A) COLLECTIVE BREECHING:
● cast in gun metal, brass or bronze, these are used to unite two lines of hose in to one.
● these are also available in designs suitable for uniting two or more suction to a common inlet.
● these are "Y" shaped.
● each of two legs are fitted with male coupling and female coupling is attached to a third leg.
B) DIVIDING BREECHINGS:
● cast in gun metal, brass or bronze, these are used to divide one lines in to two.
● these are also "Y" shaped
● each of two legs has a female coupling and the third leg has a male coupling.
these are metal casting suitable for joining
● male - male coupling
● male - female coupling
● threaded - threaded
● threaded - interlocking coupling
● coupling - hydrant plug
MALE THREADED - FEMALE THREADED
MALE THREADED - MALE INTERLOCKING
FEMALE THREADED - FEMALE INTERLOCKING
● To facilitate crossing of vehicles over the charged delivery hoses, the ramps are placed over them.
● The ramps are so constructed as to have an angle of inclination on both sides.
● Ramps can be made to accommodate one or more hoses.
● These are made with wood or steel.
A) Elbow for Nozzle: This is a metal attachment fixed between the branch and the nozzle to deliver jets at right angles. These are useful in fighting smoky fires in basements.
B) Blank Cap: Metal cover which is attached to the delivery outlet or a suction inlet when not in use.
CENTRIFUGAL PUMP:
Definition: Centrifugal pump is a machine which raises water (or any liquid) from a lower level to higher level and from one place to another by the action of centrifugal force.
Centrifugal Force:
It is that force which acts upon a body moving in a circular path, tending to force it farther away from the centre of the circle in which it is moving.
II. WORKING PRINCIPLE:
When the rotating member of the pump (Impeller) gives fast rotary motion to a mass of the liquid contained in the casing surrounding it, the centrifugal force forces it out of the casing through the discharge outlet. The vacuum thus created makes atmospheric pressure to push in more water into the casing through the center, called the "eye" of the impeller.
CONSTRUCTION:
The pump has two main components:
· Impeller
· Casing
Impeller:
· It is the only moving part in the pump.
· The vanes of the impeller extend from the Centre of rotation to the periphery.
· These vanes are closed by means of two discs one on each side.
· These discs are called shrouds. The vanes are curved slightly forward fin the same direction as that of rotation).
· It has a round opening in the Centre which is called 'eye' of the impeller.
· The main function of the impeller is to provide high velocity to the mass of water entering through its eye.
The Casing:
· The casing is the enclosure in which impeller rotates.
· This is so designed as to reduce the turbulence created by the water as it is discharged in the volute which steadily increases in diameter till it reaches the delivery outlet.
· The main function of the casing is to convert velocity energy into pressure energy.
· The high-pressure liquid in the volute recalculates behind the shroud of the impellor causing an end thrust tending to force the impellor off the shaft.
· A thrust ball bearing is installed to counteract this force.
Motor:
· The pump is connected to a motor (Electric or diesel engine) by means of a shaft with the help of a coupling joint.
· To prevent leakage of water a mechanical seal is provided between the casing and the shaft It is also done by providing a packing of fire resistant material such as asbestos called "gland packing".
· A small leakage is retained in this case to prevent its damage by the factional heat.
VITAL PARAMETERS:
Capacity: The quantity of fluid discharged per unit lime. E.g. Liters/Minute or Gallons/Minute.
Head: The increase in pressure e.g. kg/cm2.
Power: The energy consumed by the machine e.g. KWH
Efficiency: The ratio of the energy supplied to the fluid by the machine and the energy supplied to the machine
CHARACTERISTICS:
· At any given speed, when there is no flow the discharge pressure is at the maximum.
· The pressure decreases progressively with an increase in the discharge rate.
· Both pressure and flow increase with the increase in speed and vice versa.
· The power absorbed by the machine increases as the flow increases and vice versa.
· Keeping the revolutions per minute constant the discharge flow rate fails as the suction lift increases.
ADVANTAGES OF CENTRIFUGAL PUMP OVER OTHER PUMPS
· Uniform Flow
· Less Cost
· Occupies less space
· Less maintenance
· Low running cost
· Easy installation
· Simple construction
· Greater Capacity
· Flow can be stopped without stopping power
· Easy Operability