Boiler operation pdf free download

Boiler Operation Inspection and Maintenance 6. Boiler Calculations 7. Draught 8. Primary Fuels 9. Principles of Combustion The Chemistry of Combustion Coal Pulverization Pulverized Coal Fired Furnaces Upgrading PC-Fired Boilers Fuel Oil and Gas Fired Furnaces Low NOx Burners Emissions Control Boiler Operator Handbook Dust Collection Ash Handling System Carryover, Scale, and Sludge Steam Contamination and Its Control Prevention of Deposit Formation in Boiler Units Characteristics of Steam-water Flow Temperature Conditions and Heat Transfer Hydrodynamics of Closed Hydraulic System Cooling Water Treatment and Cooling Towers Water Treatment and Demineralization A Btu or British thermal unit is defined as the amount of heat necessary to change the temperature of one pound of water by one degree Fahrenheit.

The Btu is used to rate heating and cooling system capacity. A calorie is the metric version of the Btu. One calorie is the amount of heat necessary to raise the temperature of one gram of water by one degree Celsius centigrade. The steam table is a chart that shows the amount of heat carried by a pound of steam at various pressures. Laws of Thermodynamics The First Law of Thermodynamics states that heat, which is a form of energy, cannot be created nor destroyed.

Energy can be changed in form mechanical, thermal, electrical, chemical and moved, but it cannot be created nor destroyed. The Second Law of Thermodynamics states that heat always moves from a warmer material to a colder material. If there is T. If there is no T. The amount of heat in the material determines its state. The boiling point increases as the pressure increases and decreases as the pressure decreases. The Specific Heat S. Specific Heat varies by the material, and also by the state of the material.

For example, the S. The lower the S. Increase surfaced area speeds heat transfer. The more time allowed the more heat transfer that occurs. Heat Value of Fuels Different fuels have different heating values.

The higher the fuel number, the higher the heating value. In order for combustion to occur, three things must be present: fuel, oxygen, and a source of ignition. In a boiler, combustion occurs in the combustion chamber. Perfect combustion, also called Stoichiometric combustion, can occur only with precisely using the correct and minimal amounts of air and fuel. This can happen only in a laboratory environment. Complete combustion needs excess air to ensure enough air for good combustion, which is the goal in the boiler process.

Incomplete combustion occurs when there is insufficient air, leaving unburned fuel as part of the flue gases. Nitrogen is not a combustible nor does is support combustion. Oxygen is not a combustible, but it greatly enhances the combustion of most fuels. We mix air in with the burner fuel in order to create better combustion. Secondary air is added after ignition. Excess air is always part of secondary air. Dilution air is added near the boiler breeching by the barometric damper.

On smaller burners a draft hood may be used to attach the vent stack , allowing air to be pulled in around the base of the stack. In an atmospheric burner, primary air is added by use of a venturi in the gas line and secondary air is brought in by atmospheric pressure around the burner.

A power burner uses a fan to supply both primary and secondary air. Typical burners will use between 10 and 15 cubic feet of air per cubic foot of gas. A purge cycle is used to remove any unburned gases from the furnace.

If incomplete combustion occurs as a result of insufficient oxygen, carbon monoxide CO and smoke may also be by- products. Carbon monoxide is deadly as it displaces oxygen. This number increases if the opening is not directly to the outdoors. Boiler Burners and Burner Controls Boiler Controls are designed to control the activity within a boiler while ensuring safe and efficient operation.

Waterside Controls determine pressure, control temperatures and water level. Fireside Controls include burner control, flame detection, fuel temperature, and fuel pressure. Gas is burned with either high pressure or low pressure burners.

Fuel Oil is delivered for burning by using an atomization burner or a rotary cup burner. A Rotary Cup Burner atomizes fuel oil using a spinning cup and high velocity air.

A Steam Atomizing Burner uses either air or steam to vaporize the liquid fuel oil. A Pressure Atomizing Burner compensates for load change by increasing or decreasing delivery pressure.

Number 2 oil is ignited by spark ignition. Numbers 5 and 6 oils are typically ignited by a gas LP or natural pilot burner. Oil must be vaporized before it will burn. Heavy oils Nos. Combustion Control Systems regulates furnace fuel and air ratio within limits for continuous combustion and stable flame throughout the demand operating limits of the boiler and includes draft control. The fuel valve maintains the fuel flow and the air damper maintains the air flow.

The jackshaft is a shaft that drives the air damper and fuel valve on a power burner. A Parallel control system has one actuator for the fuel valve and one actuator for the air damper. A steam boiler is controlled by a pressure control commonly called a pressuretrol , while a hot water boiler is controlled by a temperature switch called an aquastat. The boiler burner primary control is the device that safely manages the burner operation. Sometimes called the programmer or burner management system, the primary control allows fuel to flow only when all of the safe conditions for fuel ignition are met.

