I'm using ABB differential Pressure Transmitter to calculate air flow in a circular pipe. The Pressure transmitter is calibrated using HART communicator in units of mmH2o at 20degcelsius.Min-0 mmH2o (4mA)Max- 78 mmH2o (20mA)I would like to convert mmH2o to m3/hr. Any functional block or formula/Standard chart available for this conversion?

The formula is Constant*(Square root of the Diff Press) where constant depends on your instrument installation. The manufacturer of the instrument should be able to tell you the constant.To get flow rate from a DP transmitter assumes that you have a primary flow element mounted in a pipe or duct, something like an orifice plate, an averaging pitot tube (Annubar), or one of several other specialized primary flow elements.

Primary flow elements are designed to produce a certain differential pressure at a certain flow rate as calculated from design information including medium viscosity, density, temperature, upstream static working pressure, and a dozen others.

The manufacturer of the primary flow element provides a "sizing sheet" with the primary flow element that includes all the data used to calculate the flow rate at a given DP. You need that sizing sheet, because that sizing sheet tells you what flow rate 100"W.C. equals for your specific primary flow element.

And you need to know whether the DP transmitter is configured to output the 'raw' DP or whether it extracts the square root of the DP.

And you should be aware that you cannot get SCFM (standard cubic feet per minute, a mass flow measurement) from just a primary flow element and a DP transmitter, unless your static working pressure and temperature never vary from the design standard, which never happens in the real world. 'Standard' cubic per minute is referenced back to STP. Your DP transmitter does not measure gas temperature and the static pressure and compensate for those changes, so your engineering units are CFM (a volumetric measurement), not SCFM (a mass flow measurement).What is three element control system how is it work?

A single element control system is one with just one control input; a two element control system is one with two control inputs, etc.

I anticipate that you have a three-element boiler water level control system in mind. This is one which typically uses the measured water level, the steam flowrate from the boiler, and the water flowrate into the boiler to regulate the flow of water into the boiler.

Although you might think that measuring water level alone is sufficient, you have to bear in mind that the boiler water contains lots of steam bubbles. Bubble size is affected by pressure, so if a boiler experiences a sudden extra demand for steam, its pressure drops. The drop in pressure causes the steam bubbles in the boiler water to expand, and the level measurement can show an increase in level.

The false high reading makes the water level control system reduce the flow of water into the boiler. Once boiler pressure is restored the steam bubbles contract, and the measured water level drops suddenly. The level control system responds to this by increasing the flow of water into the boiler, which effectively deluges the boiler with relatively cold water, and boiling is arrested. Some of the steam bubbles in the boiler water collapse, and the boiler water level drops significantly - possibly to a low-level alarm or lockout.

By adding water and steam flow measurement into the control system, we can identify any major disparity between the two, and make compensation to the measured water level. This means that any transient peak demands on the boiler are recognised as such, and the feedwater control is appropriately applied.

Incidentally, it is possible to achieve the same results using a two-element control system (level and steam flow), but it is easier to commission three-element systems.

Three-element boiler water level control systems are sometimes referred to as "feed forward" control. This is becasue the system identifies a transient high demand for steam before it has any effect on the boiler water level, and therefore starts to put extra water into the boiler in anticipation of demand.This is a topic that requires reading and operational experience to understand - and even then it can still be difficult to figure out. I took control courses in university, but it was not until I had real life experience in the field with controllers I was able to fully

understand the tuning process.

A three element control is a cascading feed-forward control loop. Its simple description/purpose is to keep water inflow the same as water outflow (where inflow is your feedwater demand). The controller applies a proportional action to the error between the drum level (signal) and the set point.

The controller looks at the drum level error + the steam flow = feedwater signal demand.

The feedwater signal is compared to the water flow input (i.e. current feedwater flow) - the difference is the new output of the feedwater controller (i.e. your new feedwater flow). This happens according to the frequency of you process logic controller. The problem is that if you constantly try to hit the set point many times each second you end up overshooting or undershooting your setpoint and you drum level fluctuates uncontrollably. This is why Integral action is also provided. The combination of proportional + integral control helps to establish predictable feed water flows at common loads and can react to load changes/adjustments as required) if the system is properly tuned (the constants used for proportional and integral control are set to match normal operations).Honeywell’s C300 Controller provides powerful and robust process control for the Experion® platform. Based on the unique and space-saving Series C form factor, the C300 joins the C200, C200E, and the Application Control Environment (ACE) node in operating Honeywell’s field-proven and deterministic Control Execution Environment (CEE) software.What Is It?Ideal for implementation across all industries, the C300 controller offers best-in-class process control. It supports a wide variety of process control situations, including continuous and batch processes and integration with smart field devices. Continuous process control is achieved through an array of standard functions that are built into control strategies. The C300 controller supports the ISA S88.01 batch control standard and integrates sequences with field devices, including valves, pumps, sensors, and analyzers. These field devices track the state of the sequences to perform pre-configured actions. This tight integration leads to quicker transitions between sequences, increasing the throughput.The controller also supports advanced process control with Honeywell’s patented Profit® Loop algorithm as well as custom algorithm blocks, which let users create custom code to run in the C300 controller.How Does It Work?Like C200/C200E and the ACE node, the C300 operates Honeywell’s deterministic Control Execution Environment (CEE) software which executes control strategies on a constant and predictable schedule. The CEE is loaded into the C300 memory providing the execution platform for the comprehensive set of automatic control, logic, data acquisition and calculation function blocks. Each function block contains a set of pre-defined features such as alarm settings and maintenance statistics. This embedded functionality guarantees consistent process control strategy execution.The controller supports many input/ output (I/O) families, including Series C I/O and Process Manager I/O, and other protocols such as FOUNDATION Fieldbus, Profibus, DeviceNet, Modbus, and HART.What Problems Does It Solve?C300 allows engineers to address their most demanding process control requirements from integration with complicated batch systems to controlling devices on a variety of networks such as FOUNDATION Fieldbus, Profibus, or Modbus. It also supports advanced control with Profit Loop, which puts model-based predictive control directly in the controller to minimize valve wear and maintenance.

The C200/C200E integrated control and safety systems are embedded in the compact Series A Chassis hardware form factor. Users of these controllers benefit from a robust and superior control execution and scheduling environment with high reliability.What Is It?Released with PlantScape R200, the C200 controller operates Honeywell’s field-proven and deterministic Control Execution Environment (CEE) core software. Introduced with Experion® PKS R400, the C200E Controller provides the same capabilities as C200 but adds more functionality and memory. For example, the C200E fully supports Experion Batch Manager and the ISA S88.01 batch control standard so that users can execute complete batch control in a redundant environment with the controller.The CEE resident in the control processor provides an efficient and effective control environment as well as access to a comprehensive library of control-related function blocks. The controllers can be implemented in a single or fully redundant configuration.How Does It Work?Like the C300 and the ACE node, the C200 and C200E integrated control and safety systems operate Honeywell’s deterministic CEE software which executes control strategies on a constant and predictable schedule. The CEE is loaded into the C200/C200E memory, providing the execution platform for the comprehensive set of automatic control logic, data acquisition and calculation function blocks. Each function block contains a set of predefined features such as alarm settings and maintenance statistics. This embedded functionality guarantees consistent process control strategy execution.The controllers support many input/output (I/O) families, including Series A I/O, Rail A I/O, Rail H I/O and Process Manager I/O, and other protocols such as FOUNDATION Fieldbus, Profibus, DeviceNet, and HART. What Problems Does It Solve?The C200 and C200E controllers enable process engineers to tackle several process control problems by supporting batch applications with ISA S88.01 and providing robust process control through CEE. When used with Honeywell’s Profit Loop that anticipates future process behavior, the controllers know exactly how much to move the process in order to meet the desired control objectives, thus offering stronger process control.

