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BoilersBoilers
Class 2 Boilers
Package Boiler
Class 2 Boilers
Safety Valves Vacuum
Breaker
Pressure Alarms / Automation
Manhole
Main Stop Pressure Gauge
Scum Valve
Sample Cock
Main and Auxiliary Feed
Blowdown Valve
Heating Coil
Burner Unit
Steam Space Stay Bars
Furnace Door - Refractory
Inspection Door
Gauge Glass
Low Level x 2, High Level and Feed Control
Class 2 Boilers
Boiler FittingsThe minimum fittings required are:• Safety valves.• Water Level indicators.• Low water alarm and shut down.• Main Stop valve• Feed Cheek valves• Pressure Gauge • Salinometer Valve• Blow Down Valve• Manhole
Class 2 Boilers
HSE Rules9 Water level controls and the first low water
alarm which also extinguishes the burner may be housed in the same external chamber or internal protection tube. Additionally a separate chamber or internal protection tube with an independent electrical control circuit is required for an overriding second low water alarm and fuel cut out; this should be a lock‑out type requiring manual reset (para 17(c)).
Class 2 Boilers
c Automatic firing controls so arranged that they effectively control the supply of fuel to the burners on oil or gas fired boilers, or air to solid fuel fired boilers, and effectively shut off the supply in the event of any one or more of the following circumstances:
(iv) when the water level falls to a predetermined point below the normal operating level. When the water level is restored the burner may be automatically refired;
Note: In the case of (i) (ii) and (v), these controls should be of the lock out type requiring manual resetting. In the case of (iv) this control should cut off the fuel/air supply and cause an audible alarm to sound.
Class 2 Boilers
Exhaust Gas BoilerSafety Valves Vacuum
Breaker
Pressure Alarms / Automation
Manhole
Main Stop
Pressure Gauge
Scum Valve
Sample Cock
Main and Auxiliary Feed
Blowdown Valve
Heating Coil
Steam Space Stay Bars
Inspection Door
Gauge Glass
Low Level x 2, High Level and Feed Control
Exhaust Trunking
Class 2 Boilers
Manhole Door
Class 2 Boilers
L
Electric Heater
PPC
T
T
Steam Heater
P
P
Q.C. Valve
Fuel Shut Off
Pressure Control
Fuel Oil Service Tank
Alarm and Shut-Down
Control
Feed Control
Class 2 Boilers
Class 2 Boilers
Boiler Tubes
Class 2 Boilers
Class 2 Boilers
Class 2 Boilers
Class 2 Boilers
Steam Guided to Act Under Valve
Increased Area for Steam Pressure to Act
Class 2 Boilers
Exhaust Steam Acts On Lower Spring Carrier Giving Extra Lift
Class 2 Boilers
Class 2 Boilers
Class 2 Boilers
NONE HARDNESS, SOLUBLE SALTS
SODIUM SALTS
HARDNESS OR SCALE FORMING SALTS
CALCIUM AND MAGNESIUM SALTS
SALTS IN FEED WATER
ALKALINE OR TEMPORARY HARDNESS SALTS
BI-CARBONATES
NON ALKALINE OR PERMANENT HARDNESS SALTS
CHLORIDES, CARBONATES, SULPHATES
DECOMPOSE TO FORM CO2 AND SCALE
FORM SCALE OR ACID SOLUTION
SOLUBLE UNLESS VERY HIGH CONCENTRATIONS
Class 2 Boilers
Class 2 Boilers
Boiler Pressure Low
Boiler Level OK
Start Burner Control
Fuel Temp and Pressure OK
Start Fan, move damper to max
Air Pressure OK
Purge Time Complete
Start IgnitersDamper to min, Fuel
Control to min
Flame Detected
Control Fuel and Air supply to Requirements
Boiler Pressure High
Reduce Fuel Pressure, Stop Pump, Switch Off
Heater
Purge Time Complete
Stop Fan
N
N
N
N
N N
N
N
Y
Y
Y
Y
Y
Y
Y
YLockout, Manual reset
Class 2 Boilers
Uptake FiresPrevention.• Regular soot-blowing to
prevent build up of carbon ash
• Ensure circulation of boiler• Early detection of soot fires.• If boiler/economiser is
leaking and has to be run dry
• Increase frequency of soot-blowing
• Remove cover to prevent build up of pressure
• Fully drain boiler
Soot Fires.• Stop engine as soon as
possible• Continue circulation of
boiler/economiser, unless water is being lost, if so drain completely.
• Do NOT use soot-blowers• Stop air circulation through
engine• Use water washing to fight
fire (if fitted) otherwise wait and prepare boundary cooling.
