Sunday, August 06, 2006

This document discusses the tuning of anti-surge controllers on centrifugal compressors, most of which are designed around standard proportional-integral controller algorithms, possibly assisted by various vendor-specific techniques to ensure that the recycle valve opens when needed. Being a PI (or PID) controller, its tuning is actually no more difficult than any other process controller. Read more

posted by John Greene @ 1:59 PM 1 comments

Monday, March 20, 2006

I am frequently asked to visit offshore production platforms to sort out problems with the oil export or the produced water quality where the ultimate issue is not poor control in the export or water-handling systems but due to over-aggressive level control at the reception end of the process. Read more

posted by John Greene @ 9:08 PM 0 comments

I bought a copy of U-Tune (www.contek-systems.co.uk) recently, partly cos I know the guy and mainly cos its only about £100. It worked well with a turbine diesel fuel system last week and its easy to use. Read more.

posted by John Greene @ 8:45 AM 0 comments

Friday, March 17, 2006

From EngineeringTalk: "Keeping process control in tune"

Tuning package gives process control engineers direct input into the process identification phase and provides easy comparison of test results. Read more.

posted by John Greene @ 9:08 AM 0 comments

Wednesday, March 15, 2006

High and low output select logic is used when two controllers are adjusting the same control valve. If not implemented correctly, integral windup will result in process instability. Read more

posted by John Greene @ 8:35 PM 0 comments

Tuesday, March 14, 2006

Split Range Control

A very common control scheme is split range control in which the output of a controller is split to two or more control valves. This article introduces the correct way to implement split range control. Read more

posted by John Greene @ 4:41 PM 0 comments

Observing and Analysing Process Data

There is frequently a tendency to ‘leap in’ and tune control loops regardless of the actual problem. It is very often the case that process instability has its root cause in operational or instrumentation issues rather than inadequate tuning. So the very first stage in approaching a tuning exercise is to observe the data. This article introduces the importance of collecting historical trends with sufficient resolution to enable fault-finding and process-learning. Detailed analysis at this stage may indicate that the problem is not a tuning issue at all. Read more

posted by John Greene @ 4:41 PM 0 comments

PID Tuning Tool based on years of offshore experience (Automation.com)

The low-priced U-Tune PID tuning package by Contek Systems Ltd was designed by hands-on process control engineers using their extensive exposure to process tuning and optimisation.

Controller tuning is something every instrument engineer or technician claims to be able to do. However, when it comes down to the facts, very few have the insight and experience to really improve the process performance and squeeze more oil out of the ground. Often it’s not the controlling tuning that’s at fault, but faulty valves and instrumentation, poor implementation of the control scheme and misinterpretation of the process data. That’s the human part of tuning: being able to see past the ‘obvious’ problems and to identify the real issues. The other part is having the right tools.

Contek Systems’ U-Tune PID Tuning package was produced after years of problem solving and de-bottlenecking control systems for the North Sea oil and gas industry. Although the vast majority of processes can be characterised by simple delay-lag dynamics, many expensive tuning packages fail to cater for the excessive noise and disturbances typifying the process response. U-Tune succeeds by giving the engineer direct input into the process identification phase and by providing easy comparison of test results.

U-Tune accepts text data, maybe downloaded from a trend display or logging device, or takes waveform files directly from Dataq data acquisition equipment. Tuning parameters are calculated in all the normal forms (gain, proportional band, repeats per minute, seconds per repeat etc.) and for the standard controller algorithms (series, parallel and ideal).

Take a look at Contek Systems’ website for other control engineering software and technical articles, even a free tuning calculator. U-Tune can be downloaded from the website for a 7-day trial.

posted by John Greene @ 4:41 PM 0 comments