1. Lesson 17 Marine Boiler

2. Contents
Introduction
Types of boilers
Comparisons
Words & Expressions

3. 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.

4. 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

5. Typical Boilers
Fire-tube Boiler
Water-tube Boiler

6. 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.

7. Fire-tube Boiler

8. Fire-tube Boiler

9. 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 kg/h steam output
Large diameter cylinders limit pressure

10. 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

11. Water-tube Boiler

12. Water-tube Boiler

13. 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

14. 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

15. Waste Heat Boiler

16. 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.

17. 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

18. 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

19. 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

20. 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

21. 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

22. 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

23. 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?