HtNode and 3095FT provide EFM System

Year 2000 Readiness Disclosure

Arcom's HtNode is currently being used in the Shell Calumet (Louisiana) gas plant as part of its recent measurement automation project. The HtNode, in conjunction with the Rosemount 3095FT flow transmitter, allows the host system to acquire process variables, read historical log data, and update gas composition data using standard Modbus protocol.

The overall system consists of the SCADA/2000 host software package acquiring data from Electronic Flow Measurement (EFM) devices, Gas Chromatograph devices, and Remote Terminal Units (RTUs). SCADA/2000 is a full-featured SCADA package provided by Integrated Information Technologies in Houston, Texas.

The HtNode connects to multi-dropped Rosemount 3095FT flow transmitters on a 2-wire connection, and communicates with them using HART protocol. All device-specific information in the transmitters is available to the HtNode. Data from the transmitters are stored in Modbus registers, allowing any Modbus host to access the information. In this application, the SCADA/2000 program is the Modbus host system.

SCADA/2000 retrieves the 3095FT process variables approximately every five minutes via the HtNode. Hourly or upon operator demand, the HtNode is commanded to collect the hourly and daily log information from the 3095FT.

SCADA/2000 acquires gas composition data from Applied Automation gas chromatographs, and calculates compressibility constants using AGA3 calculations. This information is downloaded to the 3095FT via the HtNode every 15 minutes, so that the flow calculations are adjusted dynamically based on composition of the product. Data is also acquired from Daniels 2500 flow computers and RTUs.

The Rosemount 3095FT flow transmitter was chosen by Shell Calumet because it provides greater accuracy, has a smaller physical size than many flow computers, and has a competitive price . The 3095FT provides differential pressure, absolute pressure, and temperature inputs on the same transmitter, and uses the HART protocol for communication, including many device-specific commands for the historical and configuration data.

Though the 3095FT includes many advanced features, the challenge was to access its information using HART. The transmitter comes with a Windows-based software package to manually retrieve the historical log information; but this didn't provide the system automation required by Shell's Calumet facility. Because the HtNode operates as a stand-alone protocol interface between HART devices and a Modbus host, it was the ideal choice for automating the retrieval of information from the 3095FT.

The HtNode is a standard off-the-shelf product that interfaces between one or more HART devices and a Modbus host. A configuration utility allows the HtNode to be configured to use any device-specific HART protocol command. Programming capabilities allow automated sequences to be developed, including comparisons, branching, and data manipulation. The 3095FT program for the HtNode uses many of these advanced features to simplify the work required by the host.

UK - Tel: 01223 403410 US - Tel: 888-941-2224 other European contacts