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CONTRACT No. 511-4620 PUCALA, PERU

Description of plant
1.Introduction
1.1. General
This handbook provides a full description of ono bagasse and oil fired bi-drum boiler with an output of
130,000 lb/hr of steam. The boiler is for the complejo Agro industrial Pucalá and is situated in an
outdoor location on a sugar plantation at Chiclayo, Peru. The principal items of plant are as follows: -
1 - Bi-drum boiler, with mountings, pipework and fittings: capable of a Maximum Continuous Rating
of 130,000 lb/hr of steam under initial conditions of 430 p.s.i.g. and 640ºF and final conditions (at a
later date) of 600 p.s.i.g. and 720°F.
1 - Superheater within the boiler of pendant type arranged for steam and gas in counter flow. The
Superheater design is such that the tube lengths may be increased to enable steam at the final
conditions to be produced.
1 - Furnace with water cooled walls and roof from a level approximately 8'0" above the dumping grate.
The lower portions of the walls are formed with furnace refractory.
4 - Bagasse metering conveyors which convoy the fuel to the air swept spouts from which it is
deposited on the grates.
1 - Babcock - Detroit dumping grate in four sections each section boing power operated by steam
cylinders.
4 - Auxiliary B&W. Y-jet steam atomized burners mounted in air registers through a wind box
positioned on the front of the boiler. A portable electric ignitor is provided for lighting up and pressure
type sprayer plates are provided where it is required to ignite the oil burners when atomizing steam is
not available.

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1.1. General Cont´d)
7 - Soot blowers for the boiler are provided. Three retractable soot blowers are positioned to operate
through the boiler roof and four others operate through the side walls in the vicinity of the boiler bank.
1 - Forced draught fan complete with dampers, motor and starter
1 - Induced draught fan complete with dampers, motor and starter
1 - Secondary air fan complete with dampers, motor and starter
1 - Air heater of the cross flow vertical tubular type is positioned in the flue at the rear of the boiler
before the induced draught fan
1 - Davidson Ltd type 'R' dust collector is positioned in the gas outlet duct at the roar of the boiler
ahead of the Airheater
1 - Babcock & Wilcox Ltd type s.10.EE pumping and heating unit, the pump motor and starter are also
included.
1 - Set of interlocks, instruments and controls are supplied
1 - Set of galleries and ladders are supplied to provide
access to the various items of plant and equipment.
1.2. Site Conditions
The boiler is at an outdoor location which is in a recognized earthquake zone. The design parameters
have been based on an assumed ambient temperature of 80°F and seismic bracing to a factor of 0.2g is
provided.
1.3. Electrical supplies
The electrical supplies at site are as follows: -
110v, single phase, 60 c/s for Ignitor, instruments and lighting
440v, three phase, 60 c/s for F.D., Secondary Air fan and Pulsating Damper Motors and three phase,
60 c/s for I.D. fan motor.
440 v.

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Typical description
The following description provides a general introduction
to the boiler and its associated equipment. it is not intended
to be an exhaustive treatment of a particular installation, de-
tailed instruction on the use and care of the various items and
systems installed will be found in the subsequent parts of this
manual and the use of the plant should at all times be governed
by the information therein.
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BI-DRUM BOILER-GENERAL. DESCRIPTION
This boiler is a naturally circulated two water tube unit characterized by vertically arranged water tube
generating bank connecting the upper and lower drums. The upper, steam drum, and The lower, water
drum, are transversely position with respect to the hot gas flow.
The water cooled furnace to designed to absorb radiant heat from
the combustion zone and cools the gases to a suitable temperature
before passage over the boiler bank convection surface. Active circulation through the wall water tubes
is ensured by the provision of ample supply and return connections to both drums.

There are three methods of constructing furnace floors, walls and roofs. Any one or more of these
methods may be necessary for a single installation. The methods are as follows:
(a) Spaced Tube
The heating surfaces are formed by tubes spaced at intervals, backed by refractory tiles and restrained
by external tie bars.
(b) Tangent Tube
The heating surfaces are formed by closely set tubes restrained by external tie bars stitch welded to the
individual tubes. Tangent tube walls provide maximum cooling and protection for the boiler insulation.
(c) Membrane
The heating surfaces are formed by tubes evenly spaced with the gaps between closed by metal strips
welded to adjacent tubes. This ensures a robust gas-tight wall giving ease of maintenance and
minimum refractory. This form of construction is known as a membrane wall.

