Feedback-feed-forward control scheme used in heat exchanger for temperature control Feedback control Feedback control is a control action of altering the manipulated variable in response to the deviation between the controlled variable and its set point in such a way to eliminate the deviation. Temperature Control Using Feedback Control Consider a process outlet temperature control problem in a furnace. The furnace is used to heat the process fluid stream and its outlet temperature is to be controlled. In feedback control, the outlet temperature is measured and it is compared against the reference set point. The deviation between the desired and measured temperatures is found. The flow rate of the fuel gas is adjusted in accordance with the magnitude of deviation by the controller through the control valve. The outlet stream temperature is kept at the desired value by controlling fuel gas flow rate Limitations of feedback control Feedback control takes corrective action only after the

Pressure control strategy in Condensers. Control of  condensing pressure is of interest, the system shown in Figures  These systems operate by throttling the cooling water flow through the condenser, causing a potential for high-temperature rise that is acceptable only when the water is chemically treated against fouling. For good, sensitive control, the water velocity through the condenser should be such that its residence time does not exceed 1 min. Another rule of thumb is to keep the water velocity above 4.5 ft/s (1.35 m/s)

Override control  In a Override control process, a selector is used. The two basic types of these override controllers(Selectors) are high selectors and low selectors. They are generally available as both electronic and pneumatic selectors. Selectors are also available in a number of different versions that will accommodate for varying amounts of input signals. Two or more inputs are placed into the selector and one output comes out depending on the selector. High Selectors High selectors are designed so that they filter out all but the highest value from a multiple input feed stream. The selector then sends this single highest value through to the output signal. Low Selectors Low selectors are designed so that they filter out all but the lowest value from a multiple input feed stream. The selector then sends this single lowest value through to the output signal. Override control   Override Control, also called as selective control, is a form of multivariable control in which more than

Cascade Control Cascade control involves the use of two controllers with the output of the first controller providing a set point for the second controller, a feedback loop for one controller for the other controller. Cascade control is used when there is more than one measurement, but only one control variable is available. In single-loop control, the set point of the controller is set by the operator and its output drives the final control element. Cascade control is basically a control algorithm in which the output of one control loop provides the target for another loop. The ultimate goal of a cascaded loop is to control the final process. Cascade loops are always installed to prevent external disturbances from entering and exiting the primary controlled variable. What is Cascade Control? In single-loop control, the set point of the controller is set by the operator and its output drives the final control element. For example: A level controller operates a control valve to keep the

Degrees of freedom Degrees of freedom  The degrees of freedom of a process define the maximum number of independently acting automatic controllers that can be placed on a process Degrees of freedom = number of variables – number of equations Steam heater Liquid to liquid heat exchanger Reboiler Steam heater In this case there are four process variables and one defining equation which is that of the conservation of energy based on the first low of thermodynamics  [ HsWs= CpW(T2-T1)] In a steam heater there are four process variables are two flow and two temperatures The number of degrees of freedom of that process is three thus, a maximum of three automation controller can be placed on it . Liquid to liquid heat exchanger In this case there are six process variables and one defining equation is [ CpF(Th1-Th2) = CpcFc(T2c-T1c)] Six process variables are four temperature and and two flow variable The number of degrees of freedom of that process is five thus, a maximum of five

control variables 1. What are the primary control variables? Temperature Pressure Flow The level is excluded, which is not a primary control variable because the level is controlled by manipulating flow to tank  flow meters 1. What are the different flow meters? Based on the working principle, there are 5 types of flow meters: Differential pressure(DP) flow meter:- example: Orifice plate, Venturi meter, Flow nozzle, Rotameter. Velocity Flowmeter:- Electromagnetic flowmeter, Ultrasonic flowmeter, Turbine flowmeter, Paddlewheel flow meter. Positive displacement flowmeter:- Nutating disk, Rotary vane, Gear, Diaphragm flowmeter. Mass flowmeter:- Coriolis flowmeter, Thermal dispersion meter, 2. What is Flow compensation? In steam or gas flow measurement, the density of the steam or gas changes as pressure and temperature change. This change in density can affect the accuracy of the measured flow rate if it is uncompensated. Temperature, pressure compensated flow control is a mathematically

