Boiler Basics: 17 flashcards
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1. What type of boiler is a Lancashire boiler? (fire-tube or water-tube, internally or externally fired)
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It is a **fire-tube**, **internally fired**, **horizontal**, and **natural circulation** boiler.
2. Name the two main shells (cylinders) in a Lancashire boiler and their arrangement.
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It has an **outer shell** (large cylindrical drum) and **two inner fire tubes** (flues) that run horizontally through the shell.
3. What is the purpose of the **grate** in a Lancashire boiler?
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The **grate** is a platform where solid fuel (usually coal) is burned. It supports the fuel bed and allows primary air to pass through from below.
4. Where are the **fire tubes** located in a Lancashire boiler, and what flows through them?
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The two **fire tubes** run longitudinally through the **water space** inside the shell. **Hot flue gases** from the furnace flow through them.
5. What is the function of the **brickwork** surrounding a Lancashire boiler?
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The **brickwork** provides insulation, reduces heat loss to the surroundings, and also forms a **secondary combustion chamber** or **flue gas passage** at the rear, directing gases back along the sides of the shell.
6. Describe the **working principle** of a Lancashire boiler in one sentence.
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Fuel burns on the grate inside the fire tubes, producing hot gases that transfer heat to the surrounding water, generating steam that collects at the top of the shell.
7. How does the **natural circulation** occur in a Lancashire boiler?
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Water near the fire tubes gets heated, becomes less dense, and rises; cooler, denser water from the bottom flows in to replace it, creating a natural convection current.
8. What is the role of the **mounting** called '**safety valve**' on a Lancashire boiler?
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It automatically releases excess steam pressure to prevent the boiler from exceeding its safe working pressure.
9. Name the mounting used to **measure the water level** inside the boiler shell.
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**Water level indicator** (or **gauge glass**).
10. What is the function of the **fusible plug** in a Lancashire boiler?
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It is a safety device that melts if the water level drops too low, allowing steam to escape into the furnace and extinguish the fire, preventing overheating and explosion.
11. Why is a Lancashire boiler considered **internally fired**?
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Because the **furnace** (where combustion takes place) is located **inside** the boiler shell, specifically within the fire tubes.
12. What is the typical **pressure range** and **steam capacity** of a Lancashire boiler?
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It typically operates at **low to moderate pressures** (up to about 16 bar) and can generate steam up to **9000 kg/h**.
13. What is the main **advantage** of the Lancashire boiler's **large water capacity**?
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It provides a **large water reserve**, making it capable of handling **fluctuating steam demands** without significant pressure drops, and it is **safer** due to the water acting as a heat sink.
14. What are the **two main disadvantages** of a Lancashire boiler?
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1. **Low efficiency** (due to heat loss through the brickwork and flue gases). 2. **Slow steam generation** (because of its large water volume and low heating surface area per unit volume).
15. List **three typical applications** of a Lancashire boiler.
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1. **Industries** requiring moderate steam for processing (e.g., textile, sugar, paper). 2. **Locomotives** (historically). 3. **Power plants** (small-scale or auxiliary).
16. How does the **flue gas path** in a Lancashire boiler improve efficiency?
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After passing through the fire tubes, the hot gases are **reversed** by the brickwork and pass along the **outside of the shell** (through side flues), transferring additional heat to the water before escaping through the chimney.
17. What is the purpose of the **blow-off cock** (or blowdown valve) in a Lancashire boiler?
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It is used to **remove sediment, sludge, and concentrated impurities** from the bottom of the boiler shell periodically to prevent scale formation and corrosion.
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