Instrumentation GDR

transcript

INSTRUMENTATION

(Presented by G D Rathi)

WHAT IS INSTRUMENTATION?

WHAT IT CONSISTS?

INSTRUMENTATION

IT IS WINDOW TO PROCESS OF PLANT.

PROCESS IS SEEN BY FOLLOWING

PARAMETERS.

o Flow

o Level

o Temperature

o Pressure

o Density

INSTRUMENTATION

o Viscosity

o Speed

Analyzer (Analyzing following parameters)

• pH

• Conductivity

• O2

• Sulphur

• H2S and so on.

o Vibrations of Compressor, Pumps

(Equipments)

INSTRUMENTATION

MEASUREMENT OF ALL ABOVE PROCESS PARAMETERS & CONTROLLING OF THESE PARAMETERS IS INSTRUMENTATION.

INTERFACE OF INSTRUMENTATION IS WITH PROCESS, ELECTRICAL, PIPING, MECHANICAL EQUIPMENTS.

AUTOMATION IS PART OF INSTRUMENTATION.

INSTRUMENTION PERSON SHOULD KNOW THE PROCESS.

FIRE & GAS DETECTION SYSTEM

WHAT IT CONSISTS OF?

FOLLOWING ARE MAJOR COMPONENTS OF

INSTRUMENTATION CLOSED LOOP.

TRANSDUCER, SENSOR

TRANSMITTER

CONTROLLER

FINAL CONTROL ELEMENT

FUNCTION /LOCATION OF THESE COMPONENTS IN PROCESS PLANTS.

TRANSDUCER, SENSOR Which senses the process parameters, located on pipe or

vessel or at process equipment.

Can be combined with transmitter.

Process parameter sensed by sensor is converted in to electrical signal like millivolt or resistance or current.

TRANSMITTERWhich converts the signal from sensor to standard

electrical or pneumatic signal.

Standard electrical signal = 4 to 20 ma.

Standard pneumatic signal = 3 to 15 psig. (0.2 to 1 Kg/cm2g)

FUNCTION /LOCATION OF THESE COMPONENTS IN PROCESS PLANTS.

CONTROLLER : It is arithmetical block controls through PID function which

is proportional, integral, derivative action. (PID Tuning)

It can be single loop controller or multi loop controller.

Now days these controllers resides at DCS / PLC microprocessor based computer system.

DCS – Distributed Control system

PLC – Programmable Logic Controller

FINAL CONTROL ELEMENT :Controller output goes to Final control Element.

It can be Control Valve, VFD, Damper, MOV, On/Off Valve.

INSTRUMENTATTION

LOCAL INSTRUMENTS

o PRESSURE GAUGES

o TEMPERATURE GAUGES

o LEVEL GAUGES

o DP INDICATORS

o GLASS TUBE ROTAMETERS

INSTRUMENTATTION

General software used

o INtools for inst index, hook ups,

sizing of all types instruments

o InstCal for sizing control valves,

orifice plates, safety valves and so

o PDS / PDMS for modeling.

Marshalling Rack Room

System Architecture:

DCS Operator Station

Snap Shot of Control Room

INSTRUMENTATTION

HAVE LOOK AT CONTROL LOOP

INSTRUMENTATTION

FEEDBACK CONTROL LOOP

INSTRUMENTATTION

FEEDFORWARD CONTROL LOOP

TYPES OF FLOW MEASUREMENTS

THEIR APPLICATIONS

TYPES OF FLOWMETERS

PRINCIPLE OF OPERATION

FEATURES OF FLOWMETERS

ADVANTAGES AND DISADVANTAGES

SELECTION/ APPLICATION OF A FLOWMETER

TYPES OF FLOWMETERS

VOLUMETRIC FLOWMETERS

Differential Head type

o Orifice plates

o Venturi meters

o Annubar

Differential Area type (Rotameters)

Electromagnetic flowmeters

Ultrasonic flowmeters

Turbine flowmeters

Vortex flowmeters

Positive Displacement Meters

MASS FLOWMETERS

Coriolis Mass flowmeter

Thermal Mass flowmeters

DIFFERENTIAL HEAD TYPE FLOWMETERS (ORIFICE)

Difference in pressure exists betweenthe upstream & downstream sides of arestriction in a confined fluid stream,which related to the square of fluidvelocity.

– Q α √ ▲P

– Q = Volume flow rate

– ▲P = Differential pressure between taps

DIFFERENTIAL HEAD TYPE FLOWMETERS (ORIFICE)

Types of Orifice plates

Concentric orifice plate:

Most commonly used

Segmental & Eccentric orifice plate

Used for fluids containing

suspended solids.

Tappings for the Orifice plates

Integral orifice plate (< = 1”)

Calibrated Meter run with

Corner Taps for 1.5”

Flange taps ( 2” to 12”)

D and D/2 taps ( <= 14”)

FEATURES OF ORIFICE PLATES

Design Pressure: No limitation. Limited by DP transmitter

Design Temperature: No limitation. Limited by DP transmitter

Sizes: Maximum size is pipe size

Flow range: limited only by pipe size.

Fluids/ Applications: Cryogenic(- Low Temp) / clean gases & liquids/

Steam (saturated/superheated)

MOC: No limitation (Steel/ monel/nickel/ haste alloy)

Accuracy : Totality It is from ±0.1% to ±1% of actual flow.

Rangeability is 3:1 to 5:1.

Upstream length/ Downstream straight length is 20D / 5D (D is pipe diameter)

ADVANTAGES OF ORIFICE PLATES

Easily installed between flanges.

Fabrication simple and inexpensive.

