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20EI501-Process Control

Department: Electronics and Instrumentation Engineering

Batch/Year: 2021-25/III

Created by:

Ms. K.R. Chairma Lakshmi AP/EIE

1.TABLE OF CONTENTS

2. COURSE OBJECTIVES

3. PRE REQUISITES

4. SYLLABUS

SUBJECT CODE : 20EI501

SUBJECT NAME: PROCESS CONTROL

L T P C :3 2 0 4

UNIT I PROCESS MODELLING AND DYNAMICS

Need for process control – Mathematical Modeling of Processes: Level, Flow, Pressure and Thermal processes – Continuous and batch processes – Interacting and Non-Interacting system - Self regulation – Servo and regulatory operations – Lumped and Distributed parameter models – Heat exchanger – CSTR

– Linearization of nonlinear systems.

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UNIT II FINAL CONTROL ELEMENTS

Actuators: Pneumatic and electric actuators – Control Valve Terminology - Characteristic of Control Valves: Inherent and Installed characteristics - Valve Positioner – Modeling of a Pneumatically Actuated Control Valve – Control Valve Sizing: ISA S 75.01 standard flow equations for sizing Control Valves – Cavitation and flashing – Control Valve selection

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UNIT III CONTROL ACTIONS

Characteristic of ON-OFF, Proportional, Single speed floating, Integral and Derivative controllers P+I, P+D and P+I+D control modes – Practical forms of PID Controller – PID Implementation Issues: Bumpless, Auto/manual Mode transfer, Anti-reset windup Techniques – Direct/reverse action.

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UNIT IV PID CONTROLLER TUNING

PID Controller Design Specifications: Criteria based on Time Response and Criteria based Frequency Response - PID Controller Tuning: Z-N and Cohen-Coon methods, Continuous cycling method and Damped oscillation method, optimization methods, Auto tuning – Cascade control – Feed-forward control

UNIT V MODEL BASED CONTROL SCHEMES

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Smith Predictor Control Scheme - Internal Model Controller – IMC PID controller –

- Three- element Boiler drum level control - Introduction to Multi-loop Control

Schemes – Control Schemes for CSTR, and Heat Exchanger - P&ID diagram.

5. COURSE OUTCOMES

6. CO-PO/CO-PSO MAPPING

7. LECTURE PLAN

8. ACTIVITY BASED LEARNING

Topic: Discuss the construction, working and applications of different control valves

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Activity: Think-Pair-Share

Students individually think about a particular question, scenario, or problem. Next, have each student pair up to discuss their ideas or answers. Then bring students together as a large class for discussion.

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Benefit

s

This activity encourages students to think about answers on their own first before talking with other students. This activity works best when students are challenged to think through a more complex or complicated idea. The benefits of the 3 step process are two-fold: first, students are generally more comfortable presenting ideas to a group with the support of a partner; second, students’ ideas have become more refined through this three-step process.

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Topic: Construction and working of different types of Actuators

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Activity: Pro-con grid

Pick a topic that lends itself to the idea of making lists of pros and cons/advantages and disadvantages for some issue (see pointers for suggestions). Break students up into small groups. Have the groups come up with at least three points for each side. Additionally, let students know whether they should be putting their lists together in point form or full sentences. Once students have had time to complete the activity, bring the class back together to share and discuss points on each side.

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Benefit s

This activity can help students in developing analytical and evaluative skills. It also requires students to go beyond their initial position and reactions, and come up with points of discussion for the other side of the issue. Finally, it also requires students to weigh the points of competing positions and claims.

9. LECTURE NOTES UNIT -II

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The final control element is the mechanism which alters the value of manipulated variable in response to the output signal from the automatic control device. The position of the final control element in the automatic control loop is shown in Fig.

Fig: Automatic control loop

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Elements of final control operation

The final control element often consists of two parts: first, an actuator which is used to translate the output signal of the automatic controller into a position of a member exerting large power; and second, a device to adjust the value of manipulated variable (usually a flow rate of a fluid).

Fig: Elements of final control element

The input control signal may be of any forms including electric current-(4-20)mA, digital signal or pneumatic pressure.

Signal Conversion:

The principle objective of signal conversion is to convert the low energy control signal to a high energy signal to drive the actuator.

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Actuators:

The result of signal conversion provides an amplified and/or converted signal that is designed to operate (actuate) a mechanism that changes a manipulated variable and thus changing the controlled variable. The actuator is a translation of the control signal into action on the control element. Thus if a valve is to be operated, then the actuator is a device that converts the control signal into physical action of opening or closing the valve.

The actuator must provide an accurate output position proportional to the input signal in spite of various forces acting on the output member

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The most important forces are

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Inertia forces caused by the mass of moving parts

Static friction forces during impending motion of two adjacent surfaces

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Thrust forces caused by weight and unbalanced fluid pressure.

Thus, the actuator is often required to employ a power-amplifying mechanism. The actuator may operate by pneumatic, hydraulic electrical, or a combination of these means.

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Final control element:

This device has direct influence on the process dynamic variable and is designed as integral part of the process.

Current to pressure converter (I/P converter)

The current to pressure converter or I/P converter is a very important element in the process control. The I/P converter gives us a linear way of translating the 4-20mA current into a 0.2 to 1 Kg/cm² signal (3-15 PSI signal). There are many designs for these converters but the basic principle always involves the use of a flapper nozzle system.

Fig: current to Pressure converter

The current through the coil produces a force that will tend to pull the flapper down and close off the gap. A high current produces a high pressure so that the device is direct acting.

Adjustment of the springs and perhaps the position relative to the pivot to which they are attached allows the unit to be calibrated so that 4 mA corresponds to 0.2Kg/cm² (or 3PSI) and 20mA corresponds to 1 Kg/cm² or 15PSI.

The flapper nozzle system provides the conversion of pressure to mechanical motion vice versa and the fig. below represents flapper and nozzle system.

A regulated supply of pressure usually over 1.5Kg/cm² provides a source of air through the restriction.

Fig: Flapper/nozzle system

The nozzle is open at the end where the gap exists between nozzle and flapper and air escapes in this region. If the flapper moves down and closes off the nozzle opening so that no air leaks, the signal pressure will rise to the supply pressure.

As the flapper moves away, the signal pressure will drop because of the leaking air. Finally when the flapper is far away, the pressure will stabilize at some value determined by the maximum leakage through the nozzle. The relation between signal pressure and gap distance is given below in graph.

Fig: Signal Pressure versus gap distance

The great sensitivity is in the central region where the slope of the line is greatest. In this region, for a very small motion of the flapper, change in pressure will be in

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Greater magnitude.

