Month: October 2016
Our last article focused on Fire Sprinkler System types and how the different types are best used in particular structures or situations. The same variation is true for fire suppression systems used in special hazard applications. Here we will review the different technologies and their purposes.
A foam-water fire sprinkler system is a special application system which discharges a mixture of water and low-, medium-, or high-expansion foam concentrate. This results in a foam spray from the sprinkler. This is usually used with special hazard occupancies associated with high challenge fires, such as flammable liquids and airport hangars. The foam-water application can be used in wet, dry, pre-action or deluge system.
Water spray systems are operationally identical to deluge systems, but the piping and discharge nozzle spray patters are designed to protect a uniquely configured hazard, usually being three-dimensional components or equipment. The nozzles are selected for a specific spray pattern to conform to the three-dimensional nature of the hazard. Some typical spray patterns are oval, fan, full circle, and narrow jet. Examples of hazards protected by water spray systems are electrical transformers containing oil for cooling or turbo-generator bearings. Water spray systems can also be used on the surfaces of tanks containing flammable liquids or gases (such as hydrogen). In this case, the water spray is intended to cool the tank and its contents to prevent tank rupture and fire spread.
A water mist system works by creating a heat absorbent vapor. This type of system is used when water damage is a concern or where water supplies are limited. By using a mist, an equal volume of water will create a larger total surface area exposed to the fire. The larger total surface area better facilitates the transfer of heat, thus allowing more water droplets to turn to steam more quickly. A water mist, which absorbs more heat than water per unit time, due to exposed surface area, will more effectively cool the room, thus reducing the temperature of the flame. NFPA 750 defines water mist as a water spray with a droplet size of “less than 1000 microns at the minimum operation pressure of the discharge nozzle.” Water mist systems use a compressed gas as an atomizing medium, which is pumped through the sprinkler pipe. Instead of compressed gas, some systems us a high-pressure pump to pressurize the water so it atomizes as it exits the sprinkler nozzle. Water mist systems can operate with the same functionality as deluge, wet pipe, dry pipe, or pre-action systems.
Clean Agent (Gaseous Fire Suppression)
NFPA 2001 defines clean agent as, “Electrically nonconductive, volatile, or gaseous fire extinguishant that does not leave a residue upon evaporation.” Clean agents are used when protecting high dollar, mission critical assets that would be destroyed by water, such as IT systems, data storage rooms, and manufacturing equipment, or irreplaceable items like intellectual property, art, and antiques. There are three ways clean agents can extinguish a fire: reduction of heat, reduction or isolation of oxygen, and inhibiting the chain reaction of the heat and oxygen.
Clean agent fire protection systems are comprised of the agent, agent storage containers, agent release valves, fire detectors, fire detection system (wiring control panel, actuation signaling), agent delivery piping, and agent dispersion nozzles. Less typically, the agent may be delivered by means of solid propellant gas generators that produce either inert or chemically active gas. Clean agents are applied with either total flooding or local application. Total flooding systems apply an extinguishing agent to a three dimensional enclosed space in order to achieve a concentration of the agent (volume percent of the agent in air) adequate to extinguish the fire. These types of systems may be operated automatically by detection and related controls or manually by the operation of a system actuator. Local application systems apply an extinguishing agent directly onto a fire (usually a two dimensional area), or into the three dimensional region immediately surrounding the substance or object on fire. The main difference in local application from total flooding design is the absence of physical barriers enclosing the fire space.
Condensed aerosol fire suppression is one of the most efficient forms of fire suppression. It is a particle-based form of fire extinction similar to gaseous fire suppression or dry chemical fire extinction. The aerosol employs a fire extinguishing agent consisting of very fine solid particles and gaseous matter to extinguish fires. The condensed aerosol microparticles and effluent gases are generated by the exothermic reaction; until discharged from the device, the particles remain in vapor state. They are cooled and “condensed” within the device and discharged as solid particles. Condensed aerosols release finely-divided solids of less than 10 micrometers in diameter, the solid particles have a considerably smaller mass median aerodynamic diameter than those of dry chemical suppression agents, remain airborne significantly longer, and leave much less residue within the protected area. Condensed aerosols are flooding agents and therefore effective regardless of the location and height of the fire. This system does not require a room integrity test as it is flooding the space at room pressure; this will save you money in sealing the room and annual testing.
Dry chemical fire extinguishing agents are primarily used for fast knock down of high risk gas and liquids such as dip tanks, paint booths and gas filling stations. The dry chemicals work by preventing the chemical reactions involving heat, fuel, and oxygen (combustion). The substances in dry chemicals can also stop the break-down of fuel in the fire to prevent the creation of highly reactive fragments of molecules.
