Ch. 5 Hydraulics Flashcards Preview

HOT > Ch. 5 Hydraulics > Flashcards

Flashcards in Ch. 5 Hydraulics Deck (25)
Loading flashcards...

Study of the factors that influence how the water gets to the fireground.



6 physical facts that apply to water

1)Pressure perpendicular to SURFACE on which it acts
2)Pressure in a confined body of water at rest is the same at all POINTS
3)Pressure of fluid in open container is proportional to its DEPTH
4)Pressure of water in open container is independent of the SHAPE and VOLUME. Depends solely on depth.
5)Pressure of fluid exerts is proportional to DENSITY of fluid
6)Pressure on confined fluid is transmitted EQUALLY throughout that fluid


For every foot of height that water rises, it exerts ________. This is known as ______.

.434 psi of force

Head Pressure


1 psi pushes a column of water up ______.

2.3 ft


Weight of air is equivalent to the pressure exerted by _______ of water or _______.

33.9 ft

14.7 psi (1 atm)


Most common form of resistance to flow is ______. Only _______ of this loss is due to friction. Remainder is loss due to ________.

Friction loss

A fraction
Turbulence within the stream itself


At low flows, there is almost no turbulence, and all of the water molecules move along quite smoothly, which is called ______.

Laminar flow


With friction loss, there is a _____ relationship-_______ the length ______ the friction loss.


Doubling, doubles


Supply capabilities include friction loss, ______, _____ and _______.

Capacity of pump
Capacity of water supply source
Capacity of the hose


_______ is no indicator of the volume of water available from a hydrant.

Static pressure
*misleading and of little use to firefighters*


Second type of pressure is _________.

Flowing pressure
*not residual*


Low-flowing pressure often indicates the pumper should be placed _________ rather than _________ using an inline hose stretch. This is a good policy for all but the _______________.

Near the hydrant, near the fire

Initial-arriving engine company


Minimal residual pressure is _____.

10 psi


You must take action to keep the pressure from going below 10 psi. There are two possible actions to take: _______________ or _____________.

Reduce the discharge flow (Not desirable).
Increase the supply with another source (May be impossible or impractical)


At a house fire, __________ takes priority over __________.

Speed of water delivery.
The gpm delivered


A means for a second pumper to connect to the hydrant and relay the extra available water to the first pumper.

Four-way hydrant valve OR a clappered Siamese


Models of Pumpers
500 gpm are ______, 750 and 1,000 gpm are _____ and 1,500 to 2,000 gpm are _______.

Extremely rare (500).
Found far less frequently (750-1,000).
Very common (1,500-2,000)


NFPA 1961 recommends a maximum discharge pressure of _______ for LDH.

200 psi


One advantage of LDH is _____________.

Rapid deployment and return to service with minimum personnel


Most efficient method of water delivery is ________, where the pumper is located _______________.

Positive pumping
On the hydrant


When fire exceeds the capability of a handline, a _________ is often brought into play. One of the most common reasons for doing this is that ____________.

Master stream
Fire has extended into the cockloft
*water on fire from underneath*


Advantages of tower ladder basket (2)

Basket on the ground with ability to move
Range of motion of stream


Advantages of using flow meter (2)
*conjunction with pressure gauge*

If kink develops, pump operator can fix.
Hose of unknown length stretched. Knowing type of nozzle to be supplied, simple matter to dial up the proper flow.


Ensuring proper volume of water is available

Water supply


With splitting flows into two lines, friction loss is only ______ of same flow in a single line. By splitting among three lines, the friction loss is only _______ of the one line loss.

25-35% (2)

10-15% (3)