If water were H20 and nothing else, or if all waters carried the same impurities, the treatment of water would be simple and uniform methods could be used. However, pure water never occurs in nature and impurities vary considerably.

The closest natural approach to "pure" water is rain, but even rain contains dissolved oxygen and carbon dioxide which has been picked up from the air. Impurities in natural waters depend largely on the source. Wells and springs are classed as ground waters; rivers and lakes as surface waters.

BOILER CONTROL SYSTEMS

Boiler control may be divided into four main sections:

Control of feedwater,

Control of steam pressure,

Control of fuel, and

Control of superheat and reheat temperatures.

Control of feedwater is the most critical. Watertube boiler evaporation rates are high in relation to the steam drum volume and consequently demand rapid response of feedwater flow. The situation becomes progressively more acute with increase of boiler size and pressure and reaches the limit in the case of oncethrough, supercritical pressure boilers. Three-element feedwater control is used on all modern watertube boilers and correlates steam flow, feed flow and drum level.

BOILER SAFETY DEVICES and PROGRAMMED CONTROL

Many furnace explosions occur during the lighting up period due to insufficient

purging of the furnace to remove all the combustible gases from inside the boiler.

For this reason it is common to interlock the controls so that no fuel can be admitted to the boiler until a flow of air, at least 50% of full flow, has passed through the

furnace for a definite period of time to be sure that the furnace is purged of all

combustible gases.

Interlocks are electrical relays or automatically operated electrical switches

that are closed when the boiler operating conditions are normal. If some fault,

such as forced draft fan failure, low water level, low fuel pressure etc, should

occur, the respective interlock will open the electrical circuit and shut off the fuel supply.

WELDING

Much of the equipment that the power engineer is required to operate is fabricated by a welding process.

The power engineer thus is required to have a knowledge of the subject of welding,

although he need never acquire any practical ability in this field.

INTRODUCTION

Of all heat engines and prime movers the steam turbine is nearest to the ideal and it is widely used in power plants and in all industries where power and/or heat are needed for processes. These include: pulp mills, refineries, petrochemical plants, food processing plants, desalination plants, refuse incinerating and district heating plants.

INTRODUCTION

A very large proportion of the electrical energy generated throughout the world is still produced through the medium of steam in power stations, in which the generators are steam driven. There are many plants using water turbines, internal combustion engines or gas turbines, but the steam turbine still remains the most important prime mover of all. The recent development of nuclear power stations has provided an entirely new means of heat supply but to date this heat supply has been utilized to produce steam for use in steam turbines. Steam turbines have been described in an earlier lecture. This lecture

will discuss some of the items of plant which serve as auxiliaries to these prime movers.

INTRODUCTION

A dictionary definition of the word turbine reads as follows:

Turbine: any of various hydraulic motors consisting of one or more rotary units, mounted on a shaft and provided with a series of curved vanes, actuated by the impulse of steam, water, gas or other fluid under pressure.

The internal combust ion engine may be defined as an engine in which the combustion of the fuel takes place in a combustion chamber or cylinder which is actually a part of the engine itself. Examples are the gasoline engine, the natural gas engine and the diesel engine.

Almost without exception, every industry, whether manufacturing, process, or power producing, finds many uses for compressed air. 

Some of these uses are listed as follows:

1. Motive power for grinding and sanding tools, drills, wrenches, riveting hammers and chipping hammers.

2. Motive power for air motors which drive hoists and winches.

3. Blast cleaning or sandblasting of surfaces.

4. Spray painting.

5. Engine starting as with diesel engines.

6. Conveyor systems which move powdered and granular materials by means of compressed air.

7. Control systems where compressed air is used both as a signaling medium and also to power actuating-devices such as air cylinders.

8. Atomizing of liquids such as oil for use as a fuel and water for use in humidifying.

9. Soot blowing for boiler furnaces.

10. Mixing or agitating materials for a process.