Testing Pressure-Reducing Valves

BY BILL GUSTIN

Every morning at shift change, firefighters throughout North America perform daily apparatus checks and routine maintenance on their equipment. A vital portion of an apparatus check involves operating the pump so that you can depend on it to get water. Generally, this involves engaging the pump, operating the primer, and fully opening every intake and discharge valve while their caps are in place. This “exercises” the valves and facilitates a check of discharge gauges. This is followed by closing the discharge valves and relieving the pressure by operating their respective bleeder valves. Valves are occasionally lubricated to ensure that they will operate easily. No daily pump test would be complete without operating its relief valve or its automatic pressure control governor and the transfer valve on two-stage pumps. When temperatures are above freezing, conscientious driver engineers will connect their apparatus to a hydrant and flow water through every discharge. They also will regularly back flush the apparatus pump and do so after every drafting operation.

Experienced engineers realize the importance of frequently exercising and lubricating every valve on a pump and understand that without frequent use and proper maintenance, valves may become difficult to operate or won’t open completely because of corrosion. For example, my department recently found that corrosion had frozen closed some apparatus intake relief valves. We caused this problem by not periodically exercising the valves. This involves raising the pump’s intake pressure above the relief valve’s setting, causing it to open and dump water. Imagine the condition and reliability of an apparatus discharge valve that hasn’t been operated, not even cracked partially open in years. It would be irresponsible for a fire department to send firefighters into harm’s way with a hoseline connected to this valve.

However, this is exactly what fire departments do when they send firefighters to fight a fire in a high-rise building equipped with pressure-reducing valves (PRVs) for standpipe hose outlets and do not require PRVs to be tested in accordance with National Fire Protection Association (NFPA) 25, Standard for the Inspection, Testing, and Maintenance of Water-Based Fire Protection Systems. Additionally, consider that code requirements for exit travel distances, distances between stairwells, and the rating of required fire separations in high-rise buildings are often not as stringent when a building is fully sprinklered. Therefore, it is disturbing to think that the design of many modern high-rise buildings is predicated in large part on a properly designed and operating sprinkler system, a system that may not control a fire if its pressure-reducing floor control valves cannot open and flow water because they haven’t been flow tested in years.

I do not offer step-by-step instructions on testing PRVs or advocate that fire departments get into the fire protection system testing business. However, I want to give firefighters a general idea of how PRVs should be tested and heighten their awareness of the importance of testing PRVs. It is very important that firefighters have a basic understanding of the purpose and function of PRVs because their lives may depend on them when they fight a fire in a high-rise building.

EXERCISING PRVs

Every firefighter who could respond to a fire in a high-rise building that has a pressure-reducing standpipe hose outlet and sprinkler floor control valves should be familiar with their function and what can go wrong if they are improperly installed, tested, or maintained. They should learn the lessons of the 1991 One Meridian Plaza high-rise building fire in Philadephia (see “one Meridian Plaza Fire, Fire Engineering, August 1991, 51-70, http://bit.ly/18p6JoY). As a result of improperly installed and adjusted pressure-reducing standpipe outlet valves, three Philadelphia firefighters died. (For further information on PRV nomenclature and how PRVs function, see “Changes in High-Rise Buildings: Is It Time to Change Your Procedures?” Fire Engineering, April 2013, 101-126, http://bit.ly/HJFtu8.) Since 1993, NFPA 14, Standard for the Installation of Standpipe and Hose Systems, requires a minimum pressure at 2½-inch standpipe hose outlets of 100 pounds per square inch (psi) while flowing a minimum of 250 gallons per minute (gpm). To achieve that flow and pressure on upper floors, a building’s fire pumps must be designed to overcome the pressure loss from elevation (roughly five psi per floor) and the friction loss in the standpipe and the ancillary piping. This requires fire pumps to develop pressures that can be dangerously high at lower floor levels that could burst fire hose and sprinkler system components. PRVs are installed in standpipe and sprinkler systems to limit static and residual (flow) pressures downstream of the valve to safe levels, a maximum of 175 psi for 2½-inch standpipe hose outlets and 165 psi for sprinkler system floor valves. PRVs reduce both static and residual (flow) pressures through an internal floating valve that responds to pressure differences downstream of a PRV. When there is a reduction of pressure downstream of the valve, such as when a sprinkler is opened or firefighters open a nozzle of a hoseline connected to a standpipe outlet, the floating valve will lift off its seat and allow water to flow. Closing a nozzle results in an increase in pressure downstream of a hose outlet PRV, which forces its floating valve to close and keep static pressure in the hose from exceeding 175 psi. Look at the pressure-reducing sprinkler floor control valve in photo 1. Its threaded stem, rotated by the handwheel, would indicate to someone unfamiliar with PRVs that this valve is open when, in fact, its internal floating valve is closed because no water is flowing. This can be misleading because a PRV’s threaded stem is not connected to the floating valve stem, which has no threads. Opening the valve’s handwheel raises the threaded stem, which allows space for the floating valve stem to rise as the valve lifts off its seat. If you fail to test the PRVs in accordance with NFPA 25, the result may be a floating valve that is frozen closed or that cannot fully open because of corrosion. The standpipe outlet in photo 2 allows only a trickle of water to flow even when its valve wheel is in the fully open position. Note that the floating valve stem has no threads, indicative of a PRV. The floating valve could barely lift off its seat to allow water to flow because of years of corrosion, made worse by neglecting to exercise the valve since the time the standpipe system was installed several years ago. As a result of this neglect of this PRV, when it was eventually flow tested it had dangerously inadequate residual pressure and had to be replaced. Additionally, consider that a floating valve inside a PRV that fails to close completely because of lack of exercise, corrosion, or debris on its seat can allow dangerously high static pressures to build up in hoselines and sprinkler components. The exterior appearance of PRVs can be deceiving because it is internal corrosion that causes them to fail. The shiny chrome PRV in photo 3 was installed 12 years ago but had not been flowed in several years. It was removed after it failed a flow test because of the corrosion of its floating valve stem (photo 4).

