Programmable Logic Controllers: Industrial Control by Khaled Kamel & Eman Kamel

Author:Khaled Kamel & Eman Kamel [Kamel, Khaled]
Language: eng
Format: mobi, epub
Tags: -
Publisher: McGraw-Hill Professional
Published: 2013-08-16T16:00:00+00:00

Figure 5.48 West Pump Failed-to-Start Network.

• Initially, during the first scan when the West Pump is ON, Q0.1 is set, and I0.4 is OFF (because it takes up to 5 seconds to receive the pump running online contact when the pump runs successfully). The power flows to the timer block, and the timer starts timing.

• If the timer accumulated time equals the timer preset time (5 seconds), Q0.3 will turn ON, indicating that West Pump failed to start. The timer preset value is an experimental value that varies with the type and size of the motor used. Careful selection of this timer preset value is critical to prevent premature motor Failed-to-Start alarming action.

Once a pump fails to start, the associated alarm will be activated along with the common alarm, as shown in Fig. 5.49. The failed pump will not be considered until the operator takes the required action to clear the alarm and indicate to the PLC such action through the user-interface available control panels. This part of the logic is not shown here but will be included in more comprehensive coverage in Chap. 6.

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