What are Intrinsic Safety Barriers? Answer: The safety barriers for the zener diode are voltage regulators. There are two different types of barriers, one way and two-way barriers. There are two types of safety barriers: Active barriers Passive barrier

Instrumentation Cables  1. What is the difference between IS and non IS cables? Non IS cables are used in non-hazardous areas where protection needs no special consideration. Cables that are safe in faulty situations, protected from external electrical or magnetic field damage and used in intrinsic circuits are referred to as intrinsically safe cables or IS cables. 2. What differs Intrinsic earthing from usual earthing? The IS ground connection must be separated from plant earth and other electrical ground. When used in IS cables, the screens should only be grounded at one point, usually at the same point where the interface devices are grounded, and should be isolated from each other 3. What is intrinsic safety system? A system that involves equipment and interconnecting wiring in which any spark or thermal effect in any part of the system intended for use in hazardous areas is unable to cause ignition. 4. What are Intrinsic Safety Barriers? The safety barriers for the zener diode are

What are the requirements for carrying out installation inspection of any instrument? Answer: The following are the requirements at the time of execution of an inspection. Instrument datasheet. Instrument Test Certificate. Vendor instruction manual. Test Instrument instruction manual

What items inspection to be done for instrument Stand and supports? Answer: Fabrication of stand as per the drawing Deburred, primed and painted. Stand and support are secure. Stand ground point. Access to stand is unobstructed and clear for maintenance.

What are the responsibilities of the QC Inspector? Answer: The following are the extraordinary responsibilities that any QC Inspector is supposed to execute at the time of carrying out any inspection. Knowledgeable with the technology for which the inspection is carried out. Should have the reasoning capability to analyze the method. Should have in-depth knowledge about the procedure to be adopted for inspection i.e. adopted standards. Should be able to convey the irregularities found to the concerned authorities such as QC Engineer or QC Manager. Should be sincere about the job execution. Should be vigilant all the time.

Quality Control Inspector Interview Questions and Answers 1. What is an Inspection? Answer: It is a process of verifying the method and application utilizing by means of following certain documented and authenticated instruction standards are known as inspection Quality Assurance Program Installation Pre-Installation Verification Installation Process Control After Installation Verification Turnover for Commissioning 2. What are the responsibilities of the QC Inspector? Answer: The following are the extraordinary responsibilities that any QC Inspector is supposed to execute at the time of carrying out any inspection. Knowledgeable with the technology for which the inspection is carried out. Should have the reasoning capability to analyze the method. Should have in-depth knowledge about the procedure to be adopted for inspection i.e. adopted standards. Should be able to convey the irregularities found to the concerned authorities such as QC Engineer or QC Manager. Should be sincere about

Process Control and Instrumentation 1. What Is Process Control Instrumentation? Answer: Process control instrumentation focuses on the measurement and control of process variables within an industrial setting using hardware and software tools. Control systems are derived from mathematical models of industrial processes and systems. 2. Why Is Instrumentation and Process Control Essential? Answer: Instrumentation and process control is at the core of all industrial and manufacturing activities. Within a production facility, every process must be carefully monitored and controlled to proceed in a predetermined fashion that is both optimized and safe. For example, temperature monitoring and control systems at petrochemical plants prevent temperatures from rising to critical levels and causing an explosion. Without electric process heater control panels, there could be a loss of human lives and the destruction of assets. 3. Industries that Need Instrumentation and Process Control Virtually

Calibration  Question and Answer 1. What is calibration? Calibration is a set of operations that documented comparison of the measurement device to be calibrated against a traceable reference standard/device. 2. What is calibration certificates? The calibration certificate is the official document authorized for the calibration of instruments and provides traceability to the National Institute of Standards and Technology. The calibration certificate is issued by most businesses as a historical record. However, some enter data on the certificate in a local database to track the status of their test equipment inventory. 3. What is the difference between a Standard (Traceable) and Accredited Calibration Certificate? Standard (Traceable) Certificate: Instrumentation is calibrated to specifications with traceable standards. A full data report is optional with the calibration certificate. Accredited Certificate: meets the ISO / IEC 17025 requirements and the accrediting body of the laborator

instrumentation Question and Answer 1. What Is Instrumentation? Answer: The technology which is used to measured and control the process system of plant is  called instrumentation. It is branch of engineering. 2. What is the instrumentation Engineering? Answer: Instrumentation engineering is the engineering specialization deals with principle and operation of measuring devices used in electrical, pneumatic, etc. design and configuration of automated systems. Instrumentation engineers work with automated processes, such as chemical or manufacturing plants, for industries to enhance system efficiency, reliability, health, optimization and stability. 3. What is the instrumentation measurement? Answer: Instrumentation can be used to measure certain field parameters (physical values): Pressure, either differential or static Flow Temperature measurement Level Measurement Density Viscosity Radiation Current Voltage Inductance Capacitance Frequency Resistivity Conductivity Chemical compositi