Distributed System Architecture (DSA) is the ideal solution for integrating processes when there are multiple units, control rooms or geographically distributed locations. With Distributed System Architecture, users experience a single, totally integrated system instead of several independent systems, while retaining the ability to autonomously manage each system. The result: optimum functionality and flexibility.What Is It?Distributed System Architecture allows multiple Experion® Process Knowledge Systems (PKS) to operate as one across multiple units, sites and facilities across the enterprise. This single integrated system enables seamless global access to data, alarms, alerts, interactive operator control messages and history across groups of systems.

Configuration takes just minutes through automatic discovery of points, thus reducing engineering costs and improving system integrity. This also eliminates costly, error-prone database duplication.DSA delivers this integration amongst multiple systems while retaining a coherent, global security scheme. Individual Experion Systems can also be operationally integrated while retaining their own engineering autonomy.How Does It Work?Distributed System Architecture dynamically adjusts to changing user and application demands for information. Point data, alarms, history, and operator messages are delivered only to current subscribers, and only when there is a change in status. Additional efficiencies are achieved through the transfer of information between clusters of interested users, rather than between individual users. Therefore, if multiple users are interested in the same data on another site, the request is sent only once.These and other techniques allow Distributed System Architecture to be extremely efficient with its network usage, allowing satellite and other low bandwidth/high latency networking possibilities. DSA being a single integrated system also doesn’t require any dedicated networking and can leverage existing WAN infrastructure. Firewall friendly features allow Distributed System Architecture to adapt to existing firewall configurations to allow existing infrastructure to be used.What Problems Does It Solve?Honeywell’s patented Distributed System Architecture (DSA) technology offers users unmatched scalability by seamlessly integrating the operational data of multiple Experion systems together at the same site or across different geographical locations without additional engineering or configuration.Fault Tolerant Ethernet (FTE) is the industrial control network of the Experion® Process Knowledge System (PKS). Combining Honeywell’s expertise in designing robust control networks with commercial Ethernet technology, it goes beyond providing fault tolerance. FTE ensures the performance, determinism and security required for industrial control applications.

What Is It?The FTE network connects clusters or groups of nodes such as servers and stations, typically associated with the same process unit. It provides multiple communication paths between these nodes so the network can tolerate all single faults and many multiple faults.FTE ensures rapid detection and recovery in case of communication failures with a switchover time of less than a second. It allows normal Ethernet nodes to connect to the FTE control network and benefit from its highly available communications environment. With FTE, users can leverage commercial Ethernet technology found in IT networks to lower the costs of the FTE control network infrastructure, connections to IT networks and third-party Ethernet devices, and ongoing maintenance and support.How Does It Work?FTE ensures that the switchover time in case of a communication failure is less than one second. This is because it uses a single network and does not require a server or station to re-establish its network connection. In addition, the nodes in the FTE control network continually check the status of each communication path to ensure high availability. Conventional Ethernet redundancy schemes employ two separate Ethernet networks with each node connected to both networks. If a communication failure occurs, the elapsed time for a particular node to switch to the other network can be over 30 seconds, depending on network equipment and how the system is configured for network failover.What Problems Does It Solve?With FTE industrial control network, users benefit from efficient fault tolerance as well as fast response, determinism and improved security. The solution does not require purpose-built network switches as it uses commercial, off-the-shelf (COTS) technology. FTE is simpler to operate and manage since it allows seamless connection to non-FTE Ethernet nodes and online additional/removal of nodes.

Unified Simulation Environment

With a protected simulation environment, users can test their control strategies and optimize processes. Honeywell’s Unified Simulation Environment allows the entire Experion® PKS system to be simulated to offer a range of benefits, including efficient control, lower operator training costs and improved plant performance.What Is It?Each Experion PKS controller, including the Application Control Environment (ACE), C200/C200E and C300, has a matching simulation environment. The simulation system environments are identical to the real controllers in terms of control execution, supported I/O and control capacity. This guarantees that a configuration developed on a simulation system will fit the actual controller platform and vice versa.By using a protected process simulation environment, users can effectively test and modify their control strategies to implement tighter and more efficient process control. In addition, high fidelity process simulation can be used to train plant operators for normal process operations and to deal with specific abnormal situations encountered on the job. How Does It Work?The Unified Simulation Environment executes multiple simulated controllers on a PC platform. For larger systems, multiple PCs can be used. The simulated controller developed on a simulation system executes the same control execution environment (CEE) as the physical controller, so the functionality is the same regardless of the environment.Simulated control strategies can read from other on-process controllers through a restricted peer-to-peer communication architecture. This ensures that the simulation cannot influence the real process.Since the simulation system environment is comparable to the real controller from its functionality and configuration capacity point of view, changes or additions to control strategies can be tested offline before implementation.What Problems Does It Solve?The Unified Simulation Environment provides a protected environment for users to test new or existing control strategies without influencing the real process. It guarantees that a configuration developed on a simulation system will fit the actual controller platform. In addition, it delivers cost savings by providing simulation capabilities without requiring dedicated controller hardware or process connections. It enables better training for operators since it uses the same control and operation interface as the real system.

High Performance Process Manager

What Is It?

Ideal for implementation across all industries, the Process Manager controller family is the most mature and field tested controller available. The High Performance Process Manager (HPM) is a process-connected device on the UCN that provides regulatory control and sequence operations. The HPM includes a powerful set of pre-built data acquisition and control algorithms. How Does It Work?The HPM controller supports the classical process control functions for continuous, discrete and batch operations. The embedded object oriented control language provides flexibility for development of customized control functions in addition to the standard ones provided with the product. The HPM controllers have the ability for direct peer-to-peer communication with controllers connected to the UCN or to Programmable Logic Controllers (PLC) using serial interface connection.The controller supports Process Manager I/O, and other protocols such as Modbus, HART and Smart protocol for direct communication with Honeywell transmitters. What Problems Does It Solve?The High Performance Process Manager controller enables process engineers to apply field proven and customized control strategies for plant operation. It can be connected to different data acquisition and control devices using various field communication protocols.

Field Device Manager

Honeywell Field Device Manager (FDM) simplifies maintenance tasks, saves time and provides the flexibility and scalability to perform complete device configuration and management tasks in the plant environment through smart plant instrumentation.

What Is It?FDM is a centralized asset management system for remote configuration and maintenance of smart field devices based on HART, PROFIBUS and Fieldbus Foundation protocols. FDM is integral to supporting Experion-connected devices, yet it easily handles non-Experion networks. FDM supports a large number of devices through FDM clients connected to multiple, distributed FDM servers. With complete command and control of all instruments through the plant, FDM saves time by greatly reducing the number of field trips that would otherwise be required. By simplifying and reducing effort normally involved in plant debugging, FDM improves overall asset effectiveness.How Does It Work?FDM conforms to industry open standards for HART, Fieldbus and PROFIBUS and does not require additional files or programming to support devices or access device-specific features. This includes unmodified use of both Device Description (DD) and Device Type Manager (DTM) technologies as provided by the device vendors. FDM uses a unique remote communication infrastructure that allows widely distributed devices to communicate over a local or wide area network, providing anytime, anywhere access in the plant environment. FDM requires no point engineering or database building. Once the communication networks are configured, FDM automatically detects smart devices and adds them to the database. This saves considerable time for commissioning, troubleshooting or just performing routine maintenance. What Problems Does It Solve?Smart plant instrumentation requires sophisticated tools to configure, maintain, troubleshoot, and diagnose. In a large plant spread out over a considerable physical area, it is imperative that this tool will cover the distance, perform the right job, simplify the work, and save time. FDM is a versatile, accessible and predictable plant instrumentation solution that simplifies smart instrument maintenance.

