Flowserve MX HART Field Unit - Manual (Page 11)

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MX/QX HART Field Unit FCD LMENIM2340-00 – 1/14
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2.2.2 MX/QX HART Interface Board
The MX/QX HART field unit interface board is installed in the actuator controls compartment (Figures 2.1 & 2.2 and
Tables 2.1 & 2.2). This unit permits the actuator to be controlled by a DCS or other network host over the HART
network.
The following commands and feedback information are transmitted through this unit:
• OPEN, CLOSE and STOP commands
• ESD (Emergency Shutdown) commands
• Partial Stroke Test commands
• Unit output torque (0-100% rating)
• Go-to-position commands
• Actuator status, alarm and diagnostic messages
• User analog input feedback
2.2.3 Network Host
The HART network is a master/slave communication protocol. Communication to each slave (MX/QX field device) is
initiated by a master (system host device). Two masters can connect to each HART loop. Normally, the primary master
is a DCS, PLC, or PC. If desired, a handheld communicator or PC can serve as the secondary master.
2.2.4 Network Cable
Network cabling should be in accordance with the HART Communication Foundation guidelines. In general, wiring for
HART devices is the same as for conventional 4-20 mA instrumentation. It is recommended to use individually shielded
twisted pair cable. The minimum conductor size is 0.51mm diameter (#24 AWG) for cable runs less than 1500 meters
(5000 ft.), and 0.81mm diameter (#20 AWG) for distances up to the 3000 meter (10 000 ft.) theoretical limit for HART
communication. Please note that the electrical characteristics of the cable, especially capacitance, and the number of
network field devices can affect the maximum allowable cable length.
To prevent signal loop interference, tie all cable shields together and ground at only one point.
2.2.5 Typical HART Network Configuration
A typical MX/QX HART system is shown below:
Figure 2.2 – Typical HART System With a DCS Host