3 element control for boiler water level

Hi all,

I'm currently doing this 3 element control for boiler water level. The 3 elements were water level, steam flow and feed water flow. I have the idea of using PID to control the control valve at the end point but cant really figure out how to cascade or loop the PID(s) to get the result. There is only 1 set point for use input which to maintain the boiler water level at certain stage but it has to be controlled by all these 3 parameters.

Yokogawa is having this 3 element controller YS-1700 which can direct input all these 3 parameters and come out with an anologue output. But no idea how they program it.

Appreciate anyone who can help.

Thanks and regards,
Kenshin

Hello,

first you should read this. How big is your boiler and what power/steam capacity?
Steam and water flow are needed to avoid inverse response when there are changes in steam flow (consumption goes up or down). Simple single loop controller is not sufficient to handle shrink and swell which are causing inverse response especially if level is measured with differential pressure transmitters.

Read and understand this article, it will give you main idea about overall structure of a drum level control.

Regards,

Pandiani

Hi Pandiani,

The boiler capacity is 80T/Hr. I have the flow range of 0-50m3/Hr for both stream flow and water flow sensor. What I wish to do now is controlling the water level with these 3 parameters by using PLC. Generally I know there is PID involved in the control but I have no idea how to cascade or loop them to get the entire analogue output.

Just for an example let says the end user would like to maintain the boiler water level at 50%. So how the PID should works to achieve this?


Regards,
Kenshin

Hi KeNshIn,

Did you rean the article on controlglobal.com?
You should read this too: http://www.controlguru.com/wp/p44.html.
This should be more than enough to setup the correct structure.

Regards,
Pandiani

Ckeck this out....
http://www.spiraxsarco.com/resources/steam-engineering-tutorials.asp
They even provide SAMA diagrams for free.
here is more....

http://www.spiraxsarco.com/resource...se/automatic-level-control-systems.asp#head29

Bitmore

Ken

I did not recall T used to describe boiler rating - T is temperature - so looked into
http://www.spiraxsarco.com/resources...-tutorials.asp

That is a good resource and I recommend it also.

Steam boilers are nothing to take lightly and that goes double for controls. Boiler accidensts are often fatalities and in some cases result in new construction.

Here in Seattle Washington USA the local government is quite stringent - licensed operators, licensed control persons, and then there are the insurance companies who inspect the boilers.

Spirax handout
http://www.spiraxsarco.com/resources...ems.asp#head29

on level control was also good and also mentioned operating boilers in parallel.

This is not as easily done as it appears - especially so if you have varying load on the boiler(s).

I would carefully consider my ability to do this if I were you
AND what the local government requires and what your insurance company requires.
Dan Bentler

Hi all,

First of all thanks for all the replies but is sorry to say that all the info and links provided it does not help me much. Most of it is only the basic control architecture for the boiler 3-element control which I already knew in the early stage. In fact I wish to have some very details info where I cant get from the internet like the relation graph for the 3 elements, the detail close loop control, the relationship between the difference for steam flow and water flow, etc...

I wondering any1 here knows Fatek PLC? There is people who manage to do this 3 elements control in China. Hope there is expert here who can help me. Thanks in advance.


Regards,
-KeNshIn-

Ken,

I'm from Yokogawa Malaysia and I'm the windows person for Boiler Industries which is dueling with all the boiler control including the 3-elements control for drum level by YS1700.

Please contact me if you would like to have more information.

[email protected]