pressure-reducing sprinkler floor control valve
(1) Although the handwheel on this pressure-reducing sprinkler floor control valve is in the open position, its internal floating valve is closed because no water is flowing. (Photos by Eric Goodman unless otherwise noted.)
Water barely drips out of this standpipe PRV
(2) Water barely drips out of this standpipe PRV, which hasn’t been flowed in several years. Its handwheel is in the fully opened position, but its floating valve can barely lift off its seat because of corrosion. Note that the floating valve stem has no threads, which indicates a PRV. (Photo by Mac McGarry.)
Although there is pretty chrome on the outside
(3) Although there is pretty chrome on the outside,
PRV failed because of corrosion and lack of exercise
(4) there is ugly corrosion inside. Installed 12 years ago, this PRV failed because of corrosion and lack of exercise.

Corrosion, however, is not the only cause of PRV failure. PRVs that have been recently installed in newly constructed and renovated buildings can fail to deliver proper flow and pressure if they are improperly adjusted, if they are installed at the wrong floor level, or if a standpipe or sprinkler system is improperly designed. As stated, PRVs are installed in systems to limit potentially dangerous high pressures in hoselines and sprinkler systems, and that pressure loss because of elevation is roughly five psi per floor. Accordingly, the pressure-reducing effect of PRVs is greater on lower floors than higher floors. For example, a standpipe outlet PRV on the third floor will reduce pressure to a greater extent than one on the 30th floor. Now, imagine what would happen if a PRV that was designed/adjusted for the third floor was by mistake installed on the 30th floor. Its pressure-reducing effect at that elevation would result in dangerously inadequate flow and pressure or perhaps no flow at all. It is, therefore, critical to have new sprinkler and standpipe systems fully flow tested before issuing a certificate of occupancy.

TEST PROCEDURES

The following is an overview of the flow tests of sprinkler and standpipe PRVs as required in NFPA 25: Most modern and renovated high-rise buildings have combination sprinkler/standpipe systems; sprinkler piping branches off standpipes at each floor level. Flow to sprinklers on each floor is controlled by one or more “floor” or “zone” control valves (photo 5, D), typically located at a stair landing above a 2½-inch hose outlet (photo 5, C). NFPA 25 requires sprinkler systems to be flow tested annually. Static and residual pressures on the inlet side and outlet side of floor control valves are recorded and compared to the system’s original design requirements and previous test results.

 Components of a combination sprinkler/standpipe system.
(5) Components of a combination sprinkler/standpipe system. (A) The standpipe riser. (B) The supply-side pressure gauge reading 200 psi static pressure in the standpipe. (C) The pressure-reducing 2½-inch standpipe outlet valve. (D) The pressure-reducing floor control valve, which controls the flow of water from the standpipe to the sprinkler piping on the fourth floor and keeps the system static and residual pressures from exceeding 165 psi. (E) The tamper switch initiates a supervisory signal to the fire alarm system if the valve wheel is operated. (F) The flow switch. (G) The system-side pressure gauge, reading 150 psi static pressure in the sprinkler piping. (H) The relief valve is set to “open” and will dump water into the drain if the sprinkler system pressure reaches 175 psi. (I) This valve controls the flow of water to the inspector’s test/drain valve. (J) The inspector’s test/drain valve has two positions: “Test,” replicating the flow of one sprinkler head, and “drain,” to flow test the system and drain residual water in the sprinkler piping.

