A Hydraulic Power Unit for subsea installation is similar like the standard HPU, but sizing of reservoir, pumps and accumulators will be larger. The HPU is a unit that is used to generate and store hydraulic energy at one or more different pressure levels ready for later use. The controls of the Hydraulic Power Unit can be installed in an open skid or in an closed enclosure. Preferred is an closed enclosure to minimum derating due to harsh environment, but if sizing of the whole package is too big, it will be built in an open skid.
Main component in this device are:
A hydraulic reservoir (sized in accordance with the required fill-up of tubing/hoses/umbilical and swept volume of various actuators in the field).
Motor/pumps are usually redundant (two or more pumps for each pressure level). Motors can be either Electrical or Pneumatic driven.
Pressure transmitter / switches for automatic start/stop control of the pumps.
Accumulators, for hydraulic energy storage. Preferred is to have always two or more on one pressure level.
Relief valves for protection of equipment and field runs. Relief valves are always set 10% above working pressure, but should never be higher than maximum allowed working pressure of tubing/field equipment.
Motor Control Box, if required. Normally the HPU will have its own Motor Control Box so only an external power supply is required for operation of this unit.
Normally no controls are implemented to open/close valves in the field, but only hydraulic supply lines to the field.