Steam Boiler Quiz 3

The explanation for the given correct answer is that a boiler is indeed a closed vessel that uses heat to transform water into steam under pressure. This process is commonly used in various industries and heating systems to generate steam for power generation or heating purposes.

A check valve is a type of valve that allows fluid to flow in one direction only. It is designed to prevent backflow or reverse flow of fluid in a piping system. This means that when fluid flows in the desired direction, the valve opens and allows the fluid to pass through. However, when there is a reversal in the flow direction, the valve closes and prevents the fluid from flowing back. Therefore, a check valve is indeed a one-way flow valve for fluids.

This statement is true because a British thermal unit (Btu) is a unit of energy commonly used in the United States. It is defined as the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit. Therefore, one Btu is indeed the amount of heat necessary to raise the temperature of 1 lb of water 1 degree F.

Condensate refers to the water that is formed when steam loses its heat and undergoes a phase change from a gaseous state to a liquid state. This process occurs when steam comes into contact with a colder surface or when it is cooled down. Therefore, the statement that condensate is water that results from steam losing its heat is true.

A low-pressure boiler is defined as having a maximum allowable working pressure (MAWP) of 15 psi or less. This means that the pressure within the boiler should not exceed 15 psi during operation. Therefore, the statement "A low-pressure boiler has an MAWP of 15 psi or less" is true.

Water boils at 212 degrees Fahrenheit under normal atmospheric pressure. This is the boiling point of water, which is the temperature at which water changes from a liquid to a gas. At this temperature, the water molecules have enough energy to break free from the liquid phase and become steam.

Heat always travels from a body at a high temperature toward a body of low temperature due to the principle of thermodynamics known as the second law of thermodynamics. This law states that heat naturally flows from regions of higher temperature to regions of lower temperature, until both bodies reach thermal equilibrium. This is because heat energy tends to distribute itself evenly, resulting in a transfer of heat from hotter objects to cooler objects. Therefore, the given statement is true.

The majority of leaks in a firetube boiler occur near the tube ends because these areas are subjected to high temperatures and thermal stress. Over time, the constant heating and cooling cycles cause the metal to expand and contract, leading to wear and tear. Additionally, the tube ends are more susceptible to corrosion and erosion due to the intense heat and combustion gases. These factors contribute to the weakening and eventual leakage of the tubes near their ends.

The three most common fuels used in steam production are natural gas, fuel oil, and coal. These fuels are commonly used in steam production due to their high energy content and availability. Natural gas is a clean-burning fuel that is widely used in steam generation due to its low emissions. Fuel oil, also known as heavy oil, is commonly used in steam production as it is easily transported and has a high energy density. Coal is a widely available and relatively cheap fuel source that has been traditionally used in steam production due to its high energy content.

Steam is formed when water is heated to its boiling point and undergoes a phase change from liquid to gas. During this process, the water molecules gain energy and become vapor, which is known as steam. Steam is composed of water vapor and does not contain any impurities or particles that would give it a distinct odor, color, or taste. Therefore, it is correct to say that steam is odorless, colorless, and tasteless.

Welded longitudinal joints are stronger than riveted longitudinal joints because welding creates a continuous and solid bond between the two pieces of metal, resulting in a stronger and more durable joint. On the other hand, riveted joints rely on mechanical fasteners (rivets) that can loosen or fail over time, making them less strong compared to welded joints.

The atmospheric pressure at sea level is commonly known to be around 14.7 pounds per square inch absolute (psia). This value is considered as the standard atmospheric pressure at sea level and is used as a reference point in many scientific and engineering calculations. It represents the average pressure exerted by the Earth's atmosphere at sea level under normal conditions.

Flash steam is formed when water at a high temperature and pressure is released to a lower pressure. This is because when water is at high temperature and pressure, it exists in a superheated state. When the pressure is suddenly reduced, the water undergoes a rapid phase change and turns into steam. This phenomenon is known as flashing, and the resulting steam is called flash steam. Therefore, the statement is true.

