Backflow Preventers on Fire Protection Systems

January 29, 2012

Most municipalities require UL listed or FM Global approved backflow preventers on the incoming water line feeding fire protection systems. A backflow preventer does just what the name implies, it prevents water from the fire system from flowing back into the water system.

Backflow preventers may be created in a number of ways. One way is to install a fire pump and water storage tank. The tank has a float valve which opens a fill valve on the public water supply. The water flows like a faucet into a bathtub, and the water passes through the air before filling the tank. When the tank is full, the float shuts the valve and the flow of water from the public water supply. The public water fill pipe is above the level of the water, so once the flow of water stops, there is no way to flow back into the system. This system is referred to as an air break.

Single wing-check valves have been used for a hundred years as a means to prevent backflow. Unfortunately, a simple check valve is not leak proof, and conditions were found where the single check valve was allowing water to back up into the public system. Then double swing-check valves were used, doubling the reliability of backflow prevention.

An improvement in the swing-check valve was the addition of weight inside the valve body and hung on the downstream face of the check valve. The additional weight prevented the swing check from floating open and allowing seepage backwards through the valve and into the public side of the piping. A down side to the design of many older check valves is the inability to actually test the valves to verify that the valves are seating positively.

Today, the design of the check valves for fire systems has improved significantly. Many newer backflow prevention check valve assemblies do not rely on a swing check system. They use a more sophisticated spring loaded system in which the seat moves perpendicular to the valve seat. Other valves which are of the swing design have a spring loaded cam arm to maintain positive seating force against the top of the clapper. Most valves have means of testing the valves to verify that the seats are definitely holding. Most of the valves available today are on an angled seat that create a greater differential over the face of the clapper to help hold the valve closed. Many are weighted or spring loaded.

Reduced pressure zone valves are considered more reliable at backflow prevention. The assembly has two check valves in series. The volume between the check valves is monitored for pressure differential. If the differential is not great enough, water from the section between the valves will discharge to create a greater differential pressure. Constant or frequent discharge from the differential drain may indicate that the check valve seat is not holding and allowing water to flow backwards into the reduced pressure zone of the valve.

These devices must be maintained and tested on an annual basis. This inspection is usually accomplished by shutting the valves on both side of the assembly. The housing is opened and the clappers removed. Some styles have an access port which is held closed by a rubber gasket and flanges that are paired to create a full circle around the gasket and lid and are bolted together. There may be a screw type housing for the clappers. The clapper assemblies are unscrewed from the seat housing and removed from the maintenance port. The spring or spring loaded cam arm is disarmed, the clapper is cleaned, inspected, and tested. The manufacturers specifications must be closely followed, and most municipalities require the servicing technician to be trained, certified, and sometimes licensed.

For more information and to actually see videos on how the assemblies work, are disassembled and reassembled, and maintained, look on the manufacturers’ websites. Watts Water Technologies, Inc. is one company that provides videos of the inner workings of the devices. Watts is the owner of Watts, Ames, Mueller, Febco, and other brands very familiar to those in the fire protection field.

The major disadvantage of backflow prevention devices is the additional friction loss. The head loss as a result of water friction loss is substantial and becomes greater as the flow increases. If a backflow preventer is added to a fire protection system which was not originally designed for one, the friction losses across the backflow preventer assembly may be so great as to make the sprinkler system(s) inadequately supplied with pressure and volume.

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Posted by Walt Beattie

ASSE Helps Provide Fire Prevention Training for Students

January 21, 2012
Campus Fire Safety

Campus Fire Training - Demo burn of a dorm room

Each year, college students are injured and killed in preventable campus-related fires. To prevent injuries and fatalities caused by fires that occur in college residence halls, off-campus housing and fraternity/sorority houses and to raise awareness about life-saving fire prevention knowledge as students head back to school, ASSE, West Virginia University (WVU), RA Fire Academy and the Morgantown Fire Department are providing key fire prevention information and demonstrations.

According to NFPA, from 2000 to the present, 146 students have died in a combination of off-campus, residence hall and fraternity/sorority fires. The majority of campus-related fatal fires occur in off-campus housing. According to the U.S. Fire Administration, of the 146 campus-related fire fatalities that occurred from January 2000 to the present, 85% happened off campus. Today, more than two-thirds of the U.S. student population lives in off-campus housing.

WVU’s Department of Environmental Health and Safety (EH&S) recognized the importance of having a strong, vibrant fire safety program. The RA Fire Academy evolved out of several training sessions the department offered for the students, campus community and local high schools in the area. By working collaboratively with various university departments, administrators, student staff and the Morgantown Fire Department, the RA Fire Academy was created. Some form of this fire safety training has been offered since 2003 to students in the campus community. WVU EH&S envisions offering this fire academy training to all first-year students.

