Table 28 details the generic properties for the MDISValveObjectType. Any vendor specified properties that have been implemented within a project should be documented within a similar format and supplied to the DCS vendor. The addition of vendor specific properties will result in a subtype of the MDISValveObjectType. When an MDISValveObjectType Instance is disabled the MDISBaseObjectType defaults are followed and only the OpenTimeDuration and CloseTimeDuration values will be available.

Table 28 - MDISValveObjectType

Attribute

Value

BrowseName

MDISValveObjectType

IsAbstract

False

References

Node Class

BrowseName

DataType

TypeDefinition

ModellingRule

RW

Subtype of the MDISBaseObjectType

HasComponent

Variable

Position

ValvePositionEnum

BaseDataVariableType

Mandatory

R

HasComponent

Variable

CommandRejected

Boolean

BaseDataVariableType

Optional

R

HasComponent

Variable

SignatureRequestStatus

SignatureStatusEnum

BaseDataVariableType

Optional

R

HasComponent

Variable

LastCommand

CommandEnum

BaseDataVariableType

Optional

R

HasComponent

Variable

NonDefeatableOpenInterlock

Boolean

BaseDataVariableType

Optional

R

HasComponent

Variable

DefeatableOpenInterlock

Boolean

BaseDataVariableType

Optional

R

HasComponent

Variable

NonDefeatableCloseInterlock

Boolean

BaseDataVariableType

Optional

R

HasComponent

Variable

DefeatableCloseInterlock

Boolean

BaseDataVariableType

Optional

R

HasComponent

Method

Move

See 5.7.4

Mandatory

HasInterlock

Variable

<InterlockPlaceholder>

InterlockVariableType

OptionalPlaceholder

R

HasProperty

Variable

OpenTimeDuration

Duration

PropertyType

Optional

R

HasProperty

Variable

CloseTimeDuration

Duration

PropertyType

Optional

R

HasSignature

Object

<ValveSignature>

FileType

Optional

The following items describe status information from the valve:

  • SignatureRequestStatus – The collection of data required for a valve signature may take some time after the completion of a Move command. The SignatureRequestStatus Variable indicates the status of the current signature request (see 7.1.4 for a description of the possible enumerations).
  • LastCommand – The enumeration reflects the last command sent to the equipment by the SPCS (see 7.1.5 for a description of the possible enumerations).
  • Enabled – This Boolean reflects if the valve is available for control. If it is disabled (FALSE) than the valve will not act on any Move command and is not available from a functional point of view. The valve will still report any status information (CommandRejected). One of the cases for a disabled valve is when the valve is placed out of service.
  • Position – This enumeration provides information about the current position of the valve (see section 7.1.7 for additional details).
  • CommandRejected – A flag that, if set to True, indicates that the valve has rejected the last command issued to it. The command could be rejected for a number of reasons. Possible reasons for rejecting a command include:
  • Loss of subsea communication reported by the SPCS.
  • An active interlock.
  • The valve is in the disabled state.

For any of the following Variables, if they are true, there shall be at least one instance of an InterlockVariableType that describes the active interlock.

The following items are related to valve control: These items allow information to flow from the DCS to the SPCS. All commands from the DCS to SPCS may require access controls to ensure that only appropriate personnel initiate them.

  • Move – This Method causes the valve to open or close (see 5.7.4 for additional details).

<InterlockPlaceholder> –The number of interlock Variables will change based on the project and even valve instance. The Variables shall be of InterlockVariableType or a subtype of it. The interlock contains an InterlockFor Reference to one of the previously described flags. Clients can use this information to categorise the interlocks appropriately. Figure 16 provides an example of how this interlock Variable is used and could be deployed.

image018.gif

Figure 16 - Interlock example

Note: in OPC UA it is allowed to have a Node which is the target of multiple HasComponent References, this allows a single interlock to be shared between multiple Objects; such as a low pressure interlock that maybe shared by all of the valves and chokes in a system.

The following items describe configuration related items:

  • OpenTimeDuration – Estimated max time to travel to open position, used for DCS systems to indicate a move fail condition if time is exceeded. Time is provided in milliseconds. The OpenTimeDuration can be used for any kind of valve (hydraulic, electric, etc.). [Note: this time is an estimate and Clients may need to allow for additional delays in transmitting and receiving any move commands].
  • CloseTimeDuration - Estimated max time to travel to close position, used for DCS systems to indicate a move fail condition if time is exceeded. Time is provided in milliseconds. The CloseTimeDuration can be used for any kind of valve (hydraulic, electric, etc.) [Note: this time is an estimate and Clients may need to allow for additional delays in transmitting and receiving any Move commands].
  • <ValveSignature> - The reference shall point to an instance of FileType, where the file contains valve signature information. The name of this object is project or vendor specific, but it should be related to the name of the instance of the ValveObjectType. The name shall include a timestamp. The FileType ObjectType (defined in Part 5 – Information Model) includes two properties (illustrated below), for all MDIS instances both of these properties shall have the value False. For additional detail see 5.10.3.

HasProperty

Variable

Writable

Boolean

PropertyType

Mandatory

HasProperty

Variable

UserWritable

Boolean

PropertyType

Mandatory

Vendor specific subtypes of this object type are allowed. They may add additional vendor specific information or may change some Optional items to Mandatory.