This document discusses boiler mountings, accessories, and types of high pressure boilers. It describes key boiler mountings like the water level indicator, pressure gauge, and safety valves. It also covers boiler accessories that improve efficiency, such as economizers, superheaters, and air preheaters. Finally, it summarizes common high pressure boiler types including La-Mont, Loeffler, and Benson boilers, and notes advantages of high pressure boilers over conventional designs.

1. Boiler mountings and
accessories
BY – DR. RAKESH DANG
MECH. DEPT
PEC CHD

2.  Boiler mountings are the fittings which are mounted on the boiler for
the proper functioning of the boiler. Boiler does not work properly
without these mountings.
Following are some of the important boiler mountings.
1. Water level indicator
2. Pressure gauge
3. Safety valves
4. Stop valve
5. Blow off cock
6. Feed check valve
7. Fusible plug

3. Water level indicator –
1. It indicates the level of water inside
the boiler to an observer
2. It is a safety device on which proper
working of the boiler depends.
3. It is located in the front of the boiler
and generally two in numbers.
4. It consists of steam cock, water cock
and drain cock.

4. Pressure gauge –
 It is used to measure the pressure
of the boiler inside the boiler.
 It is mounted in the front of the
boiler.
 It consists of an elliptical elastic
tube bent into an arc of a circle
which is called bourden tube.
 One end of the tube is fixed and
connected to the steam space in the
boiler and other is connected to a
sector through a link.

5. Safety valves –
 These are necessary for preventing explosions due to excessive internal pressure
of steam.
 Its function is to blow off the steam when pressure of the steam inside the
exceeds the required working pressure.
 There are four types of safety valves –
1. Lever safety valve
2. Dead weight safety valve
3. High steam and low water safety valve
4. Spring loaded safety valve

6.  It is the largest valve and fitted to the
highest part of the shell by means of a large
flange.
 The body of the steam stop valve is made of
cast iron or cast steel.
 The valve, valve seat and nut through which
the spindle works are made up of brass or
gun metal
Steam Stop Valve -

7. Blow off cock –
 It is fitted to the bottom of the boiler drum and
consists of a conical plug fitted to the body or
casing.
 The casing is packed with asbestos packing, in
grooves round the top and bottom of the plug.
 The shank of plug passes through a gland and
stuffing box in the cover.
 The plug is held by a yoke and two stud bolts.
 The principal functions of blow off cock are
–
a) To empty the boiler whenever required
b) To discharge the mud, scale and sediments
which are accumulated at the bottom of the
boiler.

8. Feed check valve -
 It’s a non- return valve, fitted to a screwed
spindle to regulate the lift.
 Its function is to regulate the supply of water,
which is pumped into the boiler, by the feed
pump.
 This valve must have its spindle lifted before
the pump is started.
 It is lifted to the shell slightly below the
normal water level of the boiler.
 It is made up of brass and spindle is made up
of muntz metal.

9. Fusible plug -
 Its is fitted to the crown plate of the
furnace or the fire box.
 Its purpose is to put off the fire in the
furnace when the level of water in the
boiler falls to an unsafe limit.
 It avoid the explosion which may take
place due to overheating of the furnace
plate.
 It consists of three hollow gun metal
plug, Second plug is screwed to the first
plug and third plug is separated from
first plug by a ring of fusible metal,

10. Boiler accessories -
 These are the auxiliary parts which are required for steam boilers for their
proper operation and to increase the efficiency of the boiler.
 Followings are the boiler accessories –
1. Feed pump
2. Injector
3. Economizer
4. superheater
5. Air preheater

11. Feed pump -
 It is a pump which is used to deliver the feed water to the boiler. Double feed
pump is usually employed for medium size boilers.
 There are basically three types of feed pumps mainly :
1. Reciprocating pumps – simplex, duplex, triplex.
2. Rotary pumps
3. Centrifugal pumps

12. Injector -
 Injector is used to feed the
water in the boiler. It is usually
employed for vertical boiler
and does not find its application
in large capacity high pressure
boilers.

13. Economizer -
 Economizer increases the
temperature of feed water using
waste of heat to flue gases leaving
the boiler through chimney.
Economizer consists of large vertical
cast iron or steel water pipes.

14. Superheaters -
 The function of superheater is to
increase the temperature of the
steam above its saturation point.

15. Air preheater -
 It is a general term used to describe
any device designed to heat air
before another process with the
primary objective of increasing the
thermal efficiency of the process.
They may be used alone or to
replace a recuperative heat system
or a steam coil.

16. High pressure boiler -
 A boiler is called a high pressure boiler when it operates with a steam pressure above 80 bar. The
high pressure boilers are widely used for power generation in thermal power plants.
 Features of high pressure boilers –
1. Forced circulation of water
2. Large number of small diameter tubes
3. Higher steam pressure and temperature
4. Compactness
5. High efficiency
6. Pressurized combustion

17. Types of high pressure boilers -
1. La – Mont boiler
2. Loeffler boiler
3. Benson boiler
4. Babcock and wilcox boiler

18. La Mont boiler -
1. It is a high pressure, water tube boiler.
2. The water circulation is maintained by centrifugal pump.
3. La Mont boiler generates approximately 45 to 50 tonnes of
steam per hour at a pressure of 13 bar and a temperature of
500 c.
 Advantages of La Mont boiler –
1. Small diameters tubes are used, so that high heat transfer
rate is maintained.
2. The multiple tubes circuit gives flexibility for suitable
location of heat transfer equipments.

19. Benson boiler -
1. Difficulties of bubble formation is
eliminated.
2. The transport of benson boiler parts is easy
as no drums are required and majority of
the parts are carried to the site without pre-
assembly.
3. Required smaller floor area.
4. It has very little storage capacity compared
to drum type boiler.

20. Loeffler boiler -
 Difficulties of deposition of salt and
sediment is eliminated.
 Most of the steam is generated outside from
the feed water using part of the superheated
steam coming out from the boiler.
 Loeffler boiler with generating capacity of
94.5 tones/h and operating at 140 bar have
already been commissioned.

21. Advantages of high pressure boilers
over conventional boilers -
1. Due to forced circulation of water, evaporative capacity of
boiler is increased and size of drum is reduced.
2. Smaller diameters tubes are used, which increases heat transfer
rate and reduce fuel consumption.
3. Pressurized combustion is used which increases the rate of
firing of fuel thus increasing the rate of heat release.
4. These boilers are compact and hence less floor space is
required.
5. Due to uniform heating of all parts, there is less chances of
overheating.