boiler training

8/2/2019 Boiler Training

1/76

G CN O T E S

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~JCOCHRAN

BIB Cochran LimitedNewbie Works, AnnanDumfries & Galloway,

Scotland, UK DG 12 5QUTelephone: 01461202111

Fax: 01461 205511

E-mail: [email protected]
mailto:[email protected]://www.bibcochran.com/http://www.bibcochran.com/mailto:[email protected]


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BOILER TRAINING COURSE NOTES

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COCHRAN

SECTION NO: PAGE NO:

12. COMBINED FEED CHECK AND SHUT-OFF VALVE 14

1. INTRODUCTION 3

2. TYPICAL BOILER ARRANGEMENT ................................................................................................... 4

3. SECTIONAL DIAGRAM - HOT WATER BOILER 5

4. SECTIONAL VIEW OF BOILER SHOWING GAS FLOW 6

5. SECTIONAL VIEW - 7

6. SECTIONAL VIEW 8

7. FRONT TUBEPLATE ARRANGEMENT ; 9

8. WEE CHIEFTAIN FRONT DOOR ARRANGEMENT 10

9. DETAIL OF SMOKE TUBE AND STAY BAR AIT ACHMENT 11

10. STOP VALVE (OR CROWN VALVE) 12

11. SAFETY VALVE 13

13. PRESSURE GAUGE 15

15. WATER LEVEL GAUGE GLASS AND PROTECTOR 17

14. BOILER BLOWDOWN SYSTEM 16

16. WATER LEVEL CONTROL SYSTEMS 18

16.1 FEED WATER CONTROL LEVELS 1816.2 TOP MOUNTED FLOAT 1916.3 TOP MOUNTED FLOAT - WITH HYDRAULIC TEST DEVICE ................................................. 1916.4 ON/OFF WATER LEVEL CONTROLS (FLOAT TYPE) : 2016.5 MODULATING CONTROL SYSTEM (FLOAT TYPE) 21

16.6 SEQUENCE BLOWDOWN VALVE 2216.7 SEQUENCE OF OPERATION 2316.7.1 Daily Procedure 2316.7.2 Evaporation (Low Water) Test 23

16.8 WATER LEVEL CONTROL SYSTEMS 2416.8.1 Top Mounted Probes - Self-Monitoring Modulating - 2416.8.2 Top Mounted Probes 2516.8.3 Modulating Side Mounted Probes (N.B. Not Self-Monitoring) 2616.8.4 On/OffSide Mounted Probes (N.B. Not Self-Monitoring) 27

17. AUTOMATIC TDS CONTROLS 28

17.1 TDS SYSTEMONE(TDS - TOTALDISSOLVEDSOLIDS) 2817.2 TDS SYSTEM TWO 29

18. THERMAL ENERGY 30

19. CONVERSIONS 30

20. BOILER OUTPUT 30
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21. FROM AND AT EVAPORATION 31

21.1 EXAMPLE(IMPERIALUNITS) 3121.2 EXAMPLE(METRICUNITS) 32

.- . 22. COMBUSTION 33

24. COMBUSTION CHECK LIST 39

24.1 AN EXAMPLE OF A COMBUSTION QUALITY ASSESSMENT .4024.2 VISUAL CIlECKS .4024.3 MEASUREMENTS : .4024.4 READINGS .4024.5 TIlERMAL EFFICIENCY CHECKS .4124.6 TO ASSESS BOILER EFFICIENCY 42

24.7 IlEAT BALANCE AT FULL LOAD .4224.8 COMBUSTION CURVE - NATURAL GAS 4324.9 COMBUSTION CURVE - DIESEL OIL .4424.10 COMBUSTION CURVE - IlEA VY OIL .4524.11 COMBUSTION CHECK CHART 46

25. COMBUSTION PRACTICE AND EFFICIENCY 47

25.1 TYPICALVALUES 4725.2 CLEAN AIR ACT AND ATMOSPIlERIC POLLUTlON .4825.3 SULPHURDIOXlDE .4825.4 CARBONMONOXIDE(ANDUNBURNTHYDROCARBONS) 4825.5 COMBUSTIONPERFORMANCE .48

22.1 BASICCOMBUSTION: FUEL- AIR - IGNITION .3322.2 LIQUIDFUELS .3422.3 VISCOSITY .3422.4 CALORIFICVALUE .3422.5 CHARACTERISTICSFATYPICALFUELOIL 3522.6 ATOMISATION .3522.7 THEEFFECTOF .3622.7 ATOMISATIONOFSPECIFICSURFACE .36

22.7.1 PressureJetAtomisation. 36

22.7.2 SpinningCupAtomisation 3622.8 AIRDISTRIBUTIONANDMIXlNG .37

23. THE COMBUSTION PROCESS 38
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1. Boiler Feed Pump 8. Pressure Gauge

2. Feed Check Valve 9. Stop Valve

3 . Water Gauge Glass Assembly 10. Pressure Switches

4. Dual Control 11. Safety Valve

5 . Over-Riding Control 12. Control Panel6. Burner and Fan 13. Blowdown Valve

7. Flue Gas Exit ,~ .~C~b~&~~ u>k( v~ .

SalinometerConnection

n

N.W.L

manhole

cD

2. TYPICAL BOILER ARRANGEMENT


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1. Flow Connection 8. Second Pass Tubes

2. Return Connection 9. Third Pass Tubes

3. Mixing device 10. Flue Gas Exit

4 . Air Cock 11. Thermometer

5 . Burner 12. Mandoor

6 . Furnace (First Pass) 13. Safety Valve

7 . Reversal Chamber

3. SECTIONAL DIAGRAM - HOT WATER BOILER


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.a ; ; .

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Ch imney Ou tl et

FURNACE

FIRST PASS

Manhole F i tt edo n e it he r s id eo f Bo il er Sh ei l


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l. tII

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Page 7 09/98

:t

L

L

L

L

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s

5. SECTIONAL VIEW -

_ REVERSED FIRED STEAM BOILER SHOWING GAS FLOW

L

------------------------~


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0\ >-t::I t; C Il:> 0(JQ . . . .rJ 1 C l> r-~

00 M

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0 : :co I.Q--- ~.Q~ ~

00

~~

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0 Zt ;; ~ o~ > ("'J~ r- 0~~ -< rJJ~ M~ ~ 2!~ ~

0~

~ M

~rJJ

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~ 1111 Pass

~IIInil Furna c~ 1

~: 111LIII I'-s Sighthole II I ,!

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Blowdown Valve Safety Valve and Water Gauge Drains.

"'~ -------------------""""~

nonS l3C Jz


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Page 909/98

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2nd Pass Combustion Chamber

1 st Pass @M J l MM

7. FRONT TUBE PLATE ARRANGEMENT

(l'HREE PASS WET BACK BOILER)


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FRONT CASING

PLATE

IRING

FRONT DOOROUTLINE

HINGED FRONT DOOR

INNER SEALARRANGEMENT

EXPANDEDMETA

CASTABLEREFRACTORY

FLAT BAR RING ROPE SEAL

INSULATINGREFRACTORY

8. WEE CHIEFTAIN FRONT DOOR ARRANGEMENT


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Stay Bar

RadiusedTube End

FrontTube Plate

Standard finish ontubes at reversalchamber end,

either expandedor expanded andwelded

9. DETAIL OF SMOKE TUBE AND STAY BAR ATTACHMENT


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Indicator

Hand Wheel

Stream Main

B oi le r S he l l

10. STOP VALVE (or Crown Valve)

This valve isolates the boiler from the process of plant.

Always open the valve slowly (called cracking) to allow the steam main to heat through slowlyand evenly. This valve should not be used to control or throttle the steam supply to the plant orexcessive valve wear will result.

On single boiler installations a screw down valve is fitted. If more than one boiler is installedthe interconnecting steam main must have non-return valves fitted which shall be capable ofbeing locked in the closed position.

The system must be fully prepared to accept steam before opening the stop valve.


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11. SAFETY VALVE

Drain Boss

. .I.

- -_ _ _ _ _Drain Boss

The safety valve ensures that the boiler cannot build up excessive pressure.

The valve should be set to lift at a pressure determined by the Boiler ManufacturersRecommendation.


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COCHRAN

Handwheel

12. COMBINED FEED CHECK AND SHUT -OFF VALVE


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8-

\ ','4

Purple line (b) indicates maximum working pressure

...

/BoilerConnection

13. PRESSURE GAUGE

Red line (a) indicates normal working pressure

-10',

3 w ay plugged cock w ith inspectortest gauge connection .

Syphon


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Manual parallel slideblow down valve

To blowdown it or Vessel

14. BOILER BLOWDOWN SYSTEM

MANUAL SYSTEM

The boiler should be blown at least once per day or in the case of shift working, at the beginningof each shift.

Blowdown duration and frequency should be agreed with the water treatment suppliers.

The blowdown valve should be opened and slowly closed to prevent damage to pipework.


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Slot indicates cock

-=Open

I = Closed

r

SteamSpace

Steam Cock(normally open)

Protector

Gauge Glass

Water Cock(normally open)

Drain Cock(normally closed)

SAFETY NOTE

For safety reasons, Cochran Boilersrecommend the gauge protector isfitted before proceeding.

Connection to drainWear safety glasses andgloves as handles may be hot.

=Au handles shown in Normal operating position

15. WATER LEVEL GAUGE GLASS AND PROTECTOR

TO BLOW DOWN FIRST GAUGE GLASS

a) Close Water Cock

b) Open Drain Cock and allow to blow for 4 seconds

c) Close Drain Cock

d) Open Water Cock. If the water does not to return to its correct level quickly" clean cock at theearliest opportunity as a blockage may exist.

e) Close Steam Cock

f) Open Drain Cock and allow to blow for 4 seconds

g) Close Drain Cock

h) Open Steam Cock. If the water does not return to its correct level quickly, clean cock at theearliest opportunity as a blockage may exist.

