Saving data in PLC - possible?

flyers

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Sep 2006
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Hi guys,

I've come across an application in water treatment plant. The sites are using redundant PLC5 - RIO using SLC modules. The centre monitoring station running redundant wonderware scada is located a few hundred km away. They are linking using broadband (always ON, 4Mb line). One SCADA station will monitor 30 treatment plant around the states.

The PLC is reliable, but the wonderware SCADA is not reliable, there is some cases where both the SCADA workstations is down, so all the data during that period is lost.

To prevent this from happening in future, customer is looking for solution where the PLC is able to store the data itself when the workstations are down for 3 - 4 days, each treatment plant has about 100 data to be historical. So, when the workstation is UP again, all the historical data will be dump to the workstation.

Has anyone comes across any of this application before? What would be the best solution for this?

Your feedback is appreciate... Thank you.
 
!00 data is a broad term. do you mean a hundred dada points?? How often do they want the data collected and stored? Once a second? If so, that's 600/minute, 36000/hour, 864000/day. 100 turns into a lot very quickly. even more if they want a time stamp.

The answer to save the data is memory. But you have to decide how much data you want and how much memory is available to store that data. Use fifo's so the stored data is "rolling" with time.

Then you configure the system to always store and display this data, wheather the workstations are up or down.
 
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If your communication line is reliable I would take a look at Wonderware InSQL. First of all it can store date independently of status of SCADA. And it also has a "Store and Forward" service that can save data even if InSQL is down and forward data to it once it is back online. This service can be even run on a remote PC which can be specificaly dedicated for this purpose...
If you have many PLCs in different locations it might be pretty big job to enable each one of them to log data (especially if they are different). InSQL will allow you to do all logging within a day and without any travelling and any changes to existing PLCs.
 
I agree, set up a seperate computer on the network and use it to run INSql from wonderware (basically an overlay for customizing MSSQL). Lock it up and don't even put a monitor or keyboard on it once your set up.

It will do what you need it to do and can fail back and forth between whatever i/o d-a servers you might be using to collect info for intouch. Give it a big UPS as well.

Marc
 
I would be looking at putting in multiple servers utilizing Archestra. Archestra can be redundant, as well as if you have multiple strategically placed servers, the data can be stored and forwarded to the InSql data historian.
 
Oakley said:
I would be looking at putting in multiple servers utilizing Archestra. Archestra can be redundant, as well as if you have multiple strategically placed servers, the data can be stored and forwarded to the InSql data historian.
IAS (ArchestrA) might me a good idea as well but it might be just a little bit too expensive and complicated if only thing required is data logging for two existing SCADAs.
But on the other hand I would be great should they decide to expand the system, add new SCADAs with different fuctionality etc.
 
john paley said:
!00 data is a broad term. do you mean a hundred dada points?? How often do they want the data collected and stored? Once a second? If so, that's 600/minute, 36000/hour, 864000/day. 100 turns into a lot very quickly. even more if they want a time stamp.

The answer to save the data is memory. But you have to decide how much data you want and how much memory is available to store that data. Use fifo's so the stored data is "rolling" with time.

Then you configure the system to always store and display this data, wheather the workstations are up or down.
John, currently they are logging the data in the wonderware workstation every second. Yes, i know there is a lot of data for PLC size memory, but for workstation it should be fine since our harddrive nowadays are around 500Gigabyte each, this should be enough for a few years.
"Then you configure the system to always store and display this data, wheather the workstations are up or down." Can you please explain on this? The "system" you mean is the PLC? The customer is looking for a system which is able to save the data for a few days when both the wonderware workstation is down.



rPraveenkum said:
Have a redundant Scada system this will solve your purpose.
rPraveenkum, what if both the workstation are down? The chances for workstation to down is higher than redundant PLC to down, am I right?



n_lev said:
If your communication line is reliable I would take a look at Wonderware InSQL. First of all it can store date independently of status of SCADA. And it also has a "Store and Forward" service that can save data even if InSQL is down and forward data to it once it is back online. This service can be even run on a remote PC which can be specificaly dedicated for this purpose...
If you have many PLCs in different locations it might be pretty big job to enable each one of them to log data (especially if they are different). InSQL will allow you to do all logging within a day and without any travelling and any changes to existing PLCs.
Marc said:
I agree, set up a seperate computer on the network and use it to run INSql from wonderware (basically an overlay for customizing MSSQL). Lock it up and don't even put a monitor or keyboard on it once your set up.

