General PLC specification

  • Thread starter Kamlesh N Parmar
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Thread Starter

Kamlesh N Parmar

Help is required on what should be the general specification of PLC which is to be used for Compressor start up logic and shutdown logic
Thaanks in advance

I think you should specify the type of compressor so that one can gauge the number of inputs and outputs. it is better you do a thorough study. in general you can implement it on a 40 i/o plc with a rpm counter. Mail me if you want more details.
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please explain futher, you want to stop start from a pressuer switch or detect flow demand.

Bob Peterson

In no particular order:

1. PLC should be a name brand, preferably one the end user is familiar with, IF the end user will ever interact with the PLC. ICost is probably not that much different between PLCs. make sure you pick one your field engineers will be comfortable with or you will end up being the field engineer.

2. Almost any PLC manufacturer can do just about anything you might need. The only thing that could be an issue is if you need some kind of specialty items , such as vibration sensors that would be handy to hook directly to the PLC I/O, or need intrinsically safe I/O. You may also find it handy to have some kind of field bus capability (Devicenet for instance), or a certain type of communications capability (such as ethernet or one of the many propriatery schemes).

3. Look very closely at your list of "must haves" and "would be nice to have" features. I think you will find that virtually all the major PLC makers can accomodate your "must haves" and most will also accomodate your list of "would be nice to have" features.

4. Resist the urge to pick the lowest hardware cost solution. While this could be appropriate, the hardware cost is usually not much of an issue, compared to the overall cost, unless, you plan to make dozens, or hundreds of identical units. If they will all be custom units, the difference in hardware cost will probably be masked by the engineering and training costs,
and retraining people is VERY expensive.

5. Consider how accessible spare parts will be to the end user. Its probably not a good idea to send an odd ball PLC to rural China to save a few bucks.

6. It also matters whether this is a $5000 air compressor or a $5,000,000 hydrogen compressor. If its a very expensive piece of equipment you may want to spring for some form of hot backup PLC. Your chocies would thus be restricted by this requirement.

7. It also matters whether you are the end user or OEM. An OEM has different needs then the end user. Ideally it would be nice if the PLC chosen could satisfy both parties. Or you could be an end user or integrator retrofitting a control system to an existing unit. Particulars would be needed if you expect useful suggestions.

Bob Peterson

steve cordiner

Dont worry about, there is nothing too special required for compressor logic unless you are doing the anti-surge control as well which needs fast I/O. Go for good old Rockwell PLC5 or something, I've used them on several jobs on large
40MW, gas turbine driven compressors.