The injector is a device that uses steam to feed water into a boiler. It works by steam flowing into a steam cone, creating a vacuum that draws in water. The water and steam mix and accelerate before entering the boiler. A spindle controls the position of the steam cone to regulate the steam and water mixture based on steam pressure. The injector is a simple, compact, and efficient way to feed water to a boiler using steam power with no moving parts.

1. ACCESSORIES OF BOILER -
INJECTOR
Prepared by - Prem A. Kothavade

2. INJECTOR
 Function –
It is a simple appliance for feeding a boiler
with water by the direct use of steam
either from the same boiler or exhaust
steam .

4. CONSTRUCTION
 Steam enters at A & flows into the steam
cone B
 A Partial vacuum is formed at the lower
end of B because of a steam rushing in
cone B
 Water enters the injector from water pipe
C
 The Water mixes with the steam in the
combining cone DE
 This converges towards E

5.  The steam condenses in cone DE
 The condensation of steam augments the
vacuum
 This will increase the flow of water
 The steam rushes through the steam cone
B with a high velocity
 Considerable velocity is also given to the
water in the combination cone DE

6.  At E, velocity of water & hence its K.E. is
greatest, but its pressure energy hence the
pressure is not sufficient to overcome
boiler pressure
 Below E is a diverging cone EF
 This cone reduces the velocity & hence,
increase the pressure of the water
 The increase pressure is sufficient to
enable it to enter the boiler

7.  In order to act properly, there must be a
more or less definite relation between the
quantities of steam & water
 The relation between the quantities of the
steam & water is regulated by turning the
handle H
 This handle is attached to the top of the
spindle K
 This spindle can only rotate
 The axial motion is prevented by the collar

8.  The part of the spindle has a screw
 It fits in a nut, which is in one piece with
steam cone B
 The nut & steam cone is prevented from
rotating by the feather key N
 The rotation of a spindle K will raise or
lower the steam cone B
 The lower end of the spindle forms a
steam valve T

9.  The seat of the valve is the entrance to the
steam cone
 The lower end of the steam cone forms a
water valve U
 The seat of which is the entrance to the
combining cone
 For any particular steam pressure there is
a particular position for steam cone
 Which will give the proper mixer of water &
steam

10.  This position is obtained by turning the
handle H until the pointer B is opposite to
point on a scale engraved on the ring R
which indicates steam pressure
 The combining cone in interrupted at Q
 This gap communicates with the overflow
branch O through the flap valve V.

11. WORKING
 In starting, the steam blows through
opening of the valve V
 The steam will rush through the overflow
passage until the water arise in sufficient
quantity
 The valve V close automatically when a
partial vacuum is formed in the combining
valve

12.  If the action of the injector is interrupted
because of a temporary disorders of a
steam or water supply, the injector will
automatically restart & then the working
describe for starting taking place

13. ADVANTAGES
 Initial cost is low
 Simple in design
 Compact in nature
 No moving parts
 Thermal efficiency is very high
 Ease of operation
 Maintenance cost is low

14. DISADVANTAGE
 Low pumping efficiency
 Under extreme variation is steam
pressure, the operation is irregular

15. Thank you