We want to purchase HART communication I/O modules for DCS (Invensys I/A series) installed at our fertilizer plant. Does any body know which process variables are accessible in smart transmitters and smart positioners using HART?

The I/A series FBMs have the capability to access four process variables on HART.

Specifically for I/A series HART FBMs which process parameters I can access? e.g sensor temperature, valve travel, supply and actuator pressures in smart positioner, can we get them for continuous monitoring?

 

I can't answer for Foxboro's, but Siemens' smart positioner senses valve stem position and corrects that position to the desired setpoint. Doing so does not involve measuring supply and actuator pressures, so supply and actuator pressures are not available as HART variables.

I would think that one would pay a very large premium for any pressure measurements by a valve positioner, but maybe Foxboro does so.

Siemens does provide a positioner body temperature variable.

From memory, I think Siemens provides the number of starts and a mean value of the start position, or something close to that, but does not provide valve travel, but I'm not near a manual. I suspect you'll have to check out the Hart parameters page of Foxboro manual for details.

 

What the four "dynamic variables" in a HART device are depend on the device type. Every manufacturer and device model can be different.

Keep in mind that HART is rather slow so the data is not real-time. It is not suitable for control. For real-time control you need Foundation fieldbus.

To learn more about about HART take a look at the yellow book "Fieldbuses for Process Control: Engineering, Operation, and Maintenance" buy online: http://www.isa.org/fieldbuses

Cheers,
Jonas

 

Hi there,

In Smart positioners you can monitor the actual position of the valve and a alarm contact.

The alarm contact can be setup to alarm if the valve position on zero gets to far away from a preset value. This is useful to see how much the plug and seat have worn out and gives a alarm that a overhaul on the valves is due. Never seen it being used by anyone though. Personally I think this is a bit of a overkill and believe this will cause nuisance alarming if it is used.

We normally are only interested to monitor the feedback to confirm the valve have actually reached the commanded position from the controller.

In a Smart transmitter the only thing you can monitor is the actual process value like temperature on a temperature transmitter and pressure on a pressure transmitters ext.

There is no need to monitor anything else in positioners or transmitters.

Using something just because it is there, is not always such a good idea. You should really try to minimize your monitoring not maximizing it.