Role of Automation in Industries Manufacturing processes, basically, produce finished product from raw/unfinished material using energy, manpower and equipment and infrastructure. Since an industry is essentially a “systematic economic activity”, the fundamental objective of any industry is to make profit. Profit = (Price/unit – Cost/unit) x Production Volume So profit can be maximized by producing good quality products, which may sell at higher price, in larger volumes with less production cost and time.

Industrial Automation Automation is a technique that can be used to reduce costs and/or to improve quality. Automation can increase manufacturing speed, while reducing cost. Automation can lead to products having consistent quality, perhaps even consistently good quality. Automation is a technology concerned with application of mechanical, electronic and computer-based system to operate and control system. This technology includes; Automatic assembly machines, Automation machine tools to process parts, Industrial robots, Automatic materials handling and storage system, Automatic inspection system and quality control, Feedback control and computer process control, Computer system for planning, data collection and decision making to support manufacturing activities Examples: Automatic assembly machines Automation machine tools to process parts Industrial robots Automatic materials handling and storage system Automatic inspection system and quality control Feedback control and computer pr

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

Root Locus Effect of Addition of zeros Addition of zeros The addition of a zero to the open-loop transfer function has the effect of pulling the root locus to the left, tending to make the system more stable and to speed up the settling of the response.  Physically, the addition of a zero in the feed forward transfer function means the addition of derivative control to the system. The effect of such control is to introduce a degree of anticipation into the system and speed up the transient response. The Figure 1(a) shows the root loci for a system that is stable for small gain but unstable for large gain.  Figures 1(b), (c), and (d) show root-locus plots for the system when a zero is added to the open-loop transfer function. It becomes stable for all values of gain. However, it is not possible to add an isolated zero to a transfer function because of physical non-realizability. Therefore, in order to realize the compensating network a pair of pole-zero has to be incorporated.