DCS (Distributed Control System) is the production facility control system provides a centralised control system for the facility for the operators and is used to monitor and control the subsea production system. The DCS system will normally host the OPC UA Client.

MCS (Master Control Station) is the central control node containing application software required to control and monitor the subsea production system.

Subsea Gateway provides a communications interface on the surface to the subsea control equipment over the subsea vendor’s communication system. The Subsea Gateway may form part of the overall MCS. The MCS or Subsea Gateway will normally host the OPC UA Server.

SCV (Subsea Controls Vendor) equipment refers to the subsea vendor supplied equipment and principally includes the subsea gateway in “Integrated” architecture or the subsea gateway and MCS in “Interfaced” architecture (see section 5.1 for additional details). It is intended to classify the functionality that is delivered by the subsea vendor whether it is implemented in the MCS or subsea gateway.

Note: The MCS may be supplied by a vendor other than the subsea or DCS vendor.

HPU (Hydraulic Power Unit) is the unit which provides low pressure and high-pressure hydraulic supplies for the control of subsea wells.

EPU (Electrical Power Unit) is the unit which provides power to the subsea system.

Interlocks (Permissive Logic) is permissive logic that needs to be satisfied before the action can initiate

The Customer is the end user, typically the “Operating Company”.

The Operator is the human being executing an operation, not to be confused with the “Operating Company”.