Steam Boilers and Engines - Mechanical Engineering Interview Questions

    2 Votes

Mechanical Interview Questions and answers on Steam Boilers and Engines for freshers and experienced on Boiler Classification, Valves, Pistons, Pumps etc.

1. What is the function of a Boiler?

A Boiler supplies dry and saturated steam at the required pressure.

2. Briefly explain the Boiler mounting, and name its classifications?
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,
  • Water level
  • Supply valves
  • Pressure gauge
  • Stop valve
  • Feed check valve
  • Blow off cock
  • Anti printing pipe
  • Fusible plugs etc
3. What is a valve?

A valve is used to control the flow of fluid inside the pipeline.

4. Discuss the function of Safety, Stop, and Feed check valves?

  • 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.

5.What is meant by a piston and cylinder?

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.

6. Name the different types of materials used to made pistons?

Pistons are made by different materials such as cast iron, cast steel, aluminium ,bronze, forged steel, brass etc.

7. What is a locomotive piston?

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.

8.What is the difference between Plunger piston and Bucket piston?

  • 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.

9. What is a buck piston?

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.

10.What are piston rod and piston valve of steam engine?

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.

11.Write a short note on Steam engine piston?

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.

12.What is a cross head of a steam engine?

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.

13. Explain about a Crankshaft?

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.

14.What is a crank?

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.

15.Name the different types of packings used in steam engine?

  • 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.

16.Write the procedure for starting the power pump?

  • 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.

17.Explain briefly the metering pumps?

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.

18.Name different types of reciprocating pumps?

Steam pumps, Power pumps, Metering pumps, Axial piston pumps and Sucker rod pumps.

19.Write the operational steps of a steam pump?

  • 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.

20.What are the reasons when piping vibrates in power pumps?

In a power pump the piping vibrates when discharge pipe is undersize or suction pipe is undersize.

Page 1 of 3