Boiler: Assignment 1A: Introduction

A BOILER is an enclosed pressure vessel where heat generated through the combustion of fuel is used for converting water into steam.

The volume of water increases typically 1600 times when converted into steam. But boiler is a confined space. Therefore, instead of increasing volume, pressure is increased.

Which one or more of the following are requirements of a good boiler?

Select Which of the following are boiler systems

Any water cannot be used for boilers. Because normal water contains salts, which are less soluble at higher temperature.

When temperature rises the salts dissolved in water get precipitated at the surface, causing scaling. Scaling reduces effective heat transfer, thus decreasing boiler efficiency.

To avoid scaling in the boiler, ___________ is done.

Feed water system feeds water to the boiler. Feed water system includes:

Feed check valve is a type of non-return valve. When the liquid enters the boiler, the pressure of this system will rise, so back-flow may take place. Feed check valve is used in boiler to disallow backflow to the pump.

Which of the following is/are true?

Blow down valve is provided at the bottom of the boiler vessel. It is used to remove all liquid in the boiler when it is turned off.

A boiler may use a liquid fuel or a solid fuel. For liquid fuel, supply system uses a pump. For solid fuel (e.g. coal), certain arrangement is made at the bottom of boiler to burn the fuel and allow flue gases to move.

Air available in the combustion chamber is often not sufficient to burn the fuel. So air has to be supplied from outside, which may be obtained by any of the three means.

In order to circulate flue gases in the boiler, baffles and chimney are provided.

Grate is a perforated platform, containing several rods, on which fuel is placed. Air is circulated across the grate to burn the fuel. Ash is collected in an ash-pit below the grate.

Boilers may be classified on basis of Tube Content into following types: