When creating a welded outlet on sprinkler piping, a hole is cut into the run of the pipe. The piece of metal removed, known as a disc or coupon, can fall into the pipe. NFPA 13 explicitly requires that these discs be retrieved. This is a critical step to prevent the disc from traveling through the piping system and causing an obstruction at a fitting, valve, or sprinkler head, which could critically impair system performance during a fire. This requirement ensures the waterway remains clear and unobstructed.

B. Steel plates shall be welded to the ends of piping or fittings: This describes one method for creating a welded cap, but it is not a general requirement applicable to all welding performed on sprinkler systems.

C. Fittings shall be modified: Modifying listed fittings is expressly prohibited. Field modifications can compromise the structural integrity and hydraulic characteristics of the fitting, voiding its listing and approval for use.

D. Fittings can penetrate the internal diameter of the piping: This is incorrect. Welded outlet fittings are explicitly forbidden from penetrating the internal diameter of the pipe, as this would create a flow obstruction and a potential snag point for debris.

1. NFPA 13, Standard for the Installation of Sprinkler Systems (2022 Edition).

Section 7.5.2.4.2: "Discs shall be retrieved." (Supports Answer A)

Section 7.5.2.4.4: "Fittings or shaped nipples shall not penetrate the internal diameter of the pipe." (Refutes Answer D)

Section 7.5.2.5: "Fittings shall not be modified." (Refutes Answer C)

2. SFPE, Handbook of Fire Protection Engineering (5th Edition).

Chapter 20, "Automatic Sprinkler Systems," Section 20.5.1, "Piping." This section discusses installation standards and adherence to NFPA 13, which includes the specific welding requirements for maintaining a clear waterway, such as the retrieval of welding coupons (discs) to prevent system obstruction. (DOI: https://doi.org/10.1007/978-1-4939-2562-420)

The minimum size for the horizontal member of a trapeze hanger is determined by the size of the pipe being supported and the span of the trapeze. According to NFPA 13, Standard for the Installation of Sprinkler Systems, specific sizing tables must be used. For a trapeze hanger constructed of Schedule 40 steel pipe with a span of 8 ft (2.4 m) that is intended to support a 4 in. (102 mm) sprinkler main, the standard requires the trapeze pipe to have a minimum nominal diameter of 2 in. (50 mm). This ensures the hanger can adequately support the load without excessive deflection or stress.

A. 1.5 in. (40 mm): Per NFPA 13 tables, a 1.5 in. Schedule 40 trapeze pipe with an 8 ft span can only support a maximum pipe size of 3 in., which is insufficient.

C. 2.5 in. (65 mm): While a 2.5 in. pipe would be strong enough, it exceeds the minimum size required by the standard, making it an incorrect choice for this question.

D. 3 in. (75 mm): A 3 in. pipe is significantly oversized for this application and is not the minimum required diameter according to the prescriptive tables in NFPA 13.

1. NFPA 13, Standard for the Installation of Sprinkler Systems (2022 Edition). Chapter 17, Hangers. Table 17.4.4.3.1, "Trapeze Hanger Sizing for Schedule 40 Steel Pipe as the Trapeze." The table shows that for a "Span of Trapeze" of 8 ft, a "Nominal Pipe Size of Trapeze Hanger" of 2 in. corresponds to a "Maximum Pipe Size Permitted" of 4 in.

2. NFPA 13, Standard for the Installation of Sprinkler Systems (2019 Edition). Chapter 17, Installation of Hangers. Table 17.4.4.3.1, "Trapeze Hanger Sizing for Schedule 40 Steel Pipe as the Trapeze." This table provides the identical requirement as the 2022 edition for this specific scenario.

3. NFPA 13, Automatic Sprinkler Systems Handbook (2019 Edition). Chapter 17, Section A.17.4.4.3.1. The handbook commentary explains that the values in Table 17.4.4.3.1 are based on engineering calculations to limit the deflection of the trapeze member to L/360, ensuring structural integrity. This confirms the basis for the required 2 in. pipe size.