REPEAT FOR SECOND GAUGE GLASS


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Direct MountedControl

o 0

Steam Space

__,-OOOOOOTUbesHighest Heating Surface............... 00000

16.2 TOP MOUNTED FLOAT

Supply from Feed Pump

~ Boiler _ ; ;Q -Tubes

16.3 TOP MOUNTED FLOAT - WITH HYDRAULIC TEST DEVICE

(Dunking Cup)


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_

00

FUNCTIONS OF OVER-RIDING CONTROL

(a) Shuts burner to lock out on extra low water.

(b) Optional high water alarm with feed pumplockout can be fitted.

000

FUNCTIONS OF DUAL CONTROL

(a) Operates feed pump on/off.

(b) Shuts burner down on low water (tolockout on boilers arranged with thefurnace as the highest heatingsurface).

16.4 ON/OFF WATER LEVEL CONTROLS (FLOAT TYPE)


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Th ro tt le c on tr ol w i thop tiona l f eatu re :Modul at in g v a lv es hu td ow n o n h ig hwa te r o r p owe r f ai lu re .

Separate-Mobreyh ig h wa te r a la rm

~"9"l'V==--

Separatefuse(notsupplied)

~.t

-+- AlarmCon tr ol b ox Relay contacts

s hown in t hede -energ ised (a la rm) s ta t e

InductiveCo il (A )

Actuator

Fuse2

r _ .- BurnerI r---- Co nta ct or o r: : solenoid valve circuitI:I I-II - - - -Fi rs t low water: : : r : - Alarm circuitI t I :

- ~ :t :~ : : t ,t , -~--_=~_~_ ~~_ - :_~ _1 _! - ,Mainsinput

Chambercover

Band indicateslowest operat ingp oi nt o f l owwate r a la rm

Floatassembly

Isloat ing exhaust____ needle valve

normally closed

LH-ig-h-w-a-te-r-/p-o-w-e-r-f-ai-,u-re-~~;t-j-,~~~~~~~~~~~~~::~~ U"_~ :~ : " 'dso leno id va lve _----N-~;ii;2 ~c losed when energ ised ~=~~. , ~==== ; aTo drain

tEdkSlni

Feed waterd irection of flow ~

Modulatingvalve

Modulatingcontroller

inletsolenoidvalve

I so la ti ng i nl et _needle va lvenormal ly open _j

Feed wate rpressureto p i ston

'"d I: ;!: :IPl 0(Jq . . . .I) r-N t_!! j. . . . . :; c0'-0 0 -3. . . . . . . .

~'-000

s ;Js ;JC' : ln0d:; c00t_!! j

Z00 -3t_!! j00


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Normal

Working

Position

Blow-down

of Water

Connection

Blow-down

of Float

Chamber

16.6 SEQUENCEBLOWDOWNVALVE


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COCHRAN

16.7 SEQUENCE OF OPERATION

16.7.2 Evaporation (Low Water) Test

. 16.7.1 Daily Procedure

The level controls should be blown down at least once per day or if shifts are worked at thebeginning of each shift.

While the boiler is under pressure:

1. Tum handwheel clockwise until the valve is in mid travel position (approximately 2Y2completeturns). Remain in this position for 5-10 seconds to ensure full blow down of water leg.

2. Continue to tum handwheel clockwise to full extent of travel. Remain in this position for 5-10seconds to ensure full blowdown of float chamber.

Control should now operate as for lowered water level in boiler i.e. pump running and/or audiblealarm sounding and burner cut-out alternatively the boiler may be at lock-out on extra low water.

3. Tum handwheel anti-clockwise to full extent of travel. This is the normal working position ofthe valve.

With an authorised person in attendance the low level control/alarm equipment must be testedweekly by creating a low water condition in the boiler.

1. Shut off feed water to the boiler either by closing down the feed pump or, where applicable, byclosing the feed check valve.

2. Evaporation to first low alarm level. This should sound the first alarm and cut out the burners.

3. Blowdown boiler carefully to second alarm level. This should sound the second alarm andlockout the boiler.

~ tkw & (T tV )t ~4. Restart the pump or open the feed check valve to raise the level in the boiler. The second low

alarm should stop sounding on reaching its pre-set level. The first low alarm should stopsounding on further increase in level. The burners should NOT come in automatically.

5. On reaching normal working level, restart the burners manually.


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C/NRS1-9

Pump Control,High Level Alarm &1st Low Level Alarm

IG I I

-- ~a.a-I~ - 9

E 9It ; ; 9I

0- , . .~

CINRG 16-36

Minimum50mm

(2j clear borepipe

C/NRS1-72nd LowAlarm

Level Switches

I ! t_ ..0CHtaWO

o

CINRG 16-11

WBSP

BoilerShell

20mm~iarneter hol;----__

Minimum80mm (3j

clear bore hole

HighAlarmPump Off

Pump On

1st LowLevel

2nd LowLevel

Minumum80mm(3j

clear bore pipe

Water Level

16.8.2 Top Mounted Probes

SELF-MONITORING ONAJFF WATER LEVEL CONTROL SYSTEM


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COCHRAN

--~."..

'ltl"."Boile

W

~A~ eo.... "0

c :g~

.....................................................................................--....-=~

~NRR2-1 NRS2-1 NRS1-2Feed 1st Low HighControl 2nd Low

............................

Sequencing purge valves SPallow the steam and waterconnections to be blown throand the low alarms tested

Reclrculation_ to feed tank

Feedwater fromfeed pump

16.8.3 Modulating Side Mounted Probes (N.B. Not Self-Monitoring)


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~

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ElectrodeERS6-1

ElectrodeERS6-1

........................ ---- _ _ ... -.- - - - - - - - - - - - - ...... I-..;o=:J

~$1-1

~ ,w ' ]_p . . . . . .'"_ ,_ d b"IIII'LW 0

t"ESI.'I.W

2nd lowearth &spare tips

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Sequencing purge valves Spyallow the steam and waterconnections to be blown throughand the low alarms tested

16.8.4 On/Off Side Mounted Probes (N.B. Not Self-Monitoring)


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17. AUTOMATIC TDS CONTROLS

17.1 TDS System One (TDS - Total Dissolved Solids)

Normal

Wa ter L ev elTee p ie ce

Isolatingvalve typeC/AVB11

Sample valve

To optionalsam ple cooler .,._

Non-return valvetype C / R l - < E 6 Electr ica lly actuated

blowdown valvetyp e C IBAE36

S lowdown to h e a t r ec ov er ys ys tem, b lowdown r ece iv eror b low d own p it

Conductivty sensinge le ctr o de type CJ lRG16 -4

Contr o li e r t yp eC / L R R 1-1OSTD

with d ig ita l d is play

:. - -..:

= t ."Gm l ! l~. - i-i-m-==e~@oo.

High&LowTDSAlarms

0/4-20 mA outp utfor ener g y

mana ge ment s ys te m s


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17.2 TDS SYSTEM TWO

Example ofinstallation ona boiler topconnection

Co n tr olle r typeC/LRR1-10STOwith d ig ita I d is play

. N.WL. Boiler

Co nduct iv i ty sens ing

e lec trode typeC/LRG16-4

Conducti vi ty s en si n ge le ctr ode type CILRG16 -4 .

Tip leng ths u p to1 50 0mm to s uit b oiler .

. .!___----_.__----_.:

High&LowTOSAlarmsinstallation on

a boiler sideconnection

Isolat ing valvety pe C /AV811

0/4-20mA ou tpu t fo rene rgy managemen t

systems

Electr ical ly actuatedb lowdown v alv e ty pe

C/BAE36From side orbottom boilerconnection

.... Blo'l\do\lYT1o heat recovery system,blo'l\doVlfl receiver or blo'l\doVlfl pit

Samp le valv e Non-r etu rn v alv e ty p e C IRkE6

To o ptio na l s amp le c oo ler


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18. THERMAL ENERGY

19. CONVERSIONS

:Boiler ratings can also be measured in terms of the output of Thermal Energy and this method isoften used for both steam boilers and of water generators. The unit of measurement is the Kilowatt(kW) which is also used to measure electrical energy.

The kilowatt (kW) is being introduced to all countries adopting Systeme International (S.l.) Units,they are converted thus:-

1 kilowatt (kW) is equivalent to 3413 Btu/Hr

1 kilowatt (kW) is equivalent to 3.52Ib/hr F & A 212DF

1 kilowatt (kW) is equivalent to 3600 kJlhr

1 kilowattfkW) is equivalent to 1.595 kg/hr F & A 100De

See Table 1 f glossary Section for Table of Boiler Output Equivalentsand Table 2 for Pressure Equivalents

20. BOILER OUTPUT

Boilers are designed to produce heat in the form of steam.

As the temperature of feed water supplied to steam boiler plant can vary from as low as 10De onsimple installations to as high as 150De on more complex plants, the temperature of feed waterdirectly effects boiler output.

Similarly it takes less heat to raise steam to a pressure of 7 bar (100 lb/irr') than to a pressure of 17bar (250 lb/irr').

It is therefore important to consider both feed water temperature and steam pressure whencalculating the output of a boiler, or when comparing one plant with another.


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21. FROM AND AT EVAPORATION

Factor of Evaporation (H - h)

970.6

(1196.6 - 88.0)

970.6

1.14218

To overcome this problem a standard condition of from and at 212F (lOOC)and 14.7 lb/in'" (1.01325 Bar g) (atmospheric pressure) was evolved.

