This is PLC Program to control level of two tanks.

Problem Description:-

Two simultaneous process are to be performed in two separate tanks which are connected through a valve. First Process takes place in process tank 1 and second process takes place in tank 2. Write the ladder program for level controlling of two tanks in PLC.

Problem Diagram

Problem Solution

• Arrange two pressure tanks for processes. Process 1 will be done in process 1 tank and process 2 will be done in process 2 tank.
• Use an inlet vale for material inlet in process 1 tank. Add one more valve between two tanks as a connecting valve.
• Consider two sensors (High and Low) for process 1 tank and consider only low sensor for process 2 tank.
• For this application we can use PLC, we will write PLC program for this application.

Program

Here is PLC program for level controlling of two tanks.

List of inputs/outputs

Digital Inputs

• Cycle START:-I0.0
• Cycle STOP:-I0.1
• Low level process 1 tank (LL1):-I0.3
• Low level process 2 tank (LL2):-I0.4
• High level process tank 1 (LH1):-I0.5
• Process 1 done:-I1.0
• Process 2 done:-I1.1

Digital Outputs

• Inlet valve:-Q0.0
• Connecting valve:-Q0.1
• Outlet Valve:-Q0.2

M memory

• Cycle ON bit:-M0.0

Ladder diagram for level controlling of two tanks

Program Description

For this application we used S7-300 PLC and TIA portal software for programming. We can implement this logic by using other PLC also.

Network 1:- Network 1 is for latching circuit. Whenever START button is pressed (I0.0), Cycle ON (M0.0) bit will be ON. Cycle can be STOP by pressing STOP PB (I0.1).

Network 2:- If LL1 (I0.2) is detected and cycle START is pressed, an inlet valve (Q0.0) will be ON. Consider LH 1(I0.3) interlock during this function.

Network 3:- When the level of material of process tank 1 goes high hence LH 1(I0.3) is detected and level of material in process 2 tank goes low, connecting valve (Q0.1) will be ON. This function takes place while PLC is detecting process 1 done command.

Network 4:- When process 2 is completed and process 2 tank is not low, an outlet valve (Q0.2) will be ON. Cycle ON bit (M0.0) should be ON during the whole cycle.

Note:- Above application may be different from actual application. This example is only for explanation purpose only. We can implement this logic in other PLC also.

Runtime Test Cases

Author : Bhavesh