Because the beams are 26 in. deep but are spaced only 7 ft (2.1 m) apart, the ceiling is classified by NFPA 13 as “obstructed construction – beams spaced 7 ft 6 in (2.3 m) or less.” When a standard upright sprinkler is installed in the center of every bay formed by such closely-spaced beams, NFPA 13 directs that the installation be treated the same as for a smooth ceiling; therefore the deflector distance limits in Table 8.6.4.1.1 (2016 ed.) or Table 10.2.4.2.1 (2019/2022 ed.) apply. That table permits a standard upright sprinkler deflector to be no more than 12 in. (300 mm) below the ceiling or roof deck. Hence the maximum permitted distance is 12 in. (300 mm).

A. 1 in. – This is the minimum allowed distance for uprights under the table, not the maximum.

B. 6 in. – Within the permitted range but not the maximum limit required by the question.

D. 22 in. – 22 in. is allowed only when sprinklers are placed below very deep beams (>12 in.) at the bottom of the beams, not when they are centered in each bay.

1. NFPA 13, Standard for the Installation of Sprinkler Systems, 2016 Edition.

• Table 8.6.4.1.1, “Deflector Distance Below Ceiling for Standard Sprinklers” (p. 93) – shows 1 in. min., 12 in. max.

• 8.6.4.1.2.1(1) (p. 95) – allows sprinklers between beams ≤ 7 ft 6 in apart to follow Table 8.6.4.1.1 limits.

2. NFPA 13, 2019 Edition.

• Table 10.2.4.2.1 (p. 124) – same 1-12 in. limits for standard uprights.

• 10.2.6.1.4(1) (p. 130) – classifies beams ≤ 7 ft 6 in apart as obstructed construction where sprinklers in each bay use Table 10.2.4.2.1 distances.

3. University of Maryland, FPE 623 “Sprinkler System Design,” Lecture 5, slide 12 (Spring 2022) – summarizes NFPA 13 deflector-to-ceiling limits for smooth and closely-spaced beam ceilings.

The relationship between flow rate (Q), pressure (P), and the sprinkler discharge coefficient (K-factor) is defined by the hydraulic formula Q = K√P. To find the K-factor, the formula is rearranged to K = Q / √P.

Given:

Flow (Q) = 65 gpm

Pressure (P) = 14.9 psi

Calculation:

1. Find the square root of the pressure: √14.9 ≈ 3.86

2. Divide the flow by this value: K = 65 / 3.86 ≈ 16.84

The calculated value of 16.84 corresponds to the nominal K-factor of 16.8.

A. 8.0 (115): A K-factor of 8.0 at 14.9 psi would only discharge approximately 31 gpm (8.0 × √14.9), not the required 65 gpm.

B. 11.2 (160): A K-factor of 11.2 at 14.9 psi would discharge approximately 43 gpm (11.2 × √14.9), which is significantly less than 65 gpm.

D. 25.2 (360): A K-factor of 25.2 at 14.9 psi would discharge a much higher flow of approximately 97 gpm (25.2 × √14.9).

1. NFPA 13, Standard for the Installation of Sprinkler Systems (2022 Edition). Section 27.2.2.1.1 explicitly states the formula for calculating the discharge from a sprinkler orifice as q = k√p, where q is the flow in gpm, k is the nominal K-factor, and p is the pressure in psi. The calculation performed directly applies this fundamental formula.

2. SFPE, Handbook of Fire Protection Engineering (5th Edition). Chapter 19, "Automatic Sprinklers," Section 19.4.1, "Sprinkler K-Factor," presents the orifice equation Q = K√P and defines the terms. This peer-reviewed source validates the formula used to determine the correct K-factor from the given flow and pressure.

3. Oklahoma State University, School of Fire Protection and Safety. Course FSE 3233, Fire Protection Hydraulics and Water Supply. Course materials on hydraulic calculations for sprinkler systems use the formula K = Q / √P as the basis for determining sprinkler performance characteristics. This is a standard application taught in accredited fire protection engineering programs.

