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Dec 6, 2023

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Ch. 5 Review Questions 1. What measurable characteristics of a water supply must be deemed sufficient before a fire protection system can adequately protect a hazard? A: The fire flow, which is the number of gallons of water per minute the fire department will need at a particular location to manually fight a fire. 2. Discuss the different water supply systems that provide water to the supply network. A: A pumped system supplies water from a lower elevation than the location served, which requires a pump to generate sufficient suction to draw water into the supply network. A gravity system supplies water from a higher elevation, which eliminates the need for pumping equipment because the water flows into the network at sufficient pressure. A combined water supply system utilizes both gravity and pumps. 3. Why is it so important to ensure that fire mains only supply water to fire protection systems and fire hydrants? A: Because other connecting systems would deplete the water supply to the fire protection system. 4. Why is it important that fire mains are the correct size? A:Because fire mains must be large enough to meet the demands of the water-based fire protection system. 5. Discuss the different types of control valves found on private water systems. A: A post indicator valve (PIV)is a valve with a freestanding post that houses the stem extension of an underground valve control. A wrench is used to open and close the valve. A wall post indicator valve (WPIV) is similar to a PIV, but instead of sticking out of the ground, a WPIV mounts on the side of a building, with the valve stem feeding through the wall and connecting to the valve body located inside the building. Additionally the WPIV is opened and closed with a wheel. An outside screw and yoke valve (OS&Y) is a valve operated by turning a wheel attached to a yoke coupled to a threaded stem. When the wheel is turned, the stem rises or falls according to the turning direction and positions the gate within the valve. 6. Name and describe the different types of valves used to control the water flow in a water supply network. A: A check valve is one type of valve that is used. The main purpose of the check valve is to prevent water from flowing out of the system and back into the network. Another type of valve that controls water flow is a backflow prevention device. These types of valves greatly reduce the chance of water flowing back into the supply network. 7. Compare and contrast the different types of hydrants. A: Dry barrel hydrants are common in areas that have below freezing temperature, while wet barrel hydrants are common in areas that are above freezing temperature. Both hydrants typically have one large nozzle and two smaller nozzles. 8. Why is it important to perform periodic water flow testing on a water-based fire protection system after the system’s installation? A: Testing of the system might help to determine if there are impairments to the system, if the distribution system infrastructure needs to be improved, or if the water-based fire protection system design needs to be reevaluated. It also ensures the water supply is

delivering the minimum required flow and pressure that the system was designed to provide. 9. What role do static and residual water pressures play in the design of a water-based fire protection system? A: Static and residual water pressures give the fire protection system design professional an idea if there is adequate pressure that can support the design in that part of the community. 10. What options are available to a fire protection system designer when it is determined that the water pressure is inadequate to support the design? A: THe installation of a gravity tank, pressure tank, or stationary fire pump in conjunction with the municipal/public network water supply or natural water sources. 11. What are the two types of fire pumps listed and approved for fire service duty? How do they differ? A: The two types of fire pumps are centrifugal type and positive displacement type. The centrifugal pump creates pressure by drawing water into the center of a precision manufactured disk-shaped piece of metal called the impeller. Positive displacement pumps operate at a specific speed to deliver a predetermined pressure and constant rate of flow. Positive displacement pumps are well suited for high-pressure applications, but unlike centrifugal pumps, which deliver and maintain a maximum head pressure, the positive displacement pump can build unwanted pressure on the discharge side of the pump if the flow continues but is not able to discharge. 12. Why is it important to have a data plate attached to a fire pump? A: Because a data plate states all of the important pump performance information so that this information is available when evaluating the pump. 13. When a fire pump is running at peak load, how much flow and pressure relative to the total rated head should it be able to generate? A: It should be able to generate 150 percent of the rated flow at 65 percent of the rated pressure. 14. What are the major components of a fire pump assembly besides the fire pump? A: A fire pump assembly is made up of the driver, controller, in some installations a transfer switch, and a number of additional components, fittings, valves, and devices. 15. Why do some insurance companies prefer a diesel driver to an electric driver? A: Because they believe they are more reliable because they are self contained units. 16. What is the purpose of a pressure maintenance pump? A: A pressure maintenance pump’s purpose is to boost and maintain the system pressure above the fire pump start-pressure setting in order to avoid frequent fire pump operation and excessive component wear that could lead to repeated maintenance and costly repa irs. 17. Why is it so important to have relief valves on a fire pump? A: Because relief valves relieve excessive system pressure and stabilize the system output pressure. 18. What is the purpose of a fire pump bypass?

A: A fire pump bypass provides a path for the water in case of fire pump failure. 19. When determining the water supply demand for a water-based fire protection system at a particular location, what role does the fuel load play? A: As fuel load increases at a particular location, there is a higher water supply demand for a water-based fire protection system. 20. How does friction loss affect a water supply and what are some of the ways to overcome it? A: Friction loss is the progressive loss of water pressure that results when water flows away from the source and through a hose, pipe, pipe fittings, and water meters. Creating loops and grids in the water distribution network are ways to overcome friction loss. 21. Why is it so important to have an accurate water flow test when designing a water-based fire protection system? A: Because if not properly performed, the data will be inaccurate and the water-based fire protection design may be flawed. 22. What is the purpose of calculating fire flow for a particular location? Should reductions in the calculated fire flow be permissible if a partial or full fire sprinkler system protects a structure? A: The purpose is to determine if the delivery system is adequate for manual firefighting. Some needed fire flow models permit reducing the calculated flow by 50 percent when an NFPA 13 sprinkler system is installed or base the needed fire flow on the fire sprinkler and hose system demand if greater than the calculated needed fire flow rate.

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