During the last month I have continued to be heavily involved in the detailed design on a subsea tie-back to produce a gas reservoir back to an existing offshore platform. Part of this project is to supply a Hydraulic Power Unit (HPU).
For those of you who are not too familiar with the workings of hydrocarbon production from a subsea tie-back, the well is drilled and completed on the seabed with a subsea template, manifold and control module. It is these systems that contain all of the master wing valves and subsea safety valves. As these valves lie on the bottom of the seabed they are controlled from the surface by using hydraulic fluids pumped through umbilicals piggy-backed to the production flowline. The fluids are pumped to the subsea control manifold and then turn the valves before being expelled to the sea (don't worry though, these hydraulic fluids meet all the correct environmental regulations and restrictions!).
The HPU is the skid that resides on the platform consisting of all the pumps and hydraulic fluid tanks etc. that supply these valves. This past week I have spent in the subsea vendors factory where the HPU has been fabricated. Prior to offshore installation it is the job all involved parties to send witnesses along to a Factory Acceptance Test (FAT) to ensure that the kit does what it was designed to do and is safe to install on the facility.
The FAT involved: checking all equipment was correctly tagged and installed in the correct orientation etc.; calibrating all level and pressure instrumentation; testing all instrumentation loops; hydrotesting pipes and tubing; ensuring all alarms function correctly and any executive actions (or process trips) correctly execute when mimicing the extremes of operation. All emergency shutdown actions are also tested.
With these checks made and signed-off the equipment is fit to be installed on the platform. Any items that need to be resolved prior to installation that the FAT showed were not acceptable go onto a "PUNCH LIST". The vendor will then action each of these items and will be signed off prior to the equipment being installed.
The next few weeks for me are going to be involved around site installations and commissioning of equipment. When I return I shall post some information on this blog regarding those. Until then.....
