Difference Between Smoke tube boilers and Water tube boilers

Sr. No.

Smoke tube boilers

Water tube boilers

1.

In this the hot flue gases flow in the tubes surrounded outside by
the water.

In this the water flows in the tubes surrounded outside by the hot
gases.

2.

These boilers have large water to steam ratio and therefore :

(a) These are slower in operation and have low evaporation rates.

(b) Temperature stresses causing the failure of feed water
arrangement is minimum.

It has comparatively lower water to steam ratio. therefore,

(a) It helps in reaching the steam temperature in the shorter time thereby
increasing the evaporation rate.

(b) It is subjected to temperature stresses due to failure the feed
water arrangement.

3.

It can work only upto 20 bar pressure because of larger drum
diameters and the limitations of the boiler shell thickness and stress
consideration.

Because of smaller drum diameter it can withstand higher internal
pressures for the same limit of thickness and stress, therefore, these
boilers are suitable for higher pressure operation up to 200 bar pressure.

4.

It has a simple and rigid construction with initial low cost but has
more maintenance and operation cost.

It has complex design with high initial cost but has lesser
maintenance and operation cost.

5.

These are usually made in smaller sizes and these are not suitable
for large power houses.

These are bigger in sizes and are suitable for large large lower
plants.

6.

Transportation and installation of the boiler is difficult because of
the large size of the shell.

It is easy to transport and install since its various parts can be
dismantled easily and they can be reassembled at site.

7.

The furnace design is rigid, therefore the particular type of fuel
can only be used.

These boilers are mostly externally fired, the proportion of the
furnace can be varied to suit the fuel requirements.

8.

It requires less floor area.

It requires more floor area.