Actuators

If a valve is used to control fluid flow, some mechanism must physically open or close the valve. If a heater is to warm a system. Some device must turn the heater on or off. Actuator occupies the intermediate position between signal conversion and control valve.

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Electric Actuators

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Solenoid and electric motors act as actuators.

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Solenoid

It converts an electrical signal into mechanical motion, usually in a straight line. A simple solenoid consists of a coil and plunger. The plunger may be free standing or spring loaded. The coil may be operated by either dc or ac voltage.

Fig: A solenoid converts an electrical signal to a physical displacement

Solenoid specifications include the electrical rating and the plunger pull or push force when excited by the specified voltage. Some solenoids are rated only for intermittent duty because of thermal constraints. In this case, the maximum duty cycle (percentage on total time) will be specified. Solenoids are used when a large sudden force must be applied to perform same job.

A solenoid is used to change the gears of a two position transmission. SCR is used to activate the solenoid coil. In many process control pipelines solenoid valves (where the plunger can act as valve stem) are used for quick opening or shut off operations. In large pipe lines shut-off valves are operated with the help of pneumatic air or hydraulic oil which are in turn controlled by solenoids valves fitted in the air line or oil line.

Fig: Solenoid used to change the gears of two position transmission

Solenoid moves in straight line and therefore it require a cam or other mechanical converter to operate rotator valves. These actuators are best suited for small, short stroke on-off valves. Solenoid actuated valves can open or close in 8 to 12 milliseconds.

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Electric Motors

Electrical motors are devices that accept electrical input and provide a continuous rotation as a result. The electrical motors are used in control situations that may be broadly classified into two categories

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Motor as direct actuator

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Motor along with gear boxes (Electro mechanical Actuators).

Common varieties of Motors

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DC Motors:

Series field, shunt field, compound motors are used as servomotors. To change the direction, the polarity has to be changed with the help of interface units. Different types of braking designs are possible to stop the motor immediately when the power is cut off or direction is changed.

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AC Motors:

Synchronous AC motors and Induction motors are used. Single phase motors are used with special arrangements for starting and reversing them. When more torque is required three phase motors are used. Compared to DC motors, Ac motors are always having starting problem as they are not self starting.

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Stepping Motors:

A stepper motor is a rotating machine that actually completes a full rotation by sequencing through a series of discrete rotational steps. Continuous rotation is achieved by the input of a train of pulses, each of which causes an advance of one step. It is not really continuous rotation but discrete, step wise rotation.

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Motor as direct Actuator

Consider the situations where motor is driving some part of a process. Speed of the motor is directly controlled to control some variable in the process.

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Some of the applications where motor can be used as direct actuator are listed

below.

Control of the speed of the belt conveyors carrying coal to power plants, raw materials to metallurgical and heavy industries and carrying of components within plant units.

Control of the speed of pumps that is used for pumping water, acid, liquid etc., in process industries.

Control of the speed of roller tables carrying hot metal ingots or slabs for rolling in rolling mills.

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Control of the speed of blowers, FD fans, ID fans in small power plants.

Variable voltage drives, variable frequency drives, variable voltage variable frequency drives, pulse width modulated drives are familiar motor actuators used for above controls.

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Electro Mechanical Actuators

These actuators are electrical motor driven but coupled to mechanical gear trains. The motor runs continuously but the resultant motion after the gear box is either rotary or linear.

In the rotary actuators the motion is controlled within 90°, 180° or something less than 360°. When it is used as linear actuator, the final output spindle will be moving up and down with the travel limits fixed.

Motor speed, travel limits and final shaft torque are all designed as per the process requirement. Electromechanical actuators will have the facility to operate them manually with the help of hand wheels while initially adjusting the travel limits etc.

These actuators can utilize a reversible electric motor(either AC or DC) provided with an internal worm gear to prevent drive driven direction reversal by unbalanced loads. Servomotors are used to position valves in response with feedback signals.

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Pneumatic

Actuators

An actuator is the portion of a valve that responds to the applied signal and causes the motion of the valve stem. The actuator translates a control signal into a large force or torque as required to manipulate the control element.

Pneumatic actuators may operate directly from the pneumatic output signal from a pneumatic controller, or they may employ a separate source of compressed air.

Two general types of pneumatic actuators

Spring and Diaphragm actuator Piston actuator.

In spring and diaphragm actuator, variable air pressure is applied to a flexible diaphragm to oppose a spring. The combination of diaphragm and spring forces acts to balance the fluid forces on the valve.

In a piston actuator, a combination of fixed and variable air pressure is applied to a piston in a cylinder to balance the fluid flow forces on the valve.

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Spring and Diaphragm Actuator

It is also called diaphragm motor due to its low cost, relatively high thrust at low air supply pressures and with fail safe springs. It is available in

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Springless designs

Double diaphragm design (for high pressure)

Rolling diaphragm design(for longer strokes) Tandem designs(for more thrust)

These actuators are ideal for the use on valves requiring linear travel. A linkage or other form of linear to rotary converter is required to adapt these actuators to rotary valves such as butterfly valves.

The air transmitted from a pneumatic controller or from an electronic controller via I/P converter enters the upper diaphragm case, while the lower diaphragm case is vented to the atmosphere by the open hole H. The diaphragm is usually made of fabric-base rubber, molded to form, and supported by a backing plate. When the top pressure increases the force acting downward also increases. This starts the valve closing.

At the same time, the spring force increases. The valve movement will continue until the spring force is equal to the force due to the increased air pressure.

When the air pressure decreases, the valve moves upwards and the spring expands until a new force balance is attained.

Fig: Spring and diaphragm actuator cum valve

The position of the diaphragm at low pressure and high pressure are represented in the following diagram.

(a) (b)

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Fig: Direct actuator in a) low Pressure state b) high Pressure state

In a reverse acting actuator an increase in the pneumatic pressure applied to the diaphragm lifts the valve stem (in a normally seated valve this will open the valve and is called ‘air to open’ and in non seated valve this will close the valve and is called ‘air to close’).

In a direct acting actuator, an increase in the pneumatic pressure applied to the diaphragm extends the valve stem (for a normally seated valve this will close the valve and is called ‘air to close’).

The principle is based on the concept of pressure as force per unit area. A net pressure difference is applied to a diaphragm of surface area ‘A’ then a net force acts on the diaphragm is given by

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F= (P₁-P₂ ) A

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Force = Pressure difference x diaphragm area.

The pressure and force are linearly related and the compression of the spring is

linearly related to force acting on it.