FOUNDATION Fieldbus Interoperability Support

To allow interoperability with Experion® Process Knowledge System (PKS) and other host systems, all FOUNDATION Fieldbus device vendors create and make available files known as DD (Device Description) and/or EDDL (Electronic Device Description Language) files. The files allow Experion to understand the device functions, features, and parameters. Honeywell and Flowserve device firmware files are also available.

What Is It?DD and EDDL files are provided by every device vendor and contain the information required by Experion to utilize the device capabilities and functions in the Experion system. DD files are the original standard while EDDL represents the next generation of the technology and augments the DD technology with added features to better support the needs of more complex devices such as valves. All vendors must provide a DD for every device while EDDL is optional. Honeywell maintains a Fieldbus Interoperability Test Laboratory for testing FOUNDATION Fieldbus devices and their DD/EDDL files. Users can access test information and download the vendor device DD/EDDL files from the "Documentation" tab of this page. In addition, device firmware files are also available for select vendor devices. These files can be used to update device firmware from Experion Control Builder.How Does It Work?DD and EDDL files are used in the Experion Control Builder environment to create device-specific templates that integrate the associated device with Experion and allow the device blocks to be used in the control scheme.

Experion R400 is the first release to support EDDLs For all releases prior to R310, users must download the DD from the Honeywell website For R310 and above, users should download the DD directly from the FOUNDATION Fieldbus website In case of any DD or device-related issues, users should contact their local Technical Assistance Center (TAC)

What Problems Does It Solve?By accessing and downloading the required DD, EDDL, and Firmware files, users can seamlessly integrate Fieldbus devices into their

Experion systems.

HART Integration

HART is an open protocol that delivers the benefits of smart field devices while offering the simplicity and ease-of-use associated with traditional I/O. Experion® Process Knowledge System (PKS) integrates HART devices to improve system performance, process availability, safety and throughput, while reducing lifecycle costs for upgrading and maintaining smart field devices.

What Is It?

Honeywell ensures seamless integration with Experion with its HART enabled I/O modules. Available in the Chassis-A, PMIO, and Series-C form factors, the modules enable the effective use of HART digital data for control, display, diagnostics, parameterization and asset management. Users can improve availability by implementing the modules in an optionally redundant fashion.Experion PKS provides the freedom to communicate with HART devices removing barriers such as scan rate limitations. Access to detailed device performance and abnormal condition information lets users report device malfunction or failure and information about process-related abnormalities. In addition, the HART solution provides plant operators and maintenance personnel full access to all field device information directly through Experion.

How Does It Work?Experion’s best-in-class, ‘open’ HART solution automatically populates HART process and status data through the I/O cards into the C200 and C300 process controllers, and finally into standard operator displays. Absolutely no additional configuration is required. The I/O cards also provide a pass-through capability that enables full asset management using the Honeywell Field Device Manager (FDM) application.The complete solution is based on open standards and is fully compliant with the HART protocol specification. The handheld solution is available on open pocket PC-based platforms and works equally well with devices from all vendors. All device-specific data is gathered from the HART standard device description (DD) files and no special vendor files are required to integrate the device with the Honeywell solution. If no DD file is available, the HART universal and common practice data and diagnostics can be utilized.

What Problems Does It Solve?Smart field devices provide valuable process and diagnostic information that enhances every facet of the process and improves plant

operations and availability. Experion HART integration allows users to access and utilize this valuable information in a cost-effectively manner, using a technology that is easy to implement. This results in improved process availability and enhanced safety management of the process, plant and personnel.

Magnetic Flow Meter :

Application of Magnetic Flow Meters : Magnetic Flow meter measures the volumetric rate of flow any liquid that has adequate electrical conductivity. Most petroleum hydrocarbons have insufficient conductivity to be measured with a magnetic flow meter. It is rarely used in Petroleum Industry.

Magnetic Flow meters are widely used on slurries

Advantages of Magnetic Flow Measurement1.They respond only to the velocity of Fluid .Independent Density Viscosity and Static Pressure2.High Rangebility 10:13.Bidirectional Flow Measurement4.Fluid Temperature range -40 Deg C to +260 Deg C5.Pressure Drop is negligible6.Wide Variety of Size

Disadvantages of Magnetic Flow Measurement1.Conductivity of the process fluid should be greater the 2 micromhos per centimeter2.Special care is required for erosive application 3.Difficulties in on site calibration4.High cost5.Large Sizes are very heavy

Installation Consideration : Magnetic Flow Meter consist of two parts Primary elements installed directly in the processline

Secondary elements is an electronic transmitterMagnetic flow meter tube may be installed in any position but it must run full of liquid for accurate measurement

DP Transmitter Installation

Gas line: the transmitter is installed above the orifice plate to prevent the condensation of gas in the signal line and in the HP & LP chambers.Liquid line: the transmitter is installed below the orifice plate to prevent the gas trapping in the signal line and in the HP & LP chambers.

Static HeadStatic Head = pgh p= Density of the liquid g= Gravityh= height of the liquid columnType J Thermocouple - Iron Constantan Type T Thermocouple Copper Constantan Type K Thermocouple Chromel AlumelType N -Nicrosil Nisil Type E - Chromel ConstantanType S- Platinum 10 % RhodiumType R - Platinum 13% RhodiumType Cu - UncompensatedType C - Tungsten Rhenium

How to identify (ATEX/CENELEC/IEC) label?

ATEX MARKING FOR EXPLOSION APPARATUS (Directive 94/9/EC (ATEX 95)) Distinctive mark for the putting into circulation of explosion-protected apparatus

DEVICE GROUP (CENELEC/IEC)Device GROUP I : applies to devices for mining operations above ground and underground that may be endangered by methane gas and/or inflammable dustDevice GROUP II : applies to devices for use in all other areas that can be subject to the hazard of an explosive atmosphere

Interview Question : Hazardous Area ZoningTwo types of standards are thereFor Europe CENELEC – in process of being transferred to IEC/EN (European Committee for Electrical Standardization)IEC(International Electrotechnical Commission)

