Sprinkler heads are an important piece of your intricate sprinkler system. As such, it is necessary to understand how they work and what is required in maintaining them.
A fire sprinkler system is made up of a network of piping connected to a water supply. Individual sprinkler heads are placed along the piping to protect the area beneath them. These sprinklers individually activated by a heat source. Unlike in the movies, when a fire occurs only the sprinkler head above the fire activates, efficiently applying water only where it is needed.
How a Sprinkler Head works
Each sprinkler head consists of a plug held in place with a trigger mechanism. The most common type of trigger is a glass bulb filled with heat-sensitive, glycerin-based liquid. When the temperature around the sprinkler head is high enough to expand the glycerin-based liquid (most commonly designed at 155 degrees) the glass bulb breaks and the plug is forced out by the pressurized water or air in the pipes. This allows the water to flow out of the sprinkler and directly into the deflector plate of the sprinkler head which is designed to distribute water in an even pattern. Water will continue to flow until the main valve is shut off.
A less common trigger mechanism than the glass bulb is a two-part metal link which is held together with a solder point. When the ambient temperature is high enough to melt the solder point, the plug is released and water flows over the sprinkler head.
Smoke will not activate a fire sprinkler and only the sprinklers close enough to the heat source to reach the rated temperature activate. When a sprinkler activates, the water flows forcefully down over the flames, extinguishing them completely in most cases, or at least controlling the heat and spread of the fire and limiting the development of toxic smoke.
Sprinklers are so effective because of how quickly they react. They reduce the risk of death or injury from a fire because they dramatically reduce heat, flames and smoke which gives people time to evacuate.
Required and Recommended Inspections and Testing
As you can see, sprinkler heads are an important component of your sprinkler system. They must be inspected visually annually. Sprinkler head inspections ensure that water can discharge properly; they are checked for obstructions, damage, corrosion, and paint or other foreign material which may interfere with the sprinkler head operation.
Once your sprinkler heads are 50 years old, they should be tested at that time, followed by testing every 10 years after until they are 75 years old, at which point they must be tested every 5 years. Unlike plumbing, electrical, or HVAC systems, sprinkler systems can sit inactive for years if no fire emergency occurs. As a result of this idleness, proper testing is the only way to ensure the sprinkler system and the sprinkler heads are working correctly. To test your sprinkler heads, your Life Safety Partner will remove 1%, but at least 4, of your sprinkler heads from different areas of your sprinkler system and perform a plunge test. The plunge test measures the amount of time it takes for the sprinkler head to activate. If a sprinkler head fails, then all sprinkler heads in the area from where that particular head was taken must be replaced.
Dry-type sprinkler heads have a much higher failure rate than other types and must be tested every 10 years, starting at 10 years instead of 50. This is due to their susceptibility to corrosion both internally, when moisture condenses inside the device, and externally. In addition, dry-type sprinklers are usually installed in harsher environments which provide greater opportunity for damage to the sprinkler heads. In addition sprinklers with fast response elements should be tested every tested or replaced after 20 years and sprinklers exposed to a harsh environment every 5 years. You should consult with your Life Safety Partner about the costs of testing them versus replacing them.
Another requirement for sprinkler heads is that you have a cabinet with spare heads onsite. A sprinkler head may need to be replaced for any number of reasons, it may have become coated with a foreign material or activated due to a fire. The area the sprinkler was protecting is now unprotected until it is replaced. Worse, if the sprinkler is damaged and cannot hold pressure, the entire sprinkler system must be shut down and is rendered inoperable which leaves the entire facility unprotected. Sprinkler heads need to be replaced as quickly as possible to keep your system running or get it back in service. There are many different sprinkler head types, depending on the availability of the type you need it could take days or even weeks to order a new one. Keeping extra sprinkler heads onsite is required and ensures uninterrupted fire protection of your business, life, and property. You can read more about spare sprinkler head cabinet requirements here.
Did you know that if your building is protected by a fire sprinkler system you are required to have a stock of spare sprinkler heads?
NFPA 13 states (2010 6.2.9) “A supply of at least six (6) sprinklers (never fewer than six) shall be maintained on the premises so that any sprinklers that have operated or been damaged in any way can be promptly replaced.”
So what does this mean and why do I need them?
Fire sprinklers, like any other technology, have evolved tremendously. We have come a long way since the basic idea of automatically applying water to fire in an emergency. Sprinklers have become more effective and more specialized for specific needs. When choosing a sprinkler head the position in which it is designed to be installed, temperature rating, finish, thread size and orifice size are just a few of the variations. Today there are literally thousands of different styles, types and variations of sprinkler heads. It is important to replace a sprinkler with the exact type required and put the system back in service as quickly as possible.
Why can’t I just order a new one if I need one?
A sprinkler may need to be replaced for any number of reasons. For example it may be physically damaged, it may have become coated with a foreign material or it may have activated due to a fire. The area the sprinkler is protecting is now unprotected until it is replaced. Worse if the sprinkler is damaged and cannot hold pressure, the entire sprinkler system must be shut down and is rendered inoperable leaving the whole facility unprotected. The sprinkler must be replaced and the system put back in service as quickly as possible to protect life and property. Ordering a new one can take days or even weeks depending on availability of the type needed.
What exactly do I need and how many?
NFPA tells us;
“The sprinklers shall correspond to the types and temperature ratings of the sprinklers in the property.” (NFPA 13 2010 22.214.171.124)
“The stock of spare sprinklers shall include all types and ratings installed and shall be as follows
300 sprinklers or less = no fewer than 6
300-1000 sprinklers = no fewer than 12
Over 1000 sprinklers = no fewer than 24” (NFPA 13 2010 126.96.36.199)
“The sprinklers shall be kept in a cabinet located where the temperature to which they are subjected will at no time exceed 100 deg.” (NFPA 13 2010 188.8.131.52)
Typically this is a red metal or plastic box mounted near the sprinkler riser. As stated above at least one of each type and temperature is required however two of each is suggested.
Is that all I need?
Almost. NFPA also states;
“One sprinkler wrench as specified by the sprinkler manufacturer shall be provided in the cabinet for each type of sprinkler installed to be used for the removal and installation of sprinklers in the system.” (NFPA 13 2010 184.108.40.206)
With all the different types of sprinklers you need to be sure to use the appropriate wrench to install them. Using something other than the approved wrench may cause damage to the sprinkler head rendering it in-operable or may cause it to fail.
In addition to the spare sprinklers and wrench(s). “A list of sprinklers installed in the property shall be posted in the sprinkler cabinet.” (NFPA 13 2010 220.127.116.11)
“The list shall include the following;
Sprinkler identification number (SIN) if equipped or the manufacturer model
Quantity of each type to be contained in the cabinet
Issue or revision date of the list.” (NFPA 13 2010 18.104.22.168.1)
A properly stocked spare sprinkler cabinet is a critical component of your fire sprinkler system. This along with a comprehensive inspection and maintenance plan will insure your system is always ready to protect life and property.
For more information or a free audit of your sprinkler cabinet, please contact a professional service provider.