Location and Spacing of Sprinkler Technical Requirements

This article is about Location and Spacing of Sprinkler Technical Requirements in commercial buildings, plants and refinery projects related to Plumbing Engineering System as per international codes and standards.

Location and Spacing of Sprinkler Technical Requirements

General

1. The maximum area of coverage of any sprinkler shall not exceed 400 ft² (36m²) (NFPA 13 Para 4-5.2.2)
2. The maximum distance permitted between sprinklers shall be based on the center line distance between sprinklers on the branch line or on adjacent branch lines. The maximum distance shall be measured along the slope of the ceiling.(NFPA 13 Para 4-5.3.1)
3. The distance from sprinklers to walls shall not exceed one half of the allowable maximum distance between sprinklers. The distance from the wall to the sprinkler shall be measured perpendicular to the wall. (NFPA 13 Para 4-5.3.2)
4. A minimum distance shall be maintained between sprinklers to prevent operating sprinklers from wetting adjacent sprinklers and to prevent skipping of sprinklers. (NFPA 13 Para 4-5.3.4)
5. The distances between the sprinkler deflector and the ceiling above shall be selected based on the type of sprinkler and the type of construction. (NFPA 13 Para 4-5.4.1)
6. Deflectors of sprinklers shall be aligned parallel to ceilings, roofs, or the incline of stairs.(NFPA 4-5.4.2)
7. Sprinklers shall be located so as to minimize obstructions to discharge, or additional sprinklers shall be provided to ensure adequate coverage of the hazard.(NFPA 13 Para 4-5.5.1.1
8. Continuous or noncontinuous obstructions that interrupt the water discharge in a horizontal plane more than 18″” (457 mm) below the sprinkler deflector in a manner to limit the distribution from reaching the protected hazard shall comply with Item 87, 88, and 89. (NFPA 13 Para 4-5.5.3)

9. Sprinklers shall be installed under fixed obstructions over 4 ft (1.2 m) wide such as ducts, decks, open grate flooring, cutting tables and overhead doors.

   Exception: Sprinklers shall not be required under obstructions that are not fixed (NFPA 13 Para 4-5.5.3.1) “

10. Sprinklers installed under open gratings shall be of the intermediate level/rack storage type or otherwise shielded from the discharge of overhead sprinklers. (NFPA 13 Para 4-5.5.3.2)
11. The clearance between the deflector and the top of storage shall be 18″” (457 mm) or greater.
    Exception 1: Where other standards specify greater clearance to storage minimums, they shall be followed.
    Exception 2: A minimum clearance of 36″” (0.91m) shall be permitted for special sprinklers. (NFPA 13 Para 4-5.6)

Standard Pendent and Upright Spray Sprinkler

1. The maximum distance permitted between sprinklers shall comply with Table 4-6.2. See attachment 1 in this SAIC.
   Exception No. I : For extra hazard occupancies and high piled storage in bays 25 ft (7.6m) wide, a spacing of 12 ft 6 in (3.8 m) shall be permitted.
   Exception No. 2: For densities less than 0.25 gpm/ft2 (10.2 lpm/m2), a spacing of 15ft (4.6m) shall be permitted (NFPA 13 Para 4.6.3.1).
2. The distance from sprinklers to walls shall not exceed one-half of the allowable distance between sprinklers as indicated in Table 4-6.2. See attachment No.1 (NFPA 13 Para 4.6.3.2).
3. Where walls are angled or irregular, the maximum horizontal distance between a sprinkler and any point of floor area protected by that sprinkler shall not exceed 0.75 times the allowable distance permitted between sprinklers, provided the maximum perpendicular distance is not exceeded. (NFPA 13 Para 4.6.3.2)
4. Sprinklers shall be located a minimum of 4 in. (102 mm) from a wall. (NFPA 13 Para 4-6.3.3)
5. Minimum Distance Between Sprinklers. Sprinklers shall be spaced not less than 6 ft (1.8 m) on center.
   Exception No. 1: Sprinklers shall be permitted to be placed less than 6ft (1.8 m) on center where the following conditions are satisfied:
   (a) Baffles shall be installed and located midway between sprinklers and arranged to protect the actuating elements.
   (b) Baffles shall be of noncombustible or limited-combustible material that will stay in place before and during sprinkler operation.
   (c) Baffles shall be not less than 8 in. (203 mm) wide and 6 in. (1 52 mm) high. The tops of baffles shall extend between 2 in. to 3 in. (51 to 76 mm) above the deflectors of upright sprinklers. The bottom of baffles shall extend downward to a level at least even with the deflectors of pendent sprinklers.
   Exception No. 2: In-rack sprinkler
   Exception No. 3: Old-style sprinklers protecting for storage vaults. (NFPA 13 Para 4-6.3.4)”
6. Under unobstructed construction, the distance between the sprinkler deflector and the ceiling shall be a minimum of 1 in. (25.4 mm) and a maximum of 12 in. (305 mm).
   Exception: Ceiling-type sprinklers (concealed, recessed, and flush types) shall be permitted to have the operating element above the ceiling and the deflector located nearer to the ceiling where installed in accordance with their listing. (NFPA 13 4-6.4.1.1).
7. Under obstructed construction, the sprinkler deflector shall be located 1 to 6 in. (25.4 to 152 mm) below the structural members and a maximum distance of 22 in. (559 mm) below the ceiling / roof deck.
   Exception No. 1: Sprinklers shall be permitted to be installed with the deflector at or above the bottom of the structural member to a maximum of 22 in. (559 mm) below the ceiling/roof deck where the sprinkler is installed in conformance with table 4-6.5.1.2 and Figures 4-6.5.1.2 (a) and 4-6.5.1.2 (b). See attachments 2 & 5
   Exception No. 2: Where sprinklers are installed in each bay of obstructed construction, deflectors shall be a minimum of 1 in. (25.4 mm) and a maximum of 12 in. (305 mm) below the ceiling.
   Exception No. 3: Sprinklers shall only be permitted below composite wood joists where joist channels are fire-stopped to the full depth of the joists with material equivalent to the web construction so that individual channel are do not exceed 300 ft’ (27.9 m’).
   Exception No. 4: Deflectors of sprinklers under concrete tee construction with stem spaced less than ï1/2ft (2.3 m) but more than 3 ft (0.9 m) on centers shall, regardless of the depth of the tee, be permitted to be located at or above a horizontal plane I in. (25.4 mm) below the bottom of the stem of the tees and shall comply with Table 4-6.5.1.2. See attachment No. 2 (NFPA 13 Para 4-6.4.1.2).