21.1 Example (Imperial Units)

Boiler rating 17000 lb/hr from and at 212F. Find the evaporation when the feed water temperatureis 120F and the working pressure is 150 lb/irr' gauge.

Steam condition at 150 lb/in" (from steam tables).

Total Heat in Steam (H) 1196.6 Btu/lb

Heat in Feed Water (h) (120-32) 88.0 Btu/lb

Latent Heat of Steam at 212F 970.6 Btu/lb

Actual Boiler Evaporation 17000

1.14218

14883.8 lb/hr at 150 lb/irr' from feed water

@ 120F

Thef rom and at rating has also been adapted to Systeme International (S.l) Units.


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21.2 Example (Metric Units)

Factor of evaporation (H - h) (2772.1 - 83.735) 1.191

Boiler rating 5000 kg/hr from and at 100C. Find the evaporation when the feed water temperature.. ,is 20C and the working pressure is 8 bar gauge (9 bar absolute)

From Systeme International (S.L) Steam Tables

c Total Heat in Steam (H) (at 9 bar absolute) 2772.1 kJ/kg2772.2Heat in feed water where 4.186 is a constant, that is the amount ofheat required to raise one kg of water by one degree centigrade.

The heat in the feed water 20 x 4.186 83.7 35 k J/k g

Latent heat of steam at lOOC @ 1.01325 Bar g 2256.7 k J/k g

2256.7 2256.7

- Actual Boiler Evaporation 50001.191

4198 kglhr at 8 bar gauge from feed water at 20C


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22. COMBUSTION

Combustion is the term given to the chemical reaction which takes place when a fuel and air arecombined and ignited. During combustion heat and light are given out. -..

(a) SOLID

(b) LIQUID(c) GASEOUS

of which coal, coke and peat are examples

examples of which are Kerosene (paraffin) and fuel oilsof which Butane, Propane and North Sea Gas are examples

22.1 Basic Combustion: Fuel - Air - Ignition

Boiler fuels are usually in one of three forms.-

All these fuels are termed fossil fuels as they were produced by decaying plant and manneorganisms during the earth's evolution.

Until recently liquid fuel was the cheapest and most easily available fuel. Over the past few years the bulkof modem packaged boiler plant in the United Kingdom has been designed to bum Natural Gas.

Each form of fuel has its own particular advantages and disadvantages, and much depends upon thecomparative costs of obtaining, storing, handling or burning a particular type of fuel. Because ofrapidly changing World politics and economics we can expect major changes in the types of fuelused from time to time.


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22.2 Liquid Fuels

The more expensive distillate fuel oils are lighter, flow easily at normal temperatures and can bepumped and atomised easily.

Fuels are made up of a combination of carbon and hydrogen and are commonly known asHydrocarbon Fuels.

All fuels, whether solid, liquid or gaseous bum faster and more effectively if they are broken up intosmall particles. With fuel oil this process is called atomisation.

Fuel oils are divided into classes for easy identification, and the ones we are concerned with areClasses C, D, E, F and G. Class C and Class D are distillates and of these Class D is the mostcommonly used in industry where it is often referred to as gas oil, diesel oil or 35 seconds oil.Classes E, F and G are residual oils and are often identified by their maximum viscosity's which istheir "stiffness" or resistance to flow.

Because of their comparative cheapness residual oils are commonly used as boiler fuels, but they areheavy and syrupy and must be heated to bring them to a viscosity at which they can be pumped,distributed and atomised.

22.3 Viscosity

Viscosity is the measure of the ''thickness'' of a fluid. Viscosity is usually expressed in Centistokes (cSt)given at 180F (82.2C). The Redwood scale of viscosity (seconds) is still used in the United Kingdom.

22.4 Calorific Value

The calorific value of a fuel is the amount of heat produced by a unit quantity when it is completelyburned. This is expressed in kJ/kg (or kl/rrr' for gaseous fuels) or in old Imperial units of Btu/lb (orBtu/ft' for gaseous fuels).

The entire heat produced by combustion is called for the gross calorific value (G.C.V.) and this is thevalue used when calculating thermal efficiencies of boiler plant.

The net calorific value which is sometimes used, especially in some European Countries is the grossvalue less the latent heat of the water vapour formed during combustion.


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22.5 Characteristics of a Typical Fuel Oil

Ultimate analysis of a typical fuel oil would give:-

CARBON 84.10%

HYDROGEN (H2 ) 11.3%

SULPHUR (S) 3.2%

OXYGEN (0 2) 1.19%

NITROGEN (N2) 0.17%

ASH 0.04%

WATER (H2O) TRACE

43031 kJ/kg

18500 Btu/lb

Specific Gravity @ 60F (15.6C)

Viscosity Kinematic @ 82.2C

(Redwood No.1 @ 100F)

Gross Calorific Value (G.C.V.)

0.95

30 cSt

1000 sees, Max.

22.6 Atomisation

All fossil fuels bum more easily if broken into small particles or atomised. Atomisation excesses thesurface area of the fuel, allowing for improved mixing with air.

The illustration shows how surface area increases as fuel particle size decreases.

The surface presented by unit weight of material is called the "specific surface".

--V_L...--

Specific Surfaceofa cube

10mm x 10mm1-Block: 600m 2


Cut into a-blocks1200m 2

:.-1-1-:.-1-1-

1-1-

. . . . . . . . . .Specific Surface

ofa cubecut into 64-blocks

2400m 2


cut into 1,000 ODD-blocks60,OOOm 2


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22.7 The Effect of Atomisation of Specific Surface

L TANGENTIAL PORTS

An example of the importance to Combustion of fuel atomisation and of the correct proportioning ofthe AirlFuel Ratio can be seen in coal fired generating Stations. In these stations pulverised coal canbe burned very rapidly and indeed become highly explosive when it is blended to the correct air/fuelratio. Similarly dust in flour mills and saw mills can also become a fire or explosion hazard.Likewise fuel oils and petroleum are not burned as liquids but are vaporised or atomised and mixedto the correct air/fuel ratio so that combustion can readily take place.

Fuel oil can be atomised by one of the following methods:-

22.7.1 Pressure Jet Atomisation

a) A simple pressure jet where fuel oil is pumped at about 20.68 bar (300 lb/irr') through a finenozzle or jet, to form a fine mist. An aerosol can is an example of a simple pressure jetatomiser. This form of atomisation can be used with all types of fuel oil.

-

OIL

-

- -

L22.7.2 Spinning Cup Atomisation

b) A rotary cup atomiser, where a thin film of fuel oil is thrown off the periphery of a cup which isrotating at 4000 - 5600 r.p.m. The oil collides with the primary forced air supply which breaksthe oil droplets into a fine mist. This type of atomisation is used with all types of fuel oil and

with coal tar fuels.

L


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22.8 Air Distribution and Mixing

FURNACE WALL

To achieve good, clean, efficient combustion the ratio of air to fuel should be slightly in excess ofwhat is needed in theory.

In practice about 15% - 20% excess air is required to ensure that each particle of fuel obtainssufficient air. Too little air produces partly burned fuel in the form of smoke and carbon monoxide(CO), while too much excess air reduces the flame temperature and produces a loss of boilerefficiency by increasing the weight of hot gas passing up the chimney. The amount of excess airrequired depends on the fuel type.

Combustion also requires turbulence to ensure good mixing of the air and fuel, and time for thecombustion process to be completed.

Because the mixing of air and fuel, ignition and then combustion must all take place within afraction of a second, uniform air distribution and rapid mixing are important.

To improve mixing a proportion of the air is passed into the combustion space as Primary Air alongwith the atomising fuel and the rest of the air is injected into the furnace as Secondary Air.

In boiler firing, secondary air makes up the bulk of the supply.

SECONDARY AIR

PRIMARY AIR

L


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23. THE COMBUSTION PROCESS

Carbon (C) combined with oxygen (0 2) to give Carbon Dioxide (C0 2).

Hydrogen (H) combined with Oxygen (0 2) to give water vapour (H 20).

After thorough mixing of the fuel and air particles an ignition combustion will take place. During. the combustion process the combustibles in the fuel will combine with the oxygen in the air toproduce oxides.

Similarly the minor combustible.

Sulphur (S) combined with Oxygen (0 2) to give Sulphur Dioxide (S02) and a little Sulphur Trioxide(S03)

The major part of the air supply is Nitrogen (N2) which makes up 75.4% by weight, this constituenttakes no part in the combustion process and remains unchanged.

Good combustion occurs when a fuel is completely burned and this can only happen where there issufficient air to supply the correct amount of oxygen.

As the theoretical (Stoichiometric or Chemically correct) air to fuel ratio will not give goodcombustion under practical working, excess air is required.

If the air supply is not sufficient, or if the air is not correctly distributed complete combustion willnot take place and part of the Carbon (C) component of the fuel will remain only partly burned. Thiscondition results in Carbon (C) combining with Oxygen (0

2) to produce Carbon Monoxide (CO).

Black smoke may also be formed.


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~BOILER TRAINING COURSE NOTES

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24. COMBUSTION CHECK LIST

To establish the performance of a Boiler Plant five main points should be considered:-

rI

a) The exhaust gases emitted from the chimney must be clear and free from smoke or smuts. Asmoke density test can be taken using a hand pump and instrument.

b) The temperature of the exhaust gases at the exit from the boiler can be measured using athermometer or pyrometer. Care should be taken to traverse the duct to obtain an average fromseveral readings.

c) The percentage of excess air above the theoretically correct air/fuel ratio should be establishedusing either a carbon dioxide (C0 2) measurement or alternatively an oxygen (0 2) measurement.

