[FUN] many discrete devices

[Stephen Mitschke]

> Here are some questions for the FUN. My company designs Flue Gas> Desuphurization systems for large fossil fuel power plants and refineries.> The control system has about 1800 I/O, 98% is discrete control. Plenty of> tanks, pumps and on/off valves with limit switch feedback. There is alot> of redundancy built into the system because the last thing we want is for> our system to cause an outage of the host plant. > > What is the best way to handle all the valves? > > A typical slurry pump would have four valves, suction, discharge, flush,> and drain. Should I run one segment to one pump and another to the backup> pump? > > Or should I look at a different type of bus for these devices? How do I> keep my backups separated so I don't lose both when a bus goes down?> Multiple secondary busses?> > A good portion of the I/O is in the electrical system, switchgear and> motor monitoring. Are there any Fieldbus options there? My medium> voltage equipment usually comes with control relays that have MODBUS> outputs but the 480VAC breakers are individual hard-wired I/O points to> the DCS. I remember seeing some kind of Fieldbus module that can monitor> several DI's but to the best of my recollection it didn't have any DO's.> > Thanks in advance for any information, > Joseph F. Zack, P.E. > Lead I&C Design Engineer > Marsulex Environmental Technologies

[Stephen Mitschke]

> National Instruments makes a field bus to digital input and output modules> called Fieldpoint. Your application does not look like a good one for> Foundation Fieldbus. Take a look at ASi.

[Stephen Mitschke]

> Mr. Zack> > For handling discrete signals on FF, the company Burkert has developed a> binary box (see registrated devices FF website). The reason several users> in> Europe asked to develop such a device was to avoid the introduction of a> separate infrastructure for only discrete signals, like an ASI bus. > This binary box has 4 DO function blocks. It is possible to connect 4> discrete outputs and 8 discrete inputs. The status of the input signals> are> communicated to the host via the DO output blocks. In a fieldtrial this> concept is operational. Also we are engineering a plant right now the same> way (Start up 2002). So it works!!> > But handling discrete signals in FF introduces other problems. Handling> discrete signals by FF introduces a large number of Compel Data and so> VCR's. This large number of VCR's is not supported by host systems, the> large number of CD's results in a high busload or a relative bad loop> response time (2-4 seconds). > > These problems are not caused by Burkert but by FF. In this situation I> would install PB-PA. I do know a Profibus-PA installation where discrtete> signals are handled with a loop response time of less then 0.5 sec. The> binary box is also from Burkert.> > If you would like to have more information, please feel free to email me> (chris.baltus@dsm.com).> > Regards> Chris>

[Stephen Mitschke]

> I believe smar have a device with di and do, various configs > rm

[Stephen Mitschke]

> This problem is of course related in how efficient you use the Compel> Data's. Alternate options are to use a Discrete Multiplexer Function Box.> Fisher-Rosemount Systems is providing a discrete Multiplexer with 8 DI,> and> 8 DO. The closed loop turn around time is 1 sec. and bus loading will be> minimized.> > In addition we should not forget that based on "SMART" positioners limit> switches are not required anymore, reducing the amount of discretes> substantially.> > In addition there are multiple ON/OFF valve solutions where the> manufacturer> incorporates additional discretes in their offering, see for example the> El-O-Matic offerings also approved by the Fieldbus Foundation.> > Highly discrete applications, and multiple bus structures are going very> well together as long as the HOST provides native support. Just due to the> law of physics there is NOT one bus covering all requirements.> > In this case I would say that AS-i combined with Foundation Fieldbus would> be the proper implementation.> > For more direction or input don't hesitate to contact me,> > Richard Willems

[Stephen Mitschke]

> Dear All,> > That's right. The Smar device has 16 DI and 8 DO. Two of the DI can be> used> for pulse input from turbine and vortex flow meters etc. You can do some> logic in it too.> > There are many ways to reduce the need for DI and DO:> - Flowserve has an FF on/off valve> - Rotork has an FF electrical actuator> - At Smar we have a small gauge pressure transmitter that you can use> instead of pressure or level switches (with the added benefit of> diagnostics> so you never have to wonder if it is "no trip" or the switch is "dead").> > Jonas>

[Stephen Mitschke]

> Don't forget Discrete products from Buerkert, El-O-Matic, Ledeen,> Pepperl+Fuchs, TopWorx, and probably others. SMAR is not the only company> offering Discretes with diagnostics and enhancements.> > Remember when using FF, you can use the multi-state discretes in the> field, these can eliminate the need to use host blocks to perform the> discrete control.> > +Sean Vincent> Fieldbus Inc.> > Ian,> In addition to Smar's DFI (FF Registered) linking device being able to> handle discrete I/O we also have an H1 device that has 16 DI and 8 DO> which> also supports and executes FF function blocks. This is an excellent> solution> for "remote PLC like control over the H1 bus".> Please contact me or go to www.smar.com and look for the DC302 under> System302.> Thanks Bill Tatum>