Designing for Safety
Fire sprinkler acceptance testing is critical for success.
Recent editions of the International Code Council’s (ICC) model building codes employ greater emphasis on automatic sprinkler systems as a life safety and property protection alternative to passive fire-resistive construction.
Where past editions of the International Building Code and International Residential Code relied heavily on passive fire-resistive construction to confine and control unwanted fires, new materials, designs and equipment have made fire sprinklers a desirable design option at a lower cost.
This evolution is not without critics, however, as some fire safety and construction advocates are concerned that such significant reliance on fire sprinkler systems creates an unanticipated vulnerability if the fire protection system fails to operate as designed.
According to the National Fire Protection Association (NFPA), fire sprinklers are highly effective. Its June 2013 report, U.S. Experience with Sprinklers, includes the following data:
Excluding buildings under construction and buildings without sprinklers in the fire area, sprinklers operated in 91 percent of all reported structure fires large enough to activate them.
When sprinklers operated, they were effective 96 percent of the time, resulting in a combined performance of operating effectively in 87 percent of all reported fires.
Wet pipe sprinklers operated effectively 89 percent of the time, and dry pipe sprinklers operated effectively in 76 percent of cases.
As effective as they may be, like any mechanical system, fire sprinklers must be designed, installed, inspected, tested and maintained to enhance their reliability. Installing a system, then ignoring it, is a dangerous practice that can have serious consequences.
Fire sprinkler acceptance testing
Once a fire sprinkler system has been designed and installed, both the International Building Code and International Fire Code require suitable testing to confirm the system was installed as intended, and will perform as expected. In fact, the International Fire Code prohibits building occupancy until the tests have been performed and approved by the code official.
In order to assure that proper testing and documentation has been prepared, the NFPA has created a Recommended Practice for Commissioning of Fire Protection and Life Safety Systems. Although not required by the international codes, this consensus document outlines inspector and tester qualifications, and recommends the following steps in the commissioning process:
- Verify that installation is in accordance with working drawings.
- Inspect overall installation as outlined in the commissioning plan.
- Perform pre-functional testing of all systems to provide proper functionality and to ensure interoperability.
- Perform and document testing of all systems to provide proper functionality, to ensure integration, and to ensure the systems were left in a state of operational readiness.
- Update owner project requirements and address any outstanding issues.
- Update commissioning plan/record.
- Issue completion/acceptance phase commissioning progress report.
- Verify compliance and accuracy of sequence of operation.
A commissioning team following the NFPA Recommended Practice can be confident it is meeting or exceeding the current standard of care for fire sprinkler testing. Any code official would be happy to obtain this level of testing and documentation to evaluate the fire protection systems’ readiness and reliability.
Even the simplest fire sprinkler system has a series of tests that should be accomplished before the system is declared ready for service and the building ready for occupancy. A fire sprinkler system connected to a municipal water supply has at least two tests and inspections that should be accomplished before occupancy. Systems that are connected to private water supplies, elevated or suction tanks, have cross-contamination prevention apparatus or are equipped with fire pumps that have even more required tests.
Underground acceptance tests
The underground water line between the municipal source and fire protection system (or backflow prevention device, if mandated) requires two important tests outlined in NFPA 24: Standard for the Installation of Private Fire Service Mains and Their Appurtenances. The first is a hydrostatic pressure test and the second is a flush to assure there is no residual debris in the pipe before connecting it to the fire protection system.
Once laid in the trench and supported or anchored to prevent movement, underground pipe must undergo hydrostatic pressure test at a gauge pressure of 200 psi or 50 psi in excess of the system working pressure, whichever is greater. (If, for example, the incoming water pressure were 183 psi, the underground pipe would have to be tested to 233 psi.) The test pressure must be maintained at gauge pressure of ±5 psi for two hours. If there is no visible leakage or the gauge pressure loses less than 5 psi, the test is considered successful.
Underground piping, from the water supply to the system riser, and lead-in connections to the system riser also must be completely flushed at a rate of no less than 10 feet per second before the connection is made to downstream fire protection system piping (see Table 1). The flushing operation must continue until water flow is verified to be clear of debris.
If a backflow prevention assembly is installed in the supply line to isolate the fire protection system from the potable water source, the device must be “forward flow” tested to ensure proper operation.
Aboveground acceptance tests
Once inside the building, the aboveground portion of the sprinkler system must undergo a series of tests and inspections prior to occupancy. The tests are prescribed to one or more of the three NFPA standards on fire sprinkler system design and installation as well as the building and fire codes. (NFPA has sprinkler system design standards for one- and two-family dwellings and manufactured homes; for low-rise residential occupancies (generally up to four stories); and all other applications.)
Once the sprinkler pipe is installed (or portions are complete in large or complex projects) it, too, must undergo a hydrostatic pressure test to verify there are no leaks. Where the fire sprinkler system is equipped with a fire department connection that enables a fire pumper to boost the internal pressure, the system must be tested to 200 psi for two hours. The hydrostatic test gauge should be placed on the lowest branch line. If weather conditions are near freezing, an “interim” 40 psi air test may be conducted to test for leaks, but a 200 psi hydrostatic test still must be conducted before final approval.