Where the tubes are bent to form openings e.g., to accommodate burners, studding is employed. The
spaces between tubes are filled with round or plate studs welded to adjacent tube sides to provide a
foundation for the application of mouldable refractory.
Operational loads on the furnace walls are transferred through tiebars welded to the tubes to backstay
girdles which provide structural rigidity to the walls.
Provision is made in the furnace walls for viewing combustion and furnace conditions by means of
hinged sighting ports.
In most cases, the furnace is entirely water cooled and as all the water tubes are incorporated in the
natural circulation. system, both the boiler tube arrangement and the furnace cooling are designed for
specific requirements.
PAG 06
Boiler bank, furnace and circulating tubes are expanded into the boiler drum and furnace will boxes, or
alternatively, butt welded onto stub tubes which are welded to the drum and boxes during manufacture.
The drums are of fusion welded construction, the barrels being rolled and the ends pressed from steel
plate. The drum ends are provided with manholes of either at both ends or at one end only.
Saturated steam offtake to Superheater or boiler outlet is by multiple connecting pipes.
Nozzles are welded to the drums for valves and mountings which are typically as follows: -
1. One or more safety valves.
2. Water Level gauges.
3. Water Level alarms.
4. Continuous blowdown valve.
5. Intermittent blowdown/drain valve.
G. Chemical injection valve,
7. Water sampling valve.
8. Feed inlet.
9. Saturated steam to auxiliaries.
10.Saturated steam to sootblowers (where no Superheater is provided).
11. Air release valves.
12. Pressure gauge.
Within the steam drum, extension pipes are fitted to the water connections to water level gauges and
alarms to ensure accurate indication of the water level. Internal extension pipes are also fitted to the
chemical injection nozzle and the continuous blowdown nozzle ending at correct points for each duty.
An internal perforated feed pipe is connected to the feed inlet nozzle to distribute the incoming feed
water below normal water level in the drum.
The boiler operates by natural circulation. The driving force causing water flow is derived from the
density differences between water without steam in one leg of a circuit, and that in the other leg,
which, because of higher heat input, has steam mixed with water. In the bi-drum boiler steam is
generated in the furnace wall tubes and in a major part of the boiler tube bank and flow is thus up these
tubes. Recirculating water descends from the steam drum to the water drum through the final and
cooler part of the boiler bank on the gas outlet side at the rear of the boiler.
Tubes from the lower drum supply water to the inlet boxes of the furnace circuits.
This circulation pattern is ensured by the disposition of baffling within the steam drum, Riser tubes
entering the steam drum are contained behind a girth baffle on which are mounted cyclone steam
separators.
These are described more fully elsewhere. All discharge from the baffle is through the cyclone
separators which ensure both the return of steam free water to the steam drum for recirculation to the
water drum and the release of substantially water-free steam. To achieve the highest purity in steam
leaving the boiler drum, primary and secondary
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corrugated Scrubber Clements are provided at the cyclone separator steam discharge in the crown of
the drum. The normal water level in the steam drum is usually at the horizontal Centre line which
coincides with the mid height of the water level gauges.
Combustion of the fuel takes place in the furnace and the flow of combustion gas from the furnace
passes through the full width of the boiler tube-bank. Where a Superheater is provided, it forms an
integral part of the boiler and the gases pass through the Superheater before entering the main tube
bank. The Superheater may be screened from the furnace radiation by one or more rows of water-tubes
across the furnace exit.
On leaving the boiler bank the gas passes directly to the chimney or to it via any of the following plant
if provided: - economizer, air heater or grit arrestor,
Page 3
2. Operating Conditions
Evaporation at 100% M.C.R. 130,000 lb/hr =53967, 0001
Design Pressure 675 p.s.1.
Feed Temperature 250°F (120°c)