Primarily used in kitchen fire suppression, the wet chemical agent suppresses fire by cooling and reacting chemically to produce a foam layer on the grease. The foam seals combustible vapors, stopping the flames from re-igniting.
Fire Extinguishers may not be a part of the fire sprinkler system, but they are an integral part of your fire safety system. If the proper fire extinguisher is used correctly and promptly, more than 90% of fires are extinguishable. Most work environments are required by OSHA to have an emergency action plan, functioning extinguishers, and trained extinguisher operators. OSHA requirements vary, but safety does not – be safe, provide fire extinguishers and fire extinguisher training to your staff.
An estimated $14.3 billion in property damage occurred as a result of fire in 2015, an increase of 23.2 percent from the previous year. Because fire sprinklers react so quickly, they can dramatically reduce the heat, flames, and smoke produced in a fire. Properly installed and maintained fire sprinklers help save lives and property.
Fire sprinklers have been around for more than a century, protecting commercial and industrial properties and public buildings. Sprinkler systems are as varied as the structures they protect. In this article we will outline the various sprinkler system types, and in the next article we will review the special hazard fire suppression systems.
Fire Sprinkler System Types
Wet pipe sprinkler systems are the most common type of fire sprinkler system. In a wet pipe system, the sprinkler pipes are filled with water under pressure. When the sprinkler head is activated, the pressurized water pushes the plug out of the sprinkler head when the head is activated. The advantage of wet pipe sprinkler systems is that water immediately available to flow out of the sprinkler head and onto the fire, however water sitting in pipes can be an opportunity for leaks so it is very important they are properly maintained.
Dry pipe sprinkler systems have the sprinkler pipes filled with pressurized air and are the second most common type of fire sprinkler systems. The pressurized air releases the plug when the sprinkler head is activated. The air is replaced by water flowing into the pipes from the water supply. Dry pipe systems are used with the ambient temperature may be cold enough to freeze the water in a wet pipe system. Dry pipe systems are most often used in unheated buildings, parking garages, outside canopies attached to heated buildings, and refrigerated coolers. NFPA regulations require the use of a dry system in areas where the range of temperatures goes below 40 degrees Fahrenheit.
Pre-action sprinkler systems are designed for use in locations where accidental activation is especially undesired, such as in museums or data centers. A pre-action fire sprinkler system employs the same basic concept as the dry system, in that water is not contained within the pipes. The pipes are pressurized with air or nitrogen. The water source is restrained with an electrically operated valve, known as the pre-action valve.
For the pre-action system to discharge, two steps must be completed. First, the detection system identifies either smoke or heat (depending on which type of detection you have), and activates the pre-action valve to allow water to flow into the piping. Second, sprinkler head(s) are activated by heat releasing water onto the fire.
Deluge fire sprinkler systems are similar to pre-action systems in that the water is held back with an electronic deluge valve. The sprinkler heads in a deluge system are open, not plugged like they normally are. The system is directly connected to a water supply, when the detection system is tripped by smoke or heat the water is released throughout the entire system and through all open sprinkler heads. This rush of water is designed to quickly smother all varieties of chemical and mechanical fires, which is why the deluge fire sprinkler system is commonly used in high hazard industrial and commercial facilities where special hazards create a concern for rapid fire spread. The deluge system is designed to quickly cover the horizontal floor area of a room.
Keeping your fire sprinkler system running is essential to protecting your business, people, and assets. Regular inspections are required by law and checked by your Fire Marshal or AHJ.
Keeping your project on schedule can be a challenge. Planning, communicating and coordinating with the different trade professionals is important and one set-back can cause a ripple effect for others. Here are a few items Electrical Contractors can check off the list to keep the fire protection part of the plan on moving forward.
- Have background CAD Drawings available
Your fire protection project starts with installation drawings which overlay with the project’s background CAD drawing. The design of a fire protection project cannot begin until these original drawings are received. When you select your Life Safety partner, have your project’s CAD drawings ready to hand over so that the fire protection design can begin immediately. To delay the start of the design can lead to slow submittals, unnecessary delays, or even missed deadlines.
- Coordination with other trades
To have a successful fire protection design, your Life Safety partner will need to coordinate efforts with other trades during construction. Successful communication between trades will limit delays and errors in project delivery. For example, the sprinkler contractor needs to communicate the number and locations of sprinkler points to be monitored. It is recommended that your elevator contractor and fire alarm contractor meet early in the schedule to discuss the interface. Many issues and delays can occur if miscommunication occurs between the fire alarm and HVAC professionals, so A1 recommends that you use your fire alarm contractor to supply and install the system duct detectors. This cuts down on the opportunity for problems and delays, and allows the duct detectors to be programmed in a way that they can be reset at the fire alarm panel.
