Hydraulic Distribution Manifold/Module (HDM)

3.3.5. Hydraulic Distribution Manifold/Module (HDM)

The purpose of the HDM is to distribute hydraulic fluid (LP and HP) and chemicals to each of the subsea trees, production manifolds, and to future expansions. The HDM as shown in Figure 3-6 consists of multiple inboard MQC plates on a frame that is mounted on an umbilical termination assembly mudmat (UTA-MM). The hydraulic distribution depends on: • The number of valve functions; • The actuator sizes; • The frequency of valve operation while operating the system; • The location of the valves, trees, and manifolds. Stored hydraulic energy in accumulator bottles (SAM) is required to allow fast sequential opening of subsea valves without affecting the operation

of other valves in the system. The accumulators are charged up by the hydraulic supply in the umbilical. The HDM allows for the reconfiguration of services by changing logic caps during the service life. Each HDM has a spare line going to all inboard MQC plates to allow the umbilical services to be reconfigured in case of an umbilical line failure or a change in the operability and/or chemical requirements of the existing field or an expansion location. ROV valves are being used where desired functionality or isolation cannot be achieved by a logic cap. A spare manifold is included in the HDM to provide flexibility for reconfigurations. The minimum component test pressure is 50% above design pressure. Basically, all parts and components of the subsea distribution system are clean before and during assembly. The subsea hydraulic system is robust and designed to tolerate acci- dental contamination by seawater and particles. It should be designed to avoid accumulation of such contamination. All components are qualified for operation in fluid contaminated with solid particles. Vulnerable parts with very low fluid consumption (e.g., directional control valve pilot stages) should be protected by filters. Otherwise strainers should be used. A logic/crossover cap is used to reconfigure spare umbilical line to replace failed line.