INITIAL FINAL
Final Steam Pressure 430 p.s.i 600 p.s.i
Final Steam Temperature 640°F 720°F
2.1. Main Fuel
Bagasse 4150Btu/lb
Gross Calorific Value 3340 Btu/lb
Nott Calorific Value 50%
Moisture
Ash 1.5%
Anticipated Consumption 55000 lb/hr Initial and 58500 lb/hr Final
2.1.1. Supplementary Fuel
Fuel Oil 18400Btu/lb
Gross Calorific Value 17420 Btu/lb
Nott Calorific Value
Anticipated Consumption 9400 lb/hr initial and 9800 lb/hr final
3. Safety Valves
The following safety valves are fitted: -
BM1, Boiler safety valves, Hopkinson 2" Hylif, two valves both mounted on the boiler steam drum.
For the initial conditions these valves, are set at 490 p.s.i. and 485 p.s.i. respectively. Alternative sprig
and plates are supplied so that both valves may be arranged to lift at the final pressure of 675 p.s.i.
SHI, Superheater safety valve, Hopkinson 21/2" Hylif, a single valve mounted on the Superheater
outlet box. This valve is to be set to lift at 452 p.s.i. initially. A spare spring and plate are provided so
that the valve may be set to lift at 630 p.s.i, for the final conditions.
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BABCOCK & WILCOX (OPERATIONS) LTD LONDON
SUPPORT
The boiler is adequately supported on a plinth beneath the water drum and a number of pillars capped
with sliding bearing surfaces to permit thermal expansion movement beneath the furnace.
Saddles on the base carry the water drum as the main support for the boiler and the additional supports
carry the weight of the furnace. The water drum is securely anchored a neutral point and from this
point the entire assembly is free to expand on the support bearings.

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SUPERHEATER
The Superheater is an integral part of the boiler and is designed to produce the desired steam
temperature over the specified range of boiler output.
The Superheater is of non-drainable pendant type and is positioned on the furnace side of the boiler
tube bank. The Superheater sections may be screened from furnace radiation by a one or more rows of
spaced water tubes forming a furnace screen.
The Superheater inlet and outlet boxes are external to the boiler setting and the rows of tubes are either
expanded into holes in the boxes or butt welded onto stubs provided during manufacture.
On some installations the Superheater inlet box is omitted, the Superheater inlet tubes being attached
to the top of the steam drum by either method of attachment specified above.
Where the final steam temperature must be confined to a narrow range attemperation is used.
In this case the Superheater is divided into two sections, the primary and secondary superheaters
respectively. Both primary and secondary sections are provided with separate inlet and outlet boxes,
the attemperator is connected between the primary and secondary Superheater sections and may be of
the spray, drum or shell type.

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EXTERNAL INSULATION R CASING
Where the spaced title type of bounce wall construction is used the tubes are insulated as shown below.
With the tangent type of furnace wall construction, the tubes are backed by a steel skin casing lying on
the tubes. Thermal insulation is applied over the skin easing and enclosed with a metal veneer
cleading.
With the membrane wall construction thermal insulation is applied direct to the outside of the wait and
the exterior clad in metal veneer.
In all cases the thermal insulation and cleading are continued over the steam drum.
Appropriate weather proof casings are fitted to boilers in outdoor installations.
Pago 15
OIL FIRING EQUIPMENT
The oil burner is the Babcock & Wilcox Y - jot twin fluid atomiser centrally mounted in a forced
draught air register. The air register is itself enclosed in a windbox on the furnace wall a regulated,
guided turbulent air supply to the combustion zone. The atomising medium is usually steam but air
may be used to atomise the fuel.
Each atomiser is provided with individual oil and steam isolating valves. The burner functions with a
constant atomizing steam pressure and a varying oil pressure. The oil pressure to the burner is
regulated by the combustion control valve. A correctly atomised fuel discharge is maintained for clean,
efficient combustion, within the turndown ratio specified for the installation.
Where atomising steam is not available from other sources for starting up, the atomiser can be
modified for pressure atomization by using a screw on adaptor, pressure plate and cap nut.
From the pumping and heating unit heaters the oil passes via the discharge filters to the automatic
combustion control valve, a solenoid operated fuel shut-off valve, and then to the burners,
The combustion control valve regulates the fuel flow to the burners and is modulated by the boiler
final steam pressure, thereby changing the rate of firing in line with changes in the boiler load.
The solenoid operated shut-off valve is part of the interlock system, automatically shutting-off the fuel
supply to the burners in the event of a trip function operating.