North AmericaNEC 500NEC 505(National Electric Code)Hazardous Area Zoning For Gases Vapor & Mists (CENELEC & IEC)Zone 0 - Explosive gas atmosphere is present continuously or for long periods(typically > 1000 hours/year)Zone 1 - Explosive gas atmosphere is likely to occur under normal operating conditionZone 2 - Explosive gas atmosphere is not likely to occur in normal operation and if it occurs, will only exist for a short period (typically < 10 hours/year)Hazardous Area Zoning For Dusts (CENELEC & IEC)Zone 20 - Explosive gas atmosphere in the form of a cloud of combustible dust in air is present continuously or for long periods or frequentlyZone 21 - Explosive gas atmosphere in the form of a cloud of combustible dust in air is likely to occur in normal operation occasionallyZone 22 - Explosive gas atmosphere in the form of a cloud of combustible dust in air is not likely to occur in normal operation but if it occurs, will only exist for a short periodHAZARDOUS AREA ZONINGFor Gases, Vapors & Mists (NEC 500)Division 1An area in which an explosive atmosphere exist continuously or some time under normal operating conditionsDivision 2An area in which explosive atmosphere is not likely to exist under normal operating conditionsEXPLOSION MEDIUM CLASSIFICATION (NEC 500)There are 3 general classes which define the flammable materials present in the atmosphere :Class I Mixture of Gas/Vapor with atmosphereClass II Mixture of Dust with atmosphereClass III Mixture of Fibers with atmosphereLOCATION TERMINOLOGY(NEC 500)CLASS 1, DIVISION 1Location where ignitable concentrations of flammable gases, vapours or liquidsCan exist under normal operating conditionsMay exist continuously, intermittently, or periodically because of repair or maintenance operations or because of leakageMay exist because of equipment breakdown that simultaneously causes the equipment to become a source of ignitionCLASS 1, DIVISION 2Location where ignitable concentrations of flammable gases, vapours or liquidsWhere volatile flammable liquids or flammable gasesMay exist continuously, intermittently, or periodically because of repair or maintenance operations or because of leakageMay exist because of equipment breakdown that simultaneously causes the equipment to become a source of ignitionUsually for the non-incendive, non-sparking, pressurized, hermetically sealed or sealed device type

Different Types of Instrument errors areAny given instrument is prone to errors either due to aging or due to manufacturing tolerances. Here are some of the common terms used when describing the performance of an instrument.RANGE The range of an instrument is usually regarded as the difference between the maximum and minimum reading. For example a thermometer that has a scale from 20 to 100oC has a range of 80oC. This is also called the FULL SCALE DEFLECTIONACCURACY The accuracy of an instrument is often stated as a % of the range or full scale deflection. For example a pressure gauge with a range 0 to 500 kPa and an accuracy of plus or minus 2% f.s.d. could have an error of plus or minus 10 kPa. When the gauge is indicating 10 kPa the correct reading could be anywhere between 0 and 20 kPa and the actual error in the reading could be 100%. When the gauge indicates 500 kPa the error could be 2% of the indicated reading.REPEATABILITY If an accurate signal is applied and removed repeatedly to the system and it is found that the indicated reading is different each time, the instrument has poor repeatability. This is often caused by friction or some other erratic fault in the system.STABILITY Instability is most likely to occur in instruments involving electronic processing with a high degree of amplification. A common cause of this is adverse environment factors such as temperature and vibration. For example, a rise in temperature may cause a transistor to increase the flow of current which in turn makes it hotter and so the effect grows and the displayed reading DRIFTS. In extreme cases the displayed value may jump about. This, for example, may be caused by a poor electrical connection affected by vibrationTIME LAG ERROR In any instrument system, it must take time for a change in the input to show up on the indicated output. This time may be very small or very lar ge depending upon the system. This is known as the response time of the system. If the indicated output is incorrect because it has not yet responded to the change, then we have time lag error.RELIABILITY Most forms of equipment have a predicted life span. The more reliable it is, the less chance it has of going wrong during its expected life span. The reliability is hence a probability ranging from zero (it will definitely fail) to 1.0 (it will definitely not fail).DRIFT This occurs when the input to the system is constant but the output tends to change slowly. For example when switched on, the system may drift due to the temperature change as it warms up.

Bench set on a control valve actuatorOn a pneumatic control valve, this is the minimum and maximum air pressure to be applied to achieve the full stroke length of the actuator

Double seated control valveIt is a control valve whose trim (plug and seat) has two seats (contact points). A double seated control valve is commonly used in high differential, huge capacity, turbulent flow lines.

Name of the cable used to connect a thermocouple to a measuring instrumentThe intermediate cable used for connecting a thermocouple from the field to the control room instrument is called a ‘compensating cable’

Convert a pressure gauge into a level gaugeCalculate the static head in kpa using the formula “pgh”. Select a pressure gauge and calibrate it for the calculated static head. Graduate the pressure gauge scale in terms of % of level.

DCS Engineer Interview Questions - Fundamentals (Refinery ,Power Plant, Chemical Plant ,Paper)Some of the Interview questions for Control System Engineers - DCS (Distributed Control System )Q) Definition of DCS?A microprocessor based control and Data acquisition system consisting of number of modules operating over a network.Q)Typical functions available in DCS1 PID Control2 Discrete control3 Advanced control capability4 Alarm management5 Graphical and Schematic displays6 Trending of real time and historic data7 Communication between other device and subsystem8 Data acquisition9 Report generation10 Data HistorizationQ) Different type of PID function included in DCS?PID Basics controllerPID RatioPID cascadePID BiasPID Differential gapPID adaptive gainPID non linearManual stationPID self tuningExternal output trackingReset limitingQ)Math functions included in DCS?ADDSubtractMultiplyDivisionSummationDifferenceSquare rootSquareAbsolute ValueLogarithmExponentialPolynomialQ) Dynamic functions included in DCS?Lead/LagDead timeVelocity limitTotalizeQ) Logic controls included in DCS?AndORExclusive OROn/Off DelayInverterFlip-FlopPulseNand Nor

Reset action with an exampleReset action in a controller is the integration of the proportional action by the set period. The reset action repeats the proportional action’s output per the reset time set, until the error signal becomes zero or the output gets saturated.For example :if the reset action is set for 30 sec.For a 0.5 volt correction output ;by the proportional action will be repeated by the reset action every 30 secs., until the error signal becomes zero or the output gets saturated.

Fahrenheit to Centigrade temperature conversion formula

Deg C = ( Deg F – 32 ) / 1.8

Single seated balanced trimIt is a trim having a single seat and balance holes on its plug. A single seated balanced trim is used in a process line where the DP across the valve is high. These kind of trims are useful in reducing the vibration on the valve body and also assists in closing the valve.

Brief Idea About Hazard and Hazardous Area Classification?Meaning of Hazard.Anything which has the potential to cause:Harm, ill health or injury to people Damage to property, products or environmentMeaning of Hazardous AreaArea in which an explosive atmosphere is, or may be expected to be, present in quantities such as to require special precautions for the construction, installation & use of electrical apparatus ’Meaning of Hazardous Area ClassificationMethod of analyzing and classifying the environment where explosive gas atmospheres may occur so as to facilitate the proper selection an installation of apparatus to be used safely in that environment

Explosion protection enclosure typesEx d Flameproof EnclosuresMotors with sliprings & commutators3 phase squirrel cage motorsEquipment that could ignite an explosive atmosphere housed within a substantial enclosure without transmitting internal explosion to surroundingsEx eIncreased Safety3 or 1 phase rotor with cage rotorCurrent & voltage transformersIncreased measures taken to prevent generation of arcs, sparks & excessively hot areas in equipment, preventing risk of explosion inside/outside of enclosureEx iIntrinsic SafetySwitches, plugs & socket, terminal boxesEnergy is limited to this equipment in such a way that a spark or a hot surface would not be hot enough to ignite the explosive atmosphere

Ex mEncapsulation Relays, signal & control unitsApparatus is totally encapsulated by a non-porous compound & electrical connection is by flying leads

Ex nNon - Incendive*Gives a level of protection by housing electrical equipment in substantial enclosures that inhibit mechanical damage & give some degree of ingress protection

Ex oOil ImmersionSwitchgearTransformersEquipment is totally immersed in oil preventing an explosive atmosphere from reaching the equipment

Control valve parts

a) Trimb) CVc) Actuatord) Stem travele) Valve bodyf) Yoke g) Gland packing

Trim : Trim is a matched pair of ‘plug’ and ‘seat’CV : The amount of water flow in gallons through the control valve when the valve port is fully open and the pressure differential across the valve is 1 Psi.Actuator : The drive unit having a diaphragm and a piston that operates the valve stem.Stem travel: The scale that shows the stem movement in inches or centimeter.Valve body: The bottom portion of a control valve installed on a pipeline to control a process. The valve body contains a trim, pipe flange, bonnet, gaskets, guide bush, gland packing, lantern ring, grease, cooling fins…etc.Yoke : A portion of the actuator which connects the actuator to the valve body carrying a stem travel plate.Gland packing: A sealing system in the valve body which prevents the process fluid coming out through the valve stem.

