【Q&A Question 058】February 27, 2017
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This post was last edited by 955559 on 2017-7-21 21:59. [Q&A Question No. 058] How to put a cascade loop into operation on 2017.02.27? The reference answers will be visible after responding; points are awarded by identifying the key points. (Unless otherwise specified, all questions and answers are based on hydrogenation units.) ) First, feed the secondary meter of the cascade loop into automatic mode, then feed it into the cascade system; finally, feed the main meter into automatic mode. 2017 Q&A Summary Thread (updates have begun) http://bbs.hcbbs.com/thread-1657793-1-1.html 2017 Daily Question Summary Thread (updates have begun) http://bbs.hcbbs.com/thread-1657794-1-1.html 2016 Q&A Summary Thread (updates completed) http://bbs.hcbbs.com/thread-1597792-1-1.html Third Round of HAICHUAN Outstanding Management Members Selection Contest http://bbs.hcbbs.com/thread-1655902-1-1.html (Source: HAICHUAN Chemicals Forum)
Principle: Manual first, then automatic; internal settings first, then external settings; secondary circuit first, then primary circuit
The value of the secondary loop needs to be adjusted to the desired level, or at least to a value that remains stable for a while, with not too large a difference. This way, it’s possible to implement cascade control; once the secondary loop reaches the required value, the value of the primary loop will also be fairly close to that value. By connecting the secondary loop in this manner, large differences in values won’t cause excessive adjustments, which could lead to significant fluctuations in both the primary and secondary loops. In some cases, the secondary loop may not be able to be adjusted enough, resulting in an increasing deviation, and in such situations, cascade control loses its meaning
Set the given value for the main controller; use the internal given value for the main controller and the external given value for the secondary controller, and select the correct positive or negative action. By manually controlling the secondary controller and waiting for the main variable to gradually stabilize around the set value, it is possible to switch the secondary controller to automatic mode first and then the main controller, thereby completing the commissioning process in a disturbance-free manner.
First, feed the sub-table of the cascade loop into the automatic system, then feed it into the cascade setup; finally, feed the main table into the automatic system.
First, put the secondary circuit in automatic mode and the primary circuit in automatic mode, then put the secondary circuit in cascade mode
Once the operating parameters are stabilized, cascading control can be applied where appropriate, such as for liquid level and outlet flow, as well as furnace exit temperature and the amount of combustion gas used
First, operate the secondary circuit, then the primary circuit; set the secondary circuit to CAS mode and the primary circuit to AUTO mode
First, feed the sub-table of the cascade loop into the automatic system and then feed it into the cascade setup; finally, feed the main table into the automatic system
The primary variable is set to automatic mode, while the secondary variable is set to cascade mode