These should be taken at the exit from the boiler using a simple absorption device, an orsat or arecording instrument. The sample probe should traverse the duct to obtain an average fromseveral readings.

d) The burner quarl and the furnace must be visually checked to ensure that the flame must notimpinge on the furnace sides or quarl and should be symmetrical in shape. There should be nocarbon build up on the quarl, furnace or burner.

e) The loading of the boiler must be established as the efficiency of the boiler varies with the boileroutput. The variation is due to differences in the CO 2% level and variations in the percentageheat loss to radiation.

SAFETY

Use a tinted sight glass or tinted safety glasses when observing flames.

Use gloves when handing hot temperature and gas analysis probes.


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24.1 AN EXAMPLE OF A COMBUSTION QUALITY ASSESSMENT

VISCOSITY: 30 cSt @ 82.2C (950 seconds Redwood No.1 @ 100F)

FUEL: Class 'F' Fuel Oil

GROSS CALORIFIC VALUE: 43041 kJ/kg (18500 Btu/lb)

24.2 VISUAL CHECKS

a) Check the exhaust gas at the chimney top to ensure that there is no trace of smoke.

b) Check that the flame is not impinging and ensure that the burner, quad and furnace are free fromcarbon deposits. (This check is best done when the burner shut down). Any carbon deposits willglow for a few seconds and should be easily seen from the inspection port at the rear of the boiler.

c) The flame should be clear, symmetrical in shape and free from smoke.

24.3 MEASUREMENTS

a) Measure the average percentage carbon dioxide (C0 2) or oxygen (0 2) in a sample of exhaust gas.

b) Measure the average smoke number of a sample of exhaust gas.

L

L

c) Measure the average temperature of the exhaust gas using a 0-400C thermometer or pyrometer.Gas samples and temperatures are taken at the boiler exhaust gas exit. The sample probes andthe thermometer are inserted through a boss in the base of the chimney and traversed across thegas flow. Several samples and the temperatures are taken and average figures are established.

Average Smoke Number 3.0

d) Establish the boiler loading, using the fuel consumption and/or the steam output readings.

24.4 READINGS

Average Carbon Dioxide (C0 2) 13.5%

Average Exhaust Gas Temperature

Fuel Consumption/Steam Output High FirelFulI Load

Note:An indication of the state of cleanliness of the boiler and smoke tubes can be obtained bycomparing the exhaust gas temperature measurements with the figures taken under the sameload conditions during commissioning or after cleaning. As a rough guide a rise of 10C (l8E)

would indicate that tube cleaning is required.

L


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~_CHIMNEY

INSTRUMENTCONNECTIONS

COMBUSTION ~~::........::.:.:.=::.:.:=~-----....ANALYSISEQUIPMEN

INSPECTIONPORT

EXHAUST GASES

~

~JCOCHRAN

FURNACE

BURNER

FLAME SHAPE AND COLOUR

24.5 THERMAL EFFICIENCY CHECKS


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24.6 TOASSESS BOILER EFFICIENCY

Heat loss to flue gas

Assume a radiation and unaccounted loss

16.5%

2.0% (See Note II)

a) Plot the average CO 2 reading on the combustion curves, pages 40 to 42 (See Note I).

b) Trace vertically up from the plot on the CO 2 curve until the appropriate flue gas temperature lineis intersected.

c) Trace horizontally and read off the percentage heat loss to flue gases.

Total Heat Loss 18.5%

Boiler Efficiency 100 - 18.5 = 81.5%

Based on the Gross Calorific Value (G.C.V.) of the Fuel

Note 1:

The combustion curves can also be used to show the relationship between the Carbon Dioxide (C0 2)Oxygen (0 2) and excess air in a flue gas.

e.g. 13.5% CO 2 gives 3.0% Oxygen. 1~7.5%excess air.

."":~.~TS

Note 2:

The percentage radiation and unaccounted heat loss varies with the boiler loading.

The following are approximate:-

Full Load LossHalf Load Loss

Quarter Load Loss

1%2%

4%

24.7 HEAT BALANCE AT FULL LOAD

2 UNITSRADIATION LOSS

t j.....

'


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-

24.8 COMBUSTION CURVE - NATURAL GAS

NATURAL GASGROSS CALORIFIC VALUE 38,591 KJ/M 3

35

CI)

~ 30

w= >...JU.

oI- 25CI)

CI)

9~~ 20' ; f ! .

15

40 60 80PERCENTAGE EXCESS AIR

1 0 120 14 1

CI)

c( 15C)

w= >...JII. C oZ-.. 10

2

00zc(

~r5~._j

0>

20


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24.9 COMBUSTION CURVE - DIESEL OIL

DIESEL OIL FUEL CLASS D 1.5 - 5.5 cst @ 40CGROSS CALORIFIC VALUE 45,485 KJ/KG

35

e n

~ 30w~..Ju,

0I- 25e ne n0..J

~~ 20~0

- 15

e nc( 15C)

w~..Ju. .

Z-", 100czc(

0 18 '"5~0_j

0>

20 40 0 120PERCENTAGE EXCESS AIR


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24.10 COMBUSTIONCURVE-HEAVYOIL

II)

c( 15C)

w::I..JU.

Z-... 1000zc(

Ol85~'"_j0>

II)

~ 30w::I..JU.

oI- 25II)

II)

9~~ 2 0

~

35

HEAVY FUEL OIL CLASS G 70cst @ 82.2CMEDIUM FUEL OIL CLASS F 30cst @ 82.2CGROSS CALORIFIC VALUE 43 031 kj/kg

10

15 .....RE 150CFLUE GAS TEMPERA.

10 o 500 60 700 8 0PERCENTAGE EXCESS AIR


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---.~r:

0.6.35% CO. 11.0%

I e n I ITOO MUCH EXCESS AIR. en TOO MUCH EXCESS AIR.Check: AIR FUEL RATIO ~ TOO MUCH EXCESS AIR. Check: AIR FUEL RATIODAMPERS AND LINKAGES -c DAMPERS AND LINKAGES~- Check: AIR FUEL RATIOAIR DISTIBUTION AND t- DAMPERS AND LINKAGES AIR DISTIBUTION ANDQUARLS e n AIR DISTIBUTION AND QUARLS< t:o QUARLS. AIR LEAKAGE.

I-

An:::>

I- c0.2.95% J: CO 13.5%XUJ

TOO LITTLE AIR LOWFOULED BOILERCheck: TUBE CLEANLINESSCheck: AIR FUEL RATIO. OXYGENAIR SUPPLY ANDOVERLOADED BOILERDISTRIBUTION DAMPERS - Check: FUEL INPUT

I

WHITE BLACK NIL LOW (TO- .6.tO) HIGH (T + 50)(0-4) ( EFFICIENT I PCSMOKE INDICATION SMOKE No. COMBUSTION EXHAUST GAS TEMPERATURE

- AN EFFICIENT BOILER ISCLEAN INTERDEPENDANT UPON:

FLAME1. SMOKE INDICATION2. EXHAUST GAS

FLAME UNSTABLE ANALYSIS

Check: QUARL DAMAGE z CARBON IN THE FURNACE 3. EXHAUST GASHIGH FUEL OIL, TEMP t-- 0 Check: FOR LOW FUEL 01L TEMPERATUREWATER IN FUEL OIL i= TEMP. DAMAGED OR 4. FLAME CONDITIONFUEL OIL LEAKAGE (5 DIRTY ATOMISER OR

Check: ATOMISER, z DAMAGED QUARL.t--OIL TIP VALVE, oQUARLS SMOKY FLAME UJ CARBON ON THE ATOMISEF TEMPERATURE PC IS TH

Check: AIR/FUEL RATIO : :2 : Check: FOR HIGH FUEL TEMP. OF THE EXHAUSTCARBON ON QUARL$ t-- -c OIL TEMPERATURE GAS TAKEN DURING-'LOW OIL TEMP. u.. BOILER COMMISSIONINGBOILERHOUSE VENTILATION

AT A GIVEN LOAD.

E


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25. COMBUSTION PRACTICE AND EFFICIENCY

For any given fuel, it can be shown that there is a chemically correct (Stoichiometric) air/fuel ratio,, thus giving perfect combustion. For the common liquid and gaseous industrial fuels, these are:-

Gas Oil 1 lb of oil requires 14.6 lbs of air

Stoichiometric

HFO 1 lb of oil requires 13.83 lbs of air

Air/Fuel Ratios

Natural Gas 1 lb of gas requires 16.5 lbs of air

If a CO 2% sample were to be taken from the gases given off this combustion, they would equal:-

Gas OilHeavy Fuel Oil

Natural Gas

15.5%15.8%

11.9%

)

) These are known as the Stoichiometric CO 2 values

)

On the average shell boiler, it would be impossible to achieve the above conditions withoutexcessive smoke when firing on oil and unacceptable level of carbon monoxide when firing on gas,due to limited combustion residence time and furnace volume.

To overcome these problems and clean up the combustion process, extra air must be added, thisbeing known as EXCESS AIR.

However, this excess air gives rise to two further problems:-

a) Causes the CO 2% to fall below the stoichiometric value, hence reducing the overall combustionefficiency.

b) Absorbs heat and exhausts it to atmosphere via the chimney, hence increasing the stack loss andagain reducing the combustion efficiency.

Therefore, a compromise has to be reached whereby sufficient excess air is used to achieve cleancombustion and no more. The assessment of clean combustion on a normal boilerlburner plant isdetermined by:-

Oil Firing

Gas Firing

CO 2% and smoke spot number (below number 4)

02% and CO ppm (less than 100)

25.1 Typical Values

Below Number 4

Below Number 4

.- , --,-.

i . :q :q :pPITI . . . .n tqk( \p9tN' l . l I l1P

100

100

Gas Oil High Fire 12 - 13.5

Low Fire 10.5 - 11.5

Heavy Fuel Oil High Fire 13 - 13.5

Low Fire 11 - 11.5

Natural Gas High Fire 9.5 - 10.25

7.5 - 9.0

4.7 - 2.7

6.8 - 5.4

Below Number 4

Below Number 4

3.7 - 3.1

6.4 - 5.7

4.2 - 2.9

7.8-5.1

AIMS: To achieve the highest CO 2% possible, consistent with clean combustion at all firingpositions.


