Lesson 17 Marine Boiler

Contents Introduction Types of boilers Comparisons Words & Expressions

Introduction 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 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 Boilers Fire-tube Boiler Water-tube Boiler

Fire-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 Boiler

Fire-tube Boiler

Fire-tube Boiler Advantages: Disadvantages: 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 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 Boiler

Water-tube Boiler

Water-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 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 Boiler

Boiler 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 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 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 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 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 & 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 & 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

Assignments 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?