NFPA 13 permits the “small-room design method” only for Light-Hazard occupancies whose room area does not exceed 800 ft² (74 m²) and whose walls run full height. Commercial kitchens are classified by NFPA 13 Table 4.3.2 as Ordinary-Hazard (Group 1). Because the kitchen’s hazard classification is not Light-Hazard, it cannot qualify as a “small room,” regardless of its 700 ft² (65 m²) size or its 2-hour rated walls.

A. Size limit met, but rule restricted to Light-Hazard; Ordinary-Hazard kitchen disqualifies.

B. 700 ft² is below 800 ft²; size is acceptable, not “too large.”

C. Wall fire-rating is irrelevant; requirement is Light-Hazard occupancy, not 1-hour construction.

1. NFPA 13, Standard for the Installation of Sprinkler Systems, 2022 ed.

• Sec. 28.4.4.2.1: “Small-room design method shall be permitted only in Light-Hazard occupancies… Room area shall not exceed 800 ft² (74 m²).”

2. NFPA 13, 2022 ed., Table 4.3.2, “Classification of Occupancies and Commodities”: lists “Kitchen, commercial” under “Ordinary Hazard (Group 1).”

3. NFPA Fire Protection Handbook, 21st ed., Vol. I, Ch. 12, p. 12-136: discussion of small-room rule notes limitation to Light-Hazard occupancies.

According to NFPA 20, the field acceptance test for a fire pump with a variable speed pressure limiting control must be conducted in the variable speed mode. The standard explicitly mandates that the pump's performance be verified at three critical points: no-flow (churn), 100 percent of its rated flow, and 150 percent of its rated flow. This three-point test ensures the pump and its controller can deliver the required performance across the entire operational curve while effectively limiting pressure as designed.

A. This option is incomplete as it omits the 150% rated load test, which is a mandatory point for verifying peak performance.

C. This option includes an additional test point (50%) that is not required by the standard for minimum acceptance criteria.

D. This option lists multiple test points that are not mandated by the standard for acceptance, making the procedure unnecessarily extensive.

1. NFPA 20, Standard for the Installation of Stationary Pumps for Fire Protection, 2022 Edition, Chapter 14, Section 14.2.6.2.7. This section states, "For pumps with variable speed pressure limiting control, the pump shall be tested in variable speed mode at no flow, 100 percent of rated load, and 150 percent of rated load."

According to NFPA 20, Standard for the Installation of Stationary Pumps for Fire Protection, a centrifugal fire pump must meet three critical performance points on its characteristic curve. One of these points is the overload condition. At 150 percent of its rated capacity (flow), the pump must be capable of providing not less than 65 percent of its total rated head (pressure). This requirement ensures that the pump can still deliver adequate pressure to the system even when flowing a significantly higher volume of water than its nominal rating, which is crucial during a large fire event.

A. 50%: This pressure is below the minimum performance threshold required by NFPA 20 for the 150% flow condition.

C. 100%: This is the minimum pressure required at 100% of the rated flow, not at the 150% overload condition.

D. 120%: This value is typically associated with the maximum allowable pressure at churn (zero flow), not a minimum at 150% flow.

1. NFPA 20, Standard for the Installation of Stationary Pumps for Fire Protection, 2022 Edition.

Section 4.10.2.1: "A centrifugal fire pump for fire protection shall be selected to furnish not less than 150 percent of rated capacity at not less than 65 percent of total rated head."

2. Isman, K. E. (2017). Fire Protection Hydraulics and Water Supply Analysis (3rd ed.). Fire Protection Publications, Oklahoma State University.

Chapter 10, Fire Pumps, Page 318: "The NFPA 20 standard requires that all fire pumps have a characteristic curve with three specific points. ... The third point is at 150 percent of the rated flow. At this point, the pump must be able to produce at least 65 percent of the rated pressure."