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25.2 CLEAN AIR ACT AND ATMOSPHERIC POLLUTION

25.4 Carbon Monoxide (and unburnt hydrocarbons)

;rI

Due to the general and competitive availability of reliable burners, UK ground level pollution has".' been reduced over the last few years although, with greater energy utilisation, the total amount of

pollutants from combustion processes discharged to atmosphere was increasing but over the last fewyears has actually decreased.

Implementation of the Clean Air Act by local authorities has, of course, helped to eliminateundesirable visible pollution. However, energy demands increase every year and what follows is forgeneral information.

It is estimate that the total volume of combustion pollutants discharged annually in Great Britain isin the region of 19 million tonnes, of these, the following are the most harmful:-

25.3 Sulphur Dioxide

Annually 5.2 million tonnes with nearly 2.5 million tonnes as a consequence of coal/coke burningand oil burning the remainder. The normal exposure level is generally accepted as not greater than 5ppm.

At the rate of 9 million tonnes per annum, it being estimated that approximately 6 million tonnes areemitted by motor vehicles. For industrial gas fired plant, atmospheric discharge should be zero, orminimal, but certainly not greater than 100 ppm for gas firing and 117 ppm for oil firing, which is

the accepted maximum for European countries.

(a) (i) 15% CO 2

(ii) 13% CO 2

(iii 11% CO 2)

on average 15% stack loss (5% excess air - 1% oxygen)

on average 16% stack loss (21% excess air - 3.66% oxygen)

on average 17% stack loss (44% excess air - 6.4% oxygen)

This is only a brief introduction as, with a mild climate, the meteorological effects in this country aresuch that only during certain adverse atmospheric condition does danger occur.

25.5 Combustion Performance

It will be appreciated that pollution is limited, or the damaging effects reduced, if plant is set so thathigh CO 2 values are maintained with the minimum of excess air, gas exit temperatures from thechimneys do not fall below the acid dewpoint of the gases, remembering that the internal chimneylining temperature is usually in the region of 50F below the gas temperature, the efflux velocity ofthe exhausting gases is not (under normal conditions) below 11.3 m/s for a "good" chimney system.

The chimney height is such that effective gas dispersion is achieved and discharge buoyancymaintained. Remember that a common chimney - single bore - is unsuitable for a multiple boilerplant.

Thefollowing comments relative to the foregoing may prove helpful:-

(Above figures utilising heavy fuel oil)


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b) Heavy smoke (and unburnt or partially burnt carbon particles) contaminates the boiler, thusreducing effective heating surfaces and heat transfer, apart from increasing boiler system

resistance and contaminating the atmosphere. It should be remembered that the definition forsmoke and fume is particles below I micron, dust between I and 75 microns. Above this size,the classification would be grit. Grit is material greater in size than a British Standard 200 mesh(0.003" aperture).

e) Local Authority requirements must be met.

(NB: 1 micron = I thousandth of a millimetre).

c) Acid dewpointmust not be confused with water dewpoint, which is 113C - the temperature atwhich moisture beings to condense out of the flue gases. Acid dewpoint is variable, normallybetween I40C to I50C and is the temperature at which a proportion of the sulphur trioxide,giving rise to corrosion problems and smutting. Normal industrial practice indicates that gastemperatures have to be kept well above the acid dewpoint to prevent low chimney exittemperatures. However, decreasing the excess air depresses the acid dewpoint temperature.

d) Efflux velocities have to be calculated at all firing conditions and, for new plant, must becalculated carefully so as to comply with Local Authority recommendations. Exhaust volumescan easily be calculated, based on known thermal input/excesses air/exhaust gas temperature.

-


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,---,t. ,

,..---.,, , ,...-, r ~, ,


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26.1 TABLE OF PRESSURE EQUIVALENTSlb/in 2 Bar Nzmnr' Kg/em! lb/in! Bar Nzmm' kg/em" lb/iu' Bar Nmm' Kg/em'

5 0.345 0.0345 105 7.240 0.724 205 14.135 1.4135

10 0.690 0.0690 0.703 110 7.584 0.7584 7.734 210 14.480 1.4480 14.76

15 1.034 0.1034 115 7.930 0..930 215 14.824 1.4824

20 1.379 0.1379 1.406 120 8.274 0.8274 8.437 220 15.169 1.5169 15.47

25 1.724 0.1724 125 8.614 0.8614 225 15.514 1.5514

30 2.064 0.2064 2.109 130 8.963 0.8963 9.l40 230 15.854 1.5854 16.l7

35 2.414 0.2414 135 9.308 0.9308 235 16.204 1.6204

40 2.753 0.2753 2.812 140 9.654 0.9654 9.843 240 16.543 1.6543 16.87

45 3.103 0.3103 145 9.998 0.9998 245 16.893 1.6893

50 3.448 0.3448 3.515 150 10.343 1.0343 10.546 250 17.238 1.7238 17.58

55 3.792 0.3792 155 10.687 1.0687 255 17.583 1.758360 4.167 0.4173 4.218 160 11.032 1.1032 11.249 260 17.928 1.7928 18.2865 4.482 0.4482 165 11.376 1.1376 265 18.272 1.8272

70 4.826 0.4826 4.921 170 11.772 1.1772 11.952 270 18.617 1.8617 18.98

75 5.172 0.5172 175 12.066 1.2066 275 18.962 1.8962

80 5.516 0.5516 5.625 180 12.411 1.2411 12.655 280 19.306 1.9306 19.6985 5.861 0.5861 185 12.756 1.2756 285 19.651 1.9651

90 5.905 0.5905 6.328 190 13.l01 1.3101 13.358 290 19.994 1.9994 20.3995 6.551 0.6551 195 13.446 1.3446 295 20.341 2.0341

100 6.895 0.6895 7.031 200 13.790 1.3790 14.061 300 20.683 2.0683 21.09

NOTE: 1 - lb/ ir r' i s equivalent to 0.0689476 Bar1 - lb/irr' is equivalent to 0.00689476 Newton/rum?1 - lb/irr' is equivalent to 0.070307 Kg/ern?

1 - bar is equivalent to 14.503 lb/ ir r'1 - Newton/mrrr' is equivalent to 145.03 lb/irr'1 - Kilogram/em' is equivalent to 14.2233 lb/ ir r'

THE PRESSURES LISTED IN THE TABLE ARE GAUGE PRESSURE NOT ABSOLUTE PRESSURE


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26.2 TABLE OF BOILER OUTPUT EQUIVALENTS

Ih/hr F & A 212F BtulHr x _106 kW kJ/hr x _10 6 kg/hr F & A 100C

5 0 0 0 . 4 8 1 4 2 0 . 5 1 2 2 7

1 0 0 0 0 . 9 7 2 8 4 1 . 0 2 4 5 4

5 0 0 0 4 . 8 5 1 4 2 2 5 . 1 2 2 2 6 8

1 0 0 0 0 9 . 7 1 2 8 4 4 1 0 . 2 4 4 5 3 6

2 0 0 0 0 1 9 . 4 1 5 6 8 8 2 0 . 4 8 9 0 7 2

3 0 0 0 0 2 9 . 1 2 8 5 3 1 3 0 . 7 2 1 3 6 0 8

4 0 0 0 0 3 8 . 8 2 1 1 3 7 5 4 0 . 9 6 1 8 1 4 4

5 0 0 0 0 4 8 . 5 3 1 4 2 1 9 5 1 . 2 0 2 2 6 8 0

6 0 0 0 0 5 8 . 2 3 1 7 0 6 3 6 1 . 4 4 2 7 2 1 5


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.----. .--I J

~

( . J

COCHRAN

pump working

Firing stopped

Alarm sounded

Tested at (time)

Left in order a t

pressure gauge reading

(signature)

Observation

NOTE: 1.2.3.

To be completed by Boiler attendant(s) or person(s) responsible for safe working.Tick squares to indicate daily tests complete satisfactorily.Cross squares to indicate weekly tests completed satisfactorily.

-"= -----------------------~


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COCHRAN

27. GLOSSARY OF BOILER COMBUSTION TERMS

Convection The transfer of heat within a fluid or gas by movement of thesubstance.

Atomisation The breaking up of a fluid into fine mist to ensure good disperison andcombustion.

Calorific Value This is the amount of heat produced when a unit quantity of fuel isburned. Generally the Gross Calorific Value (G.C.V.) is used whencalculating thermal efficiencies. The unit of measurement is kJ/kg.

Carbon Dioxide(CO:;)

This gas is the product of combustion of carbon. The percentage ofCO 2 present in a boiler exhaust gas is an indication of the amount ofexcess air being supplied and therefore the efficiency of the boiler.

L Conduction The transfer of heat from one substance to another by contact.

Dew Point The temperature at which a moist gas will become saturated andcondense on a surface in the form of dew.

Dioxide Compound of two atoms of oxygen with one atom of an element e.g.

Carbon Dioxide (C0 2).

Efficiency The relationship between the input to a boiler in terms of fuel energyand the output in terms of heat energy.

Excess Air The amount of air above the exact theoretical requirement needed forcomplete combustion.

Fuel Oil A residual or distillate mineral oil, classed as a Hydrocarbon fuel.Typical analysis of a residual fuel 84% carbon, 11% hydrogen and 3%sulphur.

