AFSA Technical Challenges

May/June 2021 Answers and Explanations

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 to see if this exercise meets its criteria. For apprentice fitters, working these problems enforces lessons that should be learned through an apprenticeship program and explains how requirements from the standard are applied in the field.

Below are the questions and possible answers for the May/June 2021 technical challenges, with the correct answer in bold. An explanation for each answer follows.

AHJ CHALLENGE

The following questions are based on NFPA 13, Standard for the Installation of Sprinkler Systems, 2019 edition.

1. When witnessing the flushing of underground piping, what is the minimum acceptable velocity to flush the piping of debris?
A. 15 ft/s
B. 10 ft/s
C. 20 ft/s
D. 5 ft/s

Answer Explanation: NFPA 13 section 6.10.2.1.3 says the minimum flow rate must be according to Table 6.10.2.1.3 which provides a minimum acceptable flow that will achieve a velocity of at least 10 ft/s.

2.  When flushing underground piping what is the minimum acceptable flow rate that 6-in. piping needs to achieve a velocity of 10 ft/s?
A. 880 gpm
B. 610 gpm
C. 1560 gpm
D. 390 gpm

Answer Explanation: NFPA 13 Table 6.10.2.1.3 calculates a flow of 880 gpm for 6-inch pipe.

3. What is the maximum allowed pressure drop in PSI that is allowed when performing a hydrostatic test on 6-in. C900 PVC piping?
A. 0 psi
B. 2 psi
C. 5 psi
D. 10 psi

Answer Explanation: NFPA 13 Section 6.10.2.2.2 says an acceptable test result is determined by the indication of either a pressure loss less than 5 psi or no visual leakage.

4. Who is responsible for notifying the sprinkler contractor of corrosive conditions of the water supply?
A. The AHJ
B. The water municipality
C. The person who performed the water flow test
D.The owner

Answer Explanation: NFPA 13 section 5.1.5.2 says where conditions that contribute to corrosion are found the owner shall notify the sprinkler system installer of said conditions.

DESIGNER CHALLENGE

The following questions are based on NFPA 13, Standard for the Installation of Sprinkler Systems, 2019 edition, NFPA 22, Standard for Water Storage Tanks for Fire Protection, 2018 edition, and NFPA 291, Recommend Practice for Fire Flow Testing and Marking of Hydrants, 2019 edition.

1. What additional coefficient is required to be used when a pumper outlet with a smooth rounded outlet is utilized for a waterflow test and the pitot reading is 8 psi?
A. 0.7
B. 0.747
C. 0.83
D. 0.9

Answer Explanation: Table 4.8.2 in NFPA 291 requires the use of an additional coefficient when the pumper outlet is utilized. A smooth and round outlet required an initial coefficient of 0.9, but that must be multiplied by 0.83, which is required when the pitot reading from a pumper outlet (4.5 in.) is greater than or equal to 7 psi in accordance with Table 4.8.2.

2. A waterflow test is required to be conducted within 12 months of what project milestone?
A. Start of installation
B. System acceptance
C. Working plan submittal
D. Permit application

Answer Explanation: NFPA 13, 2019 requires waterflow tests to be within 12 months of the working plans submittal or another timeframe approved by the AHJ per section 4.6.1.1.

3. What is the minimum size of a fire main that supplies a fire hydrant?
A. No minimum, per hydraulic calculations
B. 4 in.
C. 6 in.
D. At least the size of the system riser

Answer Explanation: NFPA 13, 2019 section 5.1.3.2 requires fire mains that supply a hydrant to be at least 6 in. in diameter.

