How To Test For A Fire Sprinkler System During An Earthquake

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1 DISPELLING MISPERCEPTIONS REGARDING THE PERFORMANCE OF CPVC FIRE SPRINKLER SYSTEMS DURING SEISMIC EVENTS Third-Party Seismic Testing and Field Performance Document Superior Reliability of CPVC Pipe and Fittings By Andy Olah, Ph.D Few people in the building industry would dispute the fact that the seismic requirements in building codes have gotten tougher in recent years, especially for such critical life safety products as fire sprinkler systems. As a result, today there are additional seismic requirements for sprinkler systems that go far beyond those originally specified in NFPA 13. What prompted the changes? Seismic activity continues to monopolize news headlines in both the consumer and trade media outlets. At the core of this increased focus is the perception that earthquakes might actually be on the increase. Based on the frequency of news reports relative to earthquake damage, it may seem that we are having more earthquakes in the U.S. and abroad. However, according to the United States Geological Survey s (USGS) Earthquake Hazards Program, earthquakes of magnitude 7.0 or greater have remained fairly consistent over the years. What has changed, however, is the number of earthquakes that can now be documented each year. This is because of the tremendous increase in the number of seismograph stations in the world and the many improvements in global communications. In 1931, there were about 350 stations operating in the world. Today, there are more than 8,000 stations, and the data comes in rapidly from these stations via electronic mail, Internet and satellite. As a result of such technological advances, the National Earthquake Information Center (NEIC) now locates about 20,000 earthquakes each year, which translates into approximately 50 per day. Of course, not all earthquakes are notable from a building code standpoint. The majority, in fact, occur without any tremors felt on the earth s surface. According to long-term records that have been kept since about 1900, the USGS predicts there will be about 17 major earthquakes ( on the Richter scale) and one great earthquake (8.0 or above) in any given year. So if earthquakes are not truly on the rise, why the increased focus on the seismic performance of such nonstructural components as fire sprinkler systems? The answer likely relates to the increased amount of damage that earthquakes cause. As urban areas have continued to grow, the damage resulting from an earthquake-as measured both in terms of the loss of human lives, as well as structural collapse-have increased substantially. As a result, we have seen industry-wide initiatives to improve the post-earthquake reliability of fire safety systems through stricter bracing requirements and the selection of piping system materials.

2 Fire is a real concern during and after major earthquakes in major urban areas since the tremors are often followed by major destructive fires that result from accidental ignition due to earthquake shaking. In addition, earthquake damage to fire safety systems can likely cause a loss of water supplies for fire suppression. These were only a few of the observations documented after the 1989 Loma Prieta and the 1994 Northridge earthquakes which caused catastrophic nonstructural damage, including that to the steel fire sprinkler systems inside. What Changed? Between 2004 and 2007, there was an agreement between NFPA and ASCE to incorporate changes to NFPA 13 that made them consistent with ASCE Most changes up to 2007 focused on providing additional support to a fire sprinkler system in the form of sway bracing-both lateral and longitudinal. This added support ensures that the sprinkler system will remain integral to the structure and not undergo oscillatory modes counter to that of the surrounding structural environment. These modes can impart catastrophic damage to the system, rendering it inoperable in the time of need. More recently, there has been greater focus on the material used in the piping system. Chlorinated polyvinyl chloride (better known as CPVC) has grown steadily in popularity since it was first used in fire sprinkler systems more than 25 years ago. Today, it is the material of choice for many residential and commercial contractors and specifiers who favor its ease of installation, corrosion resistance and overall lower cost structure. Dispelling the Myths The challenge, to date, in specifying CPVC for larger commercial projects located in major seismic zones is that the industry continues to be plagued by myths regarding the performance and reliability of CPVC pipe and fittings during and after a significant seismic event. This article is designed to address two of the more common myths: 1. A CPVC piping system is more likely to be compromised as the result of seismic activity than steel 2. Since CPVC systems require twice as many support hangers as steel systems, the CPVC bracing requirement should also be doubled or, at least, increased in order for the system to withstand seismic loading. Actual field performance, as well as lab tests conducted by third-party engineers and materials scientists, proves that CPVC is at least as good, if not better, than steel during and after a seismic event. Why? Because the yield point of stress of CPVC is much greater than most people realize. In fact, the forcible bending of a BlazeMaster CPVC fire sprinkler system, in particular, can far exceed that specified by the support spacing