Class 2 Boilers
Uptake FiresHydrogen Fires.
• Stop the main engine as soon as possible
• Stop circulation of boiler/economiser and close valves
• Drain the boiler/economiser
• Stop air circulation through the engine
• Boundary cool
• Fire may be extinguished by large amounts of water directed to the heart of the fire (DnV).
Class 2 Boilers
Class 2 Boilers
Class 2 Boilers
Class 2 Boilers
Class 2 Boilers
Initial Boiler Entry• Permit to Work.• Isolate all fires by shutting off the burner fuel inlets. Close feed inlets• Let the boiler cool down until about 3‑4 bar steam pressure remains• Open the blowdown line to empty the boiler drum.• When about 2 bar pressure remains in the boiler drum open the air vent
and leave open• Prepare to open the manhole doors by loosening nuts and breaking seal
when the steam drum pressure has reduced to atmospheric (22.5.1)• Remove top doors first, and then bottom after ensuring contents drained.
Thoroughly ventilate.• Personnel should not enter boiler, furnace or flue until the unit has cooled
sufficiently. (22.5.2)• Ensure all connections to drum are either blanked off, removed or valves
locked in closed position with posted notices. (22.5.3)• All personnel working on boiler require PPE. (22.5.4)• Treat the boiler as an enclosed space, so ventilate and test atmosphere for
oxygen content (22.5.5)
Class 2 Boilers
Oil Contamination Of Boiler• Change feed to an uncontaminated supply.• Do not blow down the boiler from the bottom; just surface
blow (scum) several times. If you bottom blow the boiler, it will become totally covered in oil.
• The boiler should be shut down and released from pressure and the venting valve opened.
• Drain the boiler slowly until water stops flowing from the loosened, upper manhole door before opening up the manhole for inspection. The oil will now only cover the boiler in the normal water level range and can be manually removed.
• Hot or cold water high-pressure jet equipment together with oil dispersive additives would be efficient for removal of the oil.
• In case the boiler is completely oily inside, the cleaning work should be turned over to a cleaning company specialised in such work. A full alkaline wash of the inside and complete structural inspection would be required.
Class 2 Boilers
Boiler Inspection FIRESIDE• Loss or refractory• Condition of the refractory around the burner and the
back wall, as these areas suffer from high temperature cracking.
• Distortion to any metal surfaces including the furnace and the tube plates
• Condition of the furnace floor looking for signs of oil contamination
• Signs of overheating at the burner assembly.• Tube ends for signs of leakage, creep cracking.
Class 2 Boilers
Boiler InspectionWATERSIDE• Integrity of the bottom blow down pipe and other internal fittings.• Boiler bottom plate (furnace top‑fire tube boiler), furnace wall for
steam bubble pitting• Mechanical grooving of boilerplates at internal supports • Oxygen pitting of shell at the water line• Thinning or necking of the tubes • Pitting of the boiler tubes• Feed and scum pipe integrity• Oxygen pitting in the steam space• Condition of manhole opening, joint faces, welds, corrosion• Steam space stay condition.• Scale deposits• Condition of welds• Blockages in pipes for mountings
Class 2 Boilers
Boiler InspectionSHELL
• Condition of lagging• Signs of leakage• Fit of manhole door and condition of securing device• Overhaul all valve and fittings;
• Check for corrosion. All parts should be made from non-corrodable material
• Check valve seat faces free from defects and face width not excessive• Check valve bodies for corrosion and cracks• Hang all components and check free from cracks by NDT inspection
• For safety valves• Check spring length, and carry out NDT inspection• Check valve spindle straight• Cheek valve body drain clear• Check easing gear operation and condition
Class 2 Boilers
Refilling And Raising Steam• Replace all mountings, ensuring correct fitting and direction of flow.• Replace inspection covers, ensuring securing devices not overightened.• Refill boiler water, adding correct chemical dosage. Level should be just
above Low Level alarm.• Check operation of level alarms, feed controls, automation pressure
switches.• Ensure all valves are in their working positions, test gauge glasses.• Check burner controls and cut outs.• With the vent open, start to warm the boiler. Firing should initially be for
short periods (5 mins) with a break (15 mins) to allow the boiler to warm through evenly.
• When steam is coming out of the vent, (2 bar pressure), close vent and bring boiler to working pressure.
• Set safety valves.• Test all alarms and shutdowns.• Check tightness of glands and bolts.• Check tightness of manhole and inspection covers.
