Design Engineer Interview Preparation Guide

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FOF stands for Face of Flange. A flange has either of the two types of faces:
a) Raised face
b) Flat face
The F.O.F is used to know the accurate dimension of the flange in order to avoid the minute errors in measurement in case of vertical or horizontal pipelines.

Every mechanical engineer has to address the concerns of stress on the job. How do they deal with stress? How do they channel negative energy?

Nitrogen is used to prevent porosity in the welding member by preventing oxygen and air from entering the molten metal during the welding process. Other gases are also used for this purpose such as Argon, Helium, Carbon Dioxide, and the gases given off when the flux burns away during SMAW (stick) welding.

The ideal shape would be a sphere. The container must have the capacity to withstand the extremely high pressure of liquefied gas. A spherical shape helps in distributing these forces uniformly.

The most efficient shape for withstanding high pressure is a sphere but that would be costly to manufacture. A cylinder with a domed top and a domed bottom (look underneath, the flat base is actually welded around the outside, the bottom of the gas container is actually domed) is a much cheaper shape to manufacture whilst still having good strength to resist the internal gas pressure.

It gives you value of tensile strength and yield strength.
For eg. The tensile strength over here in 8.8 marking bolt would be 800 N/mm^2 and its yield strength is 640 which is 80% of the tensile strength.

It is a process of heating a material above the re-crystallization temperature and cooling after a specific time interval. This increases the hardness and strength if the material.

Torque is the force that causes rotation. It is a measure of how much force is acting on an object making it rotate.

The ratio of specific heat γ=CP/CV is a factor in adiabatic engine processes and in determining the speed of sound in gas. This ratio γ=1.66 for an ideal monoatomic gas and γ=1.4 for air, which is predominantly a diatomic gas.

Any system needs redundancy in work needs pneumatics, because the compressor of the pneumatic system has periodical operations (intermittent work, not as hydraulic pump). The compressed air could be accumulated in tanks with high pressures and used even if the compressor failed.

Pressure and temperature are two of the most important factors to be considered before selecting the type of material to be used. Steam is a compressible gas due to which the capacity of the pipe line depends on the size of the pipes and pressure of the steam. Since steam at even low pressure can be dangerous, extra care is to be taken. Galvanized pipes are usually not used for steam. Pipes made of mild steel with welded fittings are instead largely used.

This question is often asked and it always confuses. So here is a clear answer for difference between jigs and fixture.

☛ Jigs gives direction to cutting tool
☛ We can perform various operations like drilling, reaming ,tapping and polishing.

☛ Fixtures are used to hold the workpiece
☛ Fixture are not used to perform any of the operations

Green field projects are those projects, which do not create any environmental nuisance (pollution), follows environmental management system and EIA (environment impact assessment). These projects are usually of big magnitude.

A Process Flow Diagram (or System Flow Diagram) shows the relationships between the major components in the system. It also has basic information concerning the material balance for the process.

The Hooke`s coupling is used to connect two shafts whose axes intersect at a small angle. The two shafts are inclined at an angle and is constant. During motion it varies as the movement is transferred from one shaft to another. One of the major areas of application of this coupling is in gear boxes where the coupling is used to drive the rear wheels of trucks and other vehicles. In such usage scenarios two couplings are used each at the two ends of the coupling shaft. they are also used to transfer power for multiple drilling machines. The Hooke`s coupling is also known as the Universal coupling. The torque transmitted by the shafts is given by :
T= (pie/16) x t x (d) cube
Where T = torque, t = shear stress for the shaft material and d the diameter of the shaft.

A pipe is measured based on its inner diameter (ID) whereas a tube is measured based on the outer diameter (OD). Other than the dimensions there is no major difference between the two.

Copper conducts heat faster than steel or brass. In most cases, material that is good for conducting heat is also good for electricity.

☛ Precision & Accuracy
☛ Reduced rework cost
☛ Reduced Defects
☛ Increased understanding

Normally galvanized pipes are not used for steam. Mild steel with screwed or welded fittings are the norm. Pressure and temperature are very important factors to be considered in what type of materials to be used. Steam even at low pressures can be extremely dangerous.

LNG pipes are curved because LNG is condensed gas (-164 deg cel) so it can expand the pipes that is what engineers designed the LNG pipes are curve type.

It is the temperature below which the tendency of a material to fracture increases rather than forming. Below this temperature the material loses its ductility. It is also called Nil Ductility Temperature.

☛ Clearance fit
☛ Interference fit
☛ Transition fit

The cylinder head has two spark plugs, instead of the usual one. When two sparks are generated at either ends of the combustion chamber, the air-fuel mixture is ignited in a way that creates two flame fronts. A higher rate of combustion is achieved leading to higher rise in pressure. The outcome of this is more torque, better fuel efficiency and lower emissions.

In order to find total heat loss through the pipes it is imperative to know the thermal conductivity and the differing thicknesses of each layer. The ground that surrounds the pipe also acts as a layer of insulation. Considering this, the thermal properties of the stoneless sand is included in the heat loss calculation.

Digital Twin Spark Ignition. This is used for a better fuel combustion in the cylinder head which helps provide better efficiency and optimum use of fuel.