Calibration of a leveltrol for an interface level measurementFill the leveltrol chamber 100% with the lower density liquid and adjust its zero for 4.00mA output.Drain the liquid and fill the leveltrol chamber 100% with the higher density liquid and adjust its span for 20.00 mA output.The transmitter on line measures the percentage of higher density liquid in the lower density liquid at a known height.

Upstream and downstream straight length run is essential for an orifice plate flow measurementThe upstream can be identified by the orifice plate’s Tag number markings. Tag numbers are always marked on the upstream of the orifice plate.An upstream of 28D and a down steam of minimum 7D is essential for an a

Zero check and static zero check on a DP flow transmitterZero check- A procedure for checking the transmitter output is equal to 4.00 mA when its HP & LP chambers are equalized and are at the atmospheric pressure Static zero check- A procedure for checking the transmitter output is equal to 4.00 mA when its HP & LP chambers are equalized and are at the operating pressure.

Valve positioner and its workingValve Positioner is a unit used on a control valve to keep the valve in position. It works as a booster relay with a valve stroke feed back. A controller output is fed to the valve positioner and the valve position provides an output to the control valve actuator to achieve the pre-calibrated stroke length. In case the require stroke length isnt achieved, then the positioner either increases or decreases its output until the valve achieves the desired stroke length. This situation may occur when there is a great change in the process pressure, gland is too tight…etc.

Volumetric and Rate of flowVolumetric Flow: The total amount of fluid passed through a process line. Generally it is measured on counters. The measuring unit is cubic meter, Barrels…etc.Rate of flow: The amount of fluid moving through a process line per period of time. Generally it is measured on indicators, recorders. The measuring unit is cubic meter per day, barrels per day…etc.

Possible reasons if a control valve fails to open/closeGland packing is too tightActuator bench set is not proper or suitable Process load change is too highTrim is an unbalanced typeActuator spring is brokenAir supply to the valve positioner / actuator is close or high ..etc

Zero suppression and Zero elevation in level measurementZero suppression: when a static head transmitter is installed below the zero liquid level, the transmitter gets a +ve error in the level measurement. This error is corrected by a zero suppression kit.Zero elevation: when a static head transmitter is installed above the zero liquid level, the transmitter gets a –ve error in the level measurement. The error is corrected by a zero elevation kit.

Over sized control valveA control valve is said to be oversized when a minimum signal to the valve (minimum opening of the valve) brings process to the set point rapidly. This situation leads to an imbalance and high gain in the control loop. The problem can be solved by changing the valve trim to a reduced trim size or by replacing the control valve for the correct size.

Direct acting and Reverse acting control valveDirect acting control valve : The valve port closes on air failure.Reverse acting control valve: The valve ports Opens on an air failure.

QUESTION PAPER PAER FOR THE ELECTRICAL AND INSTRUMENTATION CANDIDATE

1. What is the supply frequency in India? a) 60HZb) 55HZc) 50HZe) 40HZ

2. What will be the total resistance in a parallel circuit?a) Higher than that of the higher resistance value b) Lower than that of the least resistance valuec) Higher than that of the all resistanced) It may all of the above

3. Mass of an electron is…….…?a) 9.109x10-31b) 109.9x10-31c) 19.109x10-13d) 0.9x10-31

4. What will be the color cored of 21x106 Ω ±10% ?a) Red , brown, blue, silverb) Red, black, blue, silverc) Red, red, black silver d) Red, brown, violet, silver

5. Unit of the inductance will be ?a) Hertz b) Faredc) Henryd) Tesla

6. Expansion of PLC will be?a) Programmable logic convertor b) Programmable logic contactor c) Programmable logic controllerd) Programmable logic connector

7. Frequency of a DC current will be ………..? a) 0HZb) 100HZc) 50HZd) None of the above

8. Dielectric of paper capacitor will be ?a) Polyesterb) Micac) Paper d) Can mica or polyester

9. 1/1000000Ampere will be? The sum of the voltage drops across the resistances of a closed circuit equals the total voltage applied to the circuita) 1 lack ampere b) Mille ampere c) Mega ampere d) Micro ampere

10. The sum of the voltage drop across the resistance of a closed circuit equal to the total voltage applied to the circuit - statement is related to ………. low ?a) Ohms low b) Lows of electro magnetic induction c) Lowsc) Kirchhoff low d) Charles low

11. What can the principle of conductivity sensor?a) Reluctance b) Both (a) and (b)

c) Resistivityd) Non of the above

12. Ladder logic is related to ………. ?a) PLCb) MCBc) ELCBd) OLR

13. VFD is controlling the …………. ?a) Speedb) HPc) Frequency of supply d) Torque

14. Total capacitance in parallel connection will be ?a) Always higher than that of series connection b) Always less than that of series connection c) Always constantd) None of the above

15. Resistance of dry skin ? a) 1000Ω to 660Ω b) 100KΩto 660kΩc) 200Ωto 300Ωd) 600 kΩ to800kΩ

16. In a sign wave maximum positive voltage will be at ?a) 2700b) 900c) 3600 d) 800

17. Formula for the inductive reactance?a) 2πfLb) 2 πxLc) 2 π Ld) π fL

18.a) High tension transformer is rated in ?b) KWAc) KVA d) KWh

19. Instead of 0mA we are taking 4mA the for the transmission ?a) Differentiate 0 input and fault disconnection of the wireb) It is the minimum current we can measure c) We can use ay current d) Non of the above

20. SCADA stands fora) Supervisory control and data Acquisitionb) Sub control data addition c) Super control data action d) No expansion is available

21. Rota meter is using for measuring?a) Conductivity b) Flow c) Pressured) Temperature

22. Working principle of the thermocouple?a) Ohms effectb) Zee back effect c) Thermal effect d) Non of the above

23. Expansion of the MMI?a) Man machine Interference b) Man mechanism interferencec) Man mechanical input d) Man made input

24. Boosting of the power factor can de by? a) Capacitorsb) Indictors c) Resistors d) Cant able to boost up

25. Write down the expansion of the following points?a) OLR………..

b) SDF…..……c) VFD………..

Working of Leveltrol

A Leveltrol in and instrument used for measuring the liquid level between two known points. The Leveltrol works on the buoyancy principal. Leveltrol has a float, which submerses proportionately with liquid level raise in the float chamber. The amount of submersion of the displacer depends on the liquid density, which produces a torque. The amount of torque produced in measured in terms of % of level.Parts of Leveltrol:Float chamber, Float, Torque lever, Knife edge, Feedback Bellows, Air Relay, Restriction, Flapper, Nozzle, Feedback link, Density range, Action change lever, HP and LP flange,

Use of a DP (differential pressure) transmitter for level measurement

A differential pressure transmitter gives a linear output for the differential pressure measured across its HP and LP chambers.Connect the transmitter’s HP leg to the bottom of the tank and its LP leg to the top of the tank. The transmitter will read the liquid level accurately irrespective of the change in process pressure above the liquid surface.Brief Idea About Thermocouple Extension and Compensation Cable?Extension and compensating cables are used for the electrical connection between the open ends of a thermocouple and the reference junction in those installations where the conductors of the thermocouple are not directly connected to the reference junction.Extension cables are manufactured from conductors having the same nominal composition as those of the corresponding thermocouple. They are designated by a letter "X" following the designation of the thermocouple, for example "JX".Compensating cables are manufactured from conductors having a composition different from the corresponding thermocouple. They are designated by a letter "C" following the designation of the thermocouple, for example "KC". Different alloys may be used for the same thermocouple type, they are distinguished by additional letters such as, for example, KCA and KCB.