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PUMPING & HEATING UNIT
The oil firing equipment includes an oil fuel pumping, and heating unit which is constructed as a
separate unit. The P&H unit components are electrically and/or steam driven oil pump(o), steam
heater(a), tot connection to the burner piping. The p& H unit is mounted on a baseplate which also
serves as an oil-tight tray.
The P & Il unit instrument panel accommodates oil temperature and pressure gauges and heater steam
pressure gauge.
Suction strainers are provided in the suction pipework to the P&H unit which unless otherwise stated is
designed to accept fuel oils of viscosity up to 2000 secs. Redwood No.1 at the suction strainer inlet.
Heavier grades of fuel, if used, will require pre-heating before delivery to the suction strainer.
From the suction strainer inlet, the oil passes to the fuel pump(s), the intakes of which are normally
under flooded conditions. The electric pumps are positive displacement screw type and each is fitted
with an integral pressure relief valve.
From the pup(s) the oil is delivered to the steam heater(s) where the fuel is heated to a preset
temperature equivalent to a. viscosity of 80 to 100 secs. Redwood No. 1 required at the burners. The
steam heaters are thermostatically controlled by means of an automatic steam control valve in the
steam supply to the heater shells, and are provided with traps for condensate removal.
For starting up when steam is not available, a separately mounted electrical in line oil heater can be
provided.
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BAGASSE FIRING - DUMPING GRATES
Bagasse is the refuse from the milling of sugar cane. Physically bagasse consists of matted cellulose
fibres and fine particles, the percentage of each varying with the milling process. Bagasse generally
contains about 50% moisture and has heat content of 3600 to 4200 Btu/lb. as fired.
Bagasse is fed through feed spouts in the front wall of the furnace and falls onto the grate. Each feed
spout is associated with its own section of grate.
The feed spouts are usually air swept, or air nozzles situated immediately beneath each feed spout are
provided.
The air passing through the spouts or nozzles carries the bagasse into the furnace. The air supply to the
spouts or nozzles is pulsated by means of variable speed rotating dampers. The pulsating action of
the air flow causes the bagasse to be evenly spread over the grate area.
The even spread of bagasse over the grate area ensures that it is largely dried out in flight, obtaining
the necessary heat from combustion gases leaving the burning fuel bed on the grate and the radiation
from the furnace walls.
The combustion air is divided into primary, as supplied to the fuel bed through spaces between the
grate bars, and secondary, as supplied through overfire air nozzles in the front and/or rear furnace
walls. Dampers control the amount of primary air passing to each plenum section beneath the grate.
Dampers also control the air supplied to the front and/or rear secondary air ducts.
The lighter partly burned particles of bagasse, known as bagacillo, are carried through the boiler gas
passes and are deposited in hoppers and, if provided, a grit arrestor. The heaviest particles of bagacillo
collected in the hoppers after the boiler may be refired into the furnace.
The grate bars of each section are supported and linked together in a manner such that they can all be
partially rotated in unison. When the grate bars are operated the ash which has accumulated drops
between the bars into conventional type rake-out pits or water immersed concrete troughs.
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AIR TEATER - RECUPERATIVE TUBEBAJIK TYPE
The Airheater is located in the flue between the boiler, or economiser and chimney and transfers heat
from the flue gases to the incoming combustion air. The combustion air temperature is thus increased
by decreasing the temperature of the flue gases. Heated combustion air results in improvements both to
the efficiency of the boiler plant and to the combustion of the fuel.
In a recuperative type of Airheater the heat is transferred directly from the hot flue gases (or from
steam) on one side of the surface to air on the other side of the surface.
Tubular airheaters are essentially a nest or nests of straight tubes expanded into tubeplates and
enclosed in a suitable reinforced steel casing. "This casing functions as the air gas flue and is provided
with air or gas connections and dampers.
The arrangements for keeping tubular airheaters clean may include sootblowers or shot cleaning
equipment. The sootblowers may operate on steam, compressed air or very occasionally water may be
supplied. Where space permits and the gas flow is over the tubes, dust hoppers may be fitted ahead of
the tubebanks. These result in substantial reduction in the amount of dust and fly-ash entering the
heaters.
During low load operation, when deposits and corrosion tend to increase because of low metal
temperatures, the Airheater can be by- passed.
The heater tube temperature must be maintained above a certain minimum during low load operation
or on starting up from cold. This temperature will vary according to installation, fuel, combustion
conditions etc. but a practical guide to the minimum temperature is obtained as follows. When the
temperature of the gas leaving the Airheater is added to the temperature of the air entering the airheater
the sum is known as the "minimum combined temperature".
For example, typical figures might be: -
Temperature of gas leaving = 300°F 148.9°C
Temperature of air entering 50°F = 10.0°C
Minimum Combined Temp. 350°F = 158.9°C
Note that this is not a direct conversion of 350°F to °c for the
minimum combined temperature since it is the sum of two temperatures