Heat Energy which can be transmitted by radiation, convection orconduction. The unit is measured in kilojoules (kJ).

Monoxide Compound of one atom of oxygen with one atom of an element e.g.Carbon Monoxide (CO).

Oxide Compound of oxygen with another element.

Primary Air The supply of air for combustion which comes in contact with the fuelfirst.

Quar/ Refractory ring or brickwork fitted in furnaces to shape the flame andprotect the burner and boiler parts from excess heat.

Radiation The transfer of heat between two substances not in contact.


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Secondary Air A supply of air for combustion which is introduced into the furnace atseparate points to promote turbulence and complete combustion.

Trioxide Compound of three atoms of oxygen with one atom of an element e.g.sulphur trioxide (S03)'

Smuts An acidic cluster of unburned carbon particles emitted from chimneysas the result of bad combustion or bad chimney design.

Stack Solids Particles of ash and partially burned fuel which are carried by the boilerexhaust gas into the atmosphere.


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~


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L

~

'. ,

-

Guidance Note PM5from theHealth and SafetyExecutive

Automaticallycontrolled steam and

hot water boilers

~~HSE

Health & SafetyExecutive

7 Modern industrial boilers are fitted with automaticwater level and firing controls which were originallyintroduced as an aid to the boiler attendant. Since theirintroduction, they have become more complex, in orderto increase boiler efficiency and reduce the amount ofsupervision required.

8 This publication draws attention to the causes of

damage and explosions some of which have resulted infatal injuries, and makes recommendations designed toprevent such occurrences. The recommendations applyto boilers of shell and water tube type with a perceptiblewater level; they may not be wholly applicable toelectrode boilers, coil boilers, waste-heat boilers, boilerswhich are continual ly attended or highly rated water tubeboilers.

Plant and Machinery 5 (December 1989, revised) Reprinted 1995

INTRODUCTION

1 This Note has been prepared by a committeeconsis ting of representatives of the Heal th and SafetyExecutive, the Associated Offices Technical Committee,the Independent Engineering Insurers Committee andThe Association of Shell Boilermakers with assistancefrom representatives of firms producing automaticcontrols and from users.

2 Acknowledgement is made to the Associated OfficesTechnical Committee for the use of their publ ication'Requirements for Automatically Controlled Steam andHotwater Boilers' on which part of this Note is based.

3 The revision of this Guidance Note recognisesdevelopments in control technology and their relatedsupervision requirements which have taken place sinceits last issue. Computer control systems are notconsidered in this Guidance Note. They are to be thesubject of a separate publication.

4 To obtain a full understanding of this guidance, thedocument should, as a first step, be read and consideredin its enti rety rather than reference made to particularsections or paragraphs in isolation.

STEAM BOILERS

General

5 This GqidanceNote is primarily directed to thedangers as'ocfated with water circuits of boilers fittedwith automatic controls. It should be appreciated,however, that there are other hazards that need to betaken into account in the correct design, installation,operation and maintenance of boiler plant. In particular,special attention is required to ensure danger does notarise from the fuel; burners and associated combustion-control equipment which should conform to the relevantBritish Standards.

6 Overheating caused by low water level is the mostfrequent cause of boiler explosion or other damage, and,as experience shows arises from the malfunction ofautomatic controls. Analysis indicates the main reasonfor such incidents to be lack of testing and maintenanceof controls and alarms, isolation of control chambers and

inadequate supervision.

9 Water level controls and the first low water alarmwhich also extinguishes the burner may be housed in thesame external chamber or internal protection tube.Additionally a separate chamber or internal protectiontube with an independent electrical control circuit is

required for an overriding second low water alarm andfuel cut out; this should be a lock-out type requiringmanual reset (para 17(c)).

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Supervision

10 Automatic controls are not a complete substitute forsupervision. A measure of supervision by a trained boilerattendant or technician familiar with the automaticcontrols and the operation of the boiler house plantshould be regarded as an essential feature of safeoperation.

11 In deciding the extent of supervision the followingshould be taken into account.

(a) The complexi ty of the installation;

(b) The extent of automation and integrity of the boilercontrols, and

(c) The operating conditions of the boiler and controls.

12 Where control systems are fitted which requireregular manual testing (para 37) by a trained boilerattendant then that person should be on site at all timeswhile the boiler is in operation. 1 he attendant need notsupervise the boiler continuously but should always be ina position to respond immediately to any alarms (para

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13 Where control systems are fitted which haveautomatic testing facilities and are self monitoring (para42), then the controls should still be checked by atrained boiler attendant on a dai ly basis. During periodssuch as the silent hours (night and weekends) while theboiler is in operation there should always be someoneavailable on site who is competent to respond to alarms,and to take appropriate action which at a minimum, maybe to shut the boiler down safely before calling for theassistance of a trained boiler attendant. (paras 50 and51).

14 Where a boiler is started up from "cold conditions"the boiler attendant should be present at start-up andremain with the boiler until satisfied that it is operatingcorrectly.

Note: The controls should be subjected to the dailyoperating test before the boiler is left.

Training of boiler attendants

15 Many cases of damage arising from low waterconditions have been caused by lack of knowledge ofcontrols on the part of the boiler attendants. Attendantswith experience limited to manually controlled boilersmay be unfamiliar with modern automatic boiler controls.It is therefore essential that before they take charge ofsuch boilers they should be properly trained in their safeoperation, in the action to be taken in emergencies andin carrying out the tests set out under 'Testing ofcontrols' (paras 34 to 46). Most boiler and controlmanufacturers provide suitable training facilities.

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L 16 The weekly tests required under paras 38 to 40should be carried out or witnessed by a responsibleperson who has been suitably trained in the safeoperation of the boiler and i ts controls.

L Standards for automatic controls for steam boilers

L 17 The minimum recommended requirements forautomatic controls for boilers not continuouslysupervised ar~ as follows:

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_ (a) Automatic water level controls so arranged that theypositively control the boi ler feed pumps or regulatethe water supply to the boi lers and effectivelymaintain the level of water in the boiler betweencertain predetermined limits.

L(b) Automatic firing controls so arranged that they

effectively control the supply of fuel to the burnerson oil or gas fired boilers, or air to solid fuel firedboilers', and effectively shut off the supply in theevent of anyone or more of the followingcircumstances:

(i) flame/pilot flame failure on oil or gas firedboilers;

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(ii) failure to ignite the fuel on oil or gas firedboilers within a predetermined time;

(iii) when a predetermined high pressure at orbelow the safety valve set pressure is reached;

(iv) when the water level fal ls to a predeterminedpoint below the normal operating level. Whenthe water level is restored the burner may beautomatically refired;

(v) failure of forced or induced draught fans, or anyautomatic flue damper, when these areprovided.

Note: In the case of (i) (ii) and (v), these controls shouldbe of the lock out type requiring manual resetting. In thecase of (iv) this control should cut off the fuel/air supplyand cause an audible alarm to sound.

(c) Independent overriding control. This control shouldcut off the fuel supply to oil orgas fired boilers or airto solid fuel fired boilers' and cause an audiblealarm to sound when the water level in the boilerfalls to a predetermined low water level below that in17(b)(iv) above. The control or its electrical circuitshould be so arranged that it has to be reset byhand before the boiler can be brought back intooperation.

The above alarm must be set to actuate whilst thewater level is still visible in the water level gauges.The water levels at which the low level alarmsactivate are determined by the boiler manufacturer.This control system including water level detector,any associated electronics, wiring, relays and alarmshould be independent and completely separatefrom those in (a) and (b) above.

18 In the event of failure of the automatic controls andwhere the boiler is capable of being brought undermanual control safely, operation under manual controlshould be in accordance with a clearly defined writtenemergency procedure that should include the immediatepresence of a trained boiler attendant. Continuoussupervision should be provided until the fault in thecontrols has been rectified and a suitable period of time

has elapsed to ensure by testing that the boiler and itscontrols are operating normally.

19 A high level cor.trol to prevent overfilling of the boilermay be considered desirable.

'In certain circumstances it may also be desirable to cut off thefuel supply to solid fuel firing equipment. The generalrequirement is to dis sipate the heat from the fuel bed quicklyand the means by which this is achieved will vary according tothe fir ing and combus tion equipment eg chain grate stoker, fluidbed etc. Manufacturers advice should be sought.

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Electrical failure to safety

20 All electrical or other equipment used for operatingcontrols detailed in para 17 should be so designed as tofail safe for mains supply or single component failure.

21 All electrical conductors and equipment in

connection with water level and firing controls should beof adequate size. and be properly insulated andprotected to prevent danger including, where necessary,adequate protection against the ingress of moisture andthe effects of high temperature.

Interruption of the electricity supply

22 In the event of the electricity supply to water leveland firing control equipment being interrupted or failing.the fuel and air supply to the burner should be cut offautomatically. Restarting on restoration of the mainssupply is subject to the same requirements as normal

start up for oil and gas burners. Start-up for solid fuelburners will depend on the system installed. Interruptionand subsequent restoration of the electricity supplyshould not override any lock-out condition which existedprior to the mains supply failure or interruption.

23 Where permitted by the relevant British Standard,burner control systems may be arranged to recycle andattempt one automatic start following a flame, pilot flameor ignition failure. If this one attempt fails the controlsystem should proceed to the lock-out condition.

Isolation of control chambers

24 Isolation of the control chambers caused by theattendant or maintenance staff closing, and leavingclosed, either the water or steam isolating valves orboth, after closing the drain, has resulted in manyincidents of damage and explosion from overheating ofthe boiler brought about by the resulting low water level.