Instrumentation Interview question : Vortex meters are used in which services?Vortex meters are commonly used in following services1.Steam2.Cooling water3.Process water4.Light hydrocarbons where large turndown is required.5.Gas flow where large turndown is requiredFunction of an orifice plate in flow measurementAn orifice plate creates a differential pressure in a flow line. The DP created is use for measuring the flow through the process line‘d’ (orifice diameter) id permitted in a pipeline

0.25 D<d<0.75 D‘d’ – the Orifice diameter should be in-between 0.25 and 0.75 of the pipeline ‘D’ diameter.The orifice plate used in a gas line will be having a small drain whole at the bottom of the orifice plate.Lantern ring location on a control valveA greasing ring placed in the valve bonnet across the gland packing. The unit provides lubrication to the valve stem when lit travels up and down.What are the regular problems occured by control valves in maintainanceMajor problems are1.Dead band2.Stiction3.Positioner overshoot4 Incorrect valve sizing5 Nonlinear flow characteristic

Flow factor and its derivationA ‘flow factor’ is to multiply the flow transmitter signal measured on a 0-10 square root or 0-100 linear scale to get the flow calculated by flow metering. This is used due to the standardization of the transmitters signals, to 20-100 kPa or 4-20mA. The following points are considered for flow calculation and in deriving the flow factor:D = pipe diameter,Small d = orifice diameter Service = gas or liquidPI = operating pressureDP = Transmitter differential pressure T =operating temperature Small p= density or molecular weightSmall v= viscosityCold junction compensation‘Cold Junction Compensation’ is used in temperature measurement by means of a thermocouple. This compensation is to correct the error caused by the room (ambient) temperature. The mv produced by a thermocouple is proportional to the temperature difference between its ‘hot’ and ‘ Cold’ junction. The cold junction is the ambient temperature (control room). Without ‘cold junction compensation’ the temperature at the hot junction will measure inaccurately.

Selection of a level switch for a particular processWhile selecting a level switch, the following points are to be considered:- The characteristic of process (corrosive or non – corrosive)- The process pressure - The liquid density - The flange ratings- Proof pressure of the switch - The micro switch contact rating

Type of orifice tapping is commonly used in P.D.OPDO in general, is using the ‘Flange Tapping’. The upstream and downstream orifice tapping are taken from the flanges.

Contact selection on high and low pressure alarm switchesOn a high pressure switch, the wiring is terminated on the “common” and the “normally close” contact terminals.On a low pressure switch, the wiring is terminated on the “common” and the “normally open” contact terminals.This type of contact termination is done to achieve a close contact from the switch during a normal (healthy) process condition which is a fail safe method.Why RTD measurement use 3 wires for a field signal connection3 wire system is used in temperature measurement by an RTD to compensate the line resistance. Three wire system provides a Wheatstone Bridge in the measuring instrument.

New flow factor if a DP transmitter is re-ranged from 25 kPa to 50 kPaA simple calculation is as follows:Q1/Q2 = Sq root of DP1/ Sq root of DP2Q1 = Q2 * Sq root of DP1/ Sq root of DP2Q1 = New flow factor, Q2 =Existing flow factorDP1 = Transmitter new range, DP2= Transmitter existing range

Q1 = Q2*SQ ROOT OF 50/25Q1 = 1.41*Q2

The new flow factor will be 1.41 times higher than the existing flow factor.

Process Instrumentation : Flow Measurement Application Advantages and Disadvantages of Turbine Meters . Installation ConsiderationApplication of Turbine Meters : Custody transfer and in line blending. Turbine Meters are used where high accuracy and range ability are required.Pulse output from the Turbine Meter may be scaled for direct totalization in engineering unit.Turbine meters are ideally suitable for batch Control application

What is the meaning of SAT and FAT ( Site Acceptance Test and Factory Acceptance Test )Factory Acceptance Test : FAT is to verify that the system and its components function properly that all manufacturing assembly software generation and configuration have been done correctly and completely and that the system performance is in compliance with the agreed upon procurement specificationSite Acceptance Test : SAT takes place after the complete installation and final configuration. This test should repeat FAT or an acceptable subset of the test to verify that no damage occurred during shipment and installation.

Analogue IO cardsNormal analog I/p is in the range of 0 to 10V or 4-20ma signals.For that type of signals normal analog input cards are used. But RTD ouput are in resistance variation and Thermocouples output are in the range of mv which require special conditioning before processing. For this type of signals , we are using special type of analog input cards. Example for Honeywell DCS, For normal analog input using HLAI cards(High Level Analog Input) and for RTD and T/C using LLAI cards(Low level Analog Input).

Function of a hair –spring in a pressure gaugeHair – spring in a pressure gage eliminates the Hysterisis (backlash/angularity) error caused in the quadrant (gear and pinion mechanism) and the weight of the pointer.

What is to be done, if a transmitter gives a maximum output , where the transmitter range (jumper) is already in maximum selectionReplace the capsule (sensor) for a higher range in the transmitter.

Separation between the ESD System and the F&G System; standard or just a good practice?Separation of systems has nothing to do with the fact that one is fail safe and the other is non-fail safe. Nor does it have anything to do with alarm segregation.There is no standard which specifies the requirement for independent ESD and F&G systems. However, if you read between the lines you will find that this is more often than not implied and common sense.One of the important things to remember here is that if going for independent systems, you can take credit for these systems as independent layers of protection. So for instance, if the pressure in a vessel goes about High and into the HiHi range you can consider the ESD HiHi trip as a layer of protection. If this fails then a flange leak may lead to loss of containment which could be picked up by F&G detectors and prevent further escalation of events. If using an integrated system, you have to ensure that there are no common mode failures because of sharing the same PLC.Generally it will be difficult to prove that no common mode failures can originate and this is why it is generally advisable to consider 2 independent systems up front, rather than changing things after orders have been placed.If your F&G system is small, localized and has specific trip actions for electrical isolation then these may be treated as F&G executive actions and you need not implement these in a separate ESD system.The design also depends on the nature of process risk associated with your operations. If risks are low then there is no need to go for independent systems. Always analyze risk before making decisions, this will make the answer clear to you.

Relation (formula) between a gain and proportional bandA controller ‘gain’ is inversely proportional to its proportional band.. g = (1/p)*100. g = gain. P = proportional band

Bump-less transfer in a controller’s auto/manual change over‘Bump-less transfer’ is to eliminate the change in the controller’s output when the controller is changed from auto to manual control and vice-versa.

