September/October 2021 Technical Challenge Answers

How Did You Do?

Each issue, AFSA’s Engineering & Technical Services Department presents technical challenges. Besides testing yourself and your co-workers, these exercises are excellent preparation for professional certification tests and also may count as continuing education hours. Check with your certification organization.  Here are the answers for the September/October 2021 issue. 

AHJ Challenge

1. During acceptance testing, the hydraulic data nameplate indicates that the dry system has a capacity of 735 gallons. If the system is equipped with a quick opening device, what is the required water delivery time per NFPA 13?

Answer: D. Section 8.2.3.4 states a dry system with a capacity of 750 gallons or less and is equipped with a quick-opening device, shall not be required to meet any specific water delivery requirement.

2. In an office area, exposed 6-in. wood beams are spaced less than 3 ft. on center. What is the maximum area of coverage permitted for a standard spray upright sprinkler?

Answer: D. Table 10.2.4.2.1(a) states that combustible unobstructed or combustible obstructed with structural members spaced less than 3 ft. on center, shall be spaced no more than 130 sq. ft. per sprinkler.

3. Which ceiling type is required to have the deflector of standard spray uprights to be installed parallel to the ceiling instead of the floor?

Answer: D. Horizontal ceilings are permitted to have the sprinkler deflectors installed parallel to the floor; however, sloped ceilings (>2 in 12 pitch) must be installed parallel to the ceiling.
10.2.6.2 Deflector Orientation.
10.2.6.2.1 Unless the requirements of 10.2.6.2.2 or 10.2.6.2.3 are met, deflectors of sprinklers shall be aligned parallel to ceilings, roofs, hips, or the incline of stairs.
10.2.6.2.2 Where sprinklers are installed in the peak below a sloped ceiling or roof surface, the sprinkler shall be installed with the deflector horizontal.
10.2.6.2.3 Roofs having a pitch not exceeding 2 in 12 (16.7 percent) are considered horizontal in the application of 10.2.6.2, and sprinklers shall be permitted to be installed with deflectors horizontal.

4. When reviewing the plans for a hotel that is using residential sprinklers, you notice that there are four ceiling pockets that are 85 ft3 in size and are separated by 10 ft from other ceiling pockets. What is the maximum depth that the ceiling pocket can be to eliminate sprinklers from them?

Answer: A. Section 12.1.12.2 requires the ceiling pocket to meet four items:
1 – Less than a 100 Cu. Ft. in size,
2 – Depth cannot exceed 12 inches,
3- – The area around the ceiling pocket is sprinklered, and
4 – The finish of the ceiling pocket is limited or non-combustible.

Designer Challenge

1. The zone of influence on a lateral brace includes 36 ft of 2-in. Schedule 40 branch line pipe and 30 ft of 4-in. Schedule 10 cross main pipe. Each of the three branch lines contains six elbows and three caps. The cross main is a straight run with a cap at the end of the pipe. Determine the weight of the system being braced (Wp).

Answer: D.  18.5.9.2 The weight of the system being braced (Wp) shall be taken as 1.15 times the weight of the water-filled piping. (See A.18.5.9.1.)
2 in. Sch. 40 = 5.13 lbs/ft x 36 = 184.68 lbs
4 in. Sch. 10 = 11.78 lbs/ft x 30 = 353.4 lbs
W_p = 1.15*Weight of Water Filled Pipe
W_p = 1.15*(184.68+352.5)
W_p = 619 lbs.

2. What is the maximum length of a 11/2-in. Schedule 40 brace that has a slenderness ratio of 200?

Answer: B. See Table 18.5.11.8(b).

3. When using schedule 40 galvanized steel in a dry system with a nitrogen generator, what factor must be applied to the equivalent length of fitting when performing hydraulic calculations?

Answer: A. See Table 27.2.4.8.1 and Table 27.2.3.2.1. The 2019 edition does not have an allowance to utilize a C Value of 120 when a nitrogen generator is used. The 2022 edition currently permits a C Value of 120 to be used when 98% nitrogen purity is maintained throughout the lifecycle of the system and when the dry system is supplied by a listed nitrogen generator.