Flow testing of sprinklers on combination systems is facilitated by a combination inspector’s test/drain valve that is downstream of the floor control valve and connected to a drain riser. Some inspector’s valves (photo 6) have three positions: “test,” “drain,” and “off”; others have just two positions, test and drain (photo 5, J). This requires an additional valve upstream, between the floor control valve and the inspector’s test/drain valve (photo 5, I). Moving the valve to the test position allows water to flow through an orifice that replicates the flow of one sprinkler head. This tests the function of the floor’s flow switch (photo 5, F). Flowing water while the valve is in the test position should initiate a water flow alarm within 90 seconds. This delay is permitted to compensate for temporary pressure surges in the system. Flowing water in the test position also checks the alarm system by ensuring that a water flow is indicated on the system’s annunciator panel as well as indicating the floor and stairway where water is flowing (photo 7). The annual flow test is conducted by moving the valve to the drain position, allowing water to flow through an orifice that is at least one inch in diameter. Additionally, the drain position has another purpose: After a fire, closing a floor control valve will stop the flow of water to the floor’s sprinkler system, but water remaining in the piping downstream of the floor control valve will continue to flow out of open sprinkler heads, causing unnecessary water damage. The drain valve, again, at least one inch in diameter, diverts residual water flowing from open sprinkler heads to the drain riser.

combination inspector's test/drain
(6) This combination inspector’s test/drain has three positions: “off,” “test,” and “drain.” (Photo by Chris Martinez.)
fire alarm annunciator panel
(7) The fire alarm annunciator panel indicates a water flow on the fourth floor, stairway 2. (Photo by Chris Martinez.)

NFPA 25 requires an annual “partial” flow test of standpipe hose outlet PRVs. Partial flow tests are relatively easy to perform because they do not require continuous flow from a hose outlet. A partial flow test involves attaching a cap gauge with an air/water bleeder cock to a hose outlet, opening the valve’s handwheel, and recording static pressure on the inlet and downstream side of the PRV (photo 8). The small amount of water that flows when bleeding air from the gauge and what drains when the gauge is removed from an outlet is easily captured in a bucket. Remember that NFPA 14 requires that standpipe outlet static and residual pressures not exceed 175 psi; hence, a pressure exceeding 175 psi on the cap gauge could indicate a PRV with a floating valve that will not fully close because of corrosion, debris on the valve seat, or maladjustment. The partial flow test is also intended to exercise the floating valve by momentarily lifting it off its seat. NFPA 25 requires a full flow test of pressure-reducing standpipe hose outlets every five years. This involves flowing every standpipe hose outlet in a building and recording static and residual pressure on the inlet and outlet sides of the valve and its gpm flow. The device in photo 9 is designed specifically for flow testing pressure-reducing standpipe outlets. It is equipped with a pressure gauge to read outlet static and residual pressure, a flow meter to measure gpm, and a gate valve to “throttle” the flow from wide open down to 250 gpm. In photos 10 and 11, a flow meter that fire departments commonly use is adapted for testing PRVs by connecting an in-line gauge and a gate valve. Data from the test will be compared to the system’s original design specifications and previous tests. An important consideration when conducting a full flow test is where to direct the flow of water for at least 250 gpm. Since 1993, NFPA 14 has required standpipes equipped with PRV hose outlets to have a three-inch-diameter express drain riser with 2½-inch inlets on every other floor (photo 12). This facilitates flow testing by connecting a hoseline between the flow meter and the drain riser. When conducting flow tests for the photos in this article, we found one 50-foot section of three-inch hose to be too long to connect to the drain riser on the floor below the outlet being tested, which resulted in severe kinks. This problem was corrected by connecting five or six short “pigtail” sections of three-inch hose used to connect to standpipe outlets in hose cabinets (photo 13).

cap gauge reading standpipe outlet static pressure
(8) The cap gauge reading standpipe outlet static pressure for an annual partial flow test.
testing standpipe PRVs, combines a pressure gauge, a flow meter, and a gate valve
(9) This device, designed specifically for testing standpipe PRVs, combines a pressure gauge, a flow meter, and a gate valve.
flow meter commonly used by fire departments
(10) A flow meter commonly used by fire departments is adapted to test standpipe PRVs by connecting an in-line pressure gauge and a gate valve.
flow meter indicates a flow of more than 250 gpm
(11) The flow meter indicates a flow of more than 250 gpm. The outlet flowed more than 500 gpm when the gate valve was fully opened.
three-inch express drain riser
(12) A three-inch express drain riser facilitates full flow testing of standpipe PRVs. Here a three-inch hose is connected between the flow meter testing the outlet on the floor above and a 2½-inch inlet required at every other floor.
Connecting
(13) Connecting “pigtail” sections of three-inch hose eliminates kinks caused by excess hose between the flow meter and the express drain riser.

