so i normally deal with the machine level of controls a difficult customer is forcing me to level up. machine was built as a stand alone unit, no comments on the controls system design, heck when i ask the project engineers where the system spec information was i was told there isnt one. customer is now here and asking a bunch of questions asking for changes, problem is one unit is crated (these are large gas engine driven natural gas compressors) and should be in the air to India in a few days, the other one is being packed for air freight as well and the last one is going by boat in a few weeks. the customer is now telling me these three systems need to connect to a DCS which is all siemens and im AB. had they spoke up earlier i could have added a modbus module and they could get all the information they want.
so he is asking me about OPC compatibility, which from my research would an appropriate response be 'AB is OPC compatible via third party solutions' unless there is something i am missing?
Short answer. Yes, AB is OPC compatible.
And NO, I don't recommend using it.
I have struggled with OPC since 2003. RSLinx is a decent server, but it gets confused sometimes and stops serving data. The tools inside OPC for monitoring the communication status are not reliable in telling you when it has stopped working. I now use a heartbeat, number of seconds since midnight, that is moved by the polling machine to another register that is written to the PLC.
I would recommend getting all of your OPC software from one supplier if you can. Otherwise, they argue about whose problem it is to fix any given issue that you find. That said, matrikon technically has support ... but they ask you to turn on logging for every problem, gather data for a week, and send them gigabytes of information. I don't recommend their software. Particularly the DataManager, which reads data from one source and writes it to another ... like reading from an ABB system and writing it to a ControlLogix for alarming.
I've spent a lot of money in the past few years getting anything that matters (in the control sense) off OPC and onto:
- a DeltaV VIM interface with the ControlLogix
- a DNP interface with our ABB hoist and power gear
- a Modbus/TCP interface to our power meters
- a serial modbus RTU interface with our standby generators
All of these solutions have been at least an order of magnitude (10X) more reliable than OPC. For the DeltaV VIM portion, it's more like 2 orders of magnitude more reliable (100X). I don't actually know what the issues are with OPC ... but between patches for the OS that the computer runs, patches for the various OPC software, security exceptions for the mis-behaved software that is part of OPC ... it just isn't reliable. *AND* no one seems to understand it all. There are not many tools in the toolbox for troubleshooting. Rebooting PCs, restarting services, and rolling back OS upgrades ... that's about it.
Our PI system will still be using RSLinx and an OPC connector to gather data. I think there is a connector running on our DeltaV Application station as well. Those are someone else's systems, and they deal with it when it stops working.
I should be OPC free, in our controls world, in about a month.