Δx = ^A ΔP k

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Shaft travel = ^{Diaphragm Area} XApplied gauge Pressure

Spring consant

Spring and diaphragm actuators are further classified into Direct acting pneumatic actuator

Reverse acting actuator.

The choice of valve action is dictated by safety considerations. In one case it may be desirable to have the valve fail fully open when the pneumatic supply fails. In another application it may be considered better if the valve fails fully shut.

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Fail safe operations

Spring actuators normally will have a definite safety position i-e., if the air pressure fails, the force of the spring will cause the valve either to open or close, depending on the least hazardous condition.

In the air to close valve as the air pressure above the stem moves down and consequently the plug restricts the flow through the orifice. If the air supply above the diaphragm lost, the valve will ‘fail open’ since the spring would push the stem and plug upward.

In the air to open valve as the air pressure above the diaphragm increases, the stem moves down and consequently the plug allows the flow through the orifice. If the air supply above the diaphragm is lost the valve will ‘fail closed’ since the spring would pull the stem and plug upward closing the flow through the orifice.

Springless Diaphragm Actuator

The springless diaphragm actuator is useful for large thrust forces. The spring of the spring and diaphragm actuator is replaced by a pressure regulator which maintains a constant pressure on the underside of the diaphragm.

Assume that the cushion regulator is set to provide 9PSI (0.6Kg/cm²) pressure on the underside of the diaphragm. At static balance and with no thrust force on the actuator stem, the upperside pressure must be 9PSI (0.6Kg/cm²)

Fig: Springless diaphragm actuator

If the input pressure increases, the nozzle back pressure increases and the upperside pressure is raised to a high value. The actuator stem then moves downward and as the actuator stem attains new position, the upperside pressure is returned to 9PSI.

If there is an upward thrust force on the actuator stem, the underside pressure remains at 9PSI but the positioner raises the upperside pressure until static balance is achieved. For a downward thrust force the upper side pressure is reduced below 9 PSI. Thus, the springless actuator can counter act a thrust force equal to approximately the underside pressure times the area of the

diaphragm. This is generally from three to ten times the thrust force handled by a spring actuator with or without a positioner.

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Piston Actuator

Piston actuators are used when the stroke of a diaphragm actuator would be too short or the thrust is too small. Compressed air is applied to a solid piston contained within a solid cylinder. Simple designs have the air fed into a central chamber and the air forces the piston upwards.

Piston actuators are either single or double acting. The single acting actuator utilizes the fixed air pressure, known as the cushion, to oppose the controller signal. This valve does not have spring or diaphragm area nonlinearities. In order to use such an actuator for throttling purposes, it is necessary to have a positioner. The positioner senses the actuator motion and causes the valve to move accordingly.

The double acting piston actuator is employed for large thrust forces. When the input pressure increases, the bellows moves to the right and pushes the pilot spool upward. This action opens the upper side of the cylinder to the air supply and opens

the lower side to the atmosphere. Thus the position of the piston is proportional to the input pressure. A double-acting piston actuator can handle a thrust force equal to about 80 percent of the supply pressure times the area of the piston.

Electro- pneumatic Actuators

When electric control systems are employed, it is often advantageous to use pneumatic Actuators. if the suitable air supply is available, a pneumatic actuators can provide very large power output. This requires transducing the electrical output of the controller into an air pressure variable for the actuator.

Fig: Electro pneumatic pilot

The electro-pneumatic pilot shown in above figure is arranged to convert an electrical signal input into a proportional air pressure output. Electric signal (usually a direct current) enters the “voice-coil” motor.

The input coil is supported in the field of a permanent magnet so that the coil affords a force proportional to the magnitude of the input DC current. The force causes a deflection of the balance beam, covers the nozzle, and results in an increase of output pressure.

The output pressure acts on the feedback bellows to cause a torque on the balance ream equal but opposite to that of the voice coil.

The output pressure therefore is proportional to the input DC current. The electro- pneumatic actuator shown in below fig. combines the voice coil and the pilot in the positioner of a pneumatic actuator. The motion of the output of the actuator is related to the balance beam through the feedback lever. The output position of the actuator is therefore proportional to input DC current.

Fig: Electro pneumatic Actuator

Comparison between Actuators

Valve Positioner

The main purpose of having a valve positioner is to guarantee that the valve move to the position where the controller wants it to be.

By adding positioner, one can correct for many variations including changes in packaging friction due to dirt, corrosion or lack of lubrication, variations in the dynamic forces of the process, sloppy linkages or non linearities in the valve actuator.

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In the following situations, valve positioner is recommended

For split range control applications a single controller output signal will control two or more control valves.

When the valve is remote manual operation (open loop), it is used to reduce the valve’s hysteresis and dead band while increasing its response.

When the valve is under automatic control (closed loop). The positioner will

be when the loop response is not fast.

Pneumatic actuators without spring always require valve positioner.

The positioner is a very sensitively tuned proportional only controller.

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Electronic valve positioner

It is used for electric actuators and also called as interface unit. It is a high gain proportional only controller.

It is used for electric actuators and also called as interface unit. It is a high gain proportional only controller.

It is considered as a slave controller of a cascade loop in which master controller is the primary controller itself. The master controller output is the set point for the slave controller. The resistance variation in actuator is converted into current signal with the help of position transmitter. The complete loop is utilized to position the control valve as required by the primary controller.

Valve positioner for pneumatic Actuator

A motion balanced positioner used along with the spring and diaphragm actuator. The positioner consists of a input bellows, nozzle, amplifying pilot, feedback levers and spring. An air supply of 20 to 100PSI must be provided.

Fig: Pneumatic valve with valve positioner

When the input air pressure increases, the input bellows moves to the right and causes the flapper to cover the nozzle. The nozzle back pressure change is amplified by the pilot and it is transmitted to the diaphragm. The diaphragm moves down and the feedback lever compresses the spring to return the flapper to a balanced position. Thus the actuator stem assumes a position dictated by input air pressure.

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Improvements in performance due to valve positioner

Hysteresis is reduced and linearity is improved because the static operation is governed by input bellows and feedback springs.

Actuator can handle higher static friction because of amplifying pilot. Variable thrust forces on the motor stem do not disturb the stem position.

Speed of response is improved because the pneumatic controller must

supply sufficient air to fill the small input bellows rather than the large actuator chamber

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Control valves

A control valve is a valve used to control fluid flow by varying the size of the flow passage as directed by a signal from a controller. This enables the direct control of flow rate and the consequential control of process quantities such as pressure, temperature, and liquid level.

Valve is defined as a pressure dissipating device designed for modifying the flow of fluid in pipe. Control valve is designed for modifying the flow of fluid in pipe and used for control purpose.

