CANopen profile for "Christmas trees"

SIIS level-2 devices include generic sensors for pressure, temperature, position, inclination, etc. as well as complex meters such as for multi-phase flow measurements or gas-in-oil monitoring

CAN in Automation (CiA) and Subsea Instrumentation Interface System (SIIS) nonprofit associations have developed jointly a communication interface for subsea tree (nick-named as Christmas trees) devices. These so-called SIIS level-2 devices include generic sensors for pressure, temperature, position, inclination, etc. as well as complex meters such as for multi-phase flow measurements or gas-in-oil monitoring. The standardized communication interfaces are based on the internationally standardized CAN serial bus system (ISO 11898 series), which is used since more than 15 years in high volumes in passenger cars and many other application fields. The selected internationally standardized CANopen higher-layer protocol (EN 50325-4, also known as CiA 301/302) simplifies system integration by means of configuration tools available from different vendors. The CiA 443 profile specification standardizes the process data, some configuration parameters, and diagnostic information.

The version 1.0 of the CiA 443 profile has been released just before Christmas 2008. Aker, Cameron, FMC, VetcoGray (a GE Oil & Gas business), Matre, Roxar, and SkoFlo developed it with the support of Ixxat and Softing, two companies providing CANopen software and tools.

"The CiA 443 profile specification is suitable for embedded networking within subsea trees," explained Ian Kent from VetcoGray, chairman of the CANopen SIG (Special Interest Group) Subsea Instrumentation. "We have standardized not only the process data, but also the boot-up procedure and several other CANopen-specific functions in order to simplify system integration." This avoids to "reinvent the wheels", and reduces possible failures during system integration.

"CAN is one of the most reliable network technologies proved in more than 2 billion nodes used in many mission-critical applications," said Holger Zeltwanger, CiA Managing Director. "The CANopen protocols and profiles provide a standardized communication but still giving enough flexibility to the system designer to tailor the subsea tree to the customers' requirements." In order to control and diagnose the subsea tree remotely from the offshore-platform, Ethernet-based (SIIS level-3) networks are used. The gateway to the CANopen-based embedded subsea tree network should be compliant to the CiA 309 specification. It specifies the communication services as well as an ASCII-based protocol and a ModbusTCP protocol. An excerpt of the CiA 443 profile specification is available on request. The CiA 301 (CANopen application layer) and CiA 309 (gateway interface) are downloadable free-of-charge from CiA's website (www.can-cia.org).