No limitations on the materials of construction, line size and flow rate

Cost relatively independent of pipe diameter since cost of DPT is fixed.

No process interruption for exchange of DP transmitter.

DISADVANTAGES OF ORIFICE PLATES

High permanent pressure loss & hence high energy consumption toovercome pressure loss.

Impractical for systems with low static pressure.

Measuring range to about 3:1 to 5:1. ``

VENTURI METERS

A venturi tube also measures flow rates by constricting fluids

and measuring a differential pressure drop.

In the upstream cone of the Venturi meter, velocity is increased,

pressure is decreased.

Pressure drop in the upstream cone is utilized to measure the

rate of flow through the instrument

FEATURES OF VENTURI METERS

Design Pressure: No limitation. Limited by DP transmitter/ pipe press.ratings.

Design Temperature: No limitation. Limited by DP transmitter/ pipe pressure ratings

Sizes: 25 mm to 3000 mm

Fluids/ Applications: Clean Liquids/ clean gases

: Limited applications: Dirty /corrosive/viscous Liquids & Dirty gases

MOC: No limitation (cast iron/ carbon steel/ SS/Monel, Titanium, Teflon, Hastelloy, Naval Bronze / haste alloy)

Upstream length/ Downstream straight length is 20D / 5D ( D is pipe diameter)

ADVANTAGES OF VENTURI METERS

Lower head losses than orifice plates reducing the capitalexpenditure on pumping eqpt. / save pump energy costs

No process interruption for exchange of DP transmitter.

Can be used for temperature extremes

– Cryogenics or High Temperatures

DISADVANTAGES OF VENTURI METERS

Highly expensive

Larger and heavier to handle.

ANNUBAR FLOWMETER

The probe is installed in the media line as apressure sensor.

With the flow, the probe records both the staticand the dynamic pressure via the probeopenings .

In the minus chamber of the annubar, lying onthe opposite side, only the static pressure hasany effect

The differential pressure corresponds to thedynamic pressure in the pipeline & the flow canis calculated directly.

ANNUBAR FLOWMETER

FEATURES OF ANNUBAR

Fluids : Clean Liquids, gases and steam

MOC: Brass / steel/ stainless steel/ Hastelloy

Upstream length/ Downstream straight length is 20D / 5D

ADVANTAGES OF ANNUBAR

Integral manifold head allows direct mounting of DPtransmitters

Hot tapping: Insertion/ installation without system shutdown

Very low pressure drop

DISADVANTAGES OF ANNUBAR

Not suitable for viscous and slurry applications

Can be used for only for clean fluids

VARIABLE AREA FLOWMETER

o A free moving

float is balanced

inside a vertical

tapered tube

o As the fluid flows

upward the float

remains steady

when the dynamic

forces acting on it

are zero.

o The flow rate

indicated by the

position of the

float relative to a

calibrated scale.`

VARIABLE AREA FLOWMETER

FEATURES OF ROTAMETERS

Sizes: upto 75 mm

Fluids/ Applications : Clean liquids, gases and vapours

Flow range: upto 920 cub.m/hr for liquids & 2210 cub.m/hr for gases

MOC: Borosilicate glass/ brass / steel/ stainless steel/ Hastelloy

Accuracy : It varies from ±1% to ±2% of actual flow.

Rangeability is 10:1

Upstream length/ Downstream straight length is 10D / 5D

ADVANTAGES OF ROTAMETERS

Simple, robust and linear output

Does not require external impulse or lead lines.

Pressure drop is minimal and fairly constant.

DISADVANTAGES OF ROTAMETERS

Vertical installation only.

Glass tubes limit pressure & temperature and subject to breakage from hydraulic & thermal shock

Metal tube meters more expensive.

Foreign particles can accumulate around the float & block the flow

MAGNETIC FLOWMETERS

Operate on Faraday’s Law

of magnetic induction.

When a conductive fluid

moves in a magnetic field,

a voltage is generated

between two electrodes at

right angles to the fluid

velocity and field

orientation.

The flow tube has a fixed

area & field intensity so

the developed voltage is

linearly proportional to the

volumetric flow rate.

MAGNETIC FLOWMETERS

FEATURES OF MAGNETIC FLOWMETERS

Design Pressure: 20 BARS to 172 BARS

Design Temperature: Upto 120 deg.C with teflon liners /

180 Deg.C with ceramic liners

Sizes: 2.5 mm to 3000 mm

Fluids : Liquids (clean/ corrosive/dirty/viscous/ slurry)

Velocity range: 0.1 to 10 m/s

MOC: Liners: ceramic/ teflon/rubber

: Electrodes: Platinum/ hastelloy/SS

Accuracy : It varies from ±0.5% to ±1% of actual flow.

Rangeability is 10:1

Upstream length/ Downstream straight length is 10 / 5

ADVANTAGES OF MAGNETIC FLOWMETER

Flow rate unaffected by fluid density, consistency, viscosity, turbulence, or pipingconfiguration.

Highly accurate due to absence of moving parts/ external sensing lines

Corrosion-resistant using Teflon liner and platinum electrodes

Wide flow measuring ranges & no pressure drop.

No Moving Parts. No Wear & Tear on components.

DISADVANTAGES OF MAGNETIC FLOWMETER

Costly, relative to other flowmeter types.

Temperature of the fluids being metered limited by the liner material rating.

Cannot be used for gas flow measurements

VORTEX FLOWMETERS

Vortex meters make use of a natural phenomenon

that occurs when a liquid flows around a bluff object.

Eddies or vortices are shed alternately downstream of

the object. The frequency of the vortex shedding is

directly proportional to the velocity of the liquid flowing

through the meter

VORTEX FLOWMETERS

An obstruction is placed across the

pipe bore at right angle to fluid flow.

