The following main parameters need to be considered/determined for the hydraulic system:

  • Hydraulic fluid reservoir sizing;
  • The time to prime the hydraulic system from a depressurized state;
  • Opening and closing response times of the process valves under conditions of minimum and maximum process pressure;
  • The time for the pressure to recover following a process valve opening;
  • The time to carry out a sequence of valve openings, such as the opening of a tree (neglecting choke valve operation);
  • The stability of opened control and process valves to pressure transients, caused by operation of the other control and process valves (sympathetic control valve de-latching, process valve partial closing, etc.);
  • Response time to close process valves in the event of a common close command, such as an emergency shutdown at the surface, venting off hydraulic control valves via supply lines;
  • The time to vent the umbilical hydraulic supplies;
  • The impact that failure of subsea accumulation has on the safe operation and closure of the process valves;
  • The extent of control fluid leakage rate that can be accommodated by the system;
  • System response times for simultaneously opening and closing multiple choke valves.

See also


  • Subsea Engineering Handbook by Yong Bai and Qiang Bai, Publication Date: January 27, 2012 | ISBN-10: 0123978041 | ISBN-13: 978-0123978042 | Edition: 1