 |
| Duct Model Sprinkler System Codes and Standards, page 4. |
Codes and Standards which recommend the installation of sprinklers
inside exhaust ducts.
FM DS 7- 78
Industrial Exhaust
Systems
( 1998 Edition)
|
2.4.2 Install sprinklers inside all ducts which have cross- sectional areas greater than or equal to 80 sq. in. ( 516 sq. cm) , or which have diameters greater than or equal to 10 in. ( 254 mm) , and which:
a. are combustible ( including non- approved plastics)
or
b. carry combustibles sufficient to cause a damaging fire.
Judgement can be used in determining if sprinklers should also be provided in smaller ducts that offer serious exposures.
2.4.3 For ducts described in No. 2.4.2 above, install sprinklers as follows:
a. Sprinklers should be spaced no more than 12 ft ( 3.7 m) on- center in horizontal and vertical ducts. Sprinkler temperature rating should be at least 50 F ( 27 C) above the temperature of the environment inside the duct.
b. An option to protect combustible ducts ( rather than combustible residue) is as follows: Sprinklers can be spaced not more than 20 ft.
( 6.6 m) on center in horizontal ducts if a density of at least 0.50 gmp/ sq. ft. ( 20 mm/ min) over the projected area of the duct ( not exceeding 100 lineal feet [30 m] can be provided.
c. To protect horizontal combustible ducts ( including non- Approved plastic) intermediate spacings ( option A and B) with interpolated demands are also acceptable.
In all three cases, the following also apply:
d. When the duct width or diameter is greater than 12 ft ( 3.7 m) , provide an additional line of automatic sprinklers at the same spacing inside the duct.
e. In systems with branch ducts, one sprinkler should be provided in each branch duct, regardless of size, within 3 ft ( 0.9 m) of its point of entry into a main duct system. Several smaller ducts may be manifolded and a single
sprinkler provided before the manifold enters the main duct system. Where not practical due to size limitations, a sprinkler may be provided in the main duct at the point where the smaller branch duct enters.
f. The supply line to the duct sprinklers should be equipped with an accessible FMRC- Approved control valve. If there is more than one exhaust duct system, and they can be operated independently, sprinklers to each system should be controlled by a separate valve. A separate water flow alarm may be advisable for duct system protection in large Installations.
|
continued...
|
|
|