25 To prevent isolation of control chambers it isrecommended that a sequencing blowdown valve isfitted which allows steam and water connections to beblown do~n independently. This ensures that the waterisolating valve cannot be closed unless the drain valve is

open. With the drain valve open, with a float type control,the float will be at the bottom of the chamber therebycutting off the fuel supply to the boiler. It will not bepossible to relight the boiler under these conditions.

26 Isolating valves in steam pipes to control chambersare not always fitted by boiler manufacturers. Whenthere are compelling reasons that boilers cannot be shutdown to enable maintenance to be carried out to controlchambers it is necessary to fit such valves. When theyare fitted, they should either be locked in the openposition and the keys kept by a responsible person, orthey should be of a type which cannot accidentally beleft closed. When a locked valve is used, a duplicate keyshould be kept in a glassfronted cabinet in the boilerhouse for emergency use.

Pipe connections

27 To reduce the possibility of pipe connections tochambers becoming blocked the internal diametershould be as large as practicable, but in no case be lessthan 25 mm (1 inch) and should be as short and straightas possible.

Drains

28 IJrains from control chambers and water gauges canbe combined but should be run independently from themain blowdown pipe to waste or main boiler blowdownvessel.

29 The use of sight glasses in control chamber drainlines is not recommended as the sudden breakage of anunprotected sight glass is potentially dangerous.

Water level gauges

30 A water gauge fitted directly to the boiler shell is alegal requirement. It is also a requirement of BS 2790Design and manufacture of shell boilers, that for boilerswith an evaporative capacity of 145 kg/hr upwards, twoindependent gauges should be fitted.

31 The steam and water connections of water gaugesshould be blown through separately when checks underparas 12 and 13 are made to ensure that they are clearand that water gauges are indicating the actual level ofwater in the boiler. Blowdown procedures may differ onhigh pressure boilers and the advice of the boilermanufacturer should be strictly followed.

Water supply and treatment

32 To ensure a sufficient feed water supply at all times,an adequately sized pipeline should be fitted direct fromthe water supply to the boiler feed water treatment plantor tank. A low level water detection device is desirableon the feed water tank.

33 It is essential for the safe operation of a boiler withautomatic controls that proper quality feed water is used.Boiler water supply and treatment should be in

accordance with BS 2486 Treatment of water for iandboilers and also in accordance with recommendations ofthe Association of Shell Boilermakers. Regular blowingdown will not prevent scale formation if the feed water isuntreated and therefore external treatment plant and/orsuitable conditioning chemicals should be incorporatedinto the system Regular blowdown, testing andmonitoring of the feed and boiler water should be carriedout and the necessary records kept (para 47).

Testing of controls

34 It is strongly emphasised that the safe operation ofan automatically controlled boiler depends on the correctfunctioning of its water level and firing controls. Suchcontrols should be regularly tested to ensure this.

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AT NO TIME DURING A TEST SHOULD THE WATERBE LOWERED TO THE EXTENT THAT ITDISAPPEARS FROM THE GAUGE GLASS.

35 Instructions for the operation and testing of allcontrols and safety devices should be prominently

displayed in the boiler house. The test programme andsequence should be carried out strictly in accordancewith the manufacturer's instructions.

36 A suitable test procedure for externally mountedwater level controls is given in para 37.

'Where controls are not of the external mounted type, thedaily test procedure will have to be modified, and theadvice of the manufacturer and the competent personcarrying out the statutory examination of the boilershould be sought on this point.

Daily manual operating test

37 The following tests should be carried out by atrained boiler attendant or technician familiar with theboi ler controls at least once per day, preferably at start-up, or in the case of shift working at the beginning ofeach shift.

(a) Water level control

With the chamber drained check that the feed wateris being automatically supplied to the boiler.

L(b) Firing controls (1st low level alarm)

With the burner operating, check that on drainingthe chamber the alarm sounds and the fuel and/orair supply is cut off.

LNote: The water level control and 1st low water alarmare often in the same chamber and if so, the two will bechecked simultaneously and the burner shouldextinguish.

L (c) Independent overriding control (2nd low level alarm)With the burner operating, check that on drainingthe chamber the alarm sounds and the fuel and/orair supply is cut off and locked out to safety.

Weekly test

38 The following tests should be carried out by suitablytrained personnel (see para 16).

39 At least once a week the water controls should bechecked by manually interrupting the feed supply andlowering the level of water in the boi ler by evaporation

until the alarm sounds and the fuel and/or air supply iscut off.

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40 The independent overriding low water control shouldbe checked separately by continuing to lower the levelby blowing down of the boiler until the alarm sounds andthe fuel and lor air supply locks-out.

Completion of tests

41 After carrying out the daily and weekly tests theperson making them should ensure that the water levelis restored and all valves are in the operating position.The boiler should not be left until the person carrying outthe test is satisfied that i t is operating normally.

Automatic testing of controls

42 There are other water level control systems whichare high integrity which may be considered for lessfrequent supervision (see para 13). High integritycontrols should be fail safe arid self monitoring or of dualchannel design.

43 Controls housed in external chambers which arefitted with automatic sequencing blow-down valves andare self-monitoring should perform the tests in regularsequence at intervals of 12 hours for each controlchamber. Level probes with self monitoring featureswhich are directly mounted within the boiler should beself testing automatically at intervals not exceeding 150seconds.

44 For controls mounted in external chambers theburner should shut down and lock out if:

(a) the water level control fails the test;

(b) the test sequence fails;(c) the test interval is exceeded, or

(d) the by-pass interval specified in para 45 isexceeded.

For directly mounted boiler controls any fai lure of thesystem shall cause the burner to shutdown and lock out.

The resul t of each functional test should be clearlyrecognisable to the boiler attendant eg by l ight signals.

45 During automatic testing the burner lock-out may beinterrupted. The period of the interruption should notexceed 300 seconds.

46 Self-monitoring controls are to be tested manually inaccordance with paras 38 to 40.

Records

47 It is strongly recommended that a record should bekept of all periodic tests and servicing and maintenanceof controls. Advice on a suitable record for the daily andweekly tests of water gauges and controls can usual lybe obtained from the boiler maker, control manufactureror competent person. It is also recommended thatrecords of blowdown and dai ly water testing are kept.Boiler logs should be inspected and countersigned by

management at least weekly. Examples are given in Figs1,2 and 3.

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48 Logs and records relating to the operation of boilerplant provide important evidence that operationalprocedures have been followed. After an accident suchrecords may be essential if the operator is to prove thatthe plant had been properly operated.

Maintenance

49 Automatic controls should be regularly serviced andmaintained by persons having the necessarycompetence and facilities for maintaining the particulartype of control. Regular maintenance should be carr iedout, at least at quarterly intervals. Manufacturers ofboilers, fittings and automatic control equipment usuallyprovide maintenance contracts for this purpose.

Siting of alarms

50 There have been many incidents where low water

alarms have sounded a warning but have been sosituated that they were not heard by the personresponsible. When a boiler is not continuouslysupervised it is not enough to have an alarm on theboiler.

ALARMS SHOULD BE PROVIDED AT POINTS WHERETHEY CAN BE HEARD BY PERSONS WHO ARECOMPETENT TO TAKE APPROPRIATE ACTION.

Alarms which give visible warning may, in certainlocations, be more acceptable.

51 When a boiler is subject to partial supervision it isrecommended that an emergency device which will shutoff the burners should be located remote from the boilerhouse and should be clearly marked. (See para 13).

Capacity of safety valves

52 Safety valves should be sized and set in accordancewith BS 6759 and BS 2790.

HOT WAT~ BOILERS

General

53 There are records of explosions of hot water boilersystems and there are also records of many seriousfailures which could have led to an explosion. These aremainly due to shortage of water and/or failure ormalfunction of automatic controls.

Training

54 Persons entrusted with the supervision of hot waterboilers should be familiar with the controls and theconditions for the safe working of the boiler and system.

The amount of training required will depend on theextent and complexity of the plant.

Testing and maintenance

55 Owing to the diversity of controls for fully-flooded hotwater boilers it is not possible to give details of testingand maintenance in these notes. The boiler and/orcontrol manufacturer's instructions or advice on regular

testing and periodic maintenance and servicing shouldbe strictly followed. Servicing and maintenance bycompetent personnel is essential to ensure that controlsare kept in good working order.

Types of system

56 For the purpose of ensuring compliance with therequirements of this section, fully flooded boiler systemscan be divided into four basic categories:

Category A Static head systems open toatmosphere (Fig 4A);

Category B Closed pressurised systems withseparate gas cushioned pressurisingvessels and provision for make-upwater (Fig 4B);

Category C Sealed pressurised systems withseparate diaphragm or bladder typepressurising vessels and provisionfor make-up water (Fig 4C);

Category D Continuously pumped pressurisedsystems with provision for make-up

water (Fig 4D).

Boilers pressurised by steam are classified as steamboilers and should comply, where applicable, with therequirements for steam boilers.

Automatic controls

57 The categories of fully flooded hot water boilers(para 56) operating with minimum supervision should beprovided with automatic controls. Such controls shouldshut off the supply of fuel to oil or gas burners, theelectricity supply to heaters on electric boilers or shouldshut off the air supply, and, if necessary, the fuel supplyto solid fuel firing equipment in the event of one or moreof the following circumstances arising;

(a) flame failure or pilot flame failure in oil or gas firedboilers. This control should be the lock-out typerequir ing manual resetting; (see para 63)

(b) failure to ignite the fuel within a predetermined timein oil or gas fired boilers. This control should be ofthe lock-out type requiring manual resetting: (seepara 63)

(c) failure of forced or induced draught fan, or anautomatic flue damper:

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-(d) when the water at or near the boiler flow outlet rises

to a predetermined temperature providing a marginof at least 17"C below the temperature of saturatedsteam corresponding with the pressure at thehighest point of the circulating system above theboiler;

(e) when the water level in the pressurising equipmentin a Category B system falls to a predeterminedlevel below the normal operating level. This controlshould also cause an audible alarm to operate:

(f) when the pressure in a Category B, Core systemfalls to a predetermined pressure below thespecified operating pressure. This predeterminedpressure should be at a level which will ensure thatthe water does not reach boiling point in any part ofthe system whilst the working temperature ismaintained;

(g) when the pressure in a Category C systemincreases to within 0.35 bar of safety valve set

pressure. The safety valve set pressure should besuch that it will not allow the design pressure of anypart of the system to be exceeded.

