The issue of valve opening degree on P&ID diagrams
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On the P&ID diagrams, the opening degree of some valves is shown as greater than 100%, while for others it is shown as less than 0%. I have a gentle question: does 100% correspond to a physical valve that isn’t fully open, and does 0% correspond to a physical valve that isn’t fully closed? If not, then what is the reason why some values show above 100% while others show below 0%? Thank you!
I don’t seem to have heard of this before; generally, it’s at most 100% and at least 0. You mean the display value on the DCS, right?
2# donganhj is the display value of DCS; why are there values greater than 100%?
This post was last edited by sonid on 2010-3-21 at 16:05. When debugging DCS, the displayed opening value is set; if this value (the limiter) is less than 0% or greater than 100%, it may be due to incorrect initial setting values, and these can be reset according to the actual opening condition.
What was said upstairs makes sense, but I’ve never encountered such a situation
I’ve never seen this happen; it’s probably a setting issue in the DCS. The maximum value I’ve seen is 100%, but it shows 120% – there must be some problem
I have also seen this in the Yokogawa DCS; the values can go as low as -17.19% and as high as 106.25%. The explanations provided indicate that the actual outputs at this time (the outputs of the module) correspond to currents of 1.25 MA and 21 MA respectively, representing the \"fully closed\" and \"fully open\" states.
7# ssln123 You make a good point, thank you!
During valve calibration, a certain degree of opening can be reserved for full open and full closed positions; this helps to protect the valve to some extent without affecting its ability to regulate flow. When the valve reaches these positions, the feedback value will be less than 0 or greater than 100.
Generally, it’s due to improper adjustment; if it’s too large, it might be broken