Consider Problem 18.13. The control logic is now modified such that the pump can be automatically started by the highlevel switch even though the stop switches are pressed. Modify the ladder diagram you developed in Problem 18.13 accordingly.

Problem 18.13

In Example 18.10, there are two switches to start the pump. In addition, consider that the pump can be automatically started by a newly installed high-level switch as long as the stop switches are not pressed. Modify the ladder diagram shown in Figure E18.10(b) accordingly.

Example 18.10

Figure E18.10

Transcribed Image Text:

Figure E18.10(a) shows the schematic of a storage vessel, V-101. Pump P-101 has two start and stop switches (one in the plant and the other in the control room). Assume that the pump start switch is a momentary signal, that is, is true as long as the start button is pushed. The pump can be started or stopped by either of the start/stop switches. Pump P-101 should stop if the level of the vessel becomes low as detected by the level switch, LSL- 101. Develop a ladder diagram for the pump.