3 criterion. Although CPVC is considered a rigid material, it offers added flexibility over steel. Such flexibility is critical to a fire sprinkler system s ability to adjust to movement and distortion. As for the debate over bracing requirements, it should be noted that hanger support requirements are based more on aesthetics than performance. Hanger spacing requirements of every six feet (for 1 pipe) have been established to prevent any appreciable sagging between the hangers. Not only is sagging an aesthetics issue, but it also relates to the NFPA requirement that wet systems must drain. Since CPVC is more flexible, added hangers are needed to eliminate trapped water that could form in sagging pipes. Therefore, it is not accurate to assume that a CPVC system would require additional hangers to withstand seismic loading. Rather, hanger requirements should reflect the mid-span deflection of the CPVC pipe. Scientific mid-span loading testing has shown that BlazeMaster CPVC 1 pipe, specifically, can withstand a mid-span load of at least 300 pounds, which parallels the amount of force of seismic loading. In the past, approvals agencies such as FM have questioned whether CPVC pipe could move enough to adapt to the hangers moving in a direction as a result of seismic activity. It was Lubrizol that led the industry effort to demonstrate how well a CPVC fire sprinkler system could perform without rupturing, despite large-scale deformation of the system. It is also important to note that seismic requirements typically start with cross-mains and feed-mains. Branch lines are seldom required to have seismic bracing. Because of the superior C-factor of BlazeMaster CPVC pipe and the fact that it is only installed in Light Hazard applications, it is not uncommon for a CPVC system to be installed without any seismic hangers, thus minimizing any concerns of the system being able to adapt to hangers moving in a contrary direction. Tests for Determining Seismic Performance It was Wiss, Janney, Elstner Associates, Inc. (WJE), a nationally renowned engineering, architectural and materials testing company that conducted not one, but two tests, utilizing different methodologies to confirm that a CPVC fire sprinkler system could better tolerate the type of motion experienced during an earthquake than threaded steel. With more than 50 years in the business, 400+ professionals and 19 offices nationwide, Chicago-based WJE is a recognized leader in both product testing and specification. WJE first tested the performance of BlazeMaster CPVC pipe and fittings and compared it to the performance of steel pipe (1 in diameter) using cyclic loading. The test setup consisted of suspending the piping from dimensional lumber connected to steel framing, which was anchored to the structural lab floor. Pipe support hangers were spaced 6ft. for each pipe. The test configuration consisted of installing 1 diameter BlazeMaster CPVC pipe in a Z-shape with two 90-degree connections to the test framing. Steel pipe 1 in diameter was assembled independently in the same design configuration. The hangers on one side of the framing were positioned and connected to the wood members such that this section of the piping was allowed to slide during loading. The pipe was filled with water and pressurized to 175 psi before the start of each test. Displacement of the pipe was controlled using a hydraulic actuator. A load cell was in-line with the actuator and pipe to measure the force required to move the pipe.

4 Both types of pipe were displaced a maximum of +3, or a total displacement of 6, during which time the connections were monitored for water leakage. The actuator moved at a frequency of 0.04 Hz (or approximately two cycles every 50 seconds) for a period of nearly 20 minutes. After 50 cycles, the BlazeMaster CPVC system remained uncompromised. Failure did not occur at the elbow connections or along the pipe length. And, the pressure remained at 175 psi throughout the test. In contrast, the steel pipe failed at a 90-degree elbow after approximately 33 cycles of +3 of displacement. The failure not only created a loss in pressure but also caused water to spray out of the joint connection. Upon careful analysis, it was determined that a fatigue failure had occurred at the elbow threaded connection. In a separate test, WJE performed displacement testing on BlazeMaser CPVC pipe in order to compare the performance of CPVC pipe to Schedule 80 steel pipe. Three different assemblies were created: BlazeMaster pipe with solvent welded connections, Schedule 80 steel pipe with fitted connections, and Schedule 80 steel pipe with welded connections. The pipe was assembled to make a straight or Z-shape configuration and then displaced a predetermined amount while pressurized with water. Before testing, each sample was pressurized with water to 175 psi for the straight segment test. A hydraulic ram was attached to one end of the pipe. The opposite end was restrained to resist the applied load from the hydraulic ram. Each sample was laterally displaced 3 at mid-length. The pipe was then pushed longitudinally 18 for 100 cycles or failure, whichever came first. The BlazeMaster CPVC sample did not develop a leak even after 100 cycles. The steel pipe with a threaded coupler failed as it was pushed longitudinally during the first cycle at the coupler threads. The steel pipe with welded coupler could be pushed 8 and 10 in longitudinally for 20 cycles without failure. When pushed 12 longitudinally, the sample failed after three cycles at the connection from hydraulic ram and developed a permanent bend. For the Z-shape configuration testing, a hydraulic ram was attached to one end of the pipe. The opposite end was restrained to resist the applied load from the hydraulic ram. Each sample was placed in a neutral position and displaced +10 for 200 cycles or failure, whichever came first. The BlazeMaster CPVC sample did not develop a leak, even after 200 cycles. The steel pipe with welded elbows did not develop a leak but had a permanent bend from the displacement. The steel pipe with welded elbows did not develop a leak but did exhibit a permanent bend from the cyclic displacement. These permanent bends, in addition to potentially compromising the long-term integrity of the pipe, also can restrict water flow. Proven Performance in the Field Only seven months after its installation-on October 10, 1986, at 11:00 a.m.-a BlazeMaster CPVC fire sprinkler system was put to one of its toughest tests when San Salvador suffered a devastating earthquake that lasted seven seconds and measured 7.5 on the Richter scale. Not only was the epicenter of the earthquake in close

