INSTRUMENTATION AND CONTROL LAB
Group No 3
2013-PE-07 2013-PE-08 2013-PE-14 2013-PE-15 2013-PE-26 2013-PE-27
Shahbano Hashmi Bushra Ameer Alvia Asif Natasha Ashraf Hira Ehsan Aqsa Aslam
Basic Process Rig The Basic Process Rig is a single loop system allowing the study of the principles of process control, using liquid level and flow rates as the measured process variables. It comprises a dual compartment process tank, linked to a sump tank by manual and solenoid operated valves. Water is pumped through the system, via a variable area flow meter and motorised control valve. Level is measured in the process tank. Flow is measured through an optical pulse flowmeter.
Figure 1. Basic Process Rig
The system is a completely self-contained, low pressure flowing water circuit supported on a benchtop-mounted panel, making it suitable for individual student work or for group demonstrations.
Possible Instrumentation The circuit includes the following elements
Sump Tank for storing water from where it may be circulated throughout the circuit
Dual-compartment Process Tank
Circulating Centrifugal Pump to circulate water throughout the pump
Visual indication Flow Meter to observe and measure flow rate. The variable area flow meter consists of a tapered shape, typically m ade of glass with a float, actually a shaped weight, inside that is pushed up by the drag force of the flow and pulled down by gravity. A higher volumetric flowrate through a given area increases flow speed and drag force, so the flow will be pushed upwards. Solenoid operated valves The valve is controlled by an electric current through a solenoid. Their tasks is to shut off, release, dose, distribute or mix fluids. They are found in many application areas. Solenoids offer fast and safe switching, high reliability, long service life, goo d medium compatibility of the materials used, low control power and compact design
Manual valves for manually controlling the flow rate.
Pulse flow sensor
Float level sensor
Servo valve A Hydraulic Servo Valve is a type of final control element that control the flow of water in response to an electrical input signal from the controller usually through a piston or cylinder. Flow control servo valves are designed to produce hydraulic flow output proportional to electrical current input signal. Different flow control devices can be used in this setup to control the flows of both circuits e.g. Venturi valve, Globe valve, Gate valve, Needle valve etc.
Features
Dual circuit benchtop system.
Water used as the process fluid.
Contains a selection of level and flow sensors and indicators.
Discovery software provides on-screen instruction and instrumentation.
Robust centrifugal pump delivers 5 liter/min
P, PI and full PID control.
May be coupled to the Temperature Rig for dual loop control.
P, PI and PID Controllers P, PI or PID controllers can be used with all instrumentation to minimize the error in the p rocess and run the process to get constant set values of process variables. They try to keep the controlled variable such as temperature, liquid level, and motor velocity at a certain value called the set point by looking at the error signal, which is the difference between where the controlled variable is, and where it should be.
P Controller In Proportional control, the actuating signal for the control action in a control system is proportional to the error signal. The error signal being the difference between the reference input signal and the feedback signal obtained from the output The main usage of the P controller is to decrease the steady state error of the system and it never manage to eliminate the steady state error of the system.
PI Controller A Proportional Integral controller continuously calculates an error, which is the difference between a set point and a measured process variable and continuously takes the integral of that error value to eliminate it and to stable the process. But as a result the speed of process lowers.
PID Controller A proportional – integral – derivative controller is a control loop feedback me chanism. It continuously calculates an error, which is the difference between a set point and a measured process variable and applies a correction based on proportional, integral, and derivative of the error. It attempts to minimize and eliminate the error over time by adjustment of a control variable such as the position of a control valve or the power supplied to a heating element.
Possible Control
Control Objective To maintain the level of water in tank Possible Disturbances Increased or decreased flow rates at inlet or outlet. Manipulated Variables Flow rates of inlet and outlet streams and flow rate of pump. State of drain valves (either open or close)