4. A sprinkler system is being upgraded with seismic bracing at AFSA headquarters (12750 Merit Drive; Dallas, TX 75251). Determine the minimum seismic coefficient (Cp) that is required to be utilized for the design of seismic protection. (Hint: visit https://seismicmaps.org/ to determine the Ss for any address.)

Answer: B. See Table 18.5.9.3. Any Ss value that is less than or equal to 0.33 will be assigned a Cp of 0.35. Texas is not an active seismic area and the Ss as determined by https://seismicmaps.org/ is equal to 0.104.

Fitter Challenge

1. True or False: In a five-story building with one 21/2-in. zone control assembly per floor located in the stair, a minimum 11/4-in. drain riser is required.

Answer: True. A minimum 1-1/2 in. drain riser is required. See Table 16.10.4.2 and 16.10.4.8 Where drain connections for floor control valves are tied into a common drain riser, the drain riser shall be one pipe size larger downstream of each size drain connection tying into it.

2. True or False: A water motor gong (mechanical operated waterflow alarm) may be connected to a dry pipe valve.

Answer: True. Since all manufactured dry valves have an alarm line supplied by an intermediate chamber, a water motor gong (mechanically operated alarm) can be connected.

3. True or False: An automatic air release valve is required to be installed on all wet pipe sprinkler systems.

Answer: False. Automatic air release valves are an option, but they are not required. 16.7* Air Venting. The vent required by 8.1.5 shall be located near a high point in the system to allow air to be removed from that portion of the system by one of the following methods:
Manual valve, minimum 1∕2 in. (15 mm) size
Automatic air vent
Remote inspector’s test valve
Other approved means

4. True or False: Where ESFR sprinkler systems are installed adjacent to sprinkler systems with standard-response sprinklers, a draft curtain of noncombustible construction and at least 1 ft in depth shall be required to separate the two areas.

Answer: False. 14.2.5.1 Where ESFR sprinkler systems are installed adjacent to sprinkler systems with standard-response sprinklers, a draft curtain of noncombustible construction and at least 2 ft (600 mm) in depth shall be required to separate the two areas.

ITM Challenge

1. A no-flow test of an electric driven vertical turbine fire pump shall be conducted at what frequency?

Answer: A. Weekly. 8.3.1.2.1 Except as permitted in 8.3.1.2.2 and 8.3.1.2.3, a weekly test frequency shall be required for the following electric fire pumps:
(1) Fire pumps that serve fire protection systems in buildings that are beyond the pumping capacity of the fire department
(2) Fire pumps with limited service controllers
(3) Vertical turbine fire pumps
(4) Fire pumps taking suction from ground-level tanks or a water source that does not provide sufficient pressure to be of material value without the pump
8.3.1.2.2 A monthly test frequency shall be permitted for electric fire pumps not identified in 8.3.1.2.1.
8.3.1.2.3* A monthly test frequency shall be permitted for electric fire pump systems having a redundant fire pump.
8.3.1.2.4* The test frequency shall be permitted to be established by an approved risk analysis.

2. Flow meters shall be calibrated to an accuracy level of +/- 3 percent at what frequency?

Answer: B. 8.3.3.5.3* Flow meters shall be calibrated annually to an accuracy level of +/- 3 percent.

3. Qualified personnel shall be able to respond to the pump location upon abnormal conditions when no-flow testing using remotely monitored automated testing in what period?

Answer: B. 8.3.2.10 Remotely Monitored Automated Testing. 8.3.2.10.4 Qualified personnel shall be able to respond to the pump location upon abnormal condition within 5 minutes.

4. While performing an operational test of a quick-opening device (QOD), you determine the QOD is not functioning correctly. How would you classify your finding?

Answer: B. Table A.3.3.8, Chapter 13: Valves, Valve Components, and Trim — Testing all be required to separate the two areas.


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