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Control valve Principles

Flow rate in process control is usually expressed as volume per unit time. If the mass flow rate is desired, it can be calculated from the particular fluid density. If a given fluid is delivered through a pipe then the volume flow rate is

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Q = A.V

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Flow rate= Pipe area x flow velocity

A close relation exists between pressure along the pipe and the flow rate so that if the pressure is changed then the flow rate is also changed.

A control valve changes flow rate by changing the pressure in a flow system because it introduces a constriction in the delivery system.

In the placement of constriction in a pipe, a pressure difference across the pipe is introduced.

Flow rate through constriction = Q = k ΔP

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k= Proportionality constant

ΔP = P₁-P₂ = Pressure difference

The constant k depends on The size of the valve.

Geometrical structure of delivery system

Material flowing through the valve

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Control valve types

Control valves are broadly classified based on five different categories as follows

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Control valve with flow characteristics

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Linear valve, Equal percentage valve, quick opening valve.

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Power applied through actuator

Electrical, Mechanical, Pneumatic, Hydraulic

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Supply pressure movement

Direct acting, reverse acting valve.

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Operation of valve

Manual valves, Automated valves

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Stem position with plug

Single seated plug valve, Double seated plug valve, mixing valve, cage valve, Angle valve.

Commercial valve bodies

The control valve is a variable resistance to flow of a fluid, in which the resistance

can be changed by a signal from process controller.

Fig: Commercial control valve

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The control valve is divided into body and trim.

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Body:

It is a type of a pressure vessel containing an orifice or an opening. The controlled liquid is allowed to flow through the body of the valve. It helps to monitor the

flow regulation behaviour.

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Trim:

Besides the body, trim is one such part of the valve that comes directly in contact with the fluid. It consists of the seat, disc, plug, and stem.

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Actuator:

It consists of electric or pneumatic mediums to provide the force required to

operate the control valve.

The actuator moves the valve stem and in turn the stem moves the plug in a valve seat in order to change the resistance to flow through the valve. That is the cross sectional area between the plug and the seat is changed to change the flow rate.

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Bonnet:

The bonnet assembly is attached to the valve body. The body stem moves through the bonnet which contains a means for sealing against leakage by packaging assembly with suitable packaging or a sealing bellows.

The blind head may be with or without guide bushings. The valve plug has extensions on top and bottom which are the valve plug guides. These guides keep the valve plug motion in alignment.

sliding stem

I. SLIDING STEM CONTROL VALVES (Global valves)

The sliding stem valves is also called as global valves. The types of

control valves are

Single seat plug valves Double seat plug valves

Lifting gate valves

1. Single seat plug valves

The single seat plug valve has only one port opening between seat and plug and the entire flow passes through this port. A few types are shown in figure

Fig: Types of single seated valves

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Features

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Simple in construction

Can be shut off to provide zero flow

There is large force acting across the port and seat area.

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2. Double seat plug valves

It has two port openings and two seats and two plugs. The port openings are not identical in size. Two types of double seat plug valves are shown in figure

V-Port type Parabolic, ratio or throttle type

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Features

Net force acting on the valve stem is small and therefore pressure balanced It

cannot be shutoff tightly because of differential temperature expansion of valve plug and body

Valve plugs

Piston type: one or more grooves. Flow passes vertically in the grooves.

V port type: Open on inside. Flow passes horizontally through the triangular shaped area.

Parabolic Plug: Annular area to flow between plug and seat ring. Poppet type: Cylindrical shaped flow area.

Single seated control valve Double seated control valve

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3. Lifting gate valves

The gate valve is used for fluids containing solid matter because it presents an open area directly to the flow fluid and does not involve a change of direction of flow stream. A gate valve can usually be shut off tightly by wedging into the seat.

Fig: Gate valve

The wier valve is suited to curtain chemical fluids because it has a smooth contour inside the body with no pockets for solid matter. A flexible diaphragm of rubber or other non metallic material is positioned by the plunger and stem. Fluid pressure inside the valve body holds the diaphragm smoothly against the plunger.

Fig: Wier valve

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II. Rotating shaft control valves

Valves in which the restriction is accomplished by the rotation of a plug or vane

called rotating shaft type.

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Types of Valves:

Rotating plug valves Butterfly valves Louvers

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1. Rotating Plug valves

The plug is a cylindrical or conical element with a transverse opening. It is rotated in the valve body by an external lever so that opening on one side of the plug is gradually covered or uncovered. The shape of the opening or part may be circular, V-shape, rectangular or any other form.

It can be closed tightly and has high rangeability. This type of valve is used for throttling the flow of oil to burner system.

The valve with spherical plug that controls flow through the valve body is called ball valve

Fig: Rotary plug valves

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2. Butterfly valves

The butterfly valve consists of a single vane rotating inside a circular or rectangular pipe or casing. The shaft projects through the casing and operated externally.

Fig: Butterfly valves

The total rotation of the vane is restricted about 60 degrees. The additional 30 degrees does not produce much increase in flow (Theoretical rotation is 90 degrees)

The V-port butterfly valve incorporates a V slot in the body so that rotation of the vane opens a portion of V-slot. Tight shutoff is obtained with special design. It is employed for air and gas control.

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3. Louvers

It consists of two or more rectangular vane mounted on shafts one above the other and interconnected to rotate together. The vanes are operated by external lever. In unidirectional louver the vanes remain parallel at all positions. In a counter rotational louver alternate vanes rotate in an opposite direction. It can not provide tight shutoff. For air flow control at low pressure it is used.

Fig: Louvers

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III. Special control valves

A cock valve consists of a tapered plug which fits closely into a tapered hole in the valve body. The plug and the mating hole are ground together to make a leak proof fit.

Fig: Cock valve

Bellows seal valves

It is used in pipelines handling toxic or valuable fluids. Bellows seal is used instead of ordinary packings to isolate valve stem action from atmosphere.

A bellow seal valve has a compact structure and is one kind of control valve to balance the pressure. Bellows are used as the valve stem sealing components of the bellow seal valves. At the same time, the valve can prevent fluids leaking to the air and guarantee zero leakage of pipelines.

Fig: Bellow seal valves

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Three way valves

It is either for diverting a stream into two separate streams or for mixing two

fluids in controlled proportions

Pinch or clamp valves

It is used in industries in mixing, water treatment, sewage and waste disposal, chemical food, cosmetics. It is used to handle all slurries in mixing industry. In water and waste treatment, it handles lime slurry, raw sewage, grit, garbage particles, grease.

Fig: Pinch valve

Rangeability

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It is defined as ratio of maximum controllable flow to minimum controllable flow.