8. Sprinklers under or near the peak of a roof or ceiling shall have deflectors located not more than 3 ft (0.9 m) vertically down from the peak. [See Attachment 3 in this SAIC, Figures 4-6.4.1.3(a) and 4-6.4.1.3(b).]

   Exception No. 1: Under saw-toothed roofs, sprinklers at the highest elevation shall not exceed a distance of 3 f t (0.9 m) measured down the slope from the peak.
   Exception No. 2: Under a steeply pitched surface, the distance from the peak to the deflectors shall be permitted to be increased to
   maintain a horizontal clearance of not less than 2p (0.6 m) from other structural members. [See attachment 4 in this SAIC, Figure 4-6.4.1.3(c).] (NFPA 13 Para 4-6..4.1.3)

9. Sprinklers shall be located so as to minimize obstructions to discharge as defined in items B10 and B11 of this SAIC or additional sprinklers shall be provided to ensure adequate coverage of the hazard. (NFPA 13 Para 4-6.5.1.1)”
10. Sprinklers shall be arranged to comply with Table 4-6.5.1.2, and Figure 4-6.5.1.2(a). See attachments No. 2 & 5 (NFPA 13 Para 4-6.5.1.2)”

11. Continuous or noncontinuous obstructions less than 18 in. (457 mm) below the sprinkler deflector that prevent the pattern from fully developing shall comply with the following:

    a) Sprinklers shall be positioned such that they are located at a distance three times greater than the maximum dimension of an obstruction up to a maximum of 24 in.

    (609 mm) (e.g., structural members, pipe, columns, and fixtures). (See Figure 4-6.5.2.2.) See attachment 6 in this SAIC
    Exception No. 1: Sprinklers shall be permitted to be spaced on opposite sides of the obstruction provided the distance from the centerline of the obstruction to the sprinklers does not exceed one-half the allowable distance between sprinklers.
    Exception No. 2: Where the obstruction consists of open trusses 20 in. (.51 m) or greater apart [24 in. (.61 m) on center], sprinklers shall be permitted to be located one-half the distance between the obstruction created by the truss provided that all truss members are not greater than 4 in. (102 mm) (nominal) in width.
    Exception No. 3: Where the sprinklers are-installed an the centerline of bar joists or a truss.
    Exception No. 4: Piping to which an upright sprinkler is directly attached less than 3 in. (75 mm) in diameter.
    Exception No. 5: Piping to which pendent sprinklers are directly attached. (NFPA 13 Para 4-6.5.2.1).

