Lesson 17Lesson 17Marine BoilerMarine Boiler

ContentsContents

• Introduction• Types of boilers• Comparisons• Words & Expressions

IntroductionIntroduction

• What is a boiler?• A vessel or an arrangement of vessels and

interconnecting parts, wherein steam or other liquid is heated at a pressure above that of the atmosphere by the application of fire, the products of combustion, electrical power or similar means.

• – It also includes valves, gauges, fittings, controls, the boiler setting and directly associated equipment.

Principal Parts of a BoilerPrincipal Parts of a Boiler

• Furnace – Energy Conversion • Heating Surfaces – Absorption of Heat from the

Furnace • Steam/Water Separators – Separate Water from

Steam • Feed water Supply – Provides the Water as the

working medium for conversion to steam • Fuel Supply – Provides the energy source • Control Equipment – Controlling Start,

Operation, Shutdown and Safe Tripping of Plant

Typical BoilersTypical Boilers

• Fire-tube Boiler• Water-tube Boiler

Fire-tube BoilerFire-tube Boiler

• Hot combustion exhaust gases travel through the tubes and transfer the heat into the water around the tubes in the shell.

• Fire tubes boilers has a large volume of water, therefore more flexible and can meet the sudden demand of steam without much drop of pressure.

• Fire tubes boiler is rigid and of simple mechanical construction, so greater reliability and low in first cost.

Fire-tube BoilerFire-tube Boiler

Fire-tube BoilerFire-tube Boiler

Fire-tube BoilerFire-tube Boiler

Advantages:• Able to purchase whole plant as package.• Able to build up a reserve of energy• Construction is straight forward• One furnace tube and burner

Disadvantages:• Only 27000 kg/h steam output• Large diameter cylinders limit pressure

Water-tube BoilerWater-tube Boiler

• Hot combustion exhaust gases travel through the shell over the tubes and transfer the heat into the water traveling through the tubes.

• Water tubes boilers are more readily accessible for cleaning, inspection and repairs, compared to the fire tube boilers.

• Used for high steam demand and pressure requirements

Water-tube BoilerWater-tube Boiler

Water-tube BoilerWater-tube Boiler

Water-tube BoilerWater-tube Boiler

Advantages:• Small water content• Small diameter tubes and steam drum• Able to produce superheated steam• Customizable design (flexibility)

Disadvantages:• More complex construction• Complex control systems required

Waste Heat BoilerWaste Heat Boiler

• Used when waste heat available at medium/high temp

• Auxiliary fuel burners used if steam demand is more than the waste heat can generate

• Used in heat recovery from exhaust gases from gas turbines and diesel engines

Waste Heat BoilerWaste Heat Boiler

Boiler MountingsBoiler Mountings

• Boiler Mountings are attached devices which perform specific tasks associated with the boiler.

• Fitting and devices which are necessary for the safety and control are knows as boiler mountings.

Boiler MountingsBoiler Mountings

• Safety Valve and Escape Pipe work• – To maintain safe operating pressure• Water Level Control Device • – To control water level to set point• Water Level Indication Device • – To provide confirmation of water level• Pressure Gauge • – To indicate boiler pressure

Boiler MountingsBoiler Mountings• Stop Valve • – To provide isolation of steam supply• Vent Valve • – To allow for venting of air on filling and

emptying• Blow down Valve• – To control water quality through blow down• Expansion System • – To allow safe expansion and contraction of the

boiler• Explosion Doors/Discs • – To minimize damage in the event of explosion

Boiler MountingsBoiler Mountings

• Feed Check Valve• – To control the final entry of water into the

boiler• Scum Valve • – To blow down or remove the scum and

impurities from the water surface • Thermometer• – To show the temperature inside the boiler

Boiler MountingsBoiler Mountings

• Soot Blower• – To blow away soot and the products of

combustion from the tube surfaces• Salinometer Valve• – To allow samples of water to be drawn off

for testing• Chemical Dosing Valve• – To add chemicals directly into the boiler

Words & ExpressionsWords & Expressions

• auxiliary a. 辅助的• furnace n. 炉膛，炉胆• illustrate vt. 举例说明 , 图解

• overpressure n. 过压 , 超压• radiant a. 辐射的• reservoir n. 容器• salinometer n. 盐度计 • scum n. 浮渣 , 浮垢

Words & ExpressionsWords & Expressions

• uptake n. 上升烟道 • steam drum 汽鼓（筒、包）• down comer 降水管，下降管• scum valve 上排污阀• soot blower 吹灰器 • blow-down valve 下排污阀• boiler mountings 锅炉装配附件• chemical dosing valve 投药阀

AssignmentsAssignments

• What are used on board ship for producing steam?

• How many basic types of boilers are in use on board ships? What are they?

• What does the Scotch boiler consist of?• What are boiler mountings?• What does a water-tube boiler include?