Gases & Instrumentation - March/April 2009

and asset management that encom-passes the SIS and the basic process control system. In this way, managers can make faster, more informed decisions about protecting people, equipment and environment, as well as a company’s bottom line.”

For a large offshore operation or a remote industrial plant, the cost savings could be millions of dollars.

Adopting a Universal
Communications and Sensing
Platform

infrared.

The XNX Universal Transmitter by Honeywell Analytics is one example of a universal transmitter. It accepts any combination of milliamp or millivolt signal inputs, converts the inputs to a standard HART digital communications protocol, and transmits the data from anywhere on the production area to the control room via an economical HART digital data link over a twisted wire pair. One twisted wire pair replaces expensive dedicated wires. Modbus or Foundation

Not so long ago, monitoring different gas families (toxic and flammable) meant using different gas transmitters — each with its own gas sensing technology, configuration challenges and maintenance problems. Today manufacturers are moving away from the stand-alone transmitter to the universal transmitter. Today’s most advanced universal gas transmitter offers a common platform that supports all major industrial communications protocols including HART, Modbus and Foundation Fieldbus (see Figure 2). Caption. Universal communications platform In addition, the universal gas detection/ transmitter platform can be built to support all major gas sensing technologies—including catalytic bead, electrochemical, point and open-path

One hour of
downtime can cost
an oil producer up
to $250,000.

H1 Fieldbus are optional protocols, and provide additional communications capabilities.

With standard HART, operators can access programming and status information for each channel from the control room, or from any termination point using the universal transmitter’s interface or by using a standard HART hand-held communicator for interrogation of the unit.

All process, status and diagnostic information can be accessed by the HART-based control system.

The transmitter can be powered by tapping into a junction box for rapid deployment in the field. For complex systems, the transmitter can be connected to an explosion-proof, intrinsically safe controller that operates on multiple channels (examples: 10-channel Honeywell Analytics HA71 model or 4-channel Honeywell Analytics HA40 model). The transmitter can also support a smaller, dedicated gas detection system where special mobility may be desired, as is found in a lightweight solar-powered wireless gas detector. The universal transmitter supports all sensing technologies through a modular choice of inputs accepting catalytic bead, electrochemical, point and open-path infrared sensing devices for both flammable and toxic gas detection. Together, these form the basis of a universal gas sensing platform (see Figure 3).

With these multiple sensing options, and Foundation FieldBus and Modbus providing multidrop network support, the universal gas transmitter effectively reduces wiring and accessories. For example, one can install ten gas detectors together on a bus system while reducing wiring requirements from 30 wires to merely four.

Finding Success in the Field:
A Summary

Figure 2. Universal communications platform

With improved diagnostics, the safety manager on the offshore oil platform mentioned earlier now has a higher degree of confidence in his ability to make informed decisions. He knows exactly how much sensor life exists in each gas detector on the system because the database provides him with a calendar countdown and timely alerts. Armed with this knowledge, he can schedule appropriate maintenance accordingly.