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The Airheater should not be operated with the GAS OUT + AIR IN temperature at less than the
recommended "minimum combined temperature". This temperature may be adjusted by using the air
bypass damper (s), the tube temperature should not be controlled by use of the gas bypass damper(s).
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GRIT ARRESTOR
The grit arrestor is positioned in the flue ahead of the 1.D. fan or chimney. its function is to remove
particulate matter from the plug gases and reduce emission from the chimney to comply with statutory
requirements.
Arrestors are of the cyclonic type in which the dust laden gases are given a rotational movement within
a truncated cone. impart a similar rotational motion to the entrained dust and this being heavier than
the gases is directed to the sides of the cone.
Discharge from the cone is arranged so that the heavily dust laden stream from the periphery (which
contains most of the particulate matter) is directed into the collecting hopper. The bulk of the gases,
containing the small percentage of remaining particulate matter, pass to the chimney. The discharge of
the two streams from the cone is arranged so that they leave with the minimum of interference with
each other, thus preventing re-entrainment of particulate matter into the main gas stream.
Arrestors normally contain a number of these cyclonic units, called cells, operating in parallel.
Booster fans of the radial blade type) may be provided to induce flow through the secondary
collectors. be running whenever the I.D. fan is running.

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DRAUGUT PLANT
Balanced Draught
The Forced Draught fan delivers air at sufficient pressure to overcome any resistance between it and
the furnace, e.g. air heater and burner registers.
The Induced Draught Inn draws combustion gases away from the furnace and has sufficient suction
available to overcome any resistance between it and the furnace, e.g. boiler and ancillary plant heating
surfaces. The Induced Draught fan is regulated so that the quantity of combustion gases drawn from
the furnace always balances, at a small furnace suction, the input of combustion air and fuel to the
furnace.
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TYPICAL MAJOR BOILER MOUNTINGS
Feed Water Stop Valve
This is required to isolate the boiler for maintenance and is normally backed up by a non-return valve
which in the case of feed pump failure prevents the back flow of water from the boiler.
Steam Drum Water Level Gauge Glass
These are a statutory requirement and are normally used as a back up feature for transmitted level
indication.
Steam Drum High und Low Water Level Alarms
These can be float or thermostatically operated and may be required by statutory regulations. Their
purpose is to give audible and/or visual warning of impending dangers. For example, a low water level
which if not corrected could lead to a loss of boiler circulation and consequent overheating of furnace
tubes; a high water level which if not corrected could lead to a loss of boiler circulation and
consequent overheating of furnace tubes; a high water level which if not corrected could lead to water
carry over from the steam drum endangering the Superheater and any equipment using steam from the
boiler.
Chemical Injection Valve
This isolates the chemical feed line to the water space of the steam drum. Chemicals are injected into
the boiler to control boiler water conditions.
Blowdown Valve
This controls a drain line from the water drum. Water concentrated with solids is blown to waste in
order to maintain correct boiler water conditions. The continuous blowdown valve fulfills the same
function but is fitted on the steam drum.
Air Cocks
Air cocks are used to vent air from the pressure parts of the boiler when filling with water and in the
early stages of pressure raising. Also they allow air to enter the boiler when it is shut down and cooling
off. If not opened before the boiler has cooled the condensing steam will create a vacuum which can be
troublesome particularly it parts of the boiler are fitted with handhole caps.
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Water Drain Valves
These are fitted at the lower points of the boiler, e.g. furnace wall bottom boxes, and are used for
draining the boiler empty. They must never be opened when the boiler is steaming as this could upset
boiler circulation and result in the overheating of furnace tubes. When steaming the furnace drain
valves must be shut and precautions taken to prevent them being opened.
Safety Valves
These are a statutory requirement and their function is to prevent the pressure generated in the boiler
from exceeding that for which the boiler parts have been designed.
