Explanation of logical interlocking
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Oxygen main pipeline oxygen valve interlock procedure: Oxygen main pipeline isolation valve 1 opens AND oxygen main pipeline vent valve 3 closes; Oxygen main pipeline isolation valve 2 opens OR oxygen main pipeline vent valve 3 opens. In this case, oxygen main pipeline isolation valve 1 closes. Can you explain what this means?
Both the main oxygen pipeline isolation valves 1 and 2 are open, and the vent is closed. If cut-off valve 1 or 2 is closed, one of them will open for venting. I’m not sure if the expression is clear.
What I mean is: the logical operation of the first part already includes the logical OR function of the second part, and the second part also includes the first part – isn’t that redundant?
This post was last edited by HEJIYUER on 2016-2-25 00:24. For a valve configuration of “double shut-off” + “mid-discharge”, it would be reasonable to proceed as follows: 1. After the interlock cut-off signal is issued, the discharge valve opens automatically after a few seconds of delay. The DO signals of the three valves (i.e., the interlock commands for the valves) are XORed with their respective valve position signals to generate alarms; this is done to detect any failure in the interlock function and to alert operators. 2. A separate reset button for the discharge valve is provided; it merely resets the discharge valve (i.e., closes it), while the \"XOR\" alarm remains active to alert the operator. 3. 2 did not trigger an alarm, and since all conditions for driving were met, the reset button of the cut-off valve was pressed; both valves opened and the system came online. The valve position signal’s “OR”/”AND” operations are not used in conjunction with the inputs for interlock functions, because valve position signals are considered to generate errors with a relatively high probability, whereas the command signals for solenoids are considered more “reliable”; otherwise, interlock actions cannot be implemented. @jiaguoyun @Big Horse with Big Bow