Doha Petroleum Construction Company Piping Supervisor Interview Questions and Answers for Experienced

The carbon percentage in carbon steel varies from 0.05% to 2.0% depending on the grade.

• Carbon steel is an alloy of iron and carbon.

• The amount of carbon in carbon steel determines its strength and hardness.

• Low carbon steel contains less than 0.3% carbon, while high carbon steel contains more than 0.6% carbon.

• Some common grades of carbon steel and their carbon percentage are: A36 (0.26%), 1018 (0.18%), and 1045 (0.45%).

Concentric reducers have a common centerline while eccentric reducers have an offset centerline.

• Concentric reducers are used in vertical piping systems to prevent accumulation of air pockets.

• Eccentric reducers are used in horizontal piping systems to prevent accumulation of solids or liquids.

• Concentric reducers are symmetrical while eccentric reducers are not.

• Concentric reducers are easier to manufacture and install th

Reinforcement fittings are used to strengthen and support piping systems.

• Common reinforcement fittings include tees, elbows, reducers, and couplings.

• Telescoping fittings are used to adjust the length of piping systems.

• Flange fittings are used to connect pipes to other equipment or structures.

• Saddles are used to support piping systems on walls or ceilings.

• Reinforcement fittings can be made of various materials, includin...read more

Elbow lets change the direction of flow in piping system.

• Elbows are used to change the direction of flow in a piping system.

• They come in different angles such as 45°, 90° and 180°.

• They are available in different materials such as PVC, copper, steel, etc.

• Elbows can be welded or threaded onto the piping system.

• They are commonly used in plumbing, HVAC, and industrial piping systems.

The bypass valve can be replaced by isolating the vessel, depressurizing it, and then replacing the valve.

• Isolate the vessel by closing the inlet and outlet valves

• Depressurize the vessel by venting the gas or liquid

• Remove the old valve and install the new one

• Repressurize the vessel and open the inlet and outlet valves

Permit to work is a formal written system used to control high-risk activities.

• It is a document that outlines the work to be done and the hazards associated with it.

• It is used to ensure that all necessary safety precautions are taken before work begins.

• It is issued by a competent authority and must be signed by all parties involved in the work.

• Examples include hot work permits, confined space permits, and excavation pe

Isolation is the process of separating a system or equipment from its energy source to ensure safety during maintenance or repair.

• Isolation involves disconnecting a system or equipment from its power source, locking it out, and tagging it to prevent accidental re-energization.

• There are two types of isolation: electrical isolation and mechanical isolation.

• Electrical isolation involves disconnecting the electrical supply...read more

Positive isolation is the process of completely isolating a section of a system to prevent any flow or transfer of material.

• Positive isolation is achieved by using valves, blinds, or other physical barriers to completely block the flow of material.

• It is important for safety and maintenance purposes, as it allows workers to safely perform tasks without the risk of exposure to hazardous materials.

• Examples of positive iso...read more

Positive isolation is the process of completely isolating a section of piping or equipment from the rest of the system to perform maintenance or repairs.

• Identify the section of piping or equipment that needs to be isolated

• Close all valves and block all lines leading to and from the section

• Use blind flanges or spectacle blinds to physically block the section

• Ensure that the isolation is secure and pressure tested before ...read more

Nitrogen purging is done to remove impurities and oxygen from pipelines before commissioning or maintenance work.

• Nitrogen purging is done to create an inert atmosphere inside the pipeline to prevent explosions or fires.

• It is required before commissioning or maintenance work to remove impurities and oxygen from the pipeline.

• Nitrogen purging is also done to prevent corrosion and contamination of the pipeline.

• It is common...read more

Pipes are used to transport fluids and gases, while tubes are used for structural purposes.

• Pipes have a standardized outer diameter and wall thickness, while tubes have a standardized inner diameter and wall thickness.

• Pipes are typically round, while tubes can be round, square, or rectangular.

• Pipes are often used in plumbing and HVAC systems, while tubes are used in construction and engineering applications.

• Pipes are u...read more

I have experience working with various pipe materials and standards including carbon steel, stainless steel, and PVC.

• I have worked with carbon steel pipes in a power plant project.

• I have also worked with stainless steel pipes in a pharmaceutical plant project.

• In a water treatment plant project, I have worked with PVC pipes.

• I am familiar with ASME B31.3, API 5L, and ASTM standards for pipe materials and welding procedur