Case History 198: Cascade control overcomes valve problems Michael Brown Control Engineering
Fieldbus & Industrial Networking
A large petrochemical refinery asked me to perform an audit on several critical base layer control loops. This article deals with a problem found on a valve controlling the flow of fuel to a heat exchanger.
Read more...Loop signature 28: Things to consider when tuning. Michael Brown Control Engineering
Editor's Choice Fieldbus & Industrial Networking
I was giving a course at a remote mine in the middle of the Namibian desert. We were discussing tuning responses, and as I always do on my courses, I mentioned that in my opinion ¼ amplitude damped tuning is not desirable, and is in fact not good.
Read more...Case History 197: Bad reboiler temperature control. Michael Brown Control Engineering
Editor's Choice Flow Measurement & Control
It is very important that reboiler temperature controls operate well in petrochemical refineries, or the product quality can really suffer. I was asked to check such a control in a refinery where they were having problems with one of these controls.
Read more...Case History 196: Unstable condensate level control. Michael Brown Control Engineering
Editor's Choice Level Measurement & Control
The operators in a petrochemical refinery were having great trouble in trying to stabilise the condensate level in a vessel, and this was adversely affecting other loops downstream. Several unsuccessful attempts had been made to retune the controller.
Read more...Loop signature: Tuning part 4 processes Michael Brown Control Engineering
Editor's Choice Fieldbus & Industrial Networking
The purpose of this particular article is to try and give those unfortunate enough to have to use SWAG (scientific wild ass guess) tuning a bit of an idea of how to go about it, and even more importantly some understanding of a couple of basic principles.
Read more...Case History 195: Unstable reboiler steam flow Michael Brown Control Engineering
Editor's Choice
A high-pressure steam flow control in a reboiler on a column in a petrochemical refinery continually cycled when placed in automatic. Several attempts had been made to tune the controller, but these had been unsuccessful.
Read more...Loop signature 25: Tuning part 3 - Results of tuning a particular simple self-regulating process by several different methods. Michael Brown Control Engineering
Editor's Choice
A couple of SWAG methods of tuning were given in the previous Loop Signature article. I have tuned a simple self-regulating process using those methods, and two other tuning methods, one of them being the sophisticated Protuner tuning package, which is the system I employ. The tests were performed on a very accurate and powerful simulation package, and the results are compared below.
Read more...Case history 194: Boiler level control problem. Michael Brown Control Engineering
Editor's Choice Fieldbus & Industrial Networking
A boiler level control in a petrochemical refinery was causing problems, as the level was cycling badly and taking a long time to recover from sudden load changes. In addition, there were frequent high-level alarms.
Read more...Case History 193: The big dipper. Michael Brown Control Engineering
Editor's Choice
This article gives an example of an important flow control system for flare gas in a petrochemical refinery. The control was suffering from serious problems, often cycling severely, and at other times the flow process variable (PV) would suddenly move quite a lot away from the setpoint (SP).
Read more...Loop signature 23: Tuning part 1. Michael Brown Control Engineering
Editor's Choice
This is the first of several articles dealing with the subject of tuning. I have found that many people think that optimisation consists solely of tuning. I would stress once again that tuning is the last thing one should do when optimising regulatory controls.
printer friendly version