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-58 For a finned tube type hot water boiler a sequencedlock out device should be fitted to ensure that the burnercan not be operated at any time unless the circulatingpump is running.

Independent overriding controls

59 In addition to the automatic controls required bypara 57, all categories of fully flooded hot water boilersshould be provided with independent overriding controlswhich cut off the fuel supply to oil or gas burners, theelectricity supply to heaters on electric boilers or cut offthe air supply and, where required, the fuel supply tosolid fuel firing equipment in the event of one or more ofthe following circumstances arising:

(a) When the temperature of water at or near the boilerflow outlet rises to a predetermined temperatureproviding a margin below the temperature ofsaturated steam corresponding with the pressure atthe highest point of the circulating system above theboiler. For 6 ;1orgas fired boilers this margin shouldbe at least 6C and for solid fuel fired boilers, be atleast 10C. This control should be of the lock-outtype requiring manual resetting.

(b) When the water level in the pressurising equipmentof a Category B system falls to a predeterminedlevel below the normal operating level lower thanthat indicated in para 57(e). This control shouldlock out the firing equipment and should be of a typewhich requires manual resetting.

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LNote: In certain circumstances it may be desirable tocut off the fuel supply to solid fuel firing equipment.

The general requirement is to dissipate the heat fromthe fuel bed quickly and the means by which this

is achieved will vary according to the firing and

combustion equipment eg chain grate stoker, fluid bedetc. Manufacturers advice should be sought.

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It is a requirement of BS 2790 that fully flooded hot waterboilers shall have provision to prevent the boiler beingfired unless it is fully flooded, it is recommended that thisprovision is applied to hot water boilers covered by thisguidance note.

Electrical failure to safety

60 All electrical equipment and systems used foroperating controls detailed in paragraphs 57 and 59should be designed to fail safe in the event of mainssupply or single component fai lure.

61 All electrical conductors and equipment inconnection with water level or temperature and firingcontrols should be of adequate size, and be properlyinsulated and protected to prevent danger including,where necessary, adequate protection against theingress of moisture and the effects of high temperature.

Interruption of the electricity supply

62 In the event of the electricity supply to water leveland firing control equipment being interrupted or failing,the fuel and air supply to the burner should be cut offautomatically. Restarting procedure on restoration of themains supply should be subject to the same requirementas normal start-up for oil and gas burners. Start-up forsolid fuel burners will depend on the system installed.Interruption and subsequent restoration of the electricitysupply should not override any lock-out condition whichexisted prior to the mains supply failure or interruption.

63 Where permitted by the relevant British Standard,burner control systems may be arranged to recycle andattempt one automatic start following a flame, pilot flameor ignition failure. If this one attempt fails the controlsystem should proceed to the lock-out condition.

Boilers using mixing valves

64 Where mixing valves are used to blend return waterwith flow water, solid fuel boilers should serve at leastone circuit which is independent of the mixing valve andwhich is capable of dissipating residual heat in the fuelbed when the mixing valve closes against the boiler. egduring mild weather, or a heat dissipation thermostatwhich will override the mixing valve control in the eventof excessive temperature rise. should be fitted in theboiler flow line.

Note: Maintaining boiler circulation should beconsidered for al/ operating conditions.

Safety valves

65 In all categories a suitable safety valve should befitted on or as near as possible to the boiler Safety

valves should be sized and set to the relevant BritishStandards BS 779. BS 855 and BS 6759.


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Log of da ily test ing of water gauges and sa fe ty con trols Boiler No . Shift No . Week commencing .

Date

Water gauges tested III

Level indicated RHglass

Level indicated LH glass

Automatic water levelcontrol tested

Feed pump working

Firing stopped I

Alarm sounded

Independent low wateralarm tested

Firing stopped and locked out

Alarm sounded

Tested at (Time)

Left in order at (Time)

Boiler pressure gauge reading

Tested by (Signature) I_.

Water tested (Time)TDS ppm

Boller blowdown (Time) I---Observations

Note Tobe completed by boiler attendent(s)or person(s) responsible forsafe working

Log examined by . . (Siqnature:

Figu re 1 Date .....


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..---.,I

Esso Petroleum Company, Limited

Log of boiler daily inspections Location . ... Boiler number . day of month 19

co

....... . . .. .. . .. .. .. . . .....

Four hourly inspections Eight hourly check Blow-down boi ler Daily tests::

Water testing daily

Check water level sight glasses Blow-down water level F ir st ! ow l ev el a la rm TO S

Bo il e r p r es s u re sight glassesTotal Total Treatment

Che ck f or f ue l, o il a nd wat er l ea ks Check condensate for

Frequency and quantity as Pump can Ira I p.pm. alkalinity hardness added

in structed F lame failure deviceo i l con t amina t ion p.p.m. CaC03

Time Boiler Signature Time Signature Time Quantity Signaturepressure

Time Signature

Daily lest: Time of S ignature

S eco nd low level alarm water te st

Time Signature

F u e l o i l r e c e ip t s Observationsl it re s a t 1 5C

Steam meter

readings (Ib)

Finish

Start

Generated

Water meter reading

(gallons)

Finish

Start

Used

Figure 2


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Esso Petroteum Company, Limited

Log of boiler weekly inspections Location Boiler number day 0 1 . month 19 .

N ot e. T he se t es ts s ho ul d b e c ar ri ed o ut w it hi n s ev en d ay s o f t he p re vi ou s t es ts

Salely controls . Checks by ' Bo il e r Spe ci a l i s ! '

F la m e f ai lu re d ev ic e

Firstlow level switch a nd p ump co nt rol }

S ec on d l ow l ev el s wi tc h

By !owenng boner ~ lrTi_m_e ~I_S i_gn_al_u re 1

w a te r l ev el s lo w iy

F i re v a lv e

Combusnon controls

Bate Flue gas temperature Ca rb o n d i ox id e Smoke number Combustion eHiciency % Dale Signature

High lire

L o w f ir e

Observations

Figure 3


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I1

)-------- --~~c-

Boiler

Category A

Make -up wa te r

Air Gas

fi ll ing po int

\ Expans ion ves se lDiaphragm '1---------- ~~ . " ' ; . . - - - ; ; - - -___ i l I!

I

IiBoiler

Cateyory C

Note.

Make -up wat er

Continuouslyrunning

pump

Pressure expansion vessel

.:

Nitrogen

bottle

Make -up wat er

Control led expansion lBoiler

Category B

Boiler

Category D

The figures show the bnsic elements which classify the system. Details of pumps, valves and tanksin the make-up supply will vary according to the system design and are not shown.

Fig. 4 Heal ing syst em ca teqons s

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Guidance Notes in HSE's Plant and Machinery Series

PM 1 Guarding of portable pipe-threading machines PM52 Safety in the use of refuse compaction vehiclesISBN 0 11 883590 4 ISBN 0 11 883522 X

PM 2 Guards for planing machines PM54 Lifting gear standards ISBN 0 11 883520 3ISBN 0 11 8830473 PM55 Safe working with overhead travelling cranes

PM 5 Automatically controlled steam and hot water ISBN 0 11 883524 6(rev) boilers ISBN 0 11 885425 9

PM56 Noise from pneumatic systemsPM 7 Lifts: thorough examination and testing ISBN 0 11 883529 7

ISBN 0 11 883546 7PM57 Safe operation of passenger carrying

PM13 Zinc embrittlement of austenitic stainless steel amusement devises - the Big WheelISBN 0 11 8831801 ISBN 0 11 883536 X

PM15 Safety in the use of timber pallets PM58 Diesel-engined lift trucks in hazardous areasISBN 0717607143 ISBN 0 11 883535 1

PM16 Eyebolts ISBN 0 11 883137 9 PM59 Safe operation of passenger carrying devices -

PM17 Pneumatic nailing and stapling tools the Paratrooper ISBN 0 11 8835343

ISBN 0 11 8831925 PM60 Steam boiler blowdown systems

PM19 Use of lasers for display purposes ISBN 0 11 883949 7

ISBN 0 11 8833707 PM61 Safe operation of passenger carryingamusement devices - the Chair-O-PlanePM20 Cable-laid slings and grommets ISBNO 11 883928 4(rev) ISBN 0 11 883952 7

PM63 Inclined hoists used in building and constructionPM22 Training advice on the mounting of abrasive work ISBN 0 11 883945 4

wheels ISBN 0 11 883568 8PM65 Worker protection at crocodile (alligator) shears

PM23 Photo-electric safety systems ISBN 0 11 883935 7ISBN 0 11 8833847 PM66 Scrap baling machines ISBN 0 11 883936 5

PM24 Safety at rack and pinion hoists PM68 Safe operation of passenger carryingISBN 0 11 883398 7 amusement devices - Roller Coasters

PM26 Safety at lift landings ISBN 011 8833839 ISBN 0 11 883942 XPM28 Working platforms on fork lift trucks PM69 Safety in the use of freight containers

ISBN 0 11 8833928 ISBN 0 11 8839446

PM29 Electrical hazards from steam/water pressure PM70 Safe operation of passenger carrying(rev) cleaners etc ISBN 0 7176

boiler training

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