All student RAs are required to participate in the RA Fire Academy in a variety of hands-on training scenarios. The RAs then share the information they learn with the students on their respective floors. Activities include:

•  smoke-filled hallway

•  hands-on fire extinguisher training

•  quizdom training

•  movie/lecture

•  competition games [Skeet Shoot Frisbee (shoot Frisbee from the air) and Medicine Ball Push (push ball with fire hose to a designated distance)]

•  live burn (A mock dormitory room is constructed with the appropriate early warning fire protection. The room is then set ablaze. Students observe how quickly a room is engulfed with smoke and flames; and, they learn the importance of smoke detectors, evacuation and sprinkler systems. Additionally, the importance of using open flames with caution is discussed.).

Each RA rotates through each training station. The training culminates in the sixth station where a dorm room mockup is lit, and students are able to see just how quickly a dorm room fire can spread. The overall goal is to provide each RA a rounded training session.

The RA Fire Academy is intended to provide student leaders with the necessary knowledge and skills to better enable them to assist others in the event of an actual fire emergency on campus. The goal is to give them some real life hands-on experience in a safe and controlled setting so if they are ever faced with a real fire emergency, they will have the confidence to make the right decisions in a quick, calm way and hopefully save lives.

See the article by John A. Principe III CSP, CHCM & Walter S. Beattie, CSP, CFPS, CSHM: ASSE Helps Provide Fire Prevention Training for Students

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Posted by Walt Beattie

Emergency Gas Shut-off Valves

January 21, 2012

An earthquake actuated gas shutoff valve installed on a gas line will go a long way to reducing the fire following earthquake risk at your facility.

During an earthquake, one of the most serious threats to your facility is from natural gas. During an earthquake your entire building shakes. The pipes in your building are under stress. They will shake and may break at the fittings. Whatever is contained within the pipes will leak, whether the material is sprinkler water, process gas, compressed gas, or natural gas. This is why earthquake bracing is required in earthquake subject areas.

If your gas line is broken inside your facility it will usually find an ignition source. The ignition source may be from broken wiring, pilot lights, or heat sources. If the gas supply is not immediately shut down, gas could flow uncontrolled from the broken pipe, feeding a fire within your facility. This condition is sometimes called a “Fire Following Earthquake” fire. The municipal fire department and emergency responders are going to be responding to the most immediate life safety crisis. That may be a bridge, the grade school, or a hospital or nursing home collapse. Emergency resources will be expended first at locations which pose the greatest life safety risks. Property emergencies will take a secondary response priority during an earthquake.

An earthquake actuated gas shutoff valve or an excess flow valve (EFV) will go a long way to reducing the fire risk at your facility. The device should be UL listed and/or FM Approved. The purpose of the devices is to shut down the gas flow in the event of a broken pipe. Each operates slightly differently. Each of these valves are available in various sizes, typically from 3/4 inch residential size to 8 inch industrial size. Most valves may be installed by any competent plumber or maintenance person.

An earthquake actuated gas shutoff valve has a ball on a post. When the ball is properly balance on the post, the gas will flow normally. When an earthquake shakes the valve, the ball will flop off the post, and the valve will immediately close in the fully shut position.

An excess flow valve will sense a larger than normal flow, and will shut down automatically. These valves will operate with not only an earthquake, but any pipe breakage. If one of your forklift operators goes too high and hits and breaks the natural gas pipe, the excess flow will immediate shut off the gas flow at the source. The excess flow valve works by placing a movable spring loaded plug within a restricted area of the valve pipeline. The plug sits in the pipe and allows gas to flow around it. If there is flow of gas beyond the flow limits of the system, or an excess flow of gas, the plug will be swept up and will plug itself against a gas shutoff seat. This will shut down the flow of gas. Some valves are spring loaded so that after repairs, the spring will allow the plug to return to its normal position. EFV’s may also be installed underground, such as at the entrance to your property. The valve will also help protect against excess flow from physical damage, such as your gas line being struck and severed by a backhoe or digging machine.

Each of these valves may be used for various gases. If you have an industrial process with a flammable or anesthetic gas, each of these valves may be employed as a safety device.

Check with your local gas provider or building code enforcement department to ensure the valves are properly installed.

Remember, once one of these devices operate, all the pilot lines will go out. You must not reset the device or turn the gas back on until the gas company or other qualified person inspects, repairs, and relights each pilot line.

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Posted by Walt Beattie