It will do what you need it to do and can fail back and forth between whatever i/o d-a servers you might be using to collect info for intouch. Give it a big UPS as well.
n_lev/MarC, the communication line is stable & fast (4Mbits). From I understanding, there is a seperate workstation running InSQL, can we run redundant InSQL? So the existing wonderware will grab data from the InSQL instead of PLC directly?
InSQL is from Wonderware? Sorry, not familiar with wonderware thingy.



Oakley said:
I would be looking at putting in multiple servers utilizing Archestra. Archestra can be redundant, as well as if you have multiple strategically placed servers, the data can be stored and forwarded to the InSql data historian.
Oakley, multiple server means more than 2 servers running redundantly? What's the purpose of running Archestra with InSQL? I taught INSQL is able to log all the data from all treatment plant (not sure if INSQL can run redundant)? Price wise should be okie, what they asking for is a reliable system.



JohnW said:
How does that saying go?

"wonderware the data went?"
When the wonderware workstations are down, all data send from PLC will not be captured & display. so if the wonderware workstations down for 6 hours, all data within that 6 hours will be lost! They cannot afford to let this happen.




1) So, based on the replies, we can summarize that the only way to prevent data lost when wonderware workstations are down is by using another set of redundant workstation running INSQL?

2) BTW, has anyone come across a korea brand PLC which has 64MB memory built in, called CIMON? Based on the info given by our customer, this PLC is able to do data logging with it's memory size, not too sure how reliable is this PLC. Does AB has something like this??
 
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Flyers,

Yes, INSql is a wonderware product that sits on top of MSSql and allows for easy interface with all of the wonderware products that you have. It is better to have each work station use there current I/O or D-A server continue to poll the PLCs for HMI scada functions. MS/INSql could run on a third machine and collect an store the data on it's own. This data would be available to any software you wanted it for (excel Access) whatever. There is a package from wonderware called active factory which allows you to access the data inside the SQL server and chart or graph it howerver you see fit. With 100 tags, I think you could get the personal edition of INSql for about a 1000 bucks (ballpark) which I believe covers 100 tags. MSSqlexpress edition 2005 is free and would ship with INSql.

Not a sales pitch here by any strech of the imagination, but I have used it and it works pretty well.

Just curious, when you say the HMI/Scada are unreliable, is it a hardware issue (unreliable PCs) of are you having problems with WW itself or is it the PLC comms that are the problem, please elaborate a little more.

Marc
 
You can even install and run InSQL on a cluster if you can afford that :)
Creating tags in InSQL is very simple... You can just import them from InTouch...
I would redirect InTouches to get data through InSQL, but Marc's opinion is as well as mine :) There is no difference basically :)
I'd recommend you to call local WW office - I believe they would be happy to answer all your questions...
 
I guess my only issue would be if the SQLserver went down, then everything would go down. Unless of course they had multiple SQL machines. :)

Marc
 
The Red Lion G3 terminal can data log to a windows based file.

or:

Where I have had this problem I have used a PC locally and written some code to save to the local HDD if the network connection was lost. On re-establishment of the network it wrote the data to the main database on the server.
 
We have encountered the same problem. It isn't really practical to save a hundred data points in a PLC every second. That is 360,000 data points for a one hour outage.

Our solution is to decide which data elements are critical, as opposed to nice to have. Chlorine residual and effluent flow rate may be critical, water level at each and every tower may be nice to have but aren't going to shut down the whole system or endanger health.

Then, we keep track of just min, max and average for each of the data points and store them in the PLC's non-volatile memory area. You may want to do this on an hourly or daily basis, depending on the criticality and volatility of each parameter. Now you have a manageable size for the data memory. When the SCADA comes back on and reads these points you won't have all the pretty trends showing ups and downs, but you will know if any critical parameters went to problem levels during the down time.

If you really need frequent data look at chart recorder, paperless or conventional.
 
These guys have a plc that can log data:

http://www.controlmicrosystems.com/index.html

I don't know if they will be able to log as much as you are asking, but you can check it out. I have never used them. I have seen a demo earlier this year where if the SCADA and PLC are disconnected the PLC keeps saving variables. Then when the SCADA is plugged back in it receives all of the saved values. I also don't know if this feature will work with your existing SCADA, or if you need to use theirs.
 
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