By Philippe Bouchard, P. Eng., NAFI-CFEI, CVFI
When properly designed, installed, inspected, and maintained, fire suppression systems are an important line of defense against fire damage. But when they malfunction, they can actually become a source of costly damage—a far cry from their intended role.
There are many different scenarios that can lead to a malfunction, but two in particular tend to be more frequent: frozen and burst pipes, and unintended sprinkler activations.
First, let’s take a look at burst pipes. There are several different types of fire suppression systems, but the two most often involved in burst pipe situations are wet pipe systems and dry pipe systems. With both systems, there’s an alarm valve between the sprinklers and the water supply. Past the alarm valve the pipes in a dry pipe system are full of air, whereas the pipes in a wet pipe system are kept under pressure by the water in the pipes.
In both types of system, the presence of fire triggers the sprinkler heads, opening the alarm valve and allowing water to pass through the sprinkler heads. A signal is usually relayed to a monitoring center at the same time.
Dry pipe systems are used in places where the pipes that run past the alarm valve could freeze. Wet pipe systems can only be used in environments where the ambient temperature remains above freezing. Neither system is immune to the possibility of a failure that causes the pipes to burst, with ensuing water damage.
With dry pipe systems, water can sometimes get past the alarm valve and into a section of pipe subject to sub‑zero temperatures. This could happen if:
- The safeguards are faulty and allow water to get past the alarm valve
- The pipes aren’t properly drained after the system is tested
- The pipes are set at an angle that doesn’t allow them to drain properly
With wet pipe systems, if the building construction is shoddy or the ventilation system is faulty, cold air can sometimes get into the space and freeze the pipes. Improper installation or a contaminated water supply can also cause certain conduits to break.
As for claims involving sprinkler systems that went off by accident, the first thing to know is that there are two main types of sprinkler heads used in commercial fire suppression systems: glass bulb sprinklers and fusible link sprinklers. With glass bulb sprinklers, the sprinkler head is held closed by a bulb containing a heat‑sensitive liquid that expands and causes the bulb to burst when exposed to heat. With fusible link sprinklers, the two‑part metal element that holds the sprinkler head closed is fused together by a heat‑sensitive alloy that melts when exposed to high heat.
Sprinklers can go off by accident for a number of reasons:
- The metals in the fusible link gradually stretch out or “creep”
- Defective sprinkler
- The ceiling temperature continually cycles up to somewhere near the activation temperature (38˚C)
- Foreign objects come into contact with the sprinklers during maintenance/renovation work or simply through use of the space
- The sprinkler’s temperature rating is lower than the usual building temperature
In addition to the scenarios described above, there are a number of other ways in which fire suppression systems can end up costing insurers a pretty penny. Our technical investigators have backgrounds in mechanical engineering, so they can analyze the situation and identify the specific cause of any claim involving a fire suppression system.
Philippe Bouchard, P. Eng., NAFI-CFEI, CVFI