In Compliance | NFPA 13
Monitoring the status of a sprinkler system
BY BRIAN O'CONNOR
According to the July 2017 NFPA report “U.S. Experience with Sprinklers,” in three out of every five fire incidents where sprinklers fail to operate, the system has been shut off.
While sprinkler systems are highly reliable, the human element can play a role in compromising the system. When an automatic sprinkler system is undergoing repairs or renovations, for example, it is often necessary to close valves that control the water supply. When work on the system is complete, the valve needs to be reopened for the system to be operable in the event of a fire. What the NFPA report tells us is that this doesn’t always happen, which is a major problem in many of the cases where the sprinkler system fails to control the fire. NFPA 13, Standard for the Installation of Sprinkler Systems, has several requirements intended to prevent this scenario though a method called supervision.
Supervision is a means of monitoring the status of a sprinkler system and indicating certain abnormal conditions that could impair the system, such as a valve that is closed when it should be open or open when it should be closed. For electronically supervised valves, the main concept is to transmit a signal to a constantly attended location when this condition occurs. This informs the appropriate personnel about both the condition and location so the appropriate actions can be taken.
There are many different valves in a sprinkler system, but not all of them need to be supervised. NFPA 13 requires valves that control the flow of water to any portion of the sprinkler system to be open and supervised. Certain valves are already required to be indicating-type valves, which means you can tell if the valve is open or closed just by looking at it. The problem with this is that sometimes these valves are located in places that are not constantly attended. This is why NFPA 13 has requirements for making sure the valves stay open and when they are closed that someone who is responsible for the system knows that they are closed.
In lieu of electronic supervision, NFPA 13 also permits valves to be locked, sealed, and tagged to prevent unauthorized closing. However, these methods require additional vigilance. For example, seals are required to be checked every week to ensure the seal has not been broken, and locks are required to be checked monthly to make sure they have not been removed. Padlocks and chains are especially useful in places where valves are subject to tampering. In addition, valves should be individually locked and the distribution of keys should be restricted to those directly responsible for the system.
A device that electrically supervises the valve is arranged to monitor the position of a component. These will often be referred to as tamper switches, because if someone is tampering with the valve, the fire alarm control panel will receive the appropriate signal.
Although several means of valve supervision are permitted by NFPA 13, a more sophisticated means includes the use of what’s known as an automatic extinguishing system supervisory device. The installation of this type of device is addressed by NFPA 72®, National Fire Alarm and Signaling Code®. As noted above, the most common type of device used here is an electronically monitored tamper switch that sounds an alarm at a constantly attended location. Other conditions that are required to be supervised include the air pressure in a dry pipe or preaction system and the water temperature in a circulating closed loop system, because if either of those fail it could lead to ice blocks forming within pipes, either breaking them or blocking water from reaching the sprinkler.
Just because the supervisory device indicates certain components are in the correct position doesn’t mean your system is in perfect operating condition. Frequent inspection, testing, and maintenance in accordance with NFPA 25, Standard for the Inspection, Testing, and Maintenance of Water-Based Fire Protection Systems, is still required to ensure all of the system components continue to function as intended. And to further reduce the chances of the valves being inadvertently left closed, NFPA 25 also requires the implementation of a robust impairment program. This includes a specific focus on ensuring all valves are open following any system repairs or updates. With proper installation, including selection of the best option to supervise critical system valves and components, coupled with an ongoing inspection, testing, and maintenance program, an automatic sprinkler system will greatly reduce your risk of loss of life and property from fires.
Brian O’Connor is a fire protection engineer at NFPA. NFPA members and AHJs can use the Technical Questions tab to post queries on NFPA 13 at nfpa.org/13.