Top 35 Boiler Questions and Answers [With PDF]

Today I am going to discuss some Boiler Questions and Answer.

As I have discussed much of boilers in the previous session, If you didn’t go through, then this is the right time to read those boilers functioning, working and more, links are at the end of this session.

Now, let’s dig into the boiler questions and answers quiz and later on you can download this whole Boiler QnA in adding more value to this session.


What is a boiler?

As the name suggests, Boiler is a closed shell appliance used to generate steam using various fuel mediums.

What is a double boiler?

The double boiler is a low pressure, externally fired boiler. It is made of a double boiler shell or pot placed one by one in an upward direction.

How to make a double boiler?

A double pot is placed under the furnace with water when hot gases are generated through burning fuel, water starts to boil and hence causes generate steam.
Generated steam heat up the next pot.
This double boiler is generally used in the kitchen to melt chocolate and butter and steam cooking items.

How to use a double boiler?

A double pot is placed one by one in an upward direction pouring water in it and then turning the fuel burner on. This causes the generation of steam into the first shell and this is further released to the second pot placed above the first pot.
This further heated up the food placed in the second pot.
Easy. Isn’t it?

What is a boiler room?

The boiler room is a mechanical room where various mechanical equipment is stored and operated from there including boilers also.

How long does a boiler last?

The average age of the boiler is from 11 to 16 years depending on the maintenance and loads on it.

What does a boiler do?

The boiler is usually used to generate steam to fulfil the mechanical and Electricity purpose.
The best example of boiler usage is – Thermal power plants.

How to turn on the boiler?

First, you need to check the essential setups and then release the feed pump to feel the required water.
Now, Need to supply the fuel source or electricity to fire up the combustion chamber. Rest is automated.

How much does a boiler cost?

The average cost of the boiler is from £450 to £3000, depending upon the type and the function of the boiler, you are looking for.

How to clean a water boiler?

Those green mould or rust can cause to happen to water boilers with continuous usage.
To get rid of this, this must be clean and to clean, you need the solution of Vinegar-water solution.
First, put vinegar and water in equal amounts and then run the boiler. This will swell the rusting from inside due to the steam formation and thus clean with hand by switching off the boiler.

How to bleed a boiler

Boiler flushing or boiler bleeding is a process to clean out the boiler inside and break out the jam inside the pipes.
To bleed the boiler, the boiler needs to be its maximum settings and needs to watch out that when to release the pressure inside generated by turning on the maximum setting of the boiler.

How to drain the boiler?

The boiler can be drained out by using a Blow-off cock in a conventional boiler.

What is the difference between a boiler and a furnace?

The basic difference between a boiler and a furnace is working. The furnace is used to supply hot gases or flue gases or heat to the boiler and Otherside the boiler is used to generate the steam.

How does the boiler work?

The combustion chamber is fired to generate hot gases to heat up the water located inside the tubes. This exchange of heat causes the generation of steam into the boiler and this steam is transferred to further use.
This is the simple and short working of the boiler.

On what factors does boiler thermal expansion depend?

It depends on the following-
Boiler operating temperature
Boiler tube materials composition
Length of tubes

What are the reasons for the fish mouth failure of boiler tubes/coils?

Erosion & corrosion

What do you mean by priming in boilers?

It is a carryover of water particles into steam

What could be the probable causes of priming?

Drum level function
Boiler load fluctuation
Boiler parameters fluctuation

What are the reasons for monitoring oxygen level in the flue gases?

To control combustion & achieve maximum efficiency of combustion by optimizing excess air.

What are the functions of the steam drum?

The steam drum acts as a water storage device
Separates steam & water
Provides space for internal chemical treatment
Removes sludge from boilers through blow dom
Accommodates safety valves to relieve excess pressure during abnormal operating conditions.

What is the function of start-up vents in boilers?

To control steam pressure during abnormal operating conditions
To increase the main steam temperature during low loads

Why drum dish end thickness is lesser than that of the cylindrical portion?

Because stress produced in dish ends is circumferential & is less as compared to stress developed in the longitudinal portion.

What is the main reason for the more mainstream temperature?

More excess air
High moisture fuel
More convective heat transfer at superheater zone due to loss of turbulence
Operating the boiler at lower feedwater temperature at economizer inlet

Why it is not recommended to give blow down during high streaming rates?

The sudden opening of 180 valves or water wall bottom heater valves will affect circulation rate & may lead to failure of water wall tubes.

What is the function of the draught system?

To force air into the combustion
To expel out products to combustion from boiler

What are the different types of draughts used in boilers?

Forced draught
Induced draught
Balanced draught

On what factors does chimney construction depend?

Quantity of flue gas generated per hour
Draught to be produced
Sulphur content in fuel
Environment clearance

Why boiler is considered a piece of explosive equipment?

Boiler involves the generation of steam at higher pressure & temperature upon release of this into the atmosphere could cause disaster.

How do you specify the boilers?

Boilers are specified by their operating pressure, temperature, steam generating capacity & even heating surface.

What are the various circuits involved in boilers?
  • Water circuit
  • Steam circuit
  • Air circuit
  • Flue gas circuit
Why steam is generated at high pressure & temperature?

High pressure & temperature steam is having more heat content & also has more potential to do work.

What is the standard method or procedure followed for boiler pressure rising during hydraulic tests?

The pressure rise is 3.5kg/cm2

What will happen, If drum safety valves have been set at higher blow-down rates?

Superheater coils may overheat due to insufficient flow of steam.

What are the reasons for the failure to superheater coils?
  • Overheating due to insufficient fuel
  • Erosion due to high flue gas
  • Internal scaling
  • Priming
What is the allowable reduction of tube thickness?

It is around 20% of the original thickness.



That’s it for now in this boiler questions and answers, I hope you liked this short session.

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Here are some suggested articles on boilers, you should read these also-

Thank you for being with me. I hope to see you in the next session.

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