As fluid flows, vortices are shed

from alternating sides of the body &

this shedding frequency is directly

proportional to fluid velocity.

Detection of the vortices by means

of pressure changes in the vortex

stream.

Rate of creation of vortices directly

proportional to the flow rate.

VORTEX FLOWMETERS

FEATURES OF VORTEX FLOWMETERS

Design Pressure: 138 bars

Design Temperature: -200 Deg. C to 400 Deg.C

Fluids : Gases (clean/ dirty) and clean liquids

Velocity range: 0.3 to 10 m/s (liquids) and 6 to 80 m/s (gases)

MOC: mostly in stainless steel, some in plastic

Accuracy : It varies from ±0.5% to ±1% of actual flow for liquids and

±1% to ±1.5% for gases

Rangeability is 20: 1

ADVANTAGES OF VORTEX FLOWMETERS:

Minimal maintenance, no moving parts.

Calibration using fluid flow not required & unaffected by viscosity, density, pressure, and temperature within operating specification.

Digital or analog output.

DISADVANTAGES OF VORTEX FLOWMETERS

At low flows, pulses are not generated and the flowmeter can read low or even zero.

Reynolds number should be greater than 10000

Vibration can cause errors in accuracy.

Correct installation is critical as a protruding gasket or weld beads can cause vortices to form, leading to inaccuracy.

Long, clear lengths of upstream pipework must be provided, as for orifice plate flowmeters.

ULTRASONIC FLOWMETERS

A pair (or pairs) of transducers, each having its own transmitter and

receiver, are placed on the pipe wall, one (set) on the upstream and

the other (set) on the downstream.

The time for acoustic waves to travel from the upstream transducer

to the downstream transducer td is shorter than the time it requires for

the same waves to travel from the downstream to the upstream tu.

The larger the difference, the higher the flow velocity.

FEATURES OF ULTRASONIC FLOWMETERS

Design Pressure: 207 bars (insertion type)/ unlimited (clamp on type)

Design Temperature: -180 Deg. C to 260 Deg.C

Fluids : clean gases, clean/corrosive liquids (with little/no solids/ bubbles)

MOC: mostly in stainless steel/ alloyic

Accuracy is

+0.5% of flowrate for insertion type

+1% to +3% of flowrate for clamp on type

Range ability is 10 : 1 to 300 : 1

Bidirectional flow measurement

For insertion type, hot tapping in pressurised pipelines possible

ADVANTAGES OF ULTRASONIC FLOWMETERS

¤ No obstruction/ moving parts in the flow path

¤ No pressure drop

¤ Low maintenance cost

¤ Multi-path models have higher accuracy for wider ranges of Reynolds number

¤ Can be used in corrosive fluid flow

¤ Portable models available for field analysis and diagnosis

DISADVANTAGES OF ULTRASONIC FLOWMETERS

Only clean liquids and gases can be measured

Higher initial set up cost

Limited Acceptance in water & chemical industries.

TURBINE FLOWMETERS

Consists of a multi-bladed rotor

mounted at right angles to the flow &

suspended in the fluid stream on a

free-running bearing.

The diameter of the rotor is slightly

less than the inside diameter of the flow

metering chamber.

Speed of rotation of rotor

proportional to the volumetric flow

FEATURES OF TURBINE FLOWMETERS

Design Pressure: 1500 PSIG

Design Temperature: 150 Deg. C

Sizes: 5 mm to 600 mm (Full bore type)/ > 75 mm for insertion type

Fluids : Clean liquids/ gases and vapours

MOC: mostly in stainless steel/ hastelloy

Accuracy is

+0.25% to + 0.5% of flowrate for full bore type

+1% to +3% of flowrate for insertion type

Range ability is 10 : 1

Upstream length/ Downstream straight length is 15/ 5

For insertion type, hot tapping in pressurized pipelines possible

ADVANTAGES OF TURBINE FLOWMETERS

Very accurate. Commonly used to prove other meters.

Digital output provides for direct totalizing, batching, or digital blending without reducing accuracy.

There is less tendency to read high in pulsating flow than in head or variable-area type meters.

DISADVANTAGES OF TURBINE FLOWMETERS

Not usable in dirty streams or with corrosive materials.

Subject to fouling by foreign materials -fibers, tars etc.

Bearings subject to wear or damage. Shift in calibration if bearings replaced

Can be damaged by overspeeding (over 150 percent) or by hydraulic shock.

Pressure loss at rated flow varies & can be high.

TURBINE FLOWMETERS

This meter repeatedly entraps the

fluid into a known quantity and than

passes it out.

The quantity of the fluid that has

passed is based on the number of

entrapments.

The volume flow rate can be

calculated from the revolution rate of

the mechanical device.

POSITIVE DISPLACEMENT METERS

FEATURES OF PD FLOWMETERS

Design Pressure: 1500 PSIG (liquids)

: 100 psig (gases)

Design Temperature : 293 Deg. C (liquids)

: -34 to 60 Deg. C (gases)

Fluids : Clean Liquids/ gases

Flow range: 0 - 20000 GPM (liquids)

: 0 - 3000 cub.m/hr (gases)

MOC: mostly in aluminum,stainless steel, plastics, hastelloy

Accuracy is + 0.5% to + 1% of flowrate

ADVANTAGES OF PD FLOWMETERS

¤ Good accuracy and high range ability

¤ Can be used in viscous liquid flow

¤ Low to medium initial set up cost

¤ Require no power supply and available in wide variety of read out devices

DISADVANTAGES OF PD FLOWMETERS

¤ Maintenance required at frequent intervals because of the `moving parts.