3. SFPE Handbook of Fire Protection Engineering (5th ed.). (2016). Springer.

Chapter 21, Water-Based Fire Protection System Design, Section 21.5.2.1, Pump Characteristics: "NFPA 20 requires that the pump characteristic curve have a shape such that at 150 % of rated flow, the head is at least 65 % of rated head." (DOI: https://doi.org/10.1007/978-1-4939-2562-421)

The relationship between flow rate (Q), pressure (P), and a sprinkler's orifice constant (K-factor) is defined by the hydraulic formula Q = K√P. To find the required pressure, this formula must be rearranged to solve for P, resulting in P = (Q/K)².

Given:

Flow (Q) = 17 gpm

K-factor (K) = 4.2

Calculation:

P = (17 gpm / 4.2)²

P = (4.0476)²

P ≈ 16.38 psi

Therefore, a pressure of 16.38 psi is required to deliver 17 gpm from a 4.2 K-factor sprinkler.

A. 4.52 psi (0.31 bar): This value is the result of an incorrect mathematical calculation and does not follow the standard hydraulic formula P = (Q/K)².

B. 9.22 psi (0.63 bar): This result is mathematically incorrect. It may stem from a misapplication of the formula, such as incorrectly manipulating the square root or the variables.

D. 36.86 psi (2.54 bar): This value is significantly higher than the correct pressure and represents a substantial error in applying the hydraulic calculation formula.

1. NFPA 13, Standard for the Installation of Sprinkler Systems (2022 ed.). Section 28.2.2.1, "Sprinkler Discharge," explicitly provides the formula for determining the pressure (p) required for a specific flow (q) from a sprinkler with a known K-factor (k): p = (q/k)².

2. SFPE, Handbook of Fire Protection Engineering (5th ed.). Chapter 21, "Automatic Sprinkler System Calculations," Section 21.3.1, "Hydraulic Calculation Principles." This section details the fundamental orifice flow equation used for sprinkler calculations as Q = K√P, which is the basis for the calculation performed. (DOI: 10.1007/978-1-4939-2562-421).

According to NFPA 13, standard-weight Schedule 40 steel pipe has sufficient wall thickness to be joined by threading without requiring a special listing for the fittings. The process of cutting threads removes material, and thinner-walled pipes, such as Schedule 5, 7, or 10, would be structurally compromised by standard threading methods. While thin-wall pipe can sometimes be joined with threads, it requires the use of fittings that are specifically listed for that particular pipe and application, which constitutes a "special listing" requirement. Schedule 40 pipe is the baseline standard for which conventional threaded fittings are designed and approved.

A. Schedule 5: This thin-wall pipe lacks the necessary wall thickness for standard threading and would require specially listed fittings for such a connection.

B. Schedule 7: Similar to Schedule 5, this is a thin-wall pipe that cannot be joined with standard threaded fittings without a specific listing.

C. Schedule 10: This pipe has a wall thickness less than Schedule 40 and is not permitted to be joined by threading unless using specially listed fittings.

1. NFPA 13, Standard for the Installation of Sprinkler Systems (2022 Edition).

Section 7.5.2.1: "Steel pipe with a wall thickness less than Schedule 30 (in sizes 8 in. and larger) or a wall thickness less than Schedule 40 (in sizes smaller than 8 in.) shall not be joined by threading." This establishes Schedule 40 as the minimum for standard threading in common pipe sizes.

Section 7.5.2.2: "Where the pipe is threaded and the fittings are listed for use with that specific pipe, the minimum pipe wall thickness shall be in accordance with the listing." This clause confirms that thinner pipes (like Sch. 10) require a special listing.

2. SFPE Handbook of Fire Protection Engineering (5th Edition).

Chapter 20, Section 20.4.1, "Pipe and Tube": This section discusses piping materials for automatic sprinkler systems, noting that "Schedule 40 is the most common pipe schedule used for threaded steel pipe systems." It further explains that lighter-weight pipes like Schedule 10 are typically joined by grooving or welding due to their thin walls. (Springer, 2016, pp. 20-12). DOI: https://doi.org/10.1007/978-1-4939-2562-420