Schneider/Modicon M340
I am in full agreement with GeoffC - hard to go past M340 and Unity for something of this size with modbus protocol I/O.
If price is really a problem then maybe look at something like Wago with CoDeSys, but over a 20 year life span the cost of hardware and software is negligable (read approaching zero in relative terms) compared to the cost of engineering, support and possible downtime.
At my company we do quite a few detailed "technology evaluations" to select the appropriate PLC/DCS for clients (sometimes very large multinational oil&gas and mining companies) - it almost always comes down to quality and availability of local support being the key differentiator.
It is also surprising how many big name brands can score poorly on support, depending on the size of their local market.
I am in full agreement with GeoffC - hard to go past M340 and Unity for something of this size with modbus protocol I/O.
If price is really a problem then maybe look at something like Wago with CoDeSys, but over a 20 year life span the cost of hardware and software is negligable (read approaching zero in relative terms) compared to the cost of engineering, support and possible downtime.
At my company we do quite a few detailed "technology evaluations" to select the appropriate PLC/DCS for clients (sometimes very large multinational oil&gas and mining companies) - it almost always comes down to quality and availability of local support being the key differentiator.
It is also surprising how many big name brands can score poorly on support, depending on the size of their local market.
