Mechanical engineer interviews questions

Back-to-back arrangement In back to back arrangement a gap is provided between inner races and when installed, this gap is closed and producing a preload on the bearings. In a back-to-back arrangement, the load lines diverge along the bearing axis. Axial loads acting in both directions can be accommodated, but only by one bearing or bearing set in each direction. Back to Back bearing arrangement is a type of duplex bearing arrangement where the two half are placed so that contact angle lines of the bearing diverge inwardly. DB (Back-to-Back) arrangement has higher moment stiffness than the DF (Face-to -Face) arrangement. Under the same preload, DB and DF have identical radial and axial stiffness. Bearings mounted back-to-back provide a relatively rigid bearing arrangement. The wide span between bearing effective centres makes this arrangement particularly well suited to support moment loads. Face-to-face arrangement Face to face bearing arrangement (DF arrangement) is a typ...

Spur gear Spur gears have their teeth parallel to the axis and are used for transmitting power between two parallel shafts. Spur gears have highest efficiency and excellent precision rating. Rack and pinion Rack is a segment of a gear of infinite diameter. The tooth can be spur or helical. This type of gearing is used for converting rotary motion into translatory motion or visa versa. helical gear Helical gears are used for parallel shaft drives. They have teeth inclined to the axis. Hence for the same width, their teeth are longer than spur gears as their teeth are inclined and have higher load carrying capacity. Their efficiency is slightly lower than spur gears. Internal gear Internal gears are used for transmitting power between two parallel shafts.

Pressure Filters Filter press 1) Plate and frame filter press 2) Chamber press Vacuum Filters 1) Batch type - Leaf filter 2)Continuous Filter - Disc filters - Belt filters

Impeller  The impeller is a vaned disk mounted on the shaft. Its function is to increase the pressure of the liquid by means of its rotating action. The impeller is the main rotating part that provides the centrifugal acceleration to the fluid. The impeller may be of open, semi-open, or enclosed type, and may have anywhere between two to ten vanes. It may also be of single, or double, suction design. It may be radial flow, axial flow or mixed flow design.  Impeller nut Function of Impeller nut is: -To lock the impeller in its proper axial position -To prevent axial movement due to hydraulic thrust Seal A pump may be provided with one of two types of sealing elements - packing rings or mechanical seal. The sealing elements prevent the leakage of the pumped liquid into the atmosphere.

Centrifugal Pump parts  The major parts of centrifugal pump are: Impeller Impeller nut Seal Casing Wear rings Shaft  Shaft sleeve  Coupling Bearings Stuffing box Back plate Bearing Housing  Gland

This standard is a standard published and developed by the American Petroleum Institute (API) that covers the inspection, repair, alteration, and reconstruction of steel above ground storage tanks used in the petroleum and chemical industries. This standard provides the minimum requirements for maintaining the integrity of welded or riveted, non-refrigerated and refrigerated, atmospheric pressure,

Feed-water purity is a matter both of quantity of impurities and nature of impurities: some impurities such as hardness, iron and silica are of more concern, for example, than sodium salts. The purity requirements for any feed-water depend on how much feed water is used as well as what the particular boiler design (pressure, heat transfer rate, etc.) can tolerate. Feed-water purity requirements therefore can vary widely. A low-pressure fire-tube boiler can usually tolerate high feed-water hardness with proper treatment while virtually all impurities must be removed from water used in some modern, high-pressure boilers. Only relatively wide ranges can be given as to maximum levels of alkalis, salt, silica, phosphates etc, in relation to working pressure. The actual maximum levels must be obtained from the boiler manufacturer, who will base them on the characteristics of the boiler in question. Dissolved impurities Mainly the dissolved solids found in water are mineral salts....

When the flow of fluid through a system is suddenly halted at one point, through valve closure or a pump trip, the fluid in the remainder of the system cannot be stopped instantaneously as well. Water hammer is caused by a pressure or shock wave that travels through the pipes, generated by a sudden stop in the velocity of the water, or a change in the direction of flow. If the pipe is suddenly closed at the outlet, the mass of water before the closure is still moving forward with some velocity, building up a high pressure and shock waves. As fluid continues to flow into the area of stoppage (upstream of the valve or pump), the fluid compresses, causing a high pressure situation at that point. Likewise, on the other side of the restriction, the fluid moves away from the stoppage point, creating a low pressure (vacuum) situation at that location. Fluid at the next elbow or closure along the pipeline is still at the original operating pressure, resulting in an unbalanced pressure force...