Flow Switch A flow switch is one detecting the flow of some fluid through a pipe. Flow switches often use “paddles” as the flow-sensing element, the motion of which actuates one or more switch contacts. A flow switch, like all switches, is a device designed to make and break an electric current in a circuit. In an industrial system, a flow switch is essential in monitoring and controlling the flow rate of process media – such as steam, liquids, and gases. Flow switches help maintain safe and manageable rates of flow by triggering actions in various machines within a system to provide on/off flow control of process media. Principle of Flow Switch The “normal” status of a switch is the resting condition of no stimulation. A flow switch will be in its “normal” status when it senses minimum flow (i.e. no fluid moving through the pipe). For a flow switch, “normal” status is any fluid flow rate below the trip threshold of the switch. Working of the flow switch  Firstly th

Multiple Choice Questions & Answers on  IOT Rasberry Pi 1. The Raspberry Pi is defined as the __________ a) Micro Computer b) Mega Computer c) Mini computer d) Nano Computer Answer: Mini computer 2. Raspbian is __________ a) Assembler b) Language c) Compiler d) OS Answer: OS 3. Raspberry Pi consists of a _______ quad-core processor or microprocessor. a) 16-bit b) 32-bit c) 64-bit d) 128-bit Answer: 64-bit 4. The Raspberry Pi has a __________ interface to allow it to perform serial data communications. a) UART b) GPIO c) I2C d) SPI Answer: UART 5. How many USB ports are present in Raspberry Pi 3? a) 5 b) 2 c) 4 d) 3 Answer: 4 6. What bit processor is used in Pi 3? a) 64-bit b) 32-bit c) 128-bit d) Both 64 and 32 bit Answer: 64-bit 7. What is the speed of operation in Pi 3? a) 900MHz b) 1.2GHz c) 1GHz d) 500MHz Answer: 1.2GHz 8. What is the Ethernet/LAN cable used in RPi? a) Cat5 b) Cat5e c) Cat6 d) RJ45 Answer: RJ45 9. How many Input/Output pins on board Raspberry Pi3 has? a) 20 b)

Brief the different stages of SDLC Stages Of SDLC (Software Development Life Cycle) Project Planning Gathering Requirements & Analysis Design Coding or Implementation Testing Deployment Maintenance Stage 1: Project Planning The first stage of SDLC is all about “What do we want?” Project planning is a vital role in the software delivery lifecycle since this is the part where the team estimates the cost and defines the requirements of the new software. Stage 2: Gathering Requirements & Analysis The second step of SDLC is gathering maximum information from the client requirements for the product. Discuss each detail and specification of the product with the customer. The development team will then analyze the requirements keeping the design and code of the software in mind. Further, investigating the validity and possibility of incorporating these requirements into the software system. The main goal of this stage is that everyone understands even the minute detail of the requireme

Arduino Arduino is a prototype platform (open-source) based on an easy-to-use hardware and software. It consists of a circuit board, which can be programmed (referred to as a microcontroller) and ready-made software called Arduino IDE (Integrated Development Environment), which is used to write and upload the computer code to the physical board.  Arduino Uno is a microcontroller board based on 8-bit ATmega328P microcontroller. Along with ATmega328P, it consists other components such as crystal oscillator, serial communication, voltage regulator, etc. to support the microcontroller. Arduino Uno has 14 digital input/output pins (out of which 6 can be used as PWM outputs), 6 analog input pins, a USB connection, A Power barrel jack, an ICSP header and a reset button. The key features are Arduino boards are able to read analog or digital input signals from different sensors and turn it into an output such as activating a motor, turning LED on/off, connect to the cloud and many other ac