_{R =} ^Qmax

^Qmin

R - Rangeable number

Q_max – Maximum controllable flow

Q_min – Minimum controllable flow

The minimum controllable flow is defined as the flow below which the valve tends to close completely. It can be changed up or down as the valve stroke is changed.

T≈ 0.7 R

Characteristics of control valves

The function of control valve is to vary the flow of fluid through the valve by means of a change of pressure to the valve top.

The relation between the flow through the valve and the valve stem position (or lift) is called the characteristic.

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Control valves exhibit

Inherent characteristics Installed characteristics

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Inherent characteristics (∆p is constant):

This control valve characteristics is assigned with the assumptions that the stem position indicates the extent of the valve opening and that the pressure difference is determined by the valve alone.

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Installed or effective characteristics (∆p is variable):

The control valve when installed in a process with pipe lines; downstream and upstream equipment will exhibit a different flow rate. Stem position relation and is called installed or effective characteristics.

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Inherent Characteristics

Based on the inherent characteristics, there are three basic types of control valves, whose relationship between stem position (as percentage of full range) and

Turn down:

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It is defined as the ratio of normal maximum flow to minimum controllable flow

_{T =} ^Qnmax

^Qmin

Q_nmax – Normal maximum flow

Normal maximum flow is taken as 70% of maximum controllable flow

flow rate(as percentage of maximum flow rate)

Different responses of the three types of control valves with respect to stem position

ASSUMPTIONS:

The actuator is linear. (valve travel is proportional with controller output)

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The pressure difference across the valve is constant.

The process fluid is not flashing, cavitating or approaching sonic velocity (Choked flow).

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Quick opening valve

This type of valve is used for full on / full off control applications. A quick opening valve plug produces a large increase in flow for a small initial change in stem travel. Near maximum flow is reached at a relatively low percentage of maximum stem lift.

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This valve is also called as decreasing sensitivity type valve. The valve sensitivity

(ΔQ/ΔS) decreases with increasing flow.

Linear valve

Flow rate varies linearly with stem position. It represents the ideal situation where the valve above determines the pressure drop.

Q ₌ S ^Qmax ^Smax

Q- flow rate

Q_max – maximum flow rate

S – stem position

S_max – maximum stem position

The valve sensitivity is more or less constant at any flow

Eg: if valve open 25% the flow through the valve is 25% of full flow. Process tank level control, De-aerated level control etc.

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Equal percentage valve

A given percentage change in stem position produces an equivalent change in flow. These valves does not shut off flow completely in its limit of stem travel.

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S

Q = Q_min R

^Smax

​

​

Q_min represents the minimum flow when the stem is at one limit(closing limit) of

its travel.

​

Rangeability, R = Qmax /Qmin

The curve depends on rangeability. The increase in flow rate for a given change in valve opening depends on the extent to which the valve is already open.

It is also called as increasing sensitivity type valve. The valve sensitivity at any given flow rate is a constant percentage of the given flow rate, thus equal percentage.

Eg: consider a valve having a maximum flow rate of 60 tonnes/hr.

Case 1 when valve delivering 10 tonnes/hr, when the valve is permitted to open 10% more, then the incremental flow is 1 tons/hr.

Case 2 when valve delivering 40 tonnes/hr, when the valve is permitted to open 10% more, then the incremental flow rate is 4 tonnes/hr.

​

Special characteristic valves

Some valves have special characteristics in which the characteristic curve depends on the geometrical shape of the plug’s surface

​

By taking into account, the density and flow characteristics, flow rate becomes

Types of valves depending on flow characteristics

​

Linear= f(x)=x Square root= f(x)= √x

Equal percentage = f(x)=a^x-1

Types of plugs for control valve

ΔP

ρ

Q = kf(x)

Hyperbolic = f(x) = _{α - (α -1)x} α can be varied

1

Installed (or effective) valve characteristics

When valve is installed as part of a process plant, its flow characteristics are no longer independent of the rest of the system. Fluid flow through the valve is subject to frictional resistances in series with that of the valve.

​

Consider a simple system with pump, valve and connected pipeline.

The installation has a very substantial effect on both flow characteristics and rangeability.

The equal percentage characteristics are distorted forward linear or quick opening under conditions of excessive distortion. The distortion coefficient D_c is

t

max

s

₌ (ΔP_t )_min ΔP

c

(ΔP ⁾ ΔP

D

The installed valve behaviour is further reduced by

Deviation in inherent valve characteristics.

Actuators without positioner will introduce nonlinearities. Pump curves will also introduce nonlinearities.

​

Control valve sizing

The proper sizing of control valve is important

If control valve is oversize, The valve must operate at low lift and the minimum controllable flow is too large. Lower part of the flow-lift characteristic is most likely to be non uniform in shape.

If control valve is undersize, the maximum flow desired for operation of a process may not be provided.

Factors that influence the sizing of control valve Pressure Drop across the control valve Flow Rate through the control valve Specific Gravity or specific weight

​

Other factors such as

type of fluid, gas or liquid,

critical flow conditions for gases and vapours

viscosity of liquids influence valve size

Before selecting valve size, valve and process characteristics must match to compensate for non linearities in the control valve and process.

​

Flow coefficient

Flow coefficient determines the size of control valve. Flow coefficient is denoted as C_v factor or K_v factor. All manufacturers supply C_v factors for their valves. These

factors form the basis for all calculations.

The flow coefficient indicates the amount of flow the control valve can handle under a given pressure drop across the control valve.

​

C_v Factor

The flow coefficient(C_v) is defined as the flow rate of water in gallons per minute at 60⁰ F through the fully opened control valve at a pressure drop of 1 PSI across the valve

​

K_v Factor

Whenever the flow coefficient is denoted in metric units, it is denoted by the symbol K_v.

It is defined as the flow rate of water in m³/hr at 30⁰ C through the fully opened control valve at a pressure drop of 1 kg/cm² across the valve.

C_v=1.17K_v K_v= 0.86C_v

The flow coefficient for 100% valve opening is termed as C_v or K_v at different valve openings is given in the form of graph ( valve characteristics)

​

Flow rate versus flow coefficient

ΔP = pressure drop across the control valve

​

SG= Specific gravity of liquid

In general, as the physical size of a valve body (i.e, size of pipe connectors) increases, the value of C_v increases. For a sliding stem and plug type of control

ΔP SG

Flowrate = Q = C_v

valve, the value of C_v is roughly equal to the square of the pipe size multiplied by ten. Using this rule, a three-inch control valve should have a C_v of about 90, with units corresponding to those of Eq.