¤ High pressure drop due to obstruction

¤ Not suitable for low flow rate

¤ Not suitable for fluids with suspended solids

¤ Gas (bubbles) in liquid could significantly decrease the accuracy

Operates by monitoring the cooling effect of a gas

stream as it passes over a heated transducer.

Gas flows passes over two PT100 RTD

transducers.

The temperature transducer monitors the actual

gas process temperature, whilst the self-heated

transducer is maintained at a constant differential

temperature by varying the current through it.

The greater the mass flow passing over the

heated transducer, the greater current required to

keep a constant differential temperature.

The measured heater current is therefore a

measure of the gas mass flowrate.

THERMAL MASS FLOWMETER

FEATURES OF THERMAL MASS FLOWMETERS

Design Pressure: 1200 PSIG

Design Temperature: 176 Deg. C

Fluids : Clean gases

Flow range: 0 – 2500 SCFM

MOC: mostly in stainless steel/ glass, teflon, monel

Accuracy is +1% to + 2% of flowrate

Range ability is 10 : 1 to 100:1

Upstream length/ Downstream straight length is 5/ 3

ADVANTAGES OF THERMAL MASS FLOWMETER

No temperature or pressure compensation required

Linear output (as temperature differential is proportional to mass flow)

Can be used on corrosive process streams if proper materials are specified

DC voltage or 4 to 20 mA dc outputs available

DISADVANTAGES OF THERMAL MASS FLOWMETER

Practical for gas flows only

Subject to blockage by foreign particles or precipitated deposits due tosmall openings in flowmeter

Power requirements excessive in larger pipe sizes

Has to taken out of process line for servicing

Accurate field calibration is difficult

When a moving mass is subjected to anoscillation perpendicular to its direction ofmovement, Coriolis forces occur depending onthe mass flow.

When the tube is moving upward during the

first half of a cycle, the fluid flowing into the

meter resists being forced up by pushing down

on the tube.

On the opposite side, the liquid flowing out

of the meter resists having its vertical motion

decreased by pushing up on the tube. This

action causes the tube to twist.

This twisting movement is sensed by a pick

up and is directly related to mass flow rate

CORIOLIS MASS FLOWMETER

When fluid is moving through the sensor's tubes, Coriolis

forces are induced in both the inlet and outlet legs of both

flow tubes. These forces cause the flow tubes to twist in

opposition to each other.

The mass flow moving through the inlet legs of the flow

tubes generate a Coriolis force that resists the vibration of

the flow tubes. As the mass flow moves through the outlet

legs, the Coriolis force adds to the vibration of the flow

tubes.

It is the opposite direction of the Coriolis force between

the inlet and outlet legs that result in the twisting motion that

is used to measure mass flow rate.

CORIOLIS MASS FLOWMETER

Coriolis Mass Flow meters also measures density. Natural Frequency is basis ofmeasurement of density in coriolis mass flow meter.

Drive coil causes the tube to oscillate at natural frequency. As the mass in

process fluid increases, natural frequency decreases. As the mass of process fluid

decreases, natural frequency of tube increases.

Frequency is measured in cycles per second and Tube period is the reciprocal

of natural frequency. Coriolis Mass Flow meter measures density by measuring

tube period in microsecond per cycles.

Fluid Density is directly related to measure tube period.

CORIOLIS MASS FLOWMETER (DENSITY)

Coriolis Mass Flow meter

FEATURES OF CORIOLIS MASS FLOWMETERS

Design Pressure: 345 bar

Design Temperature: 200 to 426 Deg. C

Sizes: 1.5 mm to 150 mm

Fluids/ Applications : Liquids (clean/ dirty/viscous/ slurries) clean /liquified gases

Flow range: 0 – 25000 lb/m

MOC: mostly in stainless steel, hastelloy/titanium

Accuracy is + 0.15% to + 0.5% of flowrate

ADVANTAGES OF CORIOLIS MASS FLOWMETERS

¤ Capable of measuring difficult handling fluids

¤ Independent of density changes, flow profile and flow turbulence.Hence straight lengths are not required.

¤ No routine maintenance required since no moving parts

¤ High accuracy

DISADVANTAGES OF CORIOLIS MASS FLOWMETERS

¤ Not available for large pipes (upto 150 mm only)

¤ High flow velocities required for detection resulting in high pressure drop

¤ Expensive compared to other flowmeters

¤ Difficulty in measuring low pressure gases.

APPLICATIONS OF FLOWMETERS

• CLEAN LIQUIDS/ GASES

• Orifices

• Venturi

• Annubar

• Variable Area

• Magnetic (only liquids)

• Ultrasonic

• Vortex

• Coriolis Mass Flowmeters

• Thermal mass flowmeter (only gases)

• PD meters

• DIRTY LIQUIDS

Most suited

• Magnetic

Limited applications

• Venturi meters

• DIRTY GASES

Most suited

• Vortex meters

• Venturi meters

• Thermal mass flowmeter

• Variable area flowmeter

CORROSIVE LIQUIDS

• Magneticflowmeters

• Ultrasonic flowmeters

VISCUOUS LIQUIDS

• Coriolis

• Magnetic

• Positive Displacement Meters

ABRASIVE SLURRIES

• Magnetic flowmeters

FIBROUS SLURRIES

• Magnetic flowmeters

• Coriolis Mass Flowmeters (limited applications)

SATURATED STEAM

Most suited

• Orifice DP meters

• Vortex flowmeters

• Venturi meters

• Variable area meters

SUPERHEATED STEAM

Most suited

• Orifice DP meters

• Venturi meters

CRYOGENIC ( Low Temperatures)

• Venturi meters

• Orifice plates

LEVEL INSTRUMENTATION

TYPES OF LEVEL INSTRUMENTS

• LEVEL GAUGEMAGNETIC LEVEL GAUGE

RELEX GLASS TYPE LEVEL GAUGE

FLOAT & TAPE TYPE LEVEL INDICATOR

• LEVEL TRANSMITTERDISPLACER TYPE

RADR LEVEL TRANSMITTER

SERVO GAUGE TYPE LT

DP TYPE LT

NUCLEONIC TYPE LT

ULTRASONIC TYPE LT

• LEVEL SWITCHES VIBRATION FORK TYPE LEVEL SWITCHES

CAPACITANCE TYPE LEVEL SWITCHES

FLOAT TYPE LEVEL SWITCHES

REED TYPE LEVEL SWITCHES

LOOK AT HOOK UP OF LEVEL INSTRUMENTS

RADAR LEVEL

INSTRUMENTS:-

- Used for Continuous Non-

contact Level

measurement of Liquids,

Paste and Slurries.

-For High Pressure and

Temperature.

- Accuracy +/- 1 to 10 mm

- Dielectric Constants shall

be > 1.4

Radar Level Transmitter (Antena Type)

RADAR LEVEL INSTRUMENTS:-

Radar Level measurement using the Time-of-Flight principle.

Radar works with high-frequency radar pulses which are emitted by an antenna and reflected from the product surface. The time of flight of the reflected radar pulse is directly proportionate to the distance traveled. If the tank geometry is known, the level can be calculated from this variable.

GUIDED WAVE RADAR LEVEL INSTRUMENTS:-

Guided Wave radar works with high-frequency radar pulses which are guided

along a probe. As the pluses impact the medium surface, the characteristic

impedance changes and part of the emitted pulse is reflected.

The time between pulse launching and receiving is measured and analyzed by

the instrument and constitutes a direct measure for the distance between the

process connection and the product surface.

Reliable and maintenance-free measurement in liquids, also in turbulent media

and foam. Unaffected by density, temperature, conductibility and humidity.

No impairment by outgassing media (steam pressure).

Process temperatures up to +400 °C

Process pressures up to 400 bar

GUIDED WAVE RADAR

LEVEL INSTRUMENTS:-

Up to 45 meter tank.

Used for Interface Level,

continuous Liquid Level

and solid level

measurement.

Accuracy +/- 2 mm to 10

DP TYPE LEVEL

INSTRUMENTS:-

Used for Liquid Level

Measurement.

Accuracy +/- 0.5 to +/-

0.075% of FS

DP TYPE LEVEL INSTRUMENTS:-

The pressure difference which acts on both sides of the sensor leads to a deflection of the diaphragm. This deflection is converted into a pressure-proportionate output signal.

Unaffected by dielectric constant, foam, turbulence and baffles. High overload resistance.

– Process temperatures up to +350 °C

– Process pressures up to 40 bar

Servo Gauge Level Instruments:-

Servo Tank Gauging measurement is based on the liquid displacement principle. A displacer is suspended in a liquid by a wire. The weight of the displacer is measured, compared to a target value, and the result of this comparison is output as level or density data.

For continuous contact level measurement of liquids and liquefied gases, including liquid surface level, the interface between 2 liquids, and tank bottom. It is also applicable for density measurement.

Servo Gauge Level Instruments:-

Accuracy +/- 0.7 mm

Measures two clear interface levels and specific

gravity of up to three liquid phases

Tank mounted intelligence makes ideal for single or

multi-task installation, converting a wide range of

measurement functions including:

Liquid level Interface level, Spot density, Density

profile, Tank bottom, Water dip

Typical areas of apllication includes - Oil (fules),

LPG/LNG, Chemicals, Water /chemical interface

measurement, Foods, Liquid Food

Capacitance Type Level Instruments:-

A capacitance probe may be compared to an electric condenser. As the tank is filled, the probe capacity increases. This change is electrically analyzed.

Available with active build-up compensation for highly viscous media.

High temperature probe or applications involving extremely high temperatures.

Process temperatures up to +400 ° c, Process pressures up to 500 bar

Used for continuous measurement of liquid .

Used for point detection level in solids, liquids.

NUECLONIC LEVEL INSTRUMENTS:-The gamma source, a cesium or cobalt isotope, emits radiation

which is attenuated as it passes through materials. The measuring

effect results from the absorption of radiation by the product to be

measured which is caused by level changes

Non-invasive measurement from outside for all extreme

applications, e.g. very corrosive, aggressive and abrasive media.

Any process temperature

Any process pressure

NUECLONIC OR RADIOMETRIC LEVEL

INSTRUMENTS:-

NUECLONIC OR RADIOMETRIC LEVEL LIMIT DETECTION:-

NUECLONIC OR RADIOMETRIC LEVEL LIMIT

DETECTION:-

The gamma source, a cesium or cobalt isotope, emits radiation which is

attenuated as it passes through matter.

The measuring effect results from the absorption of the radiation by the

product.

Non-contact from outside.

For all extreme applications like toxic or highly aggressive media or rocks.

Any process temperature

any process pressure

Vibrating Level Switch

A sensor in form of a tuning fork is excited at its resonant frequency. The

drive works piezoelectrically. The oscillating frequency or the amplitude

changes as the fork enters the medium.

The change is analyzed and translated into a switching signal.

Free of calibration and maintenance. For all liquids, also if build-up,

turbulence or air bubbles occur, unaffected by the electric properties of

the medium.

Vibrating Level Switch

Magnetic Level Gauge

Float Type Level Switch:-

As the switch floats up and down on the surface of a liquid, an

installed sensor detects its position and triggers the switching operation.

Simple and price-effective. For liquids like water, waste water, acids.

Float Type Level Switch:-

Reflex Type Level Gauges:-

INSTRUMENTATION

Pressure Instruments

Temperature Instruments

Level Instruments

PRESSURE INSTRUMENTATION

Diaphragm Type Pressure Gauges :- Used

• Bourdon Tube type Gauges

• Diaphragm Type Gauges

• Diaphragm Seal Type Gauges

• Bellows

Material:- .

• All wetted parts shall be minimum SS 316.

• Movement – SS304 minimum

Bourdon Tube PG:

• Used normally up to 60 DegC.

• Range Min. -1 to 1600 Kg/cm2g.

• Argon Arc Welded 316 SS Bourdon Tube.

• Dial Size – 40, 50, 63, 100, 150, 250 mm.

• Normally used 150 mm.

• Connection – 3/8”, ½”, ¾” up to 1.5” NPT,

BSP threads.

• Connection – Bottom, Back as specified.

Bourdon Tube Pressure Gauge

Bourdon Tube PG:

• Mounting – Field or Panel.

• Connection – ½” NPT (M) normally used.

Bourdon Tube PG:

• Over range protection :– 130% of FSD.

• Accuracy: - +/- 1 % of FSD

• Zero point adjustment.

• Blow out disc for safety.

• Glycerin filled used for vibration, shocks.

Diaphragm seal type PG:-

• Used where fluid is corrosive, viscous,

sediments, tendency to freeze, hazardous

fluid.

• To isolate Bourdon tube from process fluid.

• Seal Fluid – inert Liquid, Silicon – DC200,

DC750 based on Temperature.

• Direct mounted or else capillary to be used for

remote mounting.

Diaphragm seal type PG:-

• Connection – Bottom, ½” to 3” flanged, 150#

to 2500#, RF, RTJ, FF available.

• Diaphragm Material – SS316, Hastelloy C,

SS316+PTFE, Inconel, Nickel based on

application.

• Std. Capillary length – 3 mtr.

• Diaphragm sensing are also used without seal

for low pressure sensing, where 0 – 10000

Diaphragm seal PG Construction-

Diaphragm seal PG-

Diaphragm seal remote PG (with Capillary):-

Pressure Switches:-

• Pressure switches are used detect high or low,

normally it is blind pressure switches.

• Differential pressure switches are used to detect lo or

hi Differential pressure.

• Indicating switches are also available.

Pressure & DP Transmitters:-

Diaphragm Seal type Direct Mounted Pressure

Transmitters:-

Diaphragm Seal type Remote Pressure

Transmitters:-

Diaphragm Seal type Remote & Inline Pressure

Gauges / :-

Differential Pressure Gauge

Accessories:-

• Syphon :- Used in steam service to reduce temp.

• Snubber:- Used at Pump Discharge to reduce fluctuation, provides dampening effect.

• Gauge Saver:- Used where maximum pressure exceeds the over range pressure of gauge.

• 2-Valve manifold for PG

• 3-Valve Manifold for Differential Pressure Indicators.

3-way valve Manifold

5-way Manifold

Accessories:-

Accessoris:- 2 Valve Manifold

TEMPERATURE INSTRUMENTATION

Bimetal Dial Thermometers

• Bottom , Back entry

• Every angle type

• Range -50 to 600 DegC

• Protection – 125% of FSD.

• ½” NPT (M) standard.

• Thermo well Required

• Accuracy - +/- 1% of FSD

• Micro pointer adjustment for zero.

Mercury filled, Gas Filled Thermometer or

Temp. Gauge :

• For Remote Mounted Temp. Gauge.

• Inert Gases are used.

• Range -200 to 800 DegC

• Thermo well Required

• Accuracy - +/- 1% of FSD and above

Bimetal Temp. Gauge :

Gas Filled Capillary Temp. Gauge :

Different Types of Temp. Gauge :

Bimetal Temp. Gauge :

Thermo well :

Flanged Thermo well :

Different Thermo well :

Temperature switches are also available

Thermo well material shall be min. SS316, can

be available in SS316L, Hastelloy.

Connection shall be 1.5” 300#RF ANSI Flange

standard.

Can be available in Threaded, welded also.

Based on requirement & application.

Temperature Element :- RTD, Thermocouple

RTD :- Resistance Temperature Detector

• PT-100, PT-1000, CU-2000

Principle :- Change in Resistance is directly

proportional to Temperature.

3 wire RTD

4 wire RTD

RTD Assembly

Thermocouple

Thermocouple :

• K-type normally used.

• E Type, J type, R Type, S Type, T type.

• Principle : Works on Seebeck Effect, which is

when two dissimilar metal junction heated, a

potential difference is developed at other end.

Thermocouple

Thermocouples Types

• E Type , Chromel (+ve) – Constantan(-ve),

Recommended Range -184 to 982 DegC

• J Type , Iron (+ve) – Constantan(-ve),

Recommended Range 0 to 815 DegC

• K Type , Chromel (+ve) – Alumel (-ve),

Thermocouples Types

• R Type , Pt87-Rh13(+ve) – Platinum(-ve),

• S Type , Pt90-Rh10 (+ve) – Platinum(-ve),

• T Type , Copper (+ve) – Constantan (-ve),

RTD/TC:-

Thermo well with Temp. Element

Installed thermo well in pipe line :-

Temperature Transmitter:-

CONTROL VALVE

Section 1

PCSupply

Supply

P1 = 75-100 psig

Positioner

3-15 PSIG

What is a control valve?

Typical Pressure Control Loop

Pneumatic

Supply

P1 = 75-100 psig

Positioner

Analog

Electro-Pneumatic

Control Signal4-20mA

Process Variable4-20mA

Supply

P1 = 75-100 psig

Positioner

Digital

Control Signal

Process Variable

Bi-directional Digital communication

What is control valve?

• It is one of the final control elements

– Controls/Regulates flow rate of fluid

– Controls compressable(gas) and non-

compressable(liquid) fluids

– The other final control elements are ID fan/FD fan

dampers, VFD(for pump sped control), over head

water tank float valve

– Based on the application control loops are

functionally termed as Flow control valve(FV), Level

control valve(LV),Pressure control valve(PV),

Temperature control valve(TV )

CONTROL VALVE

• What are the various types of control

valves

- Globe: very widely used for most of

applications

- Butterfly: low pressure drop and for sizes

more than 4” generally

- Ball: tight shut off and on/off applications

- Diaphragm: corrosive and slurry services

CONTROL VALVE

• What are various parts of control valve?

- Body : consists of trim (closure member)

- Bonnet: The portion of the valve which encloses the pressure retaining parts such as packing rings, stem

- Yoke: the connecting part between body and Actuator

- Actuator: where Instrument air acts for operating the valve

- Positioner: the component which positions the valve stem at required position based on the control signal

- Travel limit switches: which gives feed back signal of valve travel

The device that positions the throttling

element inside the valve body

Stem (Piston Rod)

Travel Indicator

Body Subassembly

Throttling Element

Stem Connector

Diaphragm

Piston

CONTROL VALVE

DIAPHRAGM

CASINGS

LOCK NUT

STEM CONNECTOR

SPRING ADJUSTER

ACTUATOR STEM

ACTUATOR

SPRING

BONET FLANGE

STUFFING BOX

DIAPHRAGM

GLAND STUDS

SPRING SEAT

DIAPHRAGM

INPUT SIGNAL

INDICATOR

Pneumatic single spring diaphragm actuator

CONTROL VALVE

• Linear motion control valves

- Globe

- Gate

- Diaphragm

- Pinch

• Rotary motion control valves

- Ball

- Butterfly

- Plug

CONTROL VALVE

• Basic relation of Flow rate & Pressure drop

- Flow rate is proportional to square root of pressure drop

- The proportionality between flow rate and square root of pressure drop holds true only for fully turbulent fluid behavior

CONTROL VALVE

• Steps for sizing of control valve

• Inputs

- Fluid status(liquid/gas/steam)

- Flow rate maximum/normal/minimum

- Pressure drop

- Density /specific gravity of fluid

- Temperature of fluid

- Pipe line size

CONTROL VALVE

• Valve flow coefficient, Cv

- Number of U.S gallons per minute of water

that will pass through a given flow

restriction with a pressure drop of one psi

- a Cv of 12 means the control valve at full

open position passes 12 US gallons of

water per minute with one psi pressure

drop across it. It is a capacity index.

CONTROL VALVE

• Calculating Cv for liquid flows

- Cv = (q/N1*Fp)*√Gf/p1-p2

• For gas flow

- Cv = q/N7*Fp*p1*γ*√GgT1Z/x

Cv= valve flow coefficient

q= volumetric flow rate

N= numerical constant

Gg= gas specific gravity

Gf=specific gravity at flowing temp

T1=absolute inlet temperature

Fp=piping geometry

factor

p1=upstream pressure

p2=downstream pressure

γ = gas expansion factor

x = pressure drop ratio dp/p1

Z = gas compressibility factor

CONTROL VALVE

• Control valve size should typically not be less than half size of the line size where it is installed i.e in a 6” line CV should not be 2”. It can be 6” or 4” or 3” based on Cv calculated.

• Using line size valve with reduced trims following advantages

- saves cost on reducers( However, the cost of reducers vs CV cost to be evaluated before making this conclusion)

- permits increasing future throughput

- permits the design of piping system before final CV selection

SIZING CONTROL VALVESFactors to be considered

–Liquid sizing

– Understanding Bernoulli’s equation

– Choked Flow

– Pressure recovery coefficient

– Cavitation

– Flashing

– Noise

– Gas sizing

– Trim characteristics

– Material selection

– Stelleting

– Pipe velocity limitations

– Trim exit velocity limitations

SIZING CONTROL VALVESLiquid service – pressure recovery curve

P1 Inlet Pressure

P2 Outlet Pressure

V1 Inlet Velocity

Valve inlet Valve outlet

Pv Vapour Pressure

Single Stage LetdownP1 Inlet Pressure

SIZING CONTROL VALVES

Flashing service

Outlet Velocity

Outlet Pressure

Pv Vapour Pressure

Inlet Velocity

Inlet Pressure

SIZING CONTROL VALVESCavitating service

Outlet Pressure

Pv Vapour Pressure

Inlet Velocity

Inlet Pressure

SIZING CONTROL VALVESCavitation and Flashing

→ Cavitation & Flashing are liquid phenomena

→ There is bubble formation when the static pressure of the fluid falls below

the vapour pressure.

→The bubbles formed collapse when the static pressure increases above the

vapour pressure. This is cavitation.

→The bubbles formed are carried downstream if the outlet pressure is less

than vapour pressure. This phenomena is flashing.

→Both Cavitation and Flashing can cause excessive erosion on Trim parts,

body and downstream pipe.

→Cavitation can be fully eliminated by offering suitable trim but not flashing.

→Low recovery valves are less prone for cavitation

SIZING CONTROL VALVE

Cavitation service: solution

• Reduction of operating temperature

• Reduction in differential pressure drop

• Location of the valve

• Selecting Valve with low recovery

• Selecting multistep valve

• Cascading

SIZING CONTROL VALVECavitation service: solution

CONTROL VALVE

• Control valve basic characteristics

The relation between flow rate through a

valve and the valve travel

- Equal %

- Linear

- On/off

CONTROL VALVE - Characterstics

SIZING CONTROL VALVES

Trim characteristics100

020 40 60 80 100

Quick opening

Linear

Equal percentage

CONTROL VALVE

• How to select required valve characteristic

- select =% if the system decreases with

increasing valve load

- if the pressure drop is varying i.e not

constant pressure drop

- Typical applications with above conditions

are Pressure control and nonlinearised

flow control

CONTROL VALVE

• Linear characteristic selected for following

applications

- pressure drop is constant

Typical applications are:

- level control

- pump minimum flow bypass control

- split range

CONTROL VALVE

• Quick opening characteristic

- typically selected for On/off valve

applications

- Depressurising applications

CONTROL VALVE

• Input data for selecting proper MOC

- Design pressure & temperature

- Piping specifications

CONTROL VALVE

• Some special applications

- Coker valves used in DCU plant

- As the coke is very turbid / tendency to solidify at

low temperature valves need special

attention/design to work in these harsh

conditions

- Due to high pressures Motorised actuators are

used instead of conventional pneumatic

- Knife edge valves are used in slurry/pulp

services

SIZING CONTROL VALVE

• Control Valve Leakage

ANSI/FCI 70-2 Test Medium Pressure and temperature

Class II

Class III

Class IV

Class V Water Service DP at 10 to 52deg C

Port dia.Bubbles per

Min.mL per Min.

1 1 0.15

1 - 1/2 2 0.30

2 3 0.45

2 - 1/2 4 0.60

3 6 0.90

4 11 1.70

6 27 4.00

8 45 6.75

Maximum Leakage

0.5% valve capacity at full travel

0.0005ml/min/psid/in. port dia

Class VI

Service DP or 50 PSID

whichever is lower at 10 to

52deg C

Water / Air

Service DP or 50 PSID

whichever is lower at 10 to

52deg C

FF LOOP (DCS)

Control Valve

Globe Control ValveRotary Control Valve

Control Valve

CONTROL VALVE

COMPONENTS

• Control Valve Accessories- Positioners

- Position Transmitters

- Limit Switches

- Solenoid Valves

- Air Filter Regulators

- Lock-up relays

- Volume Tanks

• Positioners

- Pneumatic

- Electro pneumatic

- SMART / HART Type

- Foundation Fieldbus Digital Positioners

CONTROL VALVE ACTUATORS

Actuator Types

Piston Diaphragm

Linear Rotary

Pneumatic Hydraulic Electric

Actuators

CONTROL VALVE

COMPONENTS

DIFFERENT TYPES OF CONTROL VALVE

Globe valve

Angle valve

3-way valve

Ball valve

Butterfly valve

V-ball valve

CONTROL VALVE

INSTALLATION PRACTICESPERFORMANCE

• Max straight run in inlet pipe – A good thumb rule -10 to 20 D

• Allow straight run in outlet pipe – 3 to 5 D

straight run in inlet pipe – steady inlet flow – steady & repeatable

• Location of PG &

Location of CV with respect to indicator of controlled parameter

AVOID AVOID

INSTRUMENTATION

Boiler Controls

Distillation Column Controls

Boiler Control Loops

Boiler Control Loops (3 – Element)

Distillation Column

• Distillation is very common and widely

used for process of separation.

• Used to isolate & purify volatile materials.

• Separates a mixture on the basis of

difference in the composition of liquid and

that of the vapor formed from the liquid.

Distillation Column

• Distillation column is energy separating

agent equilibrium process that uses the

difference is relative volatilities or

difference in relative boiling points of

components to be separated out.

• Most commonly used in oil & Gas

Refinery, Petrochemical & Chemical

plants etc.

Distillation Column Objective

• Column Operating objectives :-

– Operating objectives includes the composition

specification for the top and the bottom product

streams.

– Other Objectives can include increasing throughput,

enhancing column stability, and operating equipment

constraints.

Distillation Column

• Proper instrumentation for distillation

column operation is vital to achieve

maximum product of satisfactory purity.

• Instrumentation is used to solve equations

necessary for proper control of distillation

column.

Distillation Column

• Primary application of instrument & control

in column is to control product purity.

• Secondary application is to minimize

upsets to unit caused by change in

process inputs.

Distillation Column Flow Sheet

Distillation Column Equipments

• Column

• Pre heater

• Condenser

• Accumulator

• Reflux pump

• Re-boiler

• Reflux System :-

– The overhead vapor leaving column is sent to a

cooler or condenser and is collected as a liquid in

accumulator or receiver.

– A part of accumulated liquid is returned to column

as a reflux.

– The remainder is withdrawn as overhead product

or distillate.

• Re-boiler System :-

– The liquid leaving the column bottom is heated in

a re-boiler (A re-boiler is a special type of heat

exchanger used to provide the heat necessary for

distillation).

– Part of this liquid is vaporized and returned into

the column as a boil up.

– The remaining liquid is withdrawn as a bottom

product or residue.

Column Re-Boiler

Variables for Distillation Operation

Distillation Column Controlled

variables• Column Controlled variables :-

– As we know controlled variables can be affected by

several manipulated variables, only one

manipulated variables used to directly affect the

value of controlled variable.

– Minimum following controlled variables for a column

need to be considered.

Distillation Column Control

Configuration

Internals of Column

Instrumentation GDR

Documents