Hydro test pressure should be calculated as follow: 1) Hydro test pressure = 1.5 Times of Design Pressure. 2) For a design temperature above the test temperature, minimum test pressure can be calculated as: Pt = (1.5 X P X St) / S Where:- P: Internal design pressure. Pt: Minimum Test Pressure. S: Allowable stress as design temperature. St: Allowable stress at test temperature.

The basic formula for find out pipe wall thickness is the general hoop stress formula for thin-wall cylinders, which is stated as T = P x D0/2(Hs + P) Where, HS = hoop stress in pipe wall, psi, D0 = outside diameter of pipe, in. T = pipe wall thickness, in., P = internal pressure of the pipe, psi,

Following are the codes and standards for designing the piping: ANSI/ASME Standard B31.1  Power Piping. For steam piping systems. ANSI/ASME Standard B31.3  Chemical Plant and Petroleum Refinery Piping. For major facilities onshore and offshore. ANSI/ASME Standard B31.4 Pipeline Transportation system for liquid hydrocarbon and other liquids. ANSI/ASME Standard B31.8  Gas Transmission and Distribution Piping Systems. For gas transmission, gathering, and distribution pipelines onshore.

Turbine is driven, engine drives. in reality nothing, both use steam pressure to create a desired output. Motion, turbine has 1 moving part that spins on its axis. Engine has many moving parts spinning an axis (crankshaft). A turbine operates in a way similar to either a jet engine, or an old water-wheel. In either case, a steam turbine converts the thermal energy of the steam to rotary mechanical energy much more efficiently. In engine, wet steam may also be used while in steam turbine, steam should be in superheated condition. Power output or steam to power ratio is comparatively very high in steam turbine as losses (e.g frictional, velocity etc) are very less. So, plant efficiency is much higher.

pH is the negative log of hydrogen ion concentration in a water-based solution. pH is an abbreviation for "power of hydrogen" where "p" is short for the German word for power, potenz and H is the element symbol for hydrogen. The H is capitalized because it is standard to capitalize element symbols. pH is a logarithmic measure of hydrogen ion concentration. PH = - log10(H+)

Hardness was originally defined as the capacity of water to precipitate soap.  Hardness of water is due to the presence of calcium and magnesium salts: bicarbonates, carbonates, chlorides, sulphates and nitrates. Presence of iron, aluminium and manganese salts also contributes to water hardness, but normally these are not present in appreciable quantities. Normal carbonates are also found, but only occasionally and in highly alkaline water. Nitrates are usually present in minor quantities while it has been found that sulphates on the average exceed chlorides. Removing hardness from water is called softening and hardness is mainly caused by calcium and magnesium salts. These salts are dissolved from geologic deposits through which water travels. The length of time water is in contact with hardness producing material helps determine how much hardness there is in raw water.

Electrostatic Precipitators or ESPs have been used in industry for over 60 years. They can collect particles sized 0.1 to 10 microns very efficiently. They are generally more efficient at collecting fine particles than scrubbers or cyclones. Electrostatic Precipitators are used for collection of fine ash particles from flue gases of boilers. Static Precipitator is a technique used to decrease the pollution content in the flue gasses. It is generally used in Thermal power plants to control the pollution caused by flue gasses.

Preventive maintenance is a schedule of planned maintenance actions aimed at the prevention of breakdowns and failures. The primary goal of preventive maintenance is to prevent the failure of equipment before it actually occurs. It is designed to preserve and enhance equipment reliability by replacing worn components before they actually fail. Preventive maintenance generally refers to routine inspections, adjustments, lubrication and cleaning of fixed and movable equipment, machinery and appliances utilized in the daily operation of a facility. Performing regular routine preventive maintenance keeps equipment in good running order, reducing the possibility of equipment failure thus insuring and extending expected equipment life. Through regular preventive maintenance, potential problems can be detected early thus reducing down time and preventing more expensive repairs.