​

Guidelines for sizing of control valves

The valve shall be sized for the actual flow condition and not for the ultimate design capacity of the system. Normal maximum flow rate is normally about 70% of the ultimate design capacity.

Most of the pressure drop of the system should be across the control valve. 70% of system drop should be across the control valve

When the pipe line is dimensioned with normal allowable velocities, the control valve will be a few sizes smaller than the pipe line. When very high velocities have been used in the pipe line, the size of the control valve will be the same as that of the pipe line.

The final selection must be done such that the calculated C_V is attained at about 75 to 80% of the full valve travel. In case of high pressure gases and steam, C_v is attained at 50 to 60 % of valve travel.

​

Cavitation and Flashing

Cavitation

The phenomenon of cavitation is related to Bernoulli’s theorem, which describes the pressure profile as the fluid flows through a pipe or passes through a narrower passage, restriction, orifice or control valve.

As the fluid accelerates, some of the pressure head is converted into velocity head. This transfer of static energy is needed to push the same mass flow through the smaller passage.

The fluid accelerates to its maximum velocity, which is also the point of minimum pressure (vena contracta) and then gradually slows down as it again expands back to the full pipe area. The static pressure also recovers back but part of it is lost due to friction.

Fig: Pressure profile of fluid passing through control valve

If the static pressure head drops below the liquid vapour pressure (P_v) at that temperature, the vapour bubbles will form downstream of the restriction. As the static pressure recovers to a point greater than the vapour pressure, the vapour bubbles collapse back into their liquid phase. The collapse of the bubbles produce high energy implosion which is called cavitation.

These implosions generate noise, fluid shock cells and get impinge upon the trim metal parts. This phenomenon generates a tremendous and concentrated imp[act force that destroys the metal as it fractures out tiny metal particles. Cavitation damage gives a appearance like sand blasting.

Cavitation damage always occurs downstream of the vena contracta when the pressure recovery in the valve causes the temporary voids to collapse. Destruction is due to the implosions, which generate the extremely high pressure shock waves in the non compressible stream. When these waves strike the solid metal surface of the valve or downstream piping, the damage gives a cinder like appearance.

Elimination of cavitation

Even mild cavitation over an extended time will attack the metal parts upon which the bubbles impinge. Hard materials survive longer, but they are not an economical solution except for services with mild intermittent cavitation. Cavitation damage also varies greatly with the type of liquid flowing. The greatest damage is caused by a dense pure liquid with high surface tension.

​

Some methods by which cavitation can be reduced or eliminated are listed below

​

Revised process conditions

A reduction of operating temperature can lower the vapour pressure sufficiently to eliminate cavitation.

Increased upstream and downstream pressure with ΔP unaffected or a reduction in ΔP can both relieve cavitation. Control valve should be installed at the lowest possible elevation in the piping system and operated at minimum ΔP

Move the valve closer to the pump will elevate upstream and downstream pressures.

If cavitating conditions are unavoidable, then it is preferred to have not only cavitation but also some permanent vaporization (flashing) through the valve This can usually be accomplished by a slight increase in operating temperature or by decreasing the outlet pressure. Flashing eliminates cavitation by converting the incompressible liquid into a compressible mixture.

​

Revised valve

The valves most likely to cavitate are the high recovery valves (ball, butterfly, gate) having low liquid pressure recovery factor(F_L) and low cavitation coefficient (K_c).

The cavitation coefficient K_c is the ratio between the valve pressure drop at which cavitation starts and the difference between the inlet and the vapor pressure of the application

Liquid pressure recovery factorise the ratio of valve pressure drop and the difference between the inlet and vena contracta pressure.

​

Gas injection

Another valve design variation that can lessen cavitation is based on the introduction of non condensable gases or air into the region where cavitation is expected.

The presence of compressible gas prevents sudden collapse of vapour bubbles as the pressure recovers above vapour pressure.

Instead of implosion, gradual condensation process occurs. The gas or air is admitted through the valve shaft or through downstream taps on either side of the pipe, in line with the shaft and as close to the valve as possible .Since the fluid vapour pressure is usually less than atmospheric pressure, the gas or air need not be under pressure.

​

Revised installation

​

In order to eliminate cavitation, install two or more control valves in series.

Flashing

​

Cavitation occurs when P₂˃P_V, while flashing takes place when P₂˂P_V.

When the outlet pressure P₂, is less than or equal to vapour pressure of process fluid, some of the liquid ‘flashes’ into vapour and stays in the vapour phase as it enters the downstream piping.

The specific volume increases as liquid changes to vapour which in turn causes an increase in the fluid velocity. If enough vapour is formed, the resulting high velocities can erode metals. So the piping downstream of a valve needs to be much larger than the inlet-piping in order to keep the velocity keep the velocity of the stream low enough to prevent erosion. In many cases flashing is a normal part of the process and it cannot be avoided. Special system and valve designs are required to accommodate it. The ideal valve to use is angle valve with an oversized outlet connection. The preferred arrangement for flashing service is to use a reduced port angle valve discharging directly into a vessel or flash tank.

The heat of vapourizaiton comes from the process liquid, causing its temperature to decrease. The relative masses of liquid, and vapour will thereby approach thermodynamic equilibrium. The amount of flashing can be calculated from an energy balance.

Even small amount of flashing (1 to 3% by weight) can significantly affect a valve’s capacity, sizing and selection. Therefore flashing should be stated in the valve specification data sheet. Large amount of flashing (10 to 25% by weight) require special valve designs such as oversized outlet, replaceable throats and special trims.

To select the right valve, the fraction of liquid which will flash into vapour and velocity of vapourized mixture is necessary

Mathematical modeling of pneumatic valve

The pneumatic valve is the most commonly used final control element. It is a system that exhibit inherent second order dynamics.

Consider a typical pneumatic valve. The position of the stem ( or the plug at the end of the stem) will determine the size of the opening for flow and the quantity of flow (flowrate). The position of the stem is determined by the balance of all forces acting on it.

​

The forces are

ρA = Force exerted by the compressed air at the top of diaphragm.

Kx = force exerted by the spring attached to the stem and the diaphragm

= Frictional force exerted upward and resulting from the close

contact of the stem with valve packing

​

Let

​

M= Mass in Kg

​

A= Area of diaphragm

K= Hooke’s constant for spring

​

X= displacement

C= Frictional coefficient between stem and packing

P= Pressure signal that opens and closes the valve

​

G_c= Conversion constant

dt

_C dx

Apply Newton’s law

​

Applied force = Sum of the opposing forces

Substitute

τ² =

The equation indicates that the stem position dynamics.