5 proximity to the embassy where the BlazeMaster system was installed, but it is estimated that roughly 1,300 aftershocks rocked the immediate area in the week after the main tremor. Estimates of casualties varied greatly but were believed to be around 1,000 with another 150,000 people left homeless. More than 200 buildings in San Salvador were destroyed or severely damaged, including those in the embassy complex. The main embassy building suffered major damage throughout and had to be immediately abandoned. In fact, a number of massive 1 and 1-1/4 thick steel reinforcement bars embedded in the building s concrete support columns were bent like pretzels from the force of the earthquake. The annex building suffered only moderate damage and remained in operation. A thorough assessment of the main building after the earthquake determined that the building was no longer usable. Although the building had previously survived several quakes along the secondary fault line that ran directly beneath the embassy compound, the damage from this latest quake was irreparable, since the quake cut through two of the building s main supporting pillars and cracked another two, causing the main beams to sag. Despite the massive structural damage, including the complete destruction of all HVAC and plumbing systems, and the fact that fire sprinkler systems are not specifically designed to withstand explosions or earthquakes, the BlazeMaster CPVC fire sprinkler system remained largely intact. Despite two breaks in the main building, the entire system substantially stayed online. Immediately following the incident, the State Department sent a team of engineering experts that confirmed that the BlazeMaster system would have been able to suppress any fire in the complex caused by the earthquake. In fact, once the two breaks were temporarily isolated by embassy personnel shortly after the earthquake, the balance of the complex was fully protected at all times. Amazingly, there were no other breaks or leaks caused by any type of sprinkler system failure. The system maintained pressure and the fire pump cycled, as designed, meaning that, had a fire accompanied the earthquake, the sprinkler system would have worked. Of the two breaks in the main building only, one was understandably caused by the crushing action of a large air conditioner duct falling on a section of distribution pipe. The other break occurred at the steel branch riser on the top level where the building experienced the most vibration. It was also later determined that the break at the branch riser on the top level resulted because the steel riser was not able to absorb the same shock that the more flexible CPVC branch line was able to withstand. The repair of the job was done with ease. The entire rehab effort at the main building (including evaluation of the sprinkler system, completion of necessary repairs, isolation of the two breaks and retesting the system) was accomplished by a three-man team in less than one day. It s also important to note that the sprinkler system in the annex was completely undamaged and required no rehabilitation efforts.

6 Since the fire sprinkler system was not compromised, the city of San Salvador had safe access to the system s water supply. This was critical as it became the only convenient source for water for domestic use immediately following the earthquake, because the municipal water distribution system was completely destroyed by fractured street mains. As amazing as this story is, it is equally interesting to note that in the 25+ years since Lubrizol introduced the first CPVC compound specifically for fire sprinkler systems under the BlazeMaster name, the company has not received notification of any system failures as the result of an earthquake (despite the fact that hundreds/thousands of BlazeMaster systems have been installed in residential and commercial buildings, many of which are located in major seismic zones). Conclusion Stricter building codes are pushing the limits of performance of today s fire sprinkler piping materials. This article has demonstrated that, despite the various myths surrounding the long-term reliability and durability of CPVC pipe and fittings, this high-performance thermoplastic can and has outperformed steel piping during and after seismic events. As a result, it deserves serious consideration when specifying and building residential and commercial projects-especially those located in areas identified as having high seismic activity. Moreover, when installed within structures not falling under the guidelines of NFPA 13 seismic hanging and bracing instructions, the performance and survivability of a BlazeMaster CPVC fire sprinkler system will equal, if not exceed, that of a steel sprinkler system. About the Author: Dr. Olah is the technical manager for BlazeMaster Fire Sprinkler Systems of The Lubrizol Corporation. He has nearly 25 years of experience in the area of CPVC research and development. Olah is a member of the National Fire Protection Association, the National Fire Sprinkler Association, the American Fire Sprinkler Association, ASTM Standards Committee E-5 on Fire Safety Products, Committee F-17 on Plastic Pipe and Building Materials and Committee D-20 on Plastics. He has also served on several Underwriters Laboratories, Standards Technical panels. His Ph.D. in polymer science is from Case Western Reserve University in Cleveland.