PID Nightmare

Peter Nachtwey said:

Ditto. I see a lot posts and where the OP is clueless and shouldn't find another job.



I also think the OP's managers should be fired. It is obvious they are just as clueless as the OP. It is obvious they threw the OP under the bus on this one.

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Should't (should not) or do you meaned to write "should" find another?

Lare said:

Should't (should not) or do you meaned to write "should" find another?

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Well it makes no sense if "should not".

Geez Peter, if you are going to bash someone at least use correct grammar.

Lare said:

Should't (should not) or do you meaned to write "should" find another?

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I stand corrected.

Thank you to those who offered their help and expertise on this issue. It has been resolved. My respects for those who are willing to help those of us who still don't understand some concepts in the more advance level. Happy Thanksgiving

mark.t said:

Thank you to those who offered their help and expertise on this issue. It has been resolved. My respects for those who are willing to help those of us who still don't understand some concepts in the more advance level. Happy Thanksgiving

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Post up the resolution, that’s how we all learn, from experience and the insight of others.

any mentioned of using PI controller here?

I think it is unlikely that a steam & chilled water would flow through the same jacket, in my experience such extremes of temperature would buckle and crack the diffusers in the jacket.

I think the valve operation is critical...when I first read the post, I interpreted it as a single coil valve. Has this been verified? What about feedback? Is it just on/off control? Without further input from OP.....

rajputaman04 said:

I think it is unlikely that a steam & chilled water would flow through the same jacket, in my experience such extremes of temperature would buckle and crack the diffusers in the jacket.

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Pretty common in food. Heat the jacket to cook, then cool the same jacket to bring temperature back down.

Not saying that is a good design or anything.

I agree, I worked in the food industry for over 30 years and never came across a vessel with single jacket for heating & cooling with the exception of what was heat/cool but the temperature extremes were 160 Deg C for heat & 80 Deg. c for cool using oil so no real massive change in temperature cooker coolers where cooking was 90-105 (105 under pressure) and cooling to < 4.0 Deg. C all had separate jackets.

parky said:

I agree, I worked in the food industry for over 30 years and never came across a vessel with single jacket for heating & cooling with the exception of what was heat/cool but the temperature extremes were 160 Deg C for heat & 80 Deg. c for cool using oil so no real massive change in temperature cooker coolers where cooking was 90-105 (105 under pressure) and cooling to < 4.0 Deg. C all had separate jackets.

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We manufacture couple of hundreds milk batch pasteurizers each year which use the same jacket for heating and cooling. I bet there are hundreds of thousands of them scattered around the world but you won't find them in big food/milk processing plants.
These jackets are usually constructed using pillowplate heat exchangers made on specialized laser welding machines.
https://en.wikipedia.org/wiki/Pillow_plate_heat_exchanger

Usually water is used as heating/cooling medium and is circulated through the jacket. This way we use the same jacket to heat up the milk up to 97 deg C in the vessel with water temperature in the jacket reaching up to 130 deg C and then almost immediately start cooling the milk to 4 deg C using a water chillers or an ice bank that can provide water close to 1 deg C or even lower when glycol is used.

Some people on this forum also forget that public forum were created so anyone can as anything they want as long as it's within the rules.
If you don't like the posted question just don't participate in the discussion.
There people like me who just don't know everything yet and sometimes need some tips or guidance from more experienced guys.

Peter Nachtwey said:

The scaling is much different. Water will cool off faster than steam will heat but it depends on the temperature difference.
The time constants will be different too.




You are guessing and what are the units of the gain?


I still want to know how the steam valve works because it makes a huge difference.


On thing the OP can do is record a trend where the CV changes in steps and record the PV. We are guessing otherwise.

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Yes, the gains are different, hence use adaptive gains and Velocity control. I've had success doing that with PIDE's and have generally followed the advice of this white paper for Rockwell. I just did one a few months ago with a chiller loop and steam control for a shear mill.

Peter, I've used alot of your teachings over the years and respect your knowledge, so would be interested in your take on this paper: https://literature.rockwellautomation.com/idc/groups/literature/documents/wp/logix-wp008_-en-p.pdf

drbitboy said:

It always cracks me up when a "new" query comes up here, and I poke at The Google, and the top useful responses are a few other threads on this very forum.


I mean, do some of us have a rare magical ability to select the right keywords, or are the OPs just not making the effort? I can't believe it's the former, and I don't like the way the latter thinks unkindly of the community, so maybe it's summat else.


But why does it feel like we're in that jokes-by-number story?

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I haven't read the entire thread and have no clue what it's about but this reply interests me.



You may have the basic knowledge to understand the topic and those asking the questions do not and while they're willing to learn their lack of those basics require answers that they may understand; and only they know how basic that is. So the answers you found in a web search maybe completely nonsensical to them.



I remember when I was trying to understand what sinking and sourcing is for PLC input and outputs and found every answer on the net to be a non-answer. Why did they keep referring to PLC inputs as sinking when they were sourcing or vice versa? I don't remember how I finally figure out that sinking and sourcing refers to the transistors inside the PLC that I'm connecting my input (sourcing) sensors to. I was looking from outside in rather than inside out. Now some basic knowledge of PLC hardware and electronics, and I do mean very basic would've made it easier to understand the terminology.



Here's a question:

What is a right hand spring?

kalabdel said:

Here's a question:

What is a right hand spring?

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The opposite of a left hand spring {To your point about non-answers}

robertmee said:

The opposite of a left hand spring {To your point about non-answers}

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It may be a non-answer but an unexpected one and likely the answer to have the most agreement.