In modern boilers, diagonal stays are welded, meaning they are joined together using a welding process. However, in older boilers, diagonal stays may be riveted, which means they are fastened together using metal rivets. This suggests that the statement is true, as it accurately describes the difference in construction methods between modern and older boilers.

A superheater is a device that increases the temperature of steam by adding additional heat energy (Btu) to it. This increase in temperature gives the steam more energy and capacity to do more work. Therefore, the statement that a superheater adds Btu to the steam and gives it the capacity to do more work is true.

In a watertube boiler, water passes through the tubes while hot gases of combustion pass across the outside surface of the tubes. This design allows for efficient heat transfer from the hot gases to the water, resulting in the generation of steam.

MAWP stands for maximum allowable working pressure, which refers to the maximum pressure at which a vessel or system can operate safely without causing damage or failure. It is an important parameter used in the design and operation of pressure vessels and equipment to ensure their integrity and prevent accidents.

The range of a pressure gauge on a steam boiler should be 1 1/2 to 2 times the MAWP (Maximum Allowable Working Pressure). This range ensures that the pressure gauge is capable of accurately measuring the pressure within the boiler without exceeding its maximum capacity. By having a range that is 1 1/2 to 2 times the MAWP, the pressure gauge can effectively monitor the pressure fluctuations and provide a reliable indication of the boiler's operating conditions.

Hot condensate contains less oxygen than cool makeup water because as water is heated, it releases dissolved gases, including oxygen. This is why hot condensate, which is formed from steam that has cooled down, has lower oxygen content compared to cool makeup water, which is fresh water added to a system.

In a firetube boiler, water does not pass through the tubes. Instead, the hot gases produced by the combustion of fuel flow through the tubes, heating the surrounding water and generating steam. This design allows for a larger heating surface area and higher heat transfer efficiency. Therefore, the correct answer is false.

The correct answer is "surface" because the question is asking for the term that describes any part of the boiler metal that is exposed to hot gases of combustion on one side and water on the other side. The term "surface" accurately describes this situation, as it refers to the outer layer or exterior of an object.

A "D" style boiler is indeed a watertube boiler. Watertube boilers are designed with water-filled tubes that are heated externally by hot gases, allowing for efficient heat transfer and high steam production. The "D" style boiler refers to the shape of the boiler, which resembles the letter "D" when viewed from the side. This type of boiler is known for its compact design, ability to handle high-pressure steam, and versatility in various industrial applications. Therefore, the statement is true.

The safety valve is designed to prevent a boiler from exceeding its maximum allowable working pressure (MAWP). It acts as a pressure relief mechanism, opening up and releasing excess pressure when the pressure inside the boiler reaches or exceeds the MAWP. This helps to ensure the safety and integrity of the boiler by preventing potential damage or explosions caused by excessive pressure.

Condensate should be removed from steam lines to prevent water hammer. Water hammer occurs when condensate accumulates in the steam lines and is suddenly displaced by a steam surge, resulting in a rapid increase in pressure. This can cause damage to the pipes, valves, and other equipment in the system. By removing the condensate, the risk of water hammer is minimized, ensuring the safe and efficient operation of the steam lines.

The explanation for the given correct answer is that a safety valve pops open fully and immediately because it is designed with a two-stage pattern. This means that the valve disc, which is responsible for closing against the seat of the safety valve, is designed in such a way that it can open quickly and completely when the pressure exceeds the set limit. This design ensures that the safety valve can rapidly release any excess pressure, preventing potential damage or accidents.

Flues, which are the pipes or channels that carry exhaust gases from a fireplace or furnace, are indeed specified by their inside diameter. This is because the inside diameter of a flue determines the amount of airflow and ventilation it can provide. By specifying the inside diameter, manufacturers and installers can ensure that the flue is properly sized to accommodate the specific appliance and its exhaust requirements. Therefore, the statement "Flues are specified by their inside diameter" is true.

