Pump Operations Flashcards
What is the most important component of the Engine?
The fire pump
What are pumps rated by?
Pumps are rated by gallons per minute (gpm)
What are the pumps to be tested at?
- 150 pounds per square inch (psi) at 100 percent of rated capacity
- 200 psi at 70 percent of rated capacity
- 250 psi at 50 percent of rated capacity
There are many types of pumps that are used throughout the fire service. What is the most common, and the one that is used by the EOFD?
The Centrifugal Pump.
What is a Centrifugal Pump?
Fire apparatus pumps use centrifugal force to deliver water to the fireground. Centrifugal force is an outward force associated with rotation. The rotation in a fire apparatus pump is powered by the same transmission output shaft
that powers the drive axle. A centrifugal pump
impeller slings liquid out of the volute creating pressure as it moves into the discharge piping. Water pressure develops in a pump volute when water accumulates faster than it can escape into a discharge. Centrifugal pumps can be classified into single or multiple stages (single or multiple impellers). A common misconception is that increasing pump pressure also increases volume, however this is not always correct. A fire pump cannot “make” water; it can only pressurize the supply it receives.
What is a single stage pump?
Single stage pumps use a single impeller to produce water pressure. There are no Volume/Pressure (Series/Parallel) Transfer valves to manipulate. Single stage fire pumps usually have larger impellers than Two-Stage Pumps to generate the desired volume and pressure combinations. For example, the Hale QMax pump on Engine 1 uses a single double suction bronze impeller capable of pumping 1500 GPM with the use of multiple intakes. Impellers of pumps are classified based on the number of points that the liquid can enter the impeller and the amount of
webbing between the impeller blades. Impellers can be either single or double suction. A single suction impeller allows liquid to enter the center of the blades from only one direction. A double-suction impeller allows liquid to enter the center of the impeller blades from both sides simultaneously and thus generate higher water flows. The impeller on the Hale QMax pump has an enclosed impeller. This enclosed impeller (also called a shrouded impeller) has circular plates attached to both sides of the blades.
What 4 Engine apparatus has a Single Stage Pumps
- Engine 1 (Currently Engine 5)
- Quint 2
- Engine 4
- Engine 6 (Luverne’s)
What is a two stage pump?
Two stage pumps were the standard in the Fire Service for many years and some departments still use them. Some EOFD reserve apparatus may still have a two-stage arrangement. The primary difference between the two stages is the volume of water pumped at a range of pressures. Pumps are transitioned between Pressure and Volume Modes using pump panel mounted Transfer Valve Controls.
Pressure Mode?
When the pump is in Pressure mode, a Transfer Valve located on the Engine Pump Panel closes clapper valves on one side of the intake piping, and one side of the discharge piping. These Clapper valves direct water into a “series” of two sequential volutes, hence this mode may also be referred to as Series. Water enters the first volute and gains pressure from the spinning impeller. This pressurized water exits the first impeller and enters the second volute where a second impeller further boosts the pressure before the water is routed to the discharge manifold. This mode is used where higher discharge pressures are needed due to friction loss, elevation loss, or other factors that mandate pressure over volume. Higher pump pressures do not equate to higher volumes of water. Pressure mode is not appropriate for pumping more than one-half of a pump’s
rated capacity. Pressure mode provides higher pressures at a cost of lower capacities.
Volume Mode?
When the pump is in Volume mode, all the clapper and change- over valves are open and intake water is distributed evenly to both impellers at the same time. The two impellers are operating in parallel to each other to feed water to the discharge manifold, hence this mode may also be referred to as Parallel. Volume Mode delivers the maximum flow capacity available from a pump. This volume is provided at a cost of lower operating pressure. Volume Mode should be used when pumping more than one-half the rated capacity of a pump. It should be used during defensive operations (i.e., Master Streams) and when drafting.
Explain Transitioning between Pressure and Volume Modes
Typically, the mode should be set at the start of pumping operations before throttling up. If conditions change and require a transition between modes, the Net Pump Pressure (NPP) must not exceed 50 psi. NPP is the mathematical difference between intake and discharge pressure. For example, if intake pressure is 150 psi and discharge pressure is 200 psi, NPP is 50 psi, and it is safe to transition between Pressure and Volume modes.
What two Apparatus with Two Stage Pump in EOFD?
- Engine 5 (Pierce) Spare apparatus
- Engine 3 (Smeal/Spartan)
PRESSURE CONTROL DEVICES:
The EOFD has a variety of pressure management systems to regulate the pressure supplied to and discharged from the apparatus to ensure safety and deliver predictable water flows. The movement of water inevitably results in pressure fluctuations that can damage equipment, increase/decrease water flow, or cause hoselines to become unmanageable. Regulation of pressure occurs in two primary ways. What are they?
- Automatic Relief Valves.
- Pump discharge pressure management devices.
Automatic Relief Valve
Automatic relief valves are generally intended to limit pressure extremes by
diverting water flow away from its destination. These valves are most often found on the main body of the pump, large diameter intakes, and large diameter discharges due to the energy created by large volumes of moving water.
Falls into two types
▪ Direct Acting- relief and adjustment mechanism located directly on the
piping
▪ Remotely Activated- relief valve located on the piping and the adjustment mechanism (pilot) is accessible on the pump panel
▪ Safety valve set at the factory to prevent excessive supply pressure or water hammer. Typically set to 125 - 150 psi
▪ Used to control a satisfactory residual pressure at the intake of the pump during a relay with changes in flow.
▪ Installed to limit pressure increases on the suction side of the pump.
•The Purpose of Discharge Relief Valve:
▪ Safety valve set at factory to prevent excessive pressure or water hammer being delivered from a specific discharge. This pressure is typically 185 psi.
