NABTEB GCE 2023 PLUMBING AND PIPE FITTING ANSWERS

O’LEVEL PLUMBING AND PIPE FITTING

PLUMBING/PIPE OBJ
01-10: CBDABBDACA
11-20: CACCCACBDB
21-30: ABDABCACDC
31-40: ACCACCADCA

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ANSWER FIVE QUESTIONS ONLY

(1a)
(i) Oxygen: Oxygen can be produced through various methods, the most common being the process of fractional distillation of air. This involves cooling and liquefying air to separate its components based on their boiling points. Oxygen has a lower boiling point than nitrogen and other gases in air, it can be collected as a gas during the distillation process. Oxygen can also be produced through electrolysis of water, where an electric current is passed through water, causing it to separate into hydrogen and oxygen gases.

(ii) Acetylene: Acetylene gas is primarily produced by the reaction between calcium carbide (CaC₂) and water (H₂O). This process is known as the carbide-water reaction. When calcium carbide reacts with water, it produces acetylene gas (C₂H₂) and calcium hydroxide (Ca(OH)₂). The reaction is exothermic, releasing heat in the process. Acetylene can also be produced by other methods such as thermal cracking of hydrocarbons, but the carbide-water reaction is the most common industrial method for its production.

(1b)
(PICK FOUR ONLY)

(i) Porosity: This defect is characterized by the presence of gas pockets or voids within the welded joint.

(ii) Incomplete fusion: It occurs when there is a lack of proper fusion between the base metal and the filler metal, resulting in an insufficiently bonded joint.

(iii) Undercutting: Undercutting happens when the base metal near the weld joint is excessively melted or eroded, creating a groove or depression.

(iv) Cracks: These are usually formed due to high stress concentrations or inadequate weld cooling, resulting in fractures in the welded joint.

(v) Inclusions: Inclusions are foreign materials, such as slag or debris, trapped within the weld, leading to weak and defective joints.

(vi) Burn-through: Burn-through refers to the excessive melting or penetration of the base metal, resulting in holes or gaps in the weld joint.

(vii) Distortion: Distortion occurs when heat causes the metal to expand and contract unevenly, leading to warping or misalignment of the welded components.

(viii) Lack of penetration: Lack of penetration indicates inadequate fusion between the weld metal and the base metal, resulting in a weak joint with poor load-carrying capacity.
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(2a)

(i) Neutral flame: The neutral flame is achieved by adjusting the proportions of fuel gas and oxygen in equal amounts. It has a balanced ratio of the two gases, resulting in a flame with a bluish-white inner cone surrounded by a pale outer cone. The neutral flame is primarily used for welding operations as it provides good heat transfer and a stable combustion environment.

(ii) Oxidizing flame: The oxidizing flame is obtained by increasing the proportion of oxygen compared to the fuel gas. It has a shorter and more pointed inner cone with a bluish-white color and a larger, well-defined outer cone. The oxidizing flame is used for applications that require intense heat, such as cutting or brazing, as it provides a higher temperature and greater oxygen concentration.

(iii) Carburizing flame: The carburizing flame is achieved by increasing the proportion of fuel gas compared to the oxygen. It has a longer, feather-like inner cone with a light blue or greenish tinge and a small outer cone. The carburizing flame enriches the weld zone with carbon, which can enhance the strength and hardness of the weld.

(2b)
(PICK THREE ONLY)

(i) Remove impurities: Flux helps in removing impurities from the welding area, such as oxides, dirt, and other contaminants that can compromise the quality of the weld.

(ii) Prevent oxidation: Flux forms a protective layer that prevents the base metal from being oxidized during the welding process. This is particularly crucial when working with metals that are prone to oxidation, such as steel.

(iii) Improve wetting action: Flux helps to improve the wetting action of the molten filler metal. It allows the filler metal to flow more easily and evenly into the joint, ensuring better fusion and a stronger weld.

(iv) Purify the weld pool: Flux acts as a purifying agent by chemically reacting with impurities and forming compounds that can be easily removed, resulting in a cleaner weld pool.

(v) Control heat distribution: Flux can help control the distribution of heat during welding. By regulating the heat flow, flux ensures that the weld area cools at an appropriate rate, minimizing the risk of distortion or cracking.

(vi) Facilitate metal transfer: Flux assists in the transfer of metal from the electrode to the workpiece by creating an electromagnetic field that influences the direction of the molten metal, promoting a stable and controlled welding process.
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(4a)
(PICK SIX ONLY)

(i) Inspect the trap: Start by examining the trap carefully to understand its design and components. This will give you a better idea of how to unseal it.

(ii) Use a key: If the trap has a lock mechanism, try using the appropriate key to unlock it. This is a common method for unsealing many types of traps.

(iii) Use a pick or lock bypass tools: In cases where the trap has a more complex lock mechanism, such as a combination lock, you may need to use lock picking or lock bypass tools to unseal it.

(iv) Apply pressure or force: Depending on the type of trap, you might be able to use pressure or force to unseal it. This could involve pushing, pulling, or using leverage to overcome any resistance.

(v) Disassemble the trap: In some situations, you may need to dismantle the trap by removing screws, bolts, or other fasteners. This approach requires caution to avoid triggering any secondary mechanisms.

(vi) Cut or break the seal: If the trap has a physical seal, such as a zip tie or plastic band, you can cut or break it to unseal the trap. Make sure to do this safely to avoid injury.