Class 2 Boilers
Adjustment Of Safety Valves.• Calibrate pressure gauge and check pipes clear• Raise steam• Steam outlet closed• Gag one valve• Raise pressure and adjust valve to open at
required pressure• Check blowdown• Change over gag• Repeat 5 & 6• Remove gag• Lock valve adjusters / make and fit spacers• Recheck opening pressure• Check easing gear and seal covers• Check alarms and burner operation
Class 2 Boilers
Soot FiresAction• Stop engine as soon as
possible• Continue circulation of
boiler/economiser, unless water is being lost, if so drain completely.
• Do NOT use soot-blowers• Stop air circulation through
engine• Use water washing to fight
fire (if fitted) otherwise wait and prepare boundary cooling.
Prevention• Regular soot-blowing to
prevent build up of carbon ash
• Ensure circulation of boiler• Early detection of soot fires.• If boiler/economiser is
leaking and has to be run dry
• Increase frequency of soot-blowing
• Remove cover to prevent build up of pressure
• Fully drain boiler
Class 2 Boilers
Hydrogen FiresConditions Required• Tube metal temperatures of over 705C• Tubes with some steam content (poor circulation)• The presence of a catalyst in the form of a carbon ash.Prevention.• Regular sootblowing to prevent build up of carbon ash• Ensure circulation of boiler• If boiler to be run dry, drain and vent to eliminate possibility
of steam presenceFighting.• Shut of air by gagging turbo blowers – wet canvass over
intakes, ensure exhaust valves closed• Boundary cool
Class 2 Boilers
Typical Analysis of Sea Water.• Calcium Bicarbonate 200ppm
Ca(HCO3)2
• Calcium Sulphate1200ppm CaSO4
• Magnesium Sulphate 2000ppm
MgSO4
• Magnesium Chloride 3300ppm
MgCl2
• Sodium Chloride 25300ppmNaCl
Typical Analysis of Fresh Water.• Sodium Chloride 50ppm• Magnesium Sulphate 30ppm• Calcium Sulphate90ppm• Calcium Carbonate
200ppm
Class 2 Boilers
Scale Forming Salts.Magnesium ChlorideDecomposes to form hydroxide and hydrochloric acids. The
former will produce hard scale and the later lowers the pH.
MgCl2 + 2H2O 2HCl + Mg(OH)2
Magnesium SulphateForms a hard scale on the heating surfacesCalcium SulphateForms a hard scale on the heating surfacesCalcium Bi-carbonate
Decomposes at a low temperature when CO2 is liberated. Remaining Calcium carbonate deposits on the heating surface as a soft scale.
Ca(HCO3)2 CaCO3 + CO2 + H2O
Class 2 Boilers
Boiler TreatmentALKALIS• Sodium Carbonate (soda ash).
Reacts with non‑alkaline hardness salts by either precipitating them, or converting into sodium salts, which stay in solution. Excess Sodium carbonate remains in solution to provide an alkalinity to reduce corrosion.
Na2CO3 + CaSO4 CaCO3 + Na2SO4
• Sodium Hydroxide. (caustic soda)Reacts with magnesium chloride producing a harmless precipitant and sodium chloride, which remains in solution.It is not suitable for pre‑mixing with other chemicals. But can be used in conjunction with other chemical treatments.
2NaOH + MgCl2 2NaCl + Mg(OH)2
Class 2 Boilers
Boiler TreatmentPHOSPHATES• Disodium Phosphate
Dissolves in water and forms a neutral solution. Reacts with magnesium and calcium sulphates and precipitates them as phosphates, or converts them to sodium salts, which will remain in solution.
Na2HPO4 + MgSO4 MgHPO4 + Na2SO4 • Trisodium Phosphate
Dissolves in water to produce disodium phosphate and sodium hydroxide, an alkaline solution.
Na3PO4 + H2O Na2HPO4 + NaOH
The function of both these chemicals is to prevent scale formation by precipitating the salts of magnesium and calcium as a soft sludge.
Class 2 Boilers
Boiler Treatment• Coagulants (Starch, Tannin, Sodium aluminate)
These chemicals attract the sludges which float in the boiler water. They keep the sludge in suspension and so avoid any build up of sludge on the heating surfaces. Can also help in the reduction of foaming and also keep any oil present in an emulsified form.
Class 2 Boilers
Boiler Treatment• OXYGEN SCAVENGERS
Presence of oxygen in the boiler water will result in serious corrosion.
To reduce the amount of oxygen present in the boiler water oxygen scavengers are used.
These are Hydrazine or Sodium Sulphite
Hydrazine N2H4 + O2 2H2O + N2
Sodium Sulphite 2NaSO3 + O2 2NaSO4