‘x’ follows inherent second order

The transfer function is

​

Τ²s²X(s)+2ζτsX(s)+X(s) = K_pP(s)

[Τ²s²+2ζτs+1]X(s) = K_pP(s)

M<<Kg_c

Therefore dynamics can be approximated by first order system.

⎟

= _⎜ frictional force exerted upward +_⎟

⎠

⎞

⎜ ⎟

^⎜_⎝ force exerted by spring

⎛ ^{Force exerted by mass +}

⎟

_⎜compressed air at the _⎟

⎜ ⎟

⎠

⎛ ^{Force exerted by the} ⎞

• C + Kx = PA dt

dt ²

⎜ ⎟

g

d ² x dx

^⎜_⎝ top of diaphragm.

2

⎛ _M ⎞

⎝ c ⎠

Divide by K on both sides

• ^{C dx} + x = P ^A K dt K

c _⎠ ^{dt 2}

⎜ ⎟

Kg

⎝

^⎛ M ^⎞2 d ²x

K

K

2ζ τ = ^C

M

_{Kp =} A

Kg_c

2

_τ2 d x

d x ₊

• 2ζτ x = PK_p

dt ² dt

P(s) τ²s² + 2ζ τs + 1

A

K_p

G(s) = ^X(s) =

K

M ^⎤

s² + ^C s + 1 K

⎢_Kg ⎥

⎣ c ⎦

G(s) = _⎡

Selection of control valves

Load changes, pressure drop, rangeability, process gain, flow capacity, process, surroundings, safety and hazardous conditions, cavitation and flashing details, valve sizing, trim material and cost are some of the parameters decide the selection of control valves.

1. Need for a control valve: Before proceeding through the selection of control valve, one should evaluate whether a control valve is really needed.
2. Collection of process data: The process that needs control valve is studied under normal operating condition and also the requirements of valve during startup, shut down and emergency conditions. Therefore all anticipated valves of flow rates, pressures, vapour pressures, densities, temperatures, viscosities must be identified in the process of collecting the data for valve sizing in addition to quality and safety requirements.
3. Assigning valve pressure drop: The selection of valve pressure drop is to first determine the total friction drop of the system at normal flow and assign 50% of that to valve pressure drop. Based on that assignment, one should determine the resulting valve drop at minimum and maximum flows and select a valve which can handle the required C_V rangeability.
4. Control valve Performance: It means that the valve is stable across the full operating range of the process, it is fast enough to correct for process upsets or disturbances, it will not be necessary to retune the controller every time when the process load changes. In order to meet the above goals following factors are considered.

​

Valve characteristics

Gain of the control loop components

Valve rangeability Control

valve sequencing Split range or floating

5. Control valve sizing: Determine both the minimum and maximum C_V requirements for the valve during the normal operation, start up and emergency conditions. The selected valve should perform adequately over a range of 0.8 to

1.2. If the results in a rangeability requirement are more than capability then two or more valves are used.

6.

Valve actuator selection: The following factors are

considered Whether electrical, pneumatic or hydraulic Actuator speed of response

Actuator power or torque

Valve failure position

7.

Valve positioner: The following factors are

considered When not to use positioner To eliminate dead band

Split range operation

8. Process application considerations: The properties of process fluid is

considered. The following factors are taken into account.

​

High pressure service

High differential pressure range

​

Vacuum service

​

High temperature service: metallic parts, packing designs

Low temperature service: cold box and cryogenic valves

Cavitation and erosion Flashing and erosion

Viscous and slurry service Leakage

Control valve noise

Piping and installation considerations

Climate and atmosphere corrosion

9. Control valve specification form: Compiling the information necessary to specify a control valve is done. With the aid of tabulation sheet. Many companies have their own customized forms.
10. Test report and test certificate: This is to be obtained from the manufacturers of control valve for future record.

Quiz

​

Unit II Quiz link

​

https://forms.gle/n3v6hBTuJFRwhWaW7

10. ASSIGNMENTS

​

1. What is a valve actuator? What does it mean if a sliding-stem valve actuator is reverse-acting? How does this compare with a direct-acting actuator?

2. Sometimes, pneumatically actuated valves are described as being either air-to- open or air-to-close. In light of what you know about “direct-acting” and “reverse- acting” valve mechanisms and actuators, what combination(s) of valve type and actuator type is necessary to make an “air-to-open” valve? What combination(s) of valve type and actuator type is necessary to make an “air-to-close” valve?
3. From an actuator’s perspective, which is an easier kind of valve to position: a single-ported globe valve, or a double-ported globe valve (all other factors being equal)? Why is this?
4. Three different forms of globe valve are shown here: stem-guided, port-guided, and cage-guided:

Describe the differences between these three globe valve designs, and identify

which one is more popular in industry today.

5. A control valve with a full Cv rating of 10, when wide open, flows 65 gallons per minute of liquid with a pressure drop of 50 PSI. Assuming that no choked flow or cavitating conditions exist in this valve, what is the density of the liquid in pounds per cubic foot?

6. How much upstream pressure is required to get 130 GPM of water (at 60o F) to flow through this valve when wide open?

7. How much water (at 60o F) will flow through this valve when wide open?

11. PART-A

12. PART-B

13. SUPPORTIVE ONLINE CERTIFICATION COURSES

• Online Course: SWAYAM

Course Name: Chemical Process control

Course Instructor: Prof. Sujit Jogwar, IIT Bombay Duration: 8 weeks

​

AICTE approved FDP course

​

• Online course:Coursera

Course Name: Sensor Manufacturing and Process Control

​

University: University of Colorado Boulder

Course Instructor: James Zweighaft, Jay Mendelson Duration: 5 weeks

​

• Online course:Udemy

Course Name: Introduction to process control and Instrumentation

Course Instructor: WR Training, Petroleum Petrochemical & Chemical Engineering

​

Duration: 10 sections,75 lectures

14. REAL TIME APPLICATIONS IN DAY TO DAY LIFE AND TO INDUSTRY

​

Valves are mechanical or electro-mechanical devices that are used to control the movement of liquids, gases, powders, etc. through pipes or tubes, or from tanks or other containers. In most instances, valves rely on some form of mechanical barrier—a plate, a ball, a diaphragm, for example—that can be inserted and removed from the flow stream of the material passing by. Some valves are designed as on-off varieties, while others allow very fine control of the passage of media.

Material selection plays an important role in specifying valves to ensure the compatibility of the wetted parts of the valve with the fluid or powder passing through it. Sizing is determined by the pipe or tubing diameter, flow rate, and the width between flanges for pipeline valves being installed as replacements.