(vii) Apply heat: When dealing with adhesives or sealants, applying heat to the area can help soften or melt them, making it easier to unseal the trap. Use caution not to damage the trap or any surrounding materials.

(viii) Solve a puzzle or combination: Certain traps may be designed with puzzle or combination mechanisms that need to be correctly solved to unseal them. Analyze the trap for any clues or hints to assist you in this process.

(ix) Use a trap-specific tool: Some specialized traps require specific tools or methods for unsealing. Research or consult experts to identify and utilize the appropriate tools for the specific trap you’re dealing with.

(4b)

=PURPOSE OF AN S TRAP IN SANITARY APPLIANCE=

(i) Prevent foul odors from the sewer lines entering the building or room by creating a water seal. The water in the trap acts as a barrier, blocking the passage of gases and odors from the sewer into the building.

(ii) Prevent the backflow of sewer gases into the appliance by providing a barrier between the appliance and the sewer line. This helps maintain a healthy indoor environment and prevents the spread of harmful bacteria and gases.

(iii) Provide a barrier against pests. The water in the trap prevents insects, rodents, and other pests from entering the building through the sewer lines.

(iv) Allow for the effective removal of wastewater from the appliance. The S-shaped design of the trap allows water to flow through it, carrying away waste and preventing clogs.

(v) Help in maintaining proper plumbing system venting. The S trap ensures that air from the vent stack can enter the plumbing system, allowing for proper drainage and preventing air pressure fluctuations.
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(5a)
(i) Soil Pipe: A soil pipe is specifically designed to carry human waste, including feces and urine, from toilets to the sewage system or septic tank. It is usually larger in diameter and made of a sturdy material like cast iron or plastic. Soil pipes are also designed to handle the additional pressure and gases generated from wastewater flowing from toilets. They are generally connected to the main drainage system of a building.

(ii) Waste Pipe: A waste pipe is responsible for carrying all other types of wastewater, such as from sinks, showers, bathtubs, and appliances like washing machines and dishwashers. It serves to transport non-sewage waste water and other liquid waste to the drainage system or sewer line. Waste pipes are typically smaller in diameter and can be made of materials like polyvinyl chloride or acrylonitrile butadiene styrene.

(4b)
=Examples of Soil Pipes=
(PICK THREE ONLY)
(i) Cast iron soil pipe
(ii) PVC soil pipe
(iii) Clay soil pipe
(iv) Copper soil pipe
(v) Stainless steel soil pipe
(vi) Galvanized steel soil pipe

=Examples of Waste Pipes=
(PICK THREE ONLY)
(i) PVC waste pipe
(ii) Copper waste pipe
(iii) Polyethylene waste pipe
(iv) Cast iron waste pipe
(v) Stainless steel waste pipe
(vi) Galvanized steel waste pipe

(4c)
(PICK SIX ONLY)
(i) PVC pipe
(ii) Copper pipe
(iii) Galvanized steel pipe
(iv) Polyethylene pipe
(v) Cross-linked polyethylene pipe
(vi) Cast iron pipe
(vii) Concrete pipe
(viii) Ductile iron pipe
(ix) Acrylonitrile Butadiene Styrene pipe
(x) High-Density Polyethylene pipe
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(5a)
(i) Sedimentation: Sedimentation is a process in water treatment where suspended particles and solids in the water settle down under the influence of gravity. During sedimentation, the water is kept still in a large basin or tank, allowing the heavier particles to settle at the bottom through the force of gravity. This helps in the removal of larger particles, such as sand, silt, and other visible solid particles, from the water.

(ii) Filtration: Filtration is a water treatment process that involves passing the water through a porous medium, typically a bed of sand, gravel, or activated carbon. The porous medium acts as a filter, physically trapping and removing suspended particles, microorganisms, and other impurities present in the water. Filtration is an effective method for removing fine particles, turbidity, and certain microorganisms from the water.

(iii) Chlorination: Chlorination is a commonly used disinfection method in water treatment. It involves adding chlorine or chlorine compounds to water to kill or inactivate harmful microorganisms, such as bacteria, viruses, and parasites. Chlorine effectively destroys the microorganisms by disrupting their cell membranes and interfering with their metabolic processes. Chlorination is a widely practiced and reliable method to ensure the safety and disinfection of water for drinking and other uses.

(5b)
(PICK SIX ONLY)

(i) Size and capacity: Determine the appropriate size and capacity of the tank based on the building’s water demand and occupancy.

(ii) Location: Select a suitable location for the tank that provides easy access for maintenance and minimizes the risk of damage or contamination.

(iii) Structural requirements: Ensure that the building’s structure can support the weight of the tank when it is filled with water.

(iv) Water quality: Assess the quality of the water source to determine if any treatment or filtration systems are needed before storing the water.

(v) Fire safety regulations: Comply with local fire safety regulations regarding the installation, placement, and capacity of the tank.

(vi) Plumbing infrastructure: Evaluate the existing plumbing infrastructure to ensure proper connections and compatibility with the tank.

(vii) Insulation: Consider the need for insulation to prevent freezing or excessive heat gain in the tank, depending on the local climate.

(viii) Maintenance and cleaning: Plan for regular maintenance and cleaning of the tank to prevent bacterial growth and maintain water quality.

(ix) Overflow and drainage: Establish proper overflow and drainage systems to handle excess water and prevent waterlogging or flooding.

(x) Accessibility and safety: Make sure the tank is easily accessible for maintenance personnel, and consider safety measures such as secure covers and guardrails to prevent accidents.

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