The sequence of burner operation does not allow fuel to flow unless all controls and safety devices agree that the burner can safely operate. If all the permissives agree, the fuel valves will open as directed by the burner control. If any one of the permissives is not satisfied, fuel cannot flow, as the permissives are wired in a series circuit.

There are five types of flame detectors when used with combustion heating equipment. They are: 1. CAD Cell Cadmium Sulfide the photocell changes resistance as cadmium sulfide is responsive to light 2. Infrared IR Light is sensitive to the infrared radiation emitted by the combustion of fuels such as natural gas, oil and coal. Photocell sensors that detect visible light 4. Ultraviolet UV Light sensors that detect ultraviolet radiation emitted from all flames 5.

Flame Rod is a sensor that has the ability to use a small amount of current, which is conducted by and through the flame. The double block and bleed gas train uses redundant safety shut-off gas valves blocking valves to provide a positive method of preventing gas flow to the burner. Between the two safety shut-offs, a bleed valve allows any gas in the line to safely flow out of the building. Most boiler accidents are caused by operator error and poor maintenance.

The Chief Engineer of a boiler plant holds the responsibility for directing boiler operations, procedures and maintenance. Log sheets are a paper record of boiler operation and maintenance, and should be used in all boiler rooms to help ensure safe operation. A log sheet will specify the task to be performed, such as blowing down the low water cut-out LWCO , and the operator can then mark the sheet to show that this operation was completed.

If the boiler is to be placed out of service for an extended period of time, proper lay-up procedures are required and must be followed. A low water condition is the most common cause of boiler failure. The first thing a boiler operator should do when entering the boiler room or taking over boiler operation is to check the NOWL. An automatic boiler feedwater regulator is designed to maintain the proper water level in the boiler.

A low water alarm in the system is designed to alert the boiler operator of a low water level. In the event of a low water alarm, secure the fire first before adding water to the boiler. The gage glass sight glass is a tube that indicates the water level in the boiler. It is installed either directly on the boiler or on the water column.

It is connected at the top into the steam section of the boiler and at the bottom into the water section, thus showing the true boiler water level.

The water level in the gage glass is tested by opening and then closing the gauge glass blowdown valve. In addition to the gage glass, some boilers also have try-cocks installed to indicate the water level. The three try-cocks which are drain valves are placed on the water column at various levels.

Blowdowns Boiler blowdown is removal of water from the boiler. It is done in order to remove the amount of solids in the water, and is performed as either bottom sludge blowdown, or continuous surface blowdown. The blowdown frequency and duration is primarily determined by the boiler water analysis.

The water quality will vary greatly based on boiler type and size, amount of condensate return, and boiler water treatment program. Inspections A boiler internal inspection is performed to allow the boiler inspection a view of all internal surfaces, i. The boiler is taken off line, cooled, drained, opened and cleaned in preparation for the internal boiler inspection.

All hand holes and manholes are opened, and the low water cut-outs are opened and cleaned. This is a water- pressure test of new installations and repaired boilers. A handhole provides access to the waterside of the firetube boiler for inspection. Boiler trim, Valves, Fittings, and Controls Boiler trim is the controls and fittings used to operate the boiler. The trim determines whether the pressure vessel is used for steam or hot water production. Trim includes devices such as the low water cut-out, the gage glass sometimes called the sight glass , the pressure gauge, etc.

Valves The safety valve also referred to a relief valve, pop-off valve, or safety relief valve provides protection to the pressure vessel from over pressurization and is the primary safety control on all boilers. They must be of sufficient size capacity to keep the boiler from developing more steam pressure than the valve can relieve, and must be set at or below the boiler MAWP Maximum Allowable Working Pressure.

Valve pressure settings cannot be changed by plant personnel, but must be calibrated by a certified repair facility. There should be no shut off valves between the boiler and the pop-off valve.

Boilers with more than sq ft. Safety valves are spring loaded valves and should be regularly tested by the boiler operator on duty, unless plant policy states otherwise. Testing a safety relief valve is performed by simply lifting the test lever on the side of the valve.

Prior to the test, determine that the valve discharge is piped to a safe place. A gate valve is an isolation valve, and is used only for the purpose of stopping or allowing flow. Gate valves are used as steam stop valves, blowdown valves, etc.

Gate valves should always be fully open or completely closed, never in- between. The stem and yoke are outside the valve body. A rising stem valve allows the boiler operator to know the position of the valve by looking at the stem.

If the stem is extended up or out the valve is open. In an open position, the valve provides no resistance to the flow of steam. If the stem is down or in, the valve is closed. These valves are typically seen in steam lines. A globe valve is a modulation valve, not an isolation valve. A globe valve disrupts the flow of the fluid, even in the fully open position. A check valve allows flow in one direction only.

These are often seen in feedwater lines between the pumps and the boiler. When opening any manual valve, the boiler operator should open the valve slowly in order to prevent water hammer. The control opens the burner circuit, stopping the burner if it senses a low-water level.

Controls may also operate the feedwater pump or valve or a make-up water valve as well as the burner. They are called dual or triple element controls.