliability.