MAIN PROJECT PRESENTATION

2012

THANGAL KUNJU MUSALIAR INSTITUTE OF TECHNOLOGY

THREE ELEMENT CONTROL ON DRUM

LEVEL USING EMBEDDED SYSTEMS

GUIDED BY PRESENTED BY

Mrs. BeenaRani B B Anju J [ 8406 ]

Lect. EI Dept. Arya M S [ 8412 ]

Devika S [ 8420 ]

Neethu Raj [ 8434 ]

Sibimol Luke [ 8449 ]

DONE AT

The Kerala Minerals and Metals Ltd.Chavara, Kollam

INTRODUCTION

Boiler is a steam generating unit.

AIM- Controlling water level in boiler drum.

3 control strategies :single element.

two element and

three-element control

3 element control implemented using embedded programmable

controller Yokogawa YS1700.

BOILER

A closed vessel made of steel in which water or other fluid is heated

to generate steam.

Slave plant or utility plant and it is maintained at negative pressure

Used to generate steam for doing mechanical work, heating,

producing vacuums, and augmenting chemical processes

An important variable to measure and control in a continuous

boiler is the level of water in the “steam drum”

This vessel’s primary function is to provide a surface area and

volume near the top of the boiler where separation of steam from

water can occur

WATER TUBE BOILER

• Used for high steam demand and pressure requirements

• Capacity range of 4,500 – 120,000 kg/hour

• Combustion efficiency enhanced by induced draft provisions

• Lower tolerance for water quality and needs water treatment plant

BOILER IN KMML

BOILER BLOCK DIAGRAM

DM WATER

TANKDEAERATOR ECONOMISER

BOILER

DRUM

STEAM

BOILER AIR SCHEME

AIR FD FAN DAMPER WIND BOX

BURNER

FLAME

OIL

BOILER FUEL SCHEME

OIL STORAGE

TANK

OIL HEATER

OIL CONTROL

VALVE

BURNER

DRUM LEVEL CONTROL

OBJECTIVE OF THE PROJECT

Operator adjustment of the set point.

Compensation for the shrink and swell effects.

Automatic control of drum level.

Bump less transfer between auto and manual modes.

Indication of drum level and steam flow.

Indication of feed water valve position and feed water flow.

Absolute/deviation alarms for drum level.

SINGLE ELEMENT CONTROL

PID CVMEASUREMENT

SET POINT

Single-Element control is the simplest strategy

Single element drum level control measures drum level only

This is a simple feedback control loop

Only one analogue input and one analogue output required

Can only be applied to single boiler / single feed pump configurations

with relatively stable loads since there is no relationship between drum

level and steam- or feed water flow

Possible inadequate control option because of the swell effect

During startup of a boiler, it is effective to use single-element control in

which the feed water controller is bypassed and the drum level

controller directly controls the feed water control valve

TWO ELEMENT CONTROL

15

LEVEL

PIDSET POINT

INFLOW

PID

CV

SET

PV PV

The two element control scheme utilizes steam flow in addition to drum

level

This is a simple feedback plus feed forward control system with a

secondary variable that has a predictable relationship with the

manipulated variable

The secondary variable, steam flow, causes the manipulated variable to

change the primary variable

Tighter control of drum level than with only one element

Steam flow acts as feed forward signal to allow faster level adjustments

Can best be applied to single boiler / single feed pump configurations

with a constant feed water pressure

THREE ELEMENT CONTROL

DRUM LEVEL

LAG

PIDSET

SAT FLOW

SUP FLOW

ADD

MATH

WATER FLOW

PV

PIDSET

PV

CV

Three element control utilizes steam and water flow in addition to

drum level

This is a simple feedback, feed forward, and cascade control loop.

The steam flow adjusts the feed water control valve based on the

steam flow signal and the drum level controller signal

The three-element system provides tighter control for drum level with

fluctuating steam load.

Ideal where a system suffers from fluctuating feed water pressure or

flow

More sophisticated level of control required

Additional input for feed water flow required

SCHEMATIC DIAGRAM

PERFORMANCE

Single element Two element Three element

APPLICATION CHART FOR DRUM LEVEL CONTROL SYSTEM

System Classification

Load Change Capabilities

Typical Applications

Magnitude Rate

Single-element Moderate Slow Institutional and industrial heating plantsSteady process conditions

Two-element Moderate Moderate Industrial plants with essentially continuous type processes and good feed water pressure regulation

Three-element Wide Fast Combination of batch and continuous type operations such that plant steam load characteristics varies continuously and usually unpredictably. Most industrial power applications fall into this category.

EMBEDDED SYSTEM

Embedded Systems is a special purpose computer system/board, which

encapsulates all the devices such as processor, memory, interface and

control in single package or board to perform only a specific application

tasks.

EXISTING CONTROLLER ‘BCE 760’

Single station ,single loop controllers having P, PI, PID functions.

LIMITATIONS

Dedicated registers. So it cannot be used for other purposes.

Lag cannot be provided directly.

No peer to peer communication.

It can do only one control action.

No graphical monitoring is possible.

Cannot be employed in emergency situations.

 

YOKOGAWA YS1700 PROGRAMABLE CONTROLLER

YS1700 is a programmable logic controller

Each YS1700 can run two PID control

algorithms, and the corresponding 4 ~

20mA output signal

YS1700 can also be used without

programming multi-function controller

The YS1700 Programmable Indicating

Controller includes over one-hundred

computation modules

RS-485 communication protocol for the

YS1000 series

FEATURES

Function block programming: GUI-based programming

method.

Large programming capacity.

More powerful control and calculation functions.

Function selection mode (needs no programming).

Expandable I/O.

Nonvolatile memory for memory backup.

Dual power supply.

YSS 1000 SOFTWARE BASIC OPERATION

FLOW CHART

START

READ DRUM LEVEL

READ SAT

FLOW

READ SUP

FLOW

READ FEED WATER FLOW

√ √X GAIN + BIAS

√

X GAIN + BIAS

X GAIN + BIAS

X GAIN + BIAS

DLC MODE = MANUAL SUM FIC

MODE = MANUAL

SUM - 50

C = A+B

MV = MAN O/P

SET = PV

PI ALGORITHM

FIC MODE =

AUTO

C = SET

PI ALGORITHM

MV = MAN O/PSET = PV

FW_CV END

YES

NO

YES

NO

NO

YES

PROGRAM

Program for Three Element Control

LD X4; drum level signal

LD P8; gain

*

LD P9; bias

+

ST T16;

LD P1; first order lag time in second

LAG 1

ST T1

ST Y2; retransmission drum level to recorder A02

LD X3; feed water flow signal

LD P10; gain

*

LD P11; bias

+

ST T2

ST P30; to display feed water flow in drum level controller face

plate

LD X1; sat steam flow signal

LD P2; 0.666 gain for ranging

*

ST T3

LD X2; super heated steam flow

LD P3; 0.333 gain for ranging

*

ST T4

LD T3

+

ST T5

ST Y3; for pressure controlling flow feed forward signal AO3

ST P6; for display total steam flow in feed water controller

face plate

LD P4; gain of total steam flow for correction if necessary now it

is 1

*

LD P5; 50 %( subtractor from drum level cont4roller output

-

ST T6

ST FF1; feed forward signal modify drum level controller

output by “T6”

LD SV2; six lines after this is for ascertaining the drum level

controller output in” T15”

LD P6

-

ST T14

LD P5

+

ST T15

LD DI1; 1=single element,0=three element

LD P7; 100=single element, 0=three element

OR

ST PRDF; true= (single element), false= (three element)

LD CAMF1; true when controller1 LIC in auto mode

NOT

GIFSUB @ abc; jump to subroutine 4 trading the PV by SV of

LIC in manual mode

LD T1; compensated drum level

LD T2; feed water flow

CSC; cascade

ST Y1; output to feed water control valve

LD PHF1; true when high level alarm occurs

ST DO3; digital output of high alarm

LD PLF1; true when low level alarm occurs

ST DO2; digital output of low alarm

LD X1

ST P12

LD X2

ST P13

LD T2

ST P14

LD T1

ST P15

LD T15 ST P16

LD CAMF2

NOT

GIFSUB @ def

END; end of main program

SUB@abc

LD PV1

ST SVI

RTN

SUB @ def

LD PV2

ST SV2

RTN

SUB @ SIMPR; test program

LD P21

ST X1

LD P22

ST X2

LD P23

ST X3

LD P24

ST X4

RTN

CONCLUSION

Successfully controlled the boiler drum level using YS1700

programmable controller.

QUESTIONS