PLC Program to Control Mixing in a Tank

 Hello and welcome back to Teckhme.This is a PLC program to control the mixing in the tank.

 Problem Description Material A and Material B are collected in one tank. The materials were mixed for a while. The mixed product is discharged through the outlet valve. This is implemented in the PLC using the Ladder Logic programming language.

problem map 

Problem Solution 

  • Two independent level switches are used to sense the level of material A 
  • and material B.To detect low level, another level switch on the bottom of the tank is used.
  • These give the output in digital form, that is, when the corresponding level is detected.
  •  To control the liquid level in this system, a single-acting spool valve with fully open or fully closed states can be used. 
  •  An agitator attached to the motor shaft is used to control mixing. Create a special time delay to mix materials within a specified time. The inlet valve is controlled based on the level switch.
  • To control mixing, agitator is used which is connected with Motor shaft.
  • Particular time delay is generate to mix the materials for a definite time.
  • Control inlet valves on the basis of Level Material switches A and B.
  • Outlet valve is then operated to drain the mixed product.

PLC program Here is a PLC program for controlling mixing in a tank, along with program descriptions and runtime test cases.

List of Inputs and Outputs
 I:1/14 = Start (Input)
 I:1/15 = Stop (Input)
 B3:0/0 = Master Coil Bit (Bit)
 I:1/0 = Level of Material B (Input)
 I:1/1 = Level of Material A (Input)
 I:1/2 = Low Level Switch (detects empty tank) (Input)
 O:2/0 = Inlet Valve 1 (Material A Feed) (Output)
 O:2/1 = Inlet Valve 2 (Material B Feed) (Output)
 O:2/2 = Agitator Motor (Mixing) (Output)
 O:2/3 = Outlet Valve (Product Outlet) (Output)
 T4:0 = Time to mix Materials (Timer)

Ladder Diagram for Controlling Mixing in Tanks

Program Program Description

  • RUNG000 contains Master Start/Stop with addresses of Start PB I:1/14 and Stop PB I:1/15.
  • RUNG001 controls the feed valve for material A at address O:2/0. It is activated when the low level switch I:1/2 detects a low level in the tank. When the switch at address I:1/1 detects level A, it closes. The start PB is also in parallel with the LLS, so if the LLS or Material A level is not detected, the inlet valve will be driven by the start PB.
  • RUNG002 controls the feed valve for material B at address O:2/1. It turns on when Material A is filled to the desired level (Level Material A). That is, when the level of material A is detected to be I:1/1, the valve of material B will open, and when the level of material B is detected or the tank is full, the valve will be closed.
  • RUNG003 and RUNG004 run the agitator motor with address O:2/2. When the tank is full of materials A and B, a high level is detected (material B level). This detection energizes O:2/2 and activates the ON timer at address T4:0. The stirrer motor is connected to address O:2/2. So, when O:2/2 is on, the motor agitator will start mixing and mixing materials A and B for 20 seconds, which is the default Timer ON. When Pre = Acc, the T4;0/DN bit goes high and turns off the agitator motor.
  • SPROSE005 is used for outlet valve with address O:2/3. It will run after the entire mixing process is complete, i.e. when Pre = Acc = 20 seconds. This will be turned off when LLS is detected again.

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