Superheater safety valves are set to lift at a lower pressure than those mounted on the steam drum. This
is to prevent the Superheater being overheated in the event of steam demand being suddenly
interrupted before firing can be readjusted or stopped.
Main Steam Stop Valve
This is required to isolate the boiler for maintenance and is normally backed up by a non-return valve
next to the boiler. The stop valve may be equipped with a bypass to warn the steam lines and equalise
the pressures before the stop valve is opened thus protecting its seat. Use of a bypass also prevents
surges in steam flow when the stop valve is opened. A drain line is fitted between the non-return valve
and the stop valve to warm and drain the dead leg at this point before opening the stop valve. This
drain also acts as a tell tale to check the tightness of the shut off valves,
Superheater Recirculating & Drain Valve
-This valve controls a drain line ahead of the main stop valve. The recirculating valve is used to induce
a flow of steam through the Superheater to protect it from overheating and assist in boiling out the
Superheater during pressure raising.
Page 32.
SOOTBLOWERS
Sootblowers are provided to maintain the correct heat absorption rates of the heating surfaces by
keeping them in a clean condition. This can be an important factor in maintaining efficiency and boiler
capacity.
The normal blowing medium is dry steam tapped off some point in the Superheater, or from the steam
drum on units without superheaters.
Furnace sootblowers, where fitted, are of the single nozzle retractable type and blow onto the furnace
walls through an are of 360 degrees. Because of the high temperatures in the furnace these blowers
have to be retracted, when not in use, to prevent overheating.
For the Superheater, rack typo sootblowers are used. These enter through the side of the boiler rotating
and blowing continuously whilst being propelled into and retracted from the setting. As in the case of
the furnace, the zones in which these blowers operate are too hot for them to be left in position when
not in use.
In cooler zones e.g. boiler tube bank and economiser, permanently positioned multi-jet sootblowers
may be fitted. To reduce steam consumption these blowers, whilst rotating 360 degrees are set to blow
only over predetermined arcs covering the areas of tubes to be cleaned. An alternative form of
sootblower frequently fitted on smaller packaged economisers is a manually operated traversing rake
type sootblower.
Fully automatic control of sootblower operation can be provided including local or remote push button
control cubicle to give complete sootblower sequential control.

Page 34.
TYPICAL ROLLER CONTROLS
Feed Water
Feed water flow is primarily controlled by the level of water in
the steam drum. To improve the response of control, secondary influences
such as steam flow and/or food water flow may be used to modify the demands placed upon the food
water control valve by the water level.
Fuel
Fuel demand is primarily controlled by boiler pressure. To improve
the response of control steam flow and/or air flow may be used as a modifying influence.
Combustion Air
Combustion air flow is primarily controlled by boiler pressure.
To improve the response of control, fuel flow and/or air flow may be
used as a modifying influence.
Furnace Draught
The Induced Draught fan is primarily controlled by the suction in
the furnace. Steam flow may be used as a secondary modifying influence.
Final Steam Temperature
The degree of attemperation used is determined by the final
steam temperature required. The amount of water supplied to a spray
type attemperator or the proportion of steam diverted through the drum
or shell types is primarily controlled by the final steam temperature.
Secondary, modifying influences, may be the steam temperature leaving
the attemperator or the rate of steam flow from the boiler.

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INTERTOCKS
A boiler interlock may be defined as a device, interrelated with others, that senses malfunction or off-
limit operation of a particular item of plant and has the facility of initiating a control, alarm or trip
sequence to prevent hazardous conditions developing.
Interlocks are thus provided as a safety feature to ensure that auxiliaries are started in the correct
sequence and trip in a correct and safe sequence in the case of plant failure.
The basic elements of the interlock scheme are Induced Draught fan, Forced Draught fan, drum water
level and fuel supply. Additionally, other drum water level sensors and Flame Monitoring equipment
can be included in the interlock schema either to give alarm only signals or to initiate fuel shut-off and
boiler trip in the event of their registering untoward conditions.