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A Boiler supplies dry and saturated steam at the required pressure.
A particular apparatus or equipment is placed on the boiler to improve its safety, maintenance convenience and steam supply, is known as Boiler mounting. Following are the different Boiler mountings,
A valve is used to control the flow of fluid inside the pipeline.
Safety valve. This type of valve is used to keep the boiler safe by controlling the working pressure in the boiler and resist the blasting due to the high pressure; the valve is mounted with boiler.
Stop valve. This type of valve is used to control the flow of steam from the boiler to the engine.
Feed Check valve. This type of valve is used to control the supply of feed water to the boiler. The water level always remains constant when it works.
A piston is a cylinder piece of metal. It is moved within a hollow cylinder by the pressure of fluid (liquid, steam or gas).Pistons are easy fit in the cylinder and piston rings are used to prevent the leakage in between piston and cylinder.
Pistons are made by different materials such as cast iron, cast steel, aluminium ,bronze, forged steel, brass etc.
Locomotive pistons are of disc type which are generally made of cast iron or steel. Its piston rings are made of cast iron and are located by dowels.
Plunger piston is suitable when the fluid pressure is acting on one side of the piston only.
Bucket piston has one or more valves which permit the fluid to pass one side to the other.
It is also known as trunk piston which is open ended and is generally made longer. Cross head or piston rod is not necessary for it.
Piston rod is fitted inside the piston. The diameter of this rod is inside the piston is reduced to about 3/4th of its diameter. Piston valve is tightened by a nut and locked out by a pin.
Generally box type or hollow type steam engine pistons are used. These are generally made of cast iron. Box type pistons are cast in one piece with hollow core. This piston is secured by a nut to the piston rod. To prevent the leakage of the steam two piston rings are provided with the piston. In the modern reciprocating steam engines the piston made of cast steel and of conical shape is used. The piston made of cast steel is costly than that of cast iron.
Cross head is used to connect the connecting rod and the piston rod. It is generally made of cast iron, cast steel or forged steel. The piston rod may be fastened to the cross head either by a screw or by a cotter pin.
The crankshaft converts the rectilinear reciprocating motion into circular motion and vice versa. When the crankshaft moves through 180 degree, the crank travels over a semicircular path of the diameter. The crank travels one complete revolution and piston completes two strokes backwards and forwards, when the crankshaft moves through 360 degree.
A Crank is a simple lever which receives the thrust of the piston through the connecting rod. Generally crank disc, eccentric crank, overhung crank, bell crank etc. are used.
Soft packing. Used for general purposes. It is not suitable for high pressures and temperatures.
Metallic packing. It is generally used where high pressures and temperatures exist because it is more desirable for this purpose.
Semi-metallic packing. It is used where medium pressures and temperatures exist.
Clean the pump.
Check the correct quantity of the recommended grade of oil to the pump.
Check the drive rotation.
Check grease or oil to the coupling if necessary.
Turn the pump by hand(it should run freely)
Open the suction, vent, bypass and discharge valves.
Start the pump.
Generally these types of reciprocating pumps are relatively small and light in weight. Small reciprocating pumps are fixed on a light structural frame and other pumps have metal base bolted with the floor. Tank mounted pumps need no foundation but the tank is to be fixed.
Steam pumps, Power pumps, Metering pumps, Axial piston pumps and Sucker rod pumps.
Make sure that all the suction, discharge, steam and exhaust lines are open.
Open steam end drain valves.
Prime by opening air cock on liquid cylinder cap.
Crack steam valve to warm the pump.
Open the steam valve until the piston begins to move slowly.
Close the drain valve and open the steam valve until the pump comes up to the working speed.
To stop the pump close the steam valve first and then close exhaust, suction and discharge valves.
In a power pump the piping vibrates when discharge pipe is undersize or suction pipe is undersize.
It is due to,
Impellers locked or not adjusted properly
Trash in casing
Too much bearing friction.
It is an automatic pump. It is generally used to lift a water falling through a small height. i.e, water falling in large quantity through a small height is lifted to a greater height in small quantity. The automatic action of the ram takes place due to the inertia force.
External gear pumps, Internal gear pumps, Sanitary type pumps, External screw pumps, Three screw pumps, Swinging and sliding vane pumps and Flexible rotor pumps.
The centrifugal pump does not deliver liquid due to:
Pump not primed
Speed too low.
Clogged or leaking suction.
Oil is too thick.
Relief valve troubles.
Liquid lever is too low.
Multistage pumps, Process type pumps, Chemical process pumps, Canned motor pumps, Paper stroke pumps and Deepwell turbine pumps.
Steam pump stops due to valve trouble. i.e, incorrectly set or worn steam valves may stop the steam pump.
It is due to ,
Suction air bound
Suction lift too high
Obstruction in suction line
Pump not primed.
It is a heat engine in which the chemical energy of combustion is released inside the engine cylinder, thus fuel is fired inside the cylinder. It is more useful as compared to the other engines.
