|"Plumbing" by Harsha K R|
NFPA 25, Standard for Inspection, Testing, and Maintenance of Water-Based Fire Protection Systems requires that an investigation of sprinkler piping be conducted to ensure that there are no obstructions. This internal piping assessment is to be conducted, at a minimum, every 5 years.
What could cause fire sprinkler piping to become obstructed? NFPA 25, Annex D lists and describes seven sources of sprinkler obstructions.
- Pipe scale - most commonly occurs in dry pipe systems that have previously had water through them then been allowed to dry; this can also result from condensation in dry pipe systems. Pipe scale are impurities in water that create a build-up in sprinkler pipes
- Careless installation or repair - this can result from parts, debris, or tools that are allowed to enter the system during installation and repair; these range from gloves, metal shavings, cutout discs/receipts, etc.
- Raw water sources - items and debris that is sucked into the system from the bottom of ponds, rivers, or reservoirs; this results when intake screens are not in place or properly installed
- Biological growth - primarily encountered in systems fed from a fresh water source (lake, pond, etc.); the most common biological growth is the Asiatic clam. The clam larvae enter and attach to the pipe, they feed on bacteria and algae that passes through
- Calcium carbonate deposits - this is an obstruction caused by "hard water" film
- Corrosion - "...deterioration of a material...resulting from a chemical or electrochemical reaction." Common types of corrosion:
- uniform corrosion
- crevice corrosion
- selective leaching
- erosion corrosion
- environmental cracking
- intergranular corrosion
For these seven reasons, ensure that an internal obstruction investigation is being conducted in conjunction with the fire protection systems 5-year NFPA 25 inspection.