Conducting a full flow test on standpipe systems installed prior to 1993 can be problematic if they do not have a drain riser of sufficient capacity to flow at least 250 gpm. One option is to run hose down stairwells to the outside connected to a diffuser at the end of the line to dissipate the velocity of discharging water (photo 14). Stairwells with a well opening of sufficient size to accommodate 2½- or three-inch hose simplify the process because one 50-foot length can be used for as many as five floors. Hose suspended in a well can be very heavy and exert a considerable amount of strain on couplings. It is, therefore, a good idea to lighten up on the hose by supporting it with rope or tubular webbing secured with a girth hitch (photo 15). When running hose down stairwells is not practical, NFPA 25 suggests an alternative: Shut down another standpipe in the building and use it as a drain riser. This requires replacing PRVs with conventional valves for inlets and at the ground floor for an outlet. This is definitely not a “Plan A” because it is a very labor- and time-intensive. When it is impossible to conduct full flow tests on hose outlets, they must be removed and bench tested. Considering the time and expense involved, it’s no wonder building owners are reluctant to have full flow tests of standpipes conducted, especially when their building does not have three-inch drain risers.

Hose from the standpipe PRV being flow tested terminates in a diffuser outside the building.
(14) Hose from the standpipe PRV being flow tested terminates in a diffuser outside the building. This is one option for flow testing standpipe PRVs that do not have a three-inch express drain riser.
Hose suspended in the well opening is supported by tubular webbing to take the strain off the couplings.
(15) Hose suspended in the well opening is supported by tubular webbing to take the strain off the couplings.

FLUSH AND FLOW

The possibility of a defective PRV is a compelling reason for firefighters to fully flush standpipe outlets before they connect a hoseline (photo 16) and to flow their hoseline with the nozzle fully open before they enter a hostile environment (photo 17). Consider what can happen to firefighters who fail to flush a pressure-reducing standpipe outlet valve that hasn’t been flowed in several years before they connect their hoseline and then fail to fully flow it: As they open the handwheel, water fills the hose, and it becomes rigid. Additionally, the in-line gauge is reading close to 100 psi-excellent pressure, they assume, to fight fire. The crew advances the hoseline to the stairwell door at the fire floor and dons self-contained breathing apparatus, face pieces, hoods, helmets, and gloves. Before members open the stairwell door and enter the fire floor, they crack the nozzle open to bleed trapped air and have a wedge in hand to chock open the door. They then advance down the smoke-filled hallway. When they reach the door to the fire apartment, they encounter fire because the door was left open by fleeing occupants. When the nozzleman opens the nozzle, the hoseline becomes limp, and water barely trickles from the nozzle. What went wrong? The members were fooled by static pressure. They connected to a pressure-reducing standpipe outlet valve that had never been tested; it had a floating valve that could barely lift off its seat because of corrosion and years of neglect. The small amount of water flowing from the valve was sufficient to make the hoseline rigid and read 100 psi on the in-line gauge, but that’s static pressure; water is not flowing, which is meaningless when assessing a hoseline’s flow and pressure capability. The crew members, who hastily followed the limp hoseline back to the stairway, learned a valuable lesson: Never leave the refuge of a fire-rated stairwell or open a door that is keeping fire within a fire apartment and out of the public hallway without first fully flushing the standpipe outlet and fully opening the nozzle to judge the quality of its stream and read the true residual pressure on the in-line gauge.

Firefighters flush a conventional standpipe outlet before connecting a hoseline.
(16) Firefighters flush a conventional standpipe outlet before connecting a hoseline.
Firefighters fully flow the two-inch hoseline into a stairwell on the floor below the fire to judge the quality of its stream and to accurately read flow pressure on the in-line gauge.
(17) Firefighters fully flow the two-inch hoseline into a stairwell on the floor below the fire to judge the quality of its stream and to accurately read flow pressure on the in-line gauge.

•••

As a company officer, I see a disconnect among fire suppression personnel, fire prevention personnel, and the fire protection system industry. I place a lot of the blame squarely on suppression personnel when they do not thoroughly familiarize themselves with high-rise building systems that they must use to fight a fire and fail to reach out to fire prevention bureau personnel and fire protection system contractors for information.

BILL GUSTIN is a 41-year veteran of the fire service and a captain with the Miami-Dade (FL) Fire Rescue Department. He began his fire service career in the Chicago area and conducts firefighting training programs in the United States, Canada, and the Caribbean. He is a lead instructor in his department’s officer training program, is a marine firefighting instructor, and has conducted forcible entry training for local and federal law enforcement agencies. He is an editorial advisory board member of Fire Engineering and an advisory board member for FDIC. He was a keynote speaker for FDIC 2011.


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