Seeking help with split-control for Yokogawa CS3000 system
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Gentle experts, we use proportional control here to operate two valves: valve A operates at 0–50%, while valve B operates at 50%–100%. Both valves move in the same direction from 0–100%. I want to switch from manual mode to proportional control; every time I make this switch, the position of the main valve always returns to zero first, without following the positions of valves A and B. I tried to manually set the main valve position to the value that corresponds to the actual position of valve A when it is operated manually (that is, half of valve A’s position value; at this point, valve B is fully closed), but whenever the main valve position was changed, it returned to zero again. It works fine under normal use; it just resets to zero whenever the main valve position is changed. In my configuration, there is a PID block followed by a split block, and then two MLD–SW blocks that control the two output channels. Experts, please help identify the issue: before the programmed control is put into use, can the PID module track the valve position to enable a seamless switchover? Thank you!
The SP value of the split block does not track the output of the MLD block!
Dear experts, how do you configure multi-stage control circuits? It is required that each branch can be controlled manually independently, and when switched to automatic mode, the transition should occur without any interference. Thank you!
This post was last edited by jlshnlhj on 2018-1-8 at 15:59. The simplest approach is to have a PID block followed by a split, and then connect it directly to AO. Managing with a sequence control table ensures that the switch position of split is always at 3, and the step values are set within split. Your method works too: a pid block followed by a split block, and then two mld–sw blocks to control the two output paths. Management using a sequence control table: 1. The switch position for split is always at 3. 2. mld–sw is always set to aut or cas mode. The split value is set within split. The key is that the switch for 1.split remains at 3, and 2.mld–sw is always in aut or cas mode. In manual mode, the PID is set to manual, so the relationship between these two proportional valves never changes: valve a operates at 0-50%, while valve b operates at 50%-100%. Even when the unit is in operation and the PID is set to manual, these two range valves maintain the same relationship.
This post was last edited by jlshnlhj on 2018-1-8 at 16:04 with the request that “each branch should be able to be controlled manually separately, and should switch to automatic mode in a way that does not disturb anything else.” Is the ability to control each branch manually separately achieved through the manual operation of mld–sw? Does this not conflict with the requirements for staged process operation? If there is no conflict, a disturbance-free switch should be possible, but specific requirements exist for the switching steps and methods.
The process requirements allow for the individual control of the two valves; sometimes, adjustments to the process necessitate such operation. I think I already know what’s causing the issue with the do-not-disturb mode right now; I’ll check it out after trying it in person.