PrayogSetu

PID Controller - Tank Level Control Practical
PID Trend Graph ↗ ← Back to Labs SYSTEM READY

Process & Instrumentation Diagram (P&ID)

Closed-Loop Feedback System
SUMP TANK PUMP (P-101) CV-101: 0% PROCESS TANK (TK-101) 100% 75% 50% 25% 0% 50.0% (SP Target) LT 101 PV Signal (4-20mA) PID CONTROLLER TAG: LIC-101 SP: 50.0 % PV: 20.0 % OP: 0.0 % AUTO Controller Output MV Signal (0-100%) DISTURBANCE VALVE

Real-Time Process Telemetry & Trend Response

Set Point (SP) 50.0 %
Process Var (PV) 20.0 %
Error (SP - PV) 30.0 %
Control Out (MV) 0.0 %
Control Valve 0.0 %
Pump Status STOPPED
Control Loop Mode:

PID Tuning Parameters

AUTO PID ACTIVE
Set Point (SP)
%
0% Target Tank Level 100%
Manual Output (OP)
%
0% (Closed) Manual Control Mode Only 100% (Open)
Proportional Gain (Kp)
0 (Off) Proportional Action 10.0
Integral Gain (Ki)
0 (Off) Eliminate Offset 10.0
Derivative Gain (Kd)
0 (Off) Damping Action 10.0

RESPONSE STATUS

At Setpoint
Kp: Controls proportional response speed.
Ki: Eliminates steady-state error (offset).
Kd: Improves damping and anticipates error change.
Outlet Disturbance Load Opens manual drain valve (creates liquid level drop)

Practical Tasks Checklist

1. Maintain tank level around 50%
2. Change Set Point to 80% & observe response
3. Turn Disturbance ON & observe closed-loop recovery
4. Increase Kp > 6.0 (Observe Oscillations)
5. Increase Ki > 3.0 (Observe Zero Steady-State Error)
6. Increase Kd > 2.0 (Observe Damped Response)

Practical Observation Data Log

Time (s) SP (%) PV (%) MV / OP (%) Error (%) Valve (%) Disturbance

Educational Working Principle

Process Model PID Tuning Reference Table

Recommended values are based on the simulated process model.

Process / Output % Recommended Kp Recommended Ki Recommended Kd Rec. Valve (%)

Closed-Loop Level Control System

In a Closed-Loop Control System, the actual output (Process Variable, PV) is continuously measured by a sensor (Level Transmitter LT-101) and fed back to the PID Controller.

The controller calculates the Error between the target Set Point (SP) and PV:

Error e(t) = Set Point (SP) - Process Variable (PV)

Based on this error, the controller computes a Manipulated Variable (MV/OP signal) to adjust the control valve CV-101 position, regulating water inflow to match liquid demand.

P, I, and D Control Effects

  • Proportional (Kp): Output is directly proportional to current error. Higher Kp increases response speed, but excessive Kp causes overshoot and sustained oscillations.
  • Integral (Ki): Sums past errors over time. Eliminates steady-state error (offset), ensuring PV reaches exact SP target.
  • Derivative (Kd): Predicts future error based on rate of change (de/dt). Acts as a damper to reduce oscillations and smooth out transient response.

Parallel PID Algorithm Formula

The continuous time domain PID controller mathematical equation is:

u(t) = Kp e(t) + Ki ∫ e(t) dt + Kd (de(t)/dt)

In this digital lab simulator, numerical integration (Euler method with anti-windup clamping) and derivative filtering are computed every time-step at 60 FPS.

Industrial Applications of PID Level Control

  • Steam Boiler Drum Level Control: Maintains critical water levels to prevent boiler burn-out or water carryover into steam turbines.
  • Chemical Reactor Surge Tanks: Buffers process flow fluctuations between refinery distillation columns.
  • Water & Wastewater Treatment Plants: Regulates aeration tank liquid levels and chemical dosing inflow.