Types of Valves and Their Applications Aerosol Valves

Aerosol Valves are used for dispensing the contents of aerosol cans. They consist of two primary components, the housing and the stem. Key specifications include the intended application, actuator type, output type, valve size, and materials of construction. Media dispensed can be a consideration as well. Aerosol valves dispense liquids, creams and ointments, gases, cleaning agents, and any other product that is packaged in an aerosol can.

​

Blind Valves

Blind Valves, or line blind valves, are mechanical devices used to stop flow through a pipeline. They are used primarily by the oil and gas industries as a means of isolating sections of a pipeline. These valves are also known as Piping Blinds. Key specifications include valve type, actuator type, port connections, valve size, as well as the material of the valve body, its seat, seal, and lining. Blind valves are common on ships and offshore platforms. They provide a visible, immediate indication as to whether a pipe is open or closed and are used to isolate portions of a pipeline to allow maintenance.

Cartridge Valves

Cartridge Valves are used to control flow in hydraulic and pneumatic fluid power systems. Their cartridge design allows them to be plugged into common manifolds and thus save weight and cost over discrete valve mounting. Key specifications include the intended application, valve type, actuator type, number of ports, valve size, and the materials of the valve body, its seat, seal, lining, and stem packing. Cartridge valves can be used in any of the common fluid power applications for which ordinary hydraulic or pneumatic valves serve, including check, directional control, flow control, logic, pressure control, motor control, etc.

​

Check Valves

Check Valves permit fluid to flow through them in one direction only. Lift-type check valves are similarly constructed as globe valves and use a ball or piston, often backed by a spring that opens under a specified pressure but closes as the pressure decreases, thus preventing backflow. These valves are often suited for high- pressure applications. A variant is the stop check valve which doubles as a shut-off valve.

Swing check valves employ hinged gates, disc wafers, or wafers that are often spring-actuated to close against ports as pressure diminishes. These devices can be effective in low-pressure applications. A tilting disc check valve varies the theme somewhat by hinging the gate slightly inward to reduce the pressure required for opening. Butterfly or double door check valves use two half-circle gates or wafers that are hinged at the centerline of the valve port and open downstream in the direction of flow.

Rubber check valves are also available and include designs such as the flap and duckbill varieties. Check valves are used on gas lines, for air service, and with pumps—anywhere that fluid needs to move in a single direction. They can be miniaturized, manufactured in plastic, and may incorporate many special features such as metal seats.

Engine Valves

Engine Valves are used in engines to seal between combustion chambers and either the intake or exhaust systems. Key specifications include the intended application, head and stem diameter, and the material. Opening and closing of engine valves are controlled by a series of cams and springs. They are available in several materials and types depending on the application which may include automobiles, trucks, motorcycles, etc. with special designs available for racing applications.

​

Faucet Valves

Faucet Valves are used for controlling fluid flow into basins or sinks and typically lack outlet connections, though some are equipped with threads for connecting hose, often called a hose bibb or spigot. Key specifications include valve type, actuator type, port connections, valve size, and the material that make up the valve body, which includes its seat, seal, lining, and stem packing. Mounting type is another consideration.

Faucet valves are used in laboratories, on drums, as hose bibbs, and can be made of inexpensive materials that can be discarded once a container's contents are emptied.

​

Casing Valves

Casing Valves are used exclusively by the oil and gas industry to provide access to well casings. Key specifications include the intended application, actuator type, port connections, valve size, and materials of construction.

15. CONTENT BEYOND SYLLABUS

​

Topic: Control valve testing

​

Introduction

Test carried out to check the proper working of control valves are commonly called as control valve pressure test. There are 3 types of Control valve pressure tests

​

Body test

​

For body test blind the output of control valve using blind flange

Valve should be fully opened position either control valve is NO or NC. It should be open at the time of test.

​

The other important parameter to check is body rating of control valve.

Body rating is the amount of total pressure which the body and stem seal can withstand without leaking.

​

If the body rating is 300 psi

​

The pressure of water that should give through inlet of control valve is 300 * 1.5

= 450 psi

With the help of pump produce 450 psi in the control valve and with the help of

master gauge we can make sure that pressure is 450 psi

​

Then close the mechanical valve.

Check whether any leakage of water through outlet of control valve.

​

If there is no leakage the body test is passed.

​

Seat leakage test (flow test)

For flow test outlet of the control valve should be open

​

The valve should be fully closed

The procedure is same as body test

​

Apply 450 psi to the valve and check for any leakage.

If there is leakage i.e. due to trim damage, seat ring damage, actuator and valve stem are not properly connected and aligned.

​

Function test

​

Check whether the valve is properly assembled.

​

The valve, i/p converter, current generator, and instrument air supply are set up.

Instrument air supply is checked. It is set according to the i/p converter requirements

4 mA current signal is applied to the i/p converter the valve stem shall be in 0% travel

​

When 20 mA is applied 100% travel should be present

​

If the valve stem travel indication didn’t show correctly then calibration is to done.

16. ASSESSMENT SCHEDULE (PROPOSED DATE & ACTUAL DATE)

17. PRESCRIBED TEXT BOOKS & REFERENCE BOOKS

​

TEXT BOOKS:

​

1. Seborg, D.E., Edgar, T.F. and Mellichamp, D.A., “Process Dynamics and Control”,

WileyJohn and Sons, 2nd Edition, 2003.

2. Bequette, B.W., “Process Control Modeling, Design and Simulation”, Prentice Hall of India, 2004.

​

• Stephanopoulos, G., “Chemical Process Control - An Introduction to Theory and

Practice”, Prentice Hall of India, 2005.

McGraw - Hill

REFERENCES:

1. Coughanowr, D.R., “Process SystemsAnalysis and Control”,

International Edition,2004.

2. Curtis D. Johnson, “Process Control Instrumentation Technology”, 8th Edition, Pearson, 2006.
3. Considine, D.M., Process Instruments and Controls Handbook, Second Edition, McGraw, 1999.

​

• Bela.G.Liptak., “Process Control and Optimization”., Instrument Engineers’

Handbook., volume 2, CRC press and ISA, 2005.

5. Ramesh C. Panda., T.Thyagarajan., “An Introduction to Process Modelling Identification and Control for Engineers” Narosa Publishing house Pvt. Ltd, 2017.

18. MINI PROJECT SUGGESTIONS

​

Project 1: Develop hardware model for controlling the flow of water through a pipe using solenoid valve

Aim: To develop hardware model for controlling the flow of water through a pipe using solenoid valve with an Arduino and a transistor

Project 2: Observe the valve opening status at different pressure levels in pneumatic valve actuators.

Aim: To find the relation between applied pressure and stem travel of different types of control valves when pneumatic actuators are used

Thank you

Disclaimer:

​

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