4. A break tank is proposed to supply an ESFR system protecting a Class II commodity stored up to 12 ft. If the system demand is 1,000 gpm, what is the required refill rate if the tank capacity is 40,000 gal and the fire pump’s rated flow is 750 gpm?
A. 367 gpm
B. 750 gpm
C. 1,100 gpm
D. 1,125 gpm

Answer Explanation: This is the example that was explained in the Sprinkler Age article “Give Me a Break (Tank).” An ESFR system protecting a Class II commodity stored up to 12 ft requires a 60 min duration per NFPA 13-2019 Table 20.12.2.6 and since the break tank can supply 30 minutes of that duration, the refill lines can be sized per NFPA 22-2018 section 14.5.2.2.1.

FITTER CHALLENGE

All questions are based on NFPA 13, Standard for the Installation of Sprinkler Systems, 2019 edition.

1.  A new sprinkler system is being connected to a new underground water supply. What document must a sprinkler contractor have in their possession before making the connection?
A. Copy of NFPA 13
B.  Copy of the signed and witnessed underground test certificate, indicating a full flush and hydrostatic test has been completed and accepted by the AHJ
C.  Copy of the signed and witnessed aboveground test certificate, indicating a hydrostatic test has been completed and accepted by the AHJ
D.  Copy of the underground water supply permit and approved shop drawings

Answer Explanation:  6.10.2.1.1 Underground piping, from the water supply to the system riser, and lead-in connection to the system riser, and lead-in connections to the system riser, including all hydrants, shall be completely flushed before connection is made to downstream fire protection system piping.

2.  True or False: A hangar is defined as a device or assembly used to support the gravity load of the system piping.

Answer Explanation:  3.3.89 Hanger. A device or assembly used to support the gravity load of the system piping.

 3. True or False: A spring-loaded check valve can be installed in the vertical flow down direction.

Answer Explanation:  16.9.5.4 Check valves shall be installed in a vertical (flow upwards) or horizontal position in accordance with their listing.

4. True or False: An arm-over is defined as a horizontal pipe that extends from the branch line to a single sprinkler or a sprinkler above and below a ceiling.

Answer Explanation: S3.3.7 Arm-Over. A horizontal pipe that etens from the branch line to a single sprinkler or a sprinkler above and below a ceiling.

ITM CHALLENGE

All questions are based on NFPA 25, Standard for the Inspection, Testing, and Maintenance of Water-Based Fire Protection Systems, 2020 edition.

1. Listed corrosion-resistant sprinklers exposed to harsh environments, including corrosive atmospheres shall be permitted to be tested at what frequency?
A. 3 years
B. 5 years
C. 10 years
D. 15 years

Answer Explanation:  5.3.1.1.3 Listed corrosion-resistant sprinklers installed in harsh environments shall be permitted to be tested on a 10-year basis.

2. Compressors that require oil for lubrication shall have the oil replaced at what frequency?
A. Semi-annually
B. Annually
C. According to manufacturer’s specifications
D. Annually, unless manufacturer’s specifications require the oil to be changed more frequently

Answer Explanation: 13.10.4.2 Compressors requiring oil shall have the oil replaced on an annual basis unless the manufacturer’s instructions require more frequent replacement.

3. While conducting an annual forward flow test of a backflow preventer you are unable to achieve the required minimum flow. How would you record your finding?
A. Noncritical deficiency
B. Critical deficiency
C. Impairment
D. Classification of this finding is not
addressed in NFPA 25

Answer Explanation: The minimum required flow for a backflow preventer is the system demand. If that cannot be achieved, then there is not enough water being supplied to the fire protection system. This is an impairment listed in Table A.3.3.8.

4. While conducting a monthly inspection of a dry pipe system you notice the control valve to the accelerator is in the closed position and not communicating with the system piping. How would you classify your finding?
A. Noncritical deficiency
B. Critical deficiency
C. Impairment
D. Classification of this finding is not addressed in NFPA 25

Answer Explanation: This is a critical deficiency listed in Table A.3.3.8.

WANT TO PARTICIPATE?

You can take part in future technical challenges! Look for the July/August 2021 issue of Sprinkler Age hitting your mailbox and online in mid-July! Questions will appear in that issue and answers will be posted online. Test your knowledge today and you might just win some industry swag!


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