Skip to main content

Basic Pumping System Application Used in Industrial Automation

 In this post, we will see the basic pumping system application that is used in industrial automation.

A pumping system is one of the widely used applications used in industrial automation.


Earlier, manual control was used where the operator had to go and start or stop the pumps according to pressure requirements from the user.


Pumping System

Basically, a pumping system in simpler terms can be viewed as the one used in your building. The society keeper (or watchman, or ourselves in our homes) controls the pump operation according to the flushing and domestic water requirements in the building.


Now, due to the use of PLC in the pumping systems, the manual intervention is reduced to a great extent, and also, the pressure control is achieved more accurately due to the use of automation.

Refer to the above image. A typical pumping system used for domestic, commercial, and industrial purposes looks like this.

It consists of multiple pumps (depending upon pressure-demand design), its corresponding discharge valves, and a pressure transmitter.

The pumps use water from a common header line and control the flow of water to the discharge line by varying its motor speed, according to the pressure sensed at the discharge line.

The automatic control in pumping system can be classified into two types

Single VFD and
Multi VFD.
Single VFD System

 
As the name suggests, this system consists of only a single VFD for multiple motors.

Refer to the below image.


In this case, the PLC IO’s will be


Digital inputs – VFD Trip feedback, Pump-1 VFD Contactor feedback, Pump-1 DOL Contactor feedback, Pump-2 VFD Contactor feedback, Pump-2 DOL Contactor feedback, Emergency Stop

Digital Outputs – VFD Run Command, Pump-1 VFD Contactor, Pump-1 DOL Contactor, Pump-2 VFD Contactor, Pump-2 DOL Contactor

Analog Inputs – Pressure Transmitter

Analog Outputs – VFD Speed Reference

Now, let us see the control philosophy. There are three set points for the control


cut- in pressure set,

PID pressure set and

cut-off pressure set.

When the pressure is below the cut-in set value, the pump with the least operating hours will operate first through the VFD contactor.


So, this pump speed will be controlled by VFD. If the pressure is still below the cut-in set value after a predefined time, then pump-2 will start through the DOL contactor.


As seen in the image, the DOL (Direct On-Line) contactor gets direct supply from the 3-phase incoming line, making the motor rotate at its full speed.


This logic ensures that any motor does not get supply from both the VFD and 3-phase direct simultaneously.


Otherwise, it will create a spark in the electrical circuit and the motor will get shorted; which can damage the environment or personnel standing nearby.


The pump VFD speed will be controlled based on PID. The PID takes the pressure sensor as input and the PID pressure set as set pressure.



 

When the pressure is below the setpoint, then the speed of VFD will increase gradually to reach its set point.


When the pressure goes above the setpoint, then the speed of VFD will decrease gradually to reach its set point. So, in short, the pressure will be tried to be maintained around the set point.


Now, when the pressure goes above the cut-off pressure set, then the DOL pump will turn off first. If the pressure is still above after a predefined time, then the VFD pump will turn off.


The cycle continues once the pressure drops again and the pump run management is done through its running hours which is calculated inside the PLC.


Pressure drop means demand is high and pressure increment means demand is low.


Through this, the running hours of both the pumps will be properly managed and also, there will not be any clash in operating of contactors.


If any pump trips in between, then the system will stop and the user has to press a reset button on a graphic display used; to restart the system once again.


Multi VFD System

It is a relatively easier system to design as compared to a single-VFD system. Each pump motor will have its individual VFD.


The only difference is that the second pump will operate at 50 Hz. This is in correlation with the DOL pump in a single-VFD system.


The electrical wiring is simpler as an individual motor will have only its single contactor for VFD output, as compared to dual contactors for a single motor in a single-VFD system.



 

In some systems, all the pumps work in PID. That means, all the pumps will run at the same speed because the pressure transmitter is one single only with the common set point.


This is the most common type of pumping system used in industrial automation. The design depends on user requirements. PLC logic too will differ depending upon the designer and his requirements.

Labels:

Comments

Post a Comment

Popular posts from this blog

PLC Program for Mixing Tank

 Create a ladder diagram for controlling a batch mixing process. Implement a PLC program for mixing tank or Mixing Process using PLC Ladder Logic. PLC Program for Mixing Tank Fig : Mixing tank A tank is used to mix two liquids. The required control circuit operates as follows: A. When the START button is pressed, solenoids A and B energize. This permits the two liquids to begin filling the tank. B. When the tank is filled, the float switch trips. This de-energizes solenoids A and B and starts the motor used to mix the liquids together. C. The motor is permitted to run for 1 minute. After 1 minute has elapsed, the motor turns off and solenoid C energizes to drain the tank. D. When the tank is empty, the float switch de- energizes solenoid C. E. A STOP button can be used to stop the process at any point. F. If the motor becomes overloaded, the action of the entire circuit will stop. G. Once the circuit has been energized, it will continue to operate until it is manually stopped. Solution...
1 comment
Read more

What is Relay? How it Works? Types, Applications, Testing

 We use relays for a wide range of applications such as home automation, cars and bikes (automobiles), industrial applications, DIY Projects, test and measurement equipment, and many more. But what is Relay? How a Relay Works? What are the Applications of Relays? Let us explore more about relays in this guide. What is a Relay? A Relay is a simple electromechanical switch. While we use normal switches to close or open a circuit manually, a Relay is also a switch that connects or disconnects two circuits. But instead of a manual operation, a relay uses an electrical signal to control an electromagnet, which in turn connects or disconnects another circuit. Relays can be of different types like electromechanical, solid state. Electromechanical relays are frequently used. Let us see the internal parts of this relay before knowing about it working. Although many different types of relay were present, their working is same. Every electromechanical relay consists of an consists of an Elect...
1 comment
Read more

Chlorine dioxide Analyzer Principle

 Chlorine dioxide measurement Chlorine dioxide (ClO2) is an instable, non-storable, toxic gas with a characteristic scent. The molecule consists of one chlorine atom and two oxygen atoms – represented in the chemical formula ClO2. It is very reactive. To avoid the risk of spontaneous explosions of gaseous chlorine dioxide or concentrated solutions, it is generally handled in dilution with low concentrations. ClO2 is soluble in water, but tends to evaporate quickly. Typically it is prepared on site, for example from hydrochloric acid and sodium chlorite. The procedure provides solutions with approx. 2 g/l ClO2 that can be safely handled and stored for several days. Image Credits : krohne Sensor Parts : Reference electrode Applied chlorine dioxide specific potential Current needed to maintain the constant potential Counter electrode Measuring electrode The disinfection effect of ClO2 is due to the transfer of oxygen instead of chlorine, so that no chlorinated byproducts are formed. C...
6 comments
Read more