Water has a density of 62.4 lb/cu ft. Therefore, if we divide the weight of water by its density, we can find the volume of water. In this case, dividing 8.33 lb by 62.4 lb/cu ft gives us a volume of approximately 0.133 cu ft. Hence, there are indeed 8.33 lb of water in 1 cu ft of water, making the statement true.

To prevent damage from vacuum when draining a boiler, it is necessary to open the vent valve. This allows the release of any trapped air or pressure inside the boiler, preventing the formation of a vacuum. If the vent valve is not opened, the vacuum can cause damage to the boiler by collapsing or imploding it. Therefore, opening the vent valve is crucial to ensure the safe and proper drainage of the boiler.

A stay is a short bolt brace that passes through the water leg of a boiler. It helps to support and reinforce the structure of the boiler, preventing it from collapsing under pressure. Stays are commonly used in boilers to ensure their stability and safety during operation.

An "A" style boiler refers to a specific type of firetube boiler that has a top drum and two bottom mud drums. This configuration allows for efficient heat transfer and steam generation. Therefore, the statement that an "A" style boiler is a firetube boiler with a top drum and two bottom mud drums is true.

Boilers that have more than 500 sq ft of heating surface must have two or more safety valves. This is because safety valves are crucial components in boilers that are designed to release excess pressure to prevent explosions or other hazardous situations. Boilers with larger heating surfaces tend to generate higher amounts of steam, which increases the risk of pressure buildup. Therefore, having multiple safety valves ensures redundancy and provides additional protection in case one valve fails or malfunctions.

A common pressure gauge uses a Bourdon tube to create movement of the pointer when pressure is applied. The Bourdon tube is a curved tube that is connected to the pressure source. When pressure is applied, the tube straightens out, causing the pointer to move. This movement is then displayed on the gauge, allowing the user to measure the pressure accurately. The Bourdon tube is a commonly used mechanism in pressure gauges due to its simplicity and reliability.

Water hammer is a phenomenon that occurs when there is a sudden change in fluid flow within a piping system, resulting in pressure surges and shock waves. These pressure surges can cause damage to the piping system, particularly at points where there are changes in direction or flow restrictions. Elbows, tees, and restrictions in the piping can all contribute to the occurrence of water hammer and are susceptible to damage as a result. Therefore, the correct answer is "all of the above".

Watertube boilers have a distinct advantage over firetube boilers in terms of generating steam from a cold start faster. This is because watertube boilers have a larger surface area for heat transfer, allowing for quicker heating of the water inside the tubes. In contrast, firetube boilers have a smaller surface area and require more time to heat up the water. Therefore, it is true that watertube boilers generate steam from a cold start faster than firetube boilers.

The maximum capacity of a boiler refers to the amount of steam it can produce in one hour at a specific pressure and temperature. This indicates the efficiency and capability of the boiler to generate steam within a given time frame. It is a crucial factor in determining the productivity and performance of the boiler system.

An HRT (Horizontal Return Tubular) boiler is a type of firetube boiler, not a watertube boiler. In firetube boilers, hot gases produced by combustion pass through tubes submerged in water, heating the water to create steam. In contrast, watertube boilers have water-filled tubes through which the hot gases flow around, heating the water inside the tubes. The HRT boiler design has a cylindrical shell with tubes running horizontally, indicating a firetube configuration. Thus, saying an HRT boiler is a watertube boiler would be incorrect.

A steam trap is a device used in a steam system to automatically remove condensate (the liquid formed when steam cools down) and vent air. Condensate can cause damage to the system if not removed, and air can hinder the efficiency of the system. Therefore, the purpose of a steam trap is to automatically drain condensate and vent air from the steam system, ensuring its proper functioning.

Temperature creates a greater stress than pressure on a boiler shell because as the temperature increases, the metal of the boiler shell expands, causing it to undergo thermal stress. This stress can lead to deformation or even failure of the boiler shell. On the other hand, while pressure also exerts stress on the shell, it is typically more manageable and can be controlled through safety valves and pressure relief systems. Therefore, temperature is considered to have a greater impact on the stress levels experienced by a boiler shell compared to pressure.

A safety valve should be manually tested when the pressure is about 75% of the normal popping pressure. This is because testing the valve at this pressure ensures that it will open and relieve excess pressure when needed, without being too sensitive and opening prematurely. It allows for a margin of safety and ensures that the valve is functioning properly within its operating range.

The downcomer tubes in a watertube boiler contain the cooler water that is descending. In a watertube boiler, the downcomer tubes are responsible for carrying the cooler water from the steam drum to the lower headers of the boiler. This cooler water is then heated in the lower headers and rises through the riser tubes to generate steam. Therefore, the correct answer is "cooler, descending."

A nonreturn valve, also known as a check valve, is a type of valve that allows fluid to flow in only one direction. It is designed to prevent backflow and ensure the flow of fluid in a single direction. Unlike other types of valves, a nonreturn valve is not meant to be manually opened or closed. It operates automatically based on the pressure difference across the valve. Therefore, the statement that a nonreturn valve can be opened manually is false.

The badge plate is commonly attached to the body of the boiler. This means that the badge plate is typically fixed to the main structure or casing of the boiler, rather than being attached to the wall, door, or outside of the boiler. The body of the boiler is where important information, such as the manufacturer's name, model number, and safety certifications, is often displayed on the badge plate.

Water cannot be compressed to 75% of its original volume. Unlike gases, liquids like water are nearly incompressible. This means that they cannot be easily squeezed or compressed into a smaller volume. Water molecules are closely packed together, and any attempt to compress them would result in a negligible change in volume. Therefore, the statement is false.

The statement is false because gauge pressure is actually the pressure above atmospheric pressure, not below it. Gauge pressure is a measurement that indicates the difference between the absolute pressure and the atmospheric pressure. It is commonly used to measure the pressure in closed systems or devices, such as tires or pressure vessels. By subtracting the atmospheric pressure from the absolute pressure, gauge pressure provides a value that represents the excess pressure above atmospheric conditions.

Superheaters do not raise the pressure of steam. They are used to increase the temperature of the steam without changing its pressure. Superheating the steam makes it more useful for various industrial processes, as it contains more energy and can be used to perform work more efficiently. However, the pressure of the steam is typically controlled by other components in the system, such as boilers or pressure regulators. Therefore, the given statement is false.

The correct formula for finding pressure is pressure = force divided by area. This formula represents the relationship between the force applied to an object and the area over which the force is distributed. Pressure is defined as the amount of force exerted per unit area, so dividing the force by the area gives us the pressure.

Superheater tubes do not need to be kept cool by maintaining a sufficient flow of water through them. In fact, superheater tubes are designed to operate at high temperatures and are used to increase the temperature of steam beyond its saturation point. They are typically located in the hottest part of the boiler and are exposed to high-temperature gases. Therefore, the correct answer is False.

The NB (National Board) administers the application of various approval stamps on boilers, pressure vessels, and safety valves.

False. The statement is incorrect because thermal shock is not caused by a sudden and drastic change in pressure, but rather by a sudden and drastic change in temperature. Thermal shock occurs when there is a rapid and extreme change in temperature, causing stress on the boiler metal.

Blowdown is the correct answer because it refers to the process of reducing the pressure in a boiler by releasing a portion of the water from the boiler. This is done to prevent the pressure from exceeding the maximum allowable working pressure (MAWP) and to ensure the safety valve reseats properly. By releasing some of the water, the pressure is lowered, allowing the safety valve to close and maintain the desired pressure level. Therefore, blowdown is the amount by which the pressure in the boiler must be reduced before the safety valve reseats.