Alist
How many of you are using networks for your hart smart devices? We are considering a large project to interface hart devices with our existing Ethernet and controlgix networks for maintenance and diagnostic purposes. If others would share their experience and anything that they would do different, I would be interested to hear the details.

Thanks, Mark

 

My last project at Rockwell (I'm now independent and only slightly biased to RA products) used some smart cards that supported HART along with the analog I/O. The provider had sample logic avaialble for use on ControlLogix platforms.

Spectrum Controls has a line of HART enabled modules; we used their 1756sc-IF8H modules for this work. The customer did not want to network the multiple transmitters on a single comms. loop for reliability so I can't comment on doing that.

The data that we could read/write was not limited and the interface worked with a bit of tweeking from the sample code. It does take some time so be sure that you really need all that data - our biggest issue was in preparing screens to interface with the module and take advantage of the information we received. Once the first RSView screen was done we could replicate easily so if you standardize the interface, it may be worth the extra time required.

As far as having it work well, once the module and code gets working it just keeps on doing its thing. We set the scan up to work every 15 seconds for updates so we didn't take too much scan time for data that wasn't being displayed often.

Good Luck,
Russ Kinner
SSOE, Inc.
Phoenix, AZ USA

 

Russ,

Thanks for the reply. I did look at the spectrum website to see the modules available and read how they work. What I question is how they are wired? It looked to me that the transmitters were landed on the interface module and there was logic and messaging from the interface module to the PLC. I had envisioned the transmitter connection to a PLC analog card and then a duplicate connection to the interface module that was dedicated to communication with the transmitter.

Regards, Mark

 

Mark,

There are many ways to get the HART signal from a transmitter connected to a PLC or DCS into a separate PC for maintenance/diagnostic purposes. It will depend slightly on what software package you want to use, has this been decided yet? Easiest way is to insert pick-off points at some point in the 4/20mA and connect these to a suitable HART multiplexer system.

I don't want to flood the AList with publicity so please contact me off line if you want more details of what solutions we have.

Steve
syates @ mtl-inst. com
www.mtl-inst.com

 

You are correct, the HART signal is superimposed on the 4-20 mA wires (as is typically done with HART tranmitters I've worked with). That is the advantage that originally made HART equiped transmitters popular; you could hook a HART handheld programming interface on the 4-20 mA wires going to some tough access locations from the relative comfort of a control room or marshalling panel.

Spectrum has just taken the next logical step in using that communications ability; you don't need the handheld unit any more. Given adequate time and programming effort you can calibrate a transmitter and access any of a number of parameters in a transmitter from an HMI screen.

I am unaware of transmitters that make the HART communications available via a separate circuit. I can't see any reason why you couldn't do that but for transmitters that are loop powered it means running additional wires. Others on this list may have done what you are suggesting but I haven't.

Regards,

Russ

 

Hi Mark,
I'm not sure of your exact project requirements but if your instruments loops are in going into a "hazardous area" and you need the loops to be intrinsically safe then i can say you should definately look at MTL's MTL8000 system. The 8000 is a "white Delta V", i believe the Delta V's made by MTL for Emerson, but don't qoute me it.

With our set up on top of the 4-20mA signal, you have access to the 4 hart varibles via Modbus TCP. It also has two configurable serial ports that can be set up with a few different comms protocols. We are using one of these ports as a Modbus master communicating to 16 looped Micromotion flow meters bringing in a lot of variables via Modbus. The other port is linked to a lot of our telemecanique intelligent motor starters for non critical information gathering.

This is working out ideally for us as on top of the aforementioned we also have access to the HART instruments over ethernet from anywhere in the plant for remote parameterisation and maintenance via Endress & Hausers Fieldcare (we may move to Emersons AMS down the track), but it will talk to a number of instrument management packages. This is making start up of this plant a treat.

I believe it can also be used with an add on to set up H1 nodes to Fieldbus instruments but i haven't really looked in to it too much.

Cheers - Chris.

 

In my personal opinion, only if you have an old system with analog modules not supporting HART do you use so-called multiplexers in parallel to tap into the HART signal. Most process control system less than 10 years of age should have HART already built-into the analog module and be able to pass HART data through to software.

Many important functions such as periodic checking of instrument health and detail diagnostics can now be done from software on a workstation at a central location - there is no need to send a guy into the field with a handheld who you need to radio in order to find out what's happening. However, handheld communicators cannot be completely eliminated. If a genuine problem is indeed found with a device, you need to go into the field to fix it - and once you are in the field it is mighty convenient to have a handheld to communicate so you don't have to radio back to the control room to get things done! This includes setting tag/address, stroke valves, calibration trim, zeroing mounting position or wet-leg, and many other things. You need both a workstation and a rugged field communicator you can hold with one hand and operate with the other.

I think you should not be spending any time designing screens in your HMI. It is time consuming, error prone, and has to be redone if devices are replaced or added. Instead you can simply use a device management software that supports EDDL. EDDL is also the technology that makes your handheld communicator tick.

To learn more about HART and EDDL take a look at chapters 3 and 11 of the yellow book "Fieldbuses for Process Control: Engineering, Operation, and Maintenance" buy online: http://www.isa.org/fieldbuses

Jonas

 

I have worked in IOCL refinery in INDIA. You can use Cornerstone Software along with P+F multiplexers modules. Since HART signals are superimposed on 4-20ma DC, it will be communicated through separate communication to PC. It's like PC HART communicator.

 

A + List,

So far I have looked at Endress Hauser Fieldcare and Yokogawa PRM. The areas in my plant are not hazardous, although one concern I have is adding hart comm modules to crowded existing panels. It may require adding panels. Since we have a fairly large plant network of PLCs there is careful planning being done to place modules strategically. There will be about 100 instruments added in this initial phase and once in place, more will be added as needed. The network hardware I have looked at is P&F, Spectrum and MUX2700. I think I will take a look at MTL. It is good to hear that MM flow meters can be on the Hart network because that is one requirement for me. Would those MM flow meters happen to use the 2700 series transmitter?

I have enjoyed everyone's response, thanks. Keep those comments coming.

Mark

 

A new source for information on EDDL http://www.eddl.org