process control on refinery unites

[wq22030202]

dear friends
can you kindly tell me how to decide when we use cascade control loop or feedforward control or just single loop control etc? do you guys have any recommendations or handbooks?
thank you sincerely!

[nhan]

- a single loop is used with the SISO process without more than one disturbance/setpoint change demand or a upstream disturbance changing fast to the response time of the loop
- Feedforward is used as there is more than one disturbance or a disturbance changing fast to the response time of the loop, can have may feedforward loops integration
- Cascade is used as to eliminate the non-linearity of the valve; or when we can save expense for the control device (i.e., the control valve) and speed up the response of the whole system as two or more processes can use a same control device to control all of those process, this is often with level and flow control- one condition is the lowest/cascade/secondary process must have the response time 3-5 times faster the upper/master/primary process

Access this web sites: opticontrols.com see his blog with many interesting articles
or controlguru.com

[wq22030202]

thank you for your reply. I will look up.