Basics of Control loopControl loop is consist of all the elements necessary to move the final control elements.Different types of final control elements are Valve,Motor,Fan etc.. Final control elements allows to keep controlled variable on target.Process measuring elements sends a signal to the controller.At the same time the already determined setpoint is compared with the signal coming from measuring device.The error detector makes a comparison between the signal from process and the setpoint signal.If there is a difference between this an error signal is sent to the control logic that changes the position of final control device. The change in the Final control device will cause a change in process.This process will continue until the setpoint is maintained.Elements of Control loop are 1.Measuring Device2.Controller3.Final control deviceTerms used are.Process VariableManipulated VariableController ErrorSet point

Instrumentation standards & codesSTANDARD DESCRIPTIONISA INSTRUMENT SOCIETY OF AMERICAANSI American National Standards Institute BS British Standard API AMERICAN PETROLEUM INSTITUTEIEC INTERNATIONAL ELECTROTECHNICAL COMMISSIONIS INDIAN STANDARDNEMA NATIONAL ELECTRICAL MANUFACTURERS ASSOCIATIONNFPA NATIONAL FIRE PROTECTION ASSOCIATIONOISD OIL INDUSTRY SAFETY DIRECTORATEIP INSTITUTE OF PETROLEUM

INSTRUMENTATION STANDARDSInstallation standards for all instruments API RP 551 Refinery Control Valves API RP 553Control Valve Seat Leakage ANSI 70.2 Hydro static testing on control valves ANSI B 16.37 Specification for PVC insulated instrument cables BS-5308 Intrinsically safe apparatus in div 1 hazardous location NFPA 493Specification for degrees of protection provided by enclosures IEC 60529

Calibration of a static head level transmitter for an interface measurementStatic head level transmitter is not commonly used for measuring the interface level. But the following procedure may be used for calibrating it to measure the interface level in a tank.Fill the vessel 100% with the lower density liquid and adjusts its zero for 4.00 mA output. Drain the liquid and fill with the vessel 100% with the higher density liquid and adjust its span for 20.00mA output. 100% transmitter level is to be continuously maintained. The transmitter on line measures the percentage of higher density liquid in the lower density liquid in a know height.

How does HART( Highway Addressable Remote Transducer) works?The HART Protocol provides two simultaneous communication channels on the same wire: 4-20mA “current loop” analog and a HART digital signal. While the analog signal continues to provide primary values to and from field instruments, the digital signal provides additional device information. This is a very robust method with roots in the Bell 202 Frequency Shift Keying (FSK) standard, which originally superimposed a digital communication signal "on top of" the 4-20mA current loop to bring Caller ID technology to the field of telephony

Common Interview Questions: Instrument and Control Engineers

1. What are the process Variables?2. Define all the process Variable and state their unit of measurement. ?3. What are the primary elements used for flow measurement?4. What are the different types of orifice plates and state their uses?5. How do you identify an orifice in the pipe line?6. Why is the orifice tab provided?

7.What is Bernoulli's theorem and where it is applicable?7. How do you identify the H. P. side or inlet of an orifice plate in line?8. How do you calibrate a D. P. transmitter?9. What is the seal liquid used for filling impulse lines on crude and viscous liquid ?10. How do you carry out piping for a Different pressure flow transmitter on liquids, Gas and steam services Why ?11. Draw and explain any flow control loop ?12. An operator tells you that flow indication is more, How would you start checking?13. How do you do a zero check on a D.P. transmitter ?14. How would you do Glycol filling or fill seal liquids in seal pots 7 Draw and explain.15. How do you calculate new factor from new range using old factor and old range?16. How will you vent air in the D.P. cell? What if seal pots are used?17. Why flow is measured in square root?18. What is absolute pressure?19. What is absolute zero pressure?20. What is the maximum Vacuum?21. What is Vacuum?22. What are the primary elements for measuring pressure?23. How will you calibrate an absolute pressure transmitter using vacuum manometer. Range 0-400mm abs?24. You are given a mercury manometer range 0 -760 mm ? A vacuum gauge reads 60 mm vacuum. The test manometer reads 50 vacuum ?

Which of the two in correct.25. Why is an inclined manometer used ?26. What is the principle of a pressure gauge ?27. Draw and explain a pressure gauge ? What is the used of a Hair spring ?28. Briefly explain the different methods of level measurement?29. Explain how you will measure level with a different pressure transmitter.30. How is D.P. transmitter applied to a close tank?31. How is D.P. transmitter applied to an open tank?32. How is D.P transmitter applied to a close tank & open tank with Dry leg?33. What is purge level system?34. Explain the working of a leveltrol.35. How will you reverse an action of the leveltrol?36. What is interface level? How do you calculate it?37. How will you calibrate a leveltrol in the field?38. How will you calibrate on interface level control. ?39. How will you apply wt. lest calibration to a leveltrol.40. What will happen if the displacer has fallen down while in line ?41. What will happen if the displacer has a hole in it while in line?42. What is the used of Suppression and elevation?43. How will you commission D.P. transmitter in field in pressurized vessel.

44. How will you check zero of a level D.P. transmitter while is line?45. Explain the working of an Enraf level gauge?46. What are the different methods of temperature measurement? Explain47. What is Pt 100 mean?48. What is two wire and three wire R.T.D. system?49. Draw a potentiometer temp. Measuring circuits and explain its?50. What is the constant voltage unit?51. Explain the working of a balancing motor.52. What is burnout feature ? Explain53. Why are Thermowells used ?54. What type of sensing element would you use to measure very low temperature ?55. What are skin temperature thermocouples ?56. What is the specialty of thermocouples lead wires ?57. What is the difference the a wheatstone bridge and a potentiometer ?58. Explain the application of proportional integral and derivative action?59. Where is on off control used?60. What is reset-wind up?61. Why is reset called integral and Rate derivative ?62. Explain tuning of controllers.63. Explain the working of an electronic P.I.D. controller.64. What is an analogue integrator and an analogue Explain the working of Rotameter?65. Explain the working of a magnetic meter.66. Explain the working of a turbine meter.67. Explain the working of a Pitot tube.68. Where is the integral orifice used ?69. What are types of taps used for orifices ?70. What is Reynolds number ?71. How would you choose differential range ?72. What is positive Displacement meters ?73. What is a control valves ?74. What are the different types of control valves ?75. What is the use of single seated valve ?76. What is the use of double seated valve ?77. What is Cv of a valve ?78. What are the different types of actuators ?79. What types of bonnets would you use of high temp. and very low temp. ?80. How will you work on a control valve while it is line ?81. What is the use of a valve positioner ?82. When can a by pass be not used on a positioner ?83. What is the use of butterfly valves ?84. What is the use of three way valves ?85. What are the different types of plugs ?86. What is a cage valve ?87. What is the use of link connected to the valve positioner ?88. What is the use of booster relays ?89. What is the use of Angle valves ?90. What are the different valve characteristic ?91. What is a solenoid valve ? Where it is used ?92. How will you change the valve characteristics with positioner ?

110.How will you change the action of a control valve ?93. How will you select the control valve characteristics ?94. What is the effect of pipe reducers on valve capacity?95. An operator tells you that a control valve in a stuck ? How will you start checking ?96. Where is an Air to close and Air to open control valves used ?97. Why does control valve operate at IS psi ?98. differentiator ?99. What is an anti reset wind up ?100. What are De-saturators ?

Types of Bourdon tubesThe following are the commonly used Bourdon tubes used in industries:- Spiral –Low range 10 –100kpa- C type –Medium range 100 – 5000kpa - Helical – High range 5000 – 20000kpa

Application of Twisted Pair Cable:Twisted pair cabling is a form of wiring in which two conductors are wound together for the purposes of canceling out electromagnetic interference (EMI) from external sources.*Twisting wires decreases interference because the loop area between the wires is reduced.

