Of Operation 2

UNMANNED OFFSHORE GAS PRODUCTION WITH HART NETWORKS

Choosing the HART communication protocol for all-digital communication in a wide-area network enabled one company to have real-time monitoring and control, access to diagnostics, and maintenance capabilities—all from a remote location.
Over half of the 500 transmitters on 15 platforms could be multidropped with update rates of three seconds (six devices), which resulted in substantial savings in wiring, I/O, and installation. The remaining devices (flowmeters) required a faster response and were wired point to point using digital HART communications to transmit the process data. The flowmeters used the optional burst mode, which provided an update rate of 3.7 times per second. All-digital communications provided maximum accuracy and eliminated potential errors from input scaling, conversion, and drift (see Multidrop on page 6).



Figure 24: RTU Application
Each platform’s RTU provided a link to approximately 50 temperature, pressure, and flow transmitters (Figure 24). The RTU used the multimaster capability of the HART protocol to enable the second RTU to act as a hot standby, which monitored activity and was able to take over if a failure occurred. The RTUs provided links with the emergency and safety systems and a local interface for maintenance personnel. The Modbus protocol was used for communication to the central SCADA system.

Remote-Operation Applications

VENEZUELA

GAS-LIFT PROJECT
In a Venezuela gas-lift project, HART multidrop technology was used for remote operation of offshore gas-lift production wells at considerable savings (Figure 25):

• 
  30% decrease in installation costs
  
• 
  16:1 reduction of input modules
  
• 
  Reduced cost of I/O cards in the RTU
  
• 
  Remote reranging
  
• 
  Remote access to the transmitter status for improved process uptime
  

Figure 25: Offshore Gas-Lift Project