Fire Pump Theory And Operations

Question 1

JFRD engines are manufactured by and pumps are what kind?

What are they rated at?

Answer 1

Pierce
Midship mounted Waterous centrifugal pumps

Rated at 1500, 1750, 2000 GPM capacity

Question 2

Engines are powered by what?

Answer 2

6 cylinder turbo charged diesel motors, manufactured by caterpillar or Cummins

Question 3

Centrifugal pump

Answer 3

If equipped with two impellers, ( two-stage pump) they are mounted on a common shaft and rotate at the same speed RPM

Question 4

What is Impeller “flow through”

Answer 4

And allows water under pressure to pass through the Impeller when the pump is not engaged and the impeller is stationary.

A pressurized water supply to the pump can be distributed to the various discharges even with the pump disengaged

Question 5

What is slippage

Answer 5

Impeller will rotate continuously when the pump is engaged even when hose lines are shut down.

This “slippage” prevents a continuous rise and discharge pressure but can generate excessive heat within the pump

Question 6

Can centrifugal pumps, pump air?

Answer 6

No
Centrifugal pumps cannot pump air due to their open design. Air can cause loss of prime and inhibit the ability of the pump to build pressure

Question 7

Can pumps be operated dry?

Answer 7

No
The engineer must begin circulating water immediately after engaging the pump. running the pump dry for more than a few minutes may cause excessive heat and pump damage

Question 8

Centrifugal pump theory of operation

Answer 8

The centrifugal force theory states that a spinning object will exert force from the center towards the outer edge. It is this energy that propels water from the center, the eye, to the outer edge of the impeller veins

Question 9

What is the Volute

Answer 9

The impeller discharge water into the valute, the chamber which directs the pressurize water into the discharge manifold.

Question 10

How does the motor speed(RPM) increase PDP

Answer 10

As rpm increases, the velocity of the impeller increases. This results in a corresponding increase in PDP. As water enters the impeller‘s at a low pressure the centrifugal force of the rotating impellers increase pressure.

Question 11

Who does pump testing

Answer 11

Underwriters laboratories, UL, in accordance with NFPA 1911.

Question 12

What does the pump test measure

Answer 12

Volume, at three pressures while drafting. The volume at 150 psi is called the rated capacity.

Question 13

Can a Centrifugal pump, pump more than the rated capacity?

Answer 13

Yes, they can pump more than the rated capacity if supplied from a pressurized source.

Question 14

Two stage pumps, PRESSURE(series)

Answer 14

Each impeller provides pressure in series. Pressure produced by the first impeller is routed to the eye of the second impeller, where the pressure is increased further.

(In simple terms where a single impeller can produce 60 psi, two impellers operating in series can produce 120 psi at the same RPM)
*for high rise fires

Question 15

Pumps operating in VOLUME(parallel)

Answer 15

The supply is divided, and water is routed to both impeller‘s at the same time. Pressure produced by each impeller is the same but the volume of water is double with each revolution of the impeller.

(This allows the pump to move a greater volume of water at the same rpm)
* normal operating mode*

Question 16

Pressure mode(RPM)=

Answer 16

Maximum pressure,

High pressure needs such as a high-rise fire would require changing to pressure mode

Question 17

Volume mode =

Answer 17

Normal position of transfer valve. Will produce max pump performance for majority of scenarios

Question 18

How to minimize water hammer while using transfer valve

Answer 18

Reduce RPMs to idle before operating.

• however do not sacrifice hand lines already in use. If unable to lower pressure to idle reduce discharge pressure safe amount and operate the transfer valve slowly allowing time for governor to adjust

Question 19

Difference in operation of single and two stage pumps

Answer 19

Motor speed

(To pump high pressures in the single stage pump requires higher RPM. In most pumping situations there will be minimal difference in pump performance between a single stage and two stage pump. A single stage pump will operate much like a two stage pump and volume.)