Sidewall Standard Spray Sprinklers

1. Maximum Distance from Walls. The distance from sprinklers to the end walls shall not exceed one-half of the allowable distance permitted between sprinklers as indicated in Table 4-7.2. See attachment 6 (NFPA 13 Para 4-7.3.2)
2. Minimum Distance from Walls. Sprinklers shall be located a minimum of 4 in. (102 mm) from a wall. The distance from the wall to the sprinkler shall be measured perpendicular to the wall.
   Exception: Horizontal and vertical sidewall sprinklers are permitted to be located with their deflectors less than 4 in. (1 02 mm) from the wall on which they are mounted. (NFPA 13 Para 4-7.3.3).
3. Minimum Distance Between Sprinklers. Sprinklers shall be spaced not less than 6 ft (1.8 m) on center.
   (NFPA 13 Para 4-7.3.4).
4. Sidewall sprinkler deflectors (vertical type) shall be located not more than 6 in. (152 mm) nor less than 4 in. (102 mm) from ceilings.
   Exception: Horizontal sidewall sprinklers are permitted to be located in a zone 6 to 12 in. (152 to 305 mm) or 12 to 18 in. (305 mm to 457 mm) below noncombustible ceilings where listed for such use. (NFPA Para 4-7.4.1.1)
5. Sidewall sprinkler deflectors shall be located not more than 6 in. (152 mm) nor less than 4 in. (102 mm) from walls. (NFPA 13 para 4-7.4.1.2)
6. Sidewall sprinklers shall only be installed along walls, lintels, or soffits where the distance from the ceiling to the bottom of the lintel or soffit is at least 2 in. (51 mm) greater than the distances from the ceiling to sidewall sprinkler deflectors. (NFPA 13 Para 4-7.4.1.3)
7. Where soffits are used for the installation of sidewall sprinklers, they shall not exceed 8 in. (203 mm) in width or projection from the wall.
   Exception: Soffits shall be permitted to exceed 8 in. (203 mm) where additional sprinklers are installed below the soffits (NFPA 13 Para 4-7.4.1.3.1).
8. Deflector Orientation. Deflectors of sprinklers shall be aligned parallel to ceilings or roofs. (NFPA 13 Para 4-7.4.2).
9. Sidewall sprinklers, where installed under a sloped ceiling, shall be located at the high point of the slope and positioned to discharge downward along the slope. (NFPA 13, Para 4-7.4.2.1)
10. 4-7.5.1.2 Sidewall sprinklers shall be installed no closer than 4 ft (2.3 m) from light fixtures or similar obstructions.
11. The distance between light fixtures or similar obstructions located more than 4 ft (2.3 m) from the sprinkler shall be in conformity with table 4-7.5.1.2 and Figure 4-7.5.1.2 See attachment 7″
12. Continuous or no continuous obstructions less than 18 in. (457 mm) below the sprinkler deflector that prevent the pattern from fully developing shall comply with the following:
    a) Sprinklers shall be positioned such that they are located at a distance three times greater than the maximum dimension of an obstruction up to a maximum of 24 in. (609 mm) (e.g., truss webs and chords, pipe, columns, and fixtures). Sidewall sprinklers shall be positioned in accordance with Figure 4-7.5.2.2 where obstructions are present. See attachment 8 in this SAIC.
    Exception: Piping to which sidewall sprinklers are directly attached. (NFPA 13, Para 4-7.5.2.1)
13. Continuous or no continuous obstructions that interrupt the water discharge in a horizontal plane more than 18 in. (457 mm) below the sprinkler deflector in a manner to limit the distribution from reaching.
    the protected hazard shall comply with the following:
    a) Sprinklers shall be installed under fixed obstructions over 4 ft (1.2 m) wide such as ducts, decks, cutting tables, and overhead doors.
    Exception: Obstructions that are not fixed in place such as conference table. (NFPA 13, Para 4-7.5.3)
14. Suspended or Floor-Mounted Vertical Obstructions. The distance from sprinklers to privacy curtains, free-standing partitions, room dividers, and similar obstructions in light hazard occupancies shall be in accordance with Table 4-7.5.4 and Figure 4-7.5.4. See attachment 9 in this SAIC. (NFPA 13, Para 4-7.5.4)
15. Clearance to Storage (Standard Sidewall Spray Sprinklers). The clearance between the deflector and the top of storage shall be 18 in. (457 mm) or greater. (NFPA 13, Para 4-7.6).

Attachment 1 – Protection areas and maximum spacing for sprinkler system

Attachment 2 – Positioning of Sprinklers to Avoid Obstruction to Discharge

Figure 4-6.4.1.3(c) Horizontal Clearance For Sprinklers at Peak of Pitched Roof

Attachment 3 – Figure 4-6.4.3.1(a) Sprinklers at pitched roofs; branch lines run up the slope

Attachment 4 – Figure 4-6.4.1.3(c) Horizontal clearance for sprinkler at  peak of pitched roof

Attachment 6 – Table 4-7-2 Protection areas and maximum spacing (standard sidewall spray sprinkler)

Attachment 7 – Positioning of Sprinklers to avoid obstruction (Standard sidewall spray sprinklers)

Attachment 8 – Minimum Distance from obstruction (standard sidewall spray spinkler)

Attachment 9 – Suspended or Floor Mounted Obstructions (Standard Sidewall Spray Sprinklers)