*The two wires typically carry equal and opposite signals which are nutralized because of phase shift. twisted pair cables are very qualitative in nature as they prevent electromagnetic interference from external sources and crosstalk from external wires. They are majorly used in telephone networks, data networks and cable shielding. Our twisted pair cables are of two types, which are: Shielded Twisted Pair Cables: These cables protect cable from external electromagnetic interferences and are used with token ring networks. Unshielded Twisted Pair Cables: Theseare the unshielded twisted pair cables which are highly flexible and long lasting in nature. Our cables are used in many Ethernet networks and telephone systems

Basics of Foundation FieldbusAll digital serial two-way communication system –interconnects field equipment (sensors, actuators and controllers) – architecture for building inter operable distributed real time control systems.Multidrop wiring ( 32 devices on a single pair of wires (called a segment)Multivariable Instruments (Multiple variables from one field device )Two-way communication New types of informationControl in the fieldInteroperability :Device from different suppliers can be communicate with each other and perform their function in multi-vendor environments. (standardize communication protocol from Physical layer through Application Layer)Interchangeability: Device from different suppliers can be functionally interchanged by providing the same functionality for the same type of devices. (Standardize various function blocks)What user wants is to provide interoperability and the same basic functionality for the same type of devices and room for innovation by suppliers for additional unique functionality (Provide a common way to describe/understand suppliers specific features (DDL).Foundation fieldbus communications modelThe Physical LayerData Link Layer and Application LayersThe User LayerPhysical Layer: Translating messages into Physical signals on the wire –and vice versaPhysical Layer: Provides the common Electrical Interface for all foundation fieldbus devices. (H1 segments -Power supply 9-32 Volts DC Power and 15-20 mA of current per device – communication rate –31.25 kbaud –32 devices per segment; upto 240 devices total with repeaters.Data link and Application layers: Control transmission of data on the fieldbus.Standard way of packaging the data as well as managing the schedule for communication and function-block execution.User Layer: contains transducer block, resource block and function blocks that describe and execute –device capabilities such as control and diagnostics. Device descriptions enable the host system to interact with and understand these blocks without custom programming.Benefits of FieldbusSystem can be built from devices manufactured by different vendorsNo single company controls the evolution of the standardInteroperabilityReduced CostLess wiring installation and maintenance cost because of multi-dropBetter diagnostics through softwareControl distributed in the fieldMore data available from the devicesDiagnostic DataMultiple variablesInterview Question for Automation,DCS,PLC Engineers

1. Draw system architecture showing PLC, SCADA/MMI, networking devices communication protocol details like IP address etc.2. Draw detailed block diagram of any field parameter like temp, pressure reading coming to PLC can be shown on SCADA/MMI.3. Explain 2 wire & 4 wire wiring concept.4. Draw block diagram of close loop control. Difference open and close.5. Draw server client architecture with example.6. Name different types of timers used in PLC.7. Subroutine, instruction types,8. Explain PID?9. PID Cascade mode, primary secondary10. Ramp, feed forward11. Name communication protocols and basic parameters required to establish communication between two nodes.12. What is difference between signal ground and power ground?13. Explain redundancy of controller.14. Master slave concept in Modbus15. Modbus addressing16. What is CRC? Parity?17. Thermocouple –RTD difference18. Room temp resistance for RTD.19. IP Address classes.20. Scan time of PLC.21. Why 4-20 ma not 0-20 ma?22. Bump less transfer

Foundation FieldbusAn open, bus-powered, digital, multi-drop communication technology for intelligent field devices and automation systems.enables digital replacement of 4-20 mAenables unification of field with business / controlenables some basic and even advanced process control in the fieldHow is Fieldbus Different from 4-20Fieldbus devices are connected in parallel on the bus, which carries digital data from/to all the devices on the busFieldbus devices provide almost unlimited information to all other devices on the network Data has cyclical redundancy checking (CRC) to ensure receiving devices use only good dataA multidrop fieldbus does not have the shortcoming of point-to-point wiringFOUNDATION Fieldbus DifferentiatorsSupports Intrinsic Safety and Existing WiringUses IEC/ISA fieldbus standard.Secure Process Data MessagesTime-critical process data first priorityAlarms and events second priorityBackground MMI messages, downloads, etc., in free bandwidthFunction BlocksStandard Set (AI, AO, DI, DO, PID, ML, SS, ...)Modeled after DCS pointsSupports distribution of control to field devicesDevice Description Language (DDL)Defines parameters and function blocks in a deviceProvides interoperability between devicesSupported by major global controls suppliersLess wiring and commissioning timeAccess to diagnostics for better asset management

what is cascade loop and how it work and why it used instead of PID single loop? In cascade, Which loop is faster and slower? Please explain with loop drawing and example...A.1) In cascade loop the parameter to be controlled is in series with another parameter which is to be measured for normal operating conditions i.e 2 manipulated variables are in seriesit is used in fractional distillation system , boiler operation in power plants etc In pid only one variable is measured and controlled at a time .it is used for temperature , pressure , flow control systemA.2) cascade loop is the combination of two pid control.where 1st controller output ie mv is the input of 2nd controller.1st contrroler more fater than second controoler.it's used in boiler three element.it's control feed water flow,drum level and steam flow.

The 250 ohm resiatance is necessary to support the communication between transmitter and HART because it equalizes1. loop resistance2. barrier resistance3.wire resistance4. receivers resistance

What is Dry Leg Calibration and Wet Leg Calibration?Dry leg calibration and Wet Leg Calibration are used for closed and pressurized vessels level measurement.Difference:Wet leg calibration is used for vapourised liquid (which will be condensated by atmosphere) level.In LP side Tapping ,liquid filled . Dry leg calibration for the liquid under pressurised condition which will not be condensated.

what is bevel? why bevel required in orifice plate?Orifice plates which are used in flow measurement are mostly concentric "square-edge" type. The bore of the orifice is not constant when one moves from the upstream side to the downstream side along the cross section. The bore size is constant for a few mm only and then expands till it reaches the downstream face. This inclined cut is called the bevel in an orifice.The main reason to have a bevel in the orifice is to avoid turbulence thereby providing more accuracy to the measurement. Restriction Orifice plates are not beveled since their intent is to reduce the pressure only.

What is difference between fault tolerant and redundant system?In a fault tolerant system, there may not be a back-up component to take over in the event of a component failure. Redundant systems will have back-up components that take over in the primary component fails.For instance, a DCS system may have redundant processors that take over control if the primary processor fails for some reason. Typically, these systems have redundant power supplies as well. You may also see redundant field devices on critical systems. Boiler drums will usually have several level transmitters set up so that any one failure would not impact the operation of the boiler.In a fault tolerant system, you may not have any back-up components. The system is designed to continue operations in the event of a failure of one or more components. In thinking about this topic, a newer model automobile engine came to my mind. The emissions controls on these newer engines use inputs from several sensors to control the engine and limit emissions. Typically, these systems would run on what is called a closed

loop control, where the sensor inputs are used by the computer to control parameters to the engine. If one of the components fails in the emissions control system, the engine will continue to run, but not as efficiently. The emissions control system will go into open loop mode where a set of fixed parameters is used to let the engine continue to operate at some reduced efficiency level.

Change a controller from auto to manual and vise-versaPneumatic controllers :While taking the controller from auto to manual, the manual output is to be balanced to the auto output and then transfer the auto-manual switch to manual. While changing the controller from manual to auto, the controller set point is matched to the manual output and then auto-manual switch is transferred.Electronic controllers :Auto to manual control may be transferred directly as the electronic circuit keeps the auto and manual output matched. But while changing the controller from manual to auto, the controller set point is to match to the process variable and then auto-manual switch is transferred