These functions are assumed to be always implemented in the SPCS vendor’s equipment. In the case that the MCS is provided by a third-party supplier, the references below to the DCS may also pertain to the MCS.
The SCV’s system will manage data traffic to and from the subsea system and issue device control commands. The protocol is typically proprietary for a particular SCV and the medium and redundancy requirements are dependent upon customer requirements. The interface from the subsea gateway to the subsea system is not within the scope of the MDIS interface.
Ultimate operation or actuation of a subsea device is executed by the SCV’s system, whether requested locally, such as from an SCV engineering workstation, or remotely from the DCS.
The SCV’s system will provide current process data (e.g., pressures, temperatures, flow rates) and statuses (e.g., valve positions) to the DCS.
This includes settings for low-level subsea system functionality, such as solenoid pulse timers, pressure check settings for evaluating valve position or unintended movement, timer setpoints for determining valve failure, etc.
Valve Profiles are made available for transmission from the SCV system. The output format may vary among vendors and the data may be transmitted according to customer requirements.
The SCV system typically calculates process engineering values if raw data is received from subsea devices, though there may be exceptions where raw data transmission is required.
This refers to any available data in the subsea system not included within the definition of other objects that may be transmitted via a “generic” discrete or analogue object. This includes data that may have been considered “alarms” in legacy subsea systems, but are simply data points that are available to the DCS to manage as alarms, events or to be logged as desired. The SCV may also implement “roll-up” statuses that condense numerous statuses into fewer bits / words in order to optimise data transfer.
Diagnostic information in regard to the health of the subsea system is managed in the SCV’s system. This data would typically not be transmitted to the DCS except for summary product status data as defined above. It would be transmitted via a “generic” discrete or analogue object as desired.
The interface to the EPU may include monitoring of the power supply to the subsea equipment including input voltage / current, umbilical voltage(s) / current(s), line insulation monitoring data and power alarm statuses (over-voltage and over-current).
The SCV defines the subsea communications system architecture. Communications link control and monitoring is also performed by the SCV. Variable scan configurations (e.g. fast scan, normal scan, slow scan) may be implemented and configured by the SCV as required.