The spark plug is the main part of the engine. In the I.C engine having spark ignition, the fuel –air mixture in the cylinder is ignited through the medium of spark ignition electrical system which occurs at the electrode of the spark plug. The charge induced into the cylinder during its cycle’s first process. In the spark ignition engine , the gases compressed in the cylinder during the compression stroke consists of the fuel and air.
The connecting rod is made of forged steel. Its big end is connected to the crank and small is connected to the piston. The brass in the big end is die cast and lined with white metal. Separate connecting rods are used for petrol, diesel and gas engines.
The control and regulation of the mixture strength can be obtained automatically in the engine by carburetor. In its operation air from the air cleaner enters the main air passage and passes through the choke. Fuel from the float chamber enters and flows to the fuel jet. The depression in the choke causes petrol to flow from the jet where atomization of the fuel takes place. The mixture of the fuel and air passing into the induction system. The suction piston will rise and fall under the influence of engine suction which combined with the position of throttle control.
In the modern oil engines the injection of the fuel into the cylinder is accomplished not by an air blast but by means of injection pump. These pumps are built strongly and accurately. For preventing after drip and consequent burning of the fuel left on the spray nozzle tips, its pressure must drop as quickly and accurately as it rises.
It is a spark ignition engine. The induced charge in its cylinder consists of a mixture of air and fuel. The fuel used in it can be vaporized readily. The petrol engine can operated on the compression-ignition principle.
It is a simple engine having Piston, Connecting rod and Crankshaft. Valves and valve actuating accessories are eliminated because intake and exhaust gases accomplished by the opening in the cylinder wall which are controlled by the piston. This type of engine has a small horse power output.
It is a engine in which a low grade oil is used. The fuel is ignited by the heat of air in this engine.
It is an engine in which two strokes of the piston are required to complete one cycle to operate the engine. The functions of both the strokes are as under:
First stroke compress the air in the engine to ignite the fuel oil.
Second stroke is the power stroke which is produced by the burning gases.
It is a slow speed engine in which gaseous fuel is used. Variety of gas fuels are used such as town gas, natural gas, blast furnace gas, oil gas, coke oven gas etc. This type of engines are generally of stationary type but portable gas engines are also available.
Single acting Engine. It is a engine in which the pressure producing power stroke is exerted only on one side of the piston. It works on both the two stroke and four stroke engines.
Double acting Engine. It is a engine in which the pressure producing power stroke is exerted first on one side of the piston and then on the other end. It makes each stroke of the piston a power stroke.
It is an engine in which four strokes of the piston are required to complete one cycle to operate the engine. The functions of each stroke is as under:
First stroke draws air to the cylinder.
Second stroke compresses the air.
Third stroke is the power stroke which is produced by the burning gases.
Fourth stroke drives out the burnt gases.
When a glass rod is rubbed with a silk cloth, it becomes positive charge and when a ebonite rod is rubbed with a woolen cloth, it becomes a negative charge. The change produced in glass or ebonite rod is known as Static electricity. There is no movement of electrons in this electricity.
The electrons move and flow along the conductor in this electricity. If direction of flow electrons is always the same, it is known as Direct Current (D.C). If the direction of flow of electrons is changed constantly, it is known as Alternative Current (A.C).
Volt is the force which causes an electron flow of one ampere through a resistance of one ohm.
A.C is produced much more as compared to D.C.
An alternative voltage can be increased to a desired limit by a transformer while D.C can not be increased.
A.C is less expensive than that of D.C.
A.C induction motors are more useful for constant speed as compared to D.C motors.
A.C motors require less maintenance as compared to D.C motors.
A.C generators can be made in large size which can run at high speed also than that of D.C generators.
It is the amount of electron flow in the current . In one ampere 6.28*10/18 electrons has a given point in the conductor within a period of one second.
A fuse is a small piece of wire which is normally used in the circuit. It protects against the bad effects of short circuiting. When a current in the circuit rises above its desired limit, the fuse will be heated and melt which causes the circuit “Open” and saves the components and appliances from the possible damage.
It has not resistor. It causes a high current flow which may heat up the wire. It may cause fire and damage the electrical appliances in the circuit.
Heating effect. When a current flows in a wire and generators heat like filament lamp, electric heater, furnace etc. is called electric effect.
Chemical Effect. When electricity passes through a chemical solution , it can make chemical like cells, batteries, electroplating etc. it is called chemical effect.
Magnetic effect. When a current flows in a coil ,it makes a magnetic field like bell, motor, generator, transformer, tape recorder etc. called magnetic effect.
Conductors. When a material allows electrons to flow through it known as conductors. Eg. Copper ,aluminium ,iron ,tin, gold .
Insulators. The materials which prevent the flow of electrons are known as insulators. Eg: Rubber ,asbestos ,plastics, mica.
It is suitable for traction work.
It is suitable for charging batteries.
It is suitable for variable speed motors used in printing machines.
It is useful lamps used in projectors.
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