- Phone Company
We all know utilities move at their own pace. Waiting on the phone company to provide a dedicated line for your fire sprinkler monitoring system can be frustrating and cause an unnecessary delay. By utilizing cell monitoring you can cut out the phone company altogether. Take back control of your project. Your Life Safety partner can install a cell dialer during construction.
Your Fire Alarm panel requires a dedicated power line with 120-volt circuit with a breaker lock marked “fire” in red. Without this power line installed and properly marked, your Life Safety partner cannot move forward with the fire alarm panel install and programming. Ensure that your power is properly run before your Life Safety partner is scheduled to perform the fire alarm install.
- Check all Circuits
This is another item that needs to be completed before your Life Safety partner can begin installation. Your electrician should check all circuits to ensure they are free of trouble, no grounds, opens or shorts. If your fire alarm panel senses these troubles it will not work properly, your Life Safety partner will have to spend valuable time rechecking all lines for the problem which can delay the schedule.
- Communicate Permit Notes/Changes
When permits are returned with comments it is imperative that these notes be passed back along to your subcontractors including your Life Safety partner. If changes are required but not implemented, you can fail your final walk-through and delay occupancy. Even small changes can take time and cause extra expense if they have to be corrected after all work is complete; however, the delay and expense can be minimized if the changes are communicated during construction.
- Communicate changes to project schedule
Changes to your project schedule need to be communicated to your Life Safety partner and other subcontractors as soon as possible. If you are changing your project to a phased project, experiencing delays, or accelerating your project getting all of your partners on-board with that change as quickly as possible can be the difference in successfully meeting your new timeline.
- 100% Pre-Check
You should test 100% of the fire alarm devices before the AHJ arrives for the final inspection. This ensures a successful final and occupancy. More importantly, it provides confidence that the fire alarm system will work in the case of an actual emergency.
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Widespread use of smoke alarms began in the 1970s, and have greatly reduced the number of home fire deaths. Prior to the 1970s, the average number of annual deaths by home fires was roughly 6,000. While there has been a dramatic decrease in home fire deaths, there is still more work to be done. Three out of every five home fire deaths occur in a home with no smoke alarms or no working smoke alarms. No smoke alarms were present in more than 1/3 of home fire deaths. In reported home fires where smoke alarms were present, but did not operate, almost half of the smoke alarms had missing or disconnected batteries. A quarter of the smoke alarm failures were due to dead batteries. NFPA estimates that there are about five million homes nationwide without smoke alarms.
In 2015, 3,280 civilians died in fires. Most fire deaths are not caused by burns, but by smoke inhalation. An individual can become incapacitated by smoke so quickly that they are overcome and can’t make it to an otherwise accessible exit. Having smoke detectors and alarms in your home and business can provide valuable time to evacuate, preventing injury and death.
A smoke alarm is a stand-alone device with a built-in sounder, a power supply, and a sensor. A smoke alarm is not connected to a fire alarm control panel, but may interconnect with other smoke alarms within the building. A smoke detector is part of a commercial fire protection system, it has only a built-in sensor and sends information to the fire alarm panel.
There are two main types of smoke detection technology used both in stand-alone devices and as the sensor in smoke alarms, ionization and photoelectric. Each has advantages, for best protection you should use both types of smoke detection technologies. There are units available which utilize both technologies in a single device for both detectors and alarms.
Ionization Smoke Detection
Ionization Smoke Detectors are generally more responsive to fires that have flames. The detectors have a small amount of radioactive material between two electrically charged plates, this ionizes the air and causes current to flow between the plates. When smoke enters the chamber, it disrupts the flow of ions thus reducing the flow of current and activating the alarm.
Photoelectric Smoke Detection
Photoelectric Smoke Detectors are more responsive to fires that begin with a long period of smoldering. Photoelectric-type detectors aim a light source into a sensing chamber at an angle away from the sensor. When smoke enters the chamber, it reflects the light onto the light sensor which triggers the alarm.
Smoke detectors have advanced technologically to be more user friendly. In addition to combination detectors which include both photoelectric and ionization technology, you can also get detectors that combine CO detection, or many have features for silencing nuisance alarms. Smoke alarms can be interconnected to allow an alarm to sound throughout the house or building when one unit detects smoke; some of these devices can be programmed to provide audio messages that state for which room the alarm has sounded.