PLC applications questions

sbailey838

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Jun 2016
Location
PA
Posts
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Hi guys, so this isn't a technical question, but rather a question to settle my own curiosity.

I've been working in a manufacturing facility that manufactures paper products, and we use PLCs for literally everything. I've been programming them for the past 4 months, and i really do enjoy it and see myself pursuing a career within this field for at least a few years, but i've been curious about how PLCs are used in other industries, renewable energy specifically, (wind, solar mainly i guess)

Also, free lancing has also been a curiosity of mine after reading a few posts on here...

Basically any career wisdom you could give outside of manufacturing would be great.
 
From what I know there are no PLCs involved in wind farms. Every turbine is identical, and whoever supplies the turbine supplies an identical controller that goes in every unit with the same programming. The SCADA system would probably be unique to each wind farm, and there could be a PLC in the substation as part of the SCADA system, but maybe not. Solar I imagine is much the same - there isn't much to program there and if it is then it is probably cookie cutter.
 
Gotcha, I have been thinking about it for a while and never really knew what COULD have been used with a PLC... what other industries are PLCs used in than?
 
I work in the geothermal power industry and we use them for all kinds of stuff. Startup sequencing of the plant, pump controls, cooling tower controls, turbine controls, burner controls, annunciators, etc. lots and lots of analog instrumentation. We also use them in the field as our RTU/ data acquisition system, well controls, pump station controls. Nothing really complicated but everything is really spread out. We've even talked about putting the control room lights on the PLC.
 
Oil and gas uses them. Water and waste water uses them. Coal, natural gas and nuclear power plants. Grain elevators. Pulp and paper, sawmills and Osb mills.
 
Solar uses them both in the construction of solar panels, and also to track the sun in more demanding applications. Some solar panels just sit fixed all day, no automation but minimum efficiency. Some have use algorithms to calculate where the sun is in the sky based on exact time and location, and point directly at it, to maximize how much is absorbed. These often use a PLC, although it may be one PLC for a whole field of panels.

V0N_hydro is right that it is pretty cookie cutter, but some of vendors decide to use PLCs to simplify things instead of designing their own greenboards. They just put the same program in every PLC, and same as they would any other controller.
 
We use PLCs in the food industry as well.

Inventory management with scale systems. Flour silos and such.
Batching systems with ingredient control. Weights and measures of many sorts.
Controlling pumps and valves for production and cleaning activities.
Controlling complex conveying systems with many possible paths and accumulation points.
Also to control boiler and ammonia systems for plant heating and cooling.
Even lighting management.

Just to name a few operations all under one roof!

There are many more possible applications as well.
 
Automotive uses them. I can't personally say to what extent they are used at the actual vehicle assembly plants, but as a Tier 1 supplier, we use them for assembly, mistakeproofing, integrating to SCADA and MES.

I have a few decommissioned PLC's at home for Christmas lights.:)
 
In general, PLC's are popular where applications are critical, unique, but not specialized. Especially where there is a lot of discrete and analog control of generic devices (i.e. solenoid valves are used everywhere but wind turbine blade positioning devices are probably specific). PLC's tend to dominate manufacturing because of this, but typically when you see applications that are many copy paste (example - solar panel controller), it's likely you'll find something specialized. Also, it's common to for manufacturers of specialized devices to also sell the controller with them.

A bit generic, but I hope that helps.
 
If an OEM is only going to build one of a particular model machine, it makes more sense to use a PLC rather than a controller developed and built for that specific machine given the overhead cost of developing the custom controller.
If the same OEM is going to build a thousand of that model, it probably makes more sense to develop the custom controller. That way the program in every machine is the same and can't be altered by the end user. When the end user calls for support, the help desk knows what program is controlling the machine.
Somewhere between one machine and thousand machines, the balance shifts from favoring the PLC to favoring the custom controller.
Also, any machine that is likely to need to be adapted to new parts or processes over its lifetime is probably better off controlled by a PLC.
 
If your going to free lance,

Don't constrain yourself to a narrow field, be open to see the possibility of PLC and programming application in everything.

Try your nearest OEM, I was sooooooo much happier when I got out of Manufacturing. They always want more. No matter how great your accomplishment, you never feel like the job is ever done. I wont even start on operators.
 
John Morris said:
I was sooooooo much happier when I got out of Manufacturing. They always want more. No matter how great your accomplishment, you never feel like the job is ever done. I wont even start on operators.
Click to expand...

While I can certainly agree with the sentiment, being in manufacturing first gave me a better perspective when I worked for an OEM, especially when you start thinking about workflow, ergonomics, and things an operator could (read will) do to muck things up.

Sadly, that's a thing lacking in some OEMs.
 
Both posts above are very true. Also, manufacturing experience is critical to have an appreciate for what can be supported from a technical/maintenance standpoint when you are in a freelance/integrator/consulting position. Without that experience, some people put some really complex solutions in place that fail due to lack of local support and comprehension after comissioning.
 
Material handling uses a lot of PLC's for conveyor motor sequencing, sorting, etc. Think of distribution centers you pass that have 100 dock doors - I suspect there are conveyor control systems in every one. I imagine there's room for a freelance troubleshooter-for-hire in many of those.
 

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