Piping between the exterior fire department connection and the check valve in the fire department connection inlet pipe must be hydrostatically tested in the same manner as the balance of the system. After repair or replacement work affecting the fire department connection, the piping between the exterior and the check valve in the fire department connection inlet pipe must be isolated and hydrostatically tested at 150 psi.
Small specialty systems or equipment in for one- and two-family dwellings and manufactured homes may not require a fire department connection. In those cases, a hydrostatic test at the normal system operating pressure is satisfactory.
Acceptance tests based on system “types”
There are four basic “types” of fire sprinkler systems described in NFPA 13, Standard for the Installation of Sprinkler Systems:
Wet pipe where there is water in the pipe network at all times. These systems generally are installed where ambient temperatures above 40 F can be maintained,
Dry pipe where the sprinkler pipe contains air or dry nitrogen under pressures sufficient to keep the main control valve closed. When a sprinkler opens, the gas is emitted and water fills the pipe network,
Pre-action that is similar to a dry pipe system where there is only a nominal, supervisory pressure in the sprinkler pipe, and some other action — such as the operation of a smoke detector — opens the main control valve to let water into the overhead pipe, and,
Deluge where another device — such as a smoke or heat detector or even a manual emergency release — opens the main control valve and water flows from every sprinkler in the system.
In addition to the hydrostatic or pneumatic tests to verify the pipe’s integrity, each of the system types requires additional performance tests.
Wet pipe systems generally are the simplest to test. There are two tests to perform: waterflow detecting devices and fire alarm system circuits must be flow tested through the inspector’s test connection and produce an audible alarm on the premises within five minutes after the flow begins and until it stops.
The second test, called the main drain test, evaluates the condition of the incoming water supply. The main drain valve located on the system riser is opened and runs at full flow until the system pressure stabilizes. The incoming pressure should be documented so it can be compared against future main drain tests as required by the International Fire Code and performed in accordance with NFPA 25, Standard for the Inspection, Testing and Maintenance of Water-Based Fire Extinguishing Systems.
For dry pipe sprinkler systems, in addition to the standard hydrostatic test, an air pressure leakage test at 40 psi must be conducted for 24 hours. Any leakage that results in a loss of pressure in excess of 11/2 psi for the 24 hours must be corrected.
A dry pipe trip test also is performed. In this test, the inspector’s test valve — located at the highest, most remote part of the system — is opened. The test measures the elapsed time to open or trip the main valve and the time for water to be discharged from the inspector’s test outlet. All times are measured from the time the inspector’s test connection is completely opened. The trip test also is used to document the system air pressure where the dry pipe valve opens. Dry pipe systems also require main drain tests similar to wet pipe systems.
Preaction and deluge sprinkler systems require that their main operating valves be tested in accordance with the manufacturer’s instructions. These systems are more complex because of the integration of other detection and operating devices that are needed to operate the main valves. When testing a deluge valve, normally the main control valve is isolated from the distribution pipe so water is not discharged, however, the client may insist that a full flow test is performed. These systems also require main drain tests similar to wet pipe systems.
If, because of excess incoming pressure, systems are equipped with pressure-reducing valves, each one must be tested to ensure proper operation under-flow and no-flow conditions. Testing is performed to verify that the device properly regulates outlet pressure at both maximum and normal inlet pressure conditions.
Finally, if the system is equipped with a backflow prevention assembly, it must be forward flow tested to ensure proper operation.
Nearly every sprinkler system installed under modern codes is required to have supervisory equipment that monitor and report water flow, high or low air pressure, high or low water temperature or “tamper” a signal that reports whether a control valve is in the open or closed position. More sophisticated systems may have even more complex supervisory devices, all of which must be tested in accordance with the manufacturer’s instructions and often in compliance with NFPA 72, National Fire Alarm and Signaling Code.
There’s a fire service adage that “the job ain’t done until the paperwork’s finished.” This is equally true for acceptance testing fire protection systems. The International Building Code, International Fire Code and all of the NFPA documents mentioned in this article require various tests and are properly documented to show they have been completed and meet the requirements of the codes and standards. The international codes also require a “statement of compliance” that the installing contractor attests the system has been installed in accordance with the approved plans, manufacturer’s equipment requirements and appropriate national standard. Any deviations from these must be included in the report.
The NFPA documents include model reporting forms, and some fire or building code officials may be able to provide forms that satisfy their requirements.
Fire sprinkler systems are highly reliable when they are designed and installed in accordance with national standards. The importance of acceptance tests required by the international codes to verify they will perform as expected cannot be overlooked. Project managers and engineers must be diligent to assure these tests are done and documented before turning the building over to their clients. NFPA 3 Recommended Practice for Commissioning of Fire Protection and Life Safety Systems can provide professional guidance to assure nothing is missed.
Rob Neale is the vice president for government relations for national fire service activities at the International Code Council in Washington, DC. A former municipal fire marshal and deputy superintendent at the National Fire Academy, Neale’s assignment at ICC is to get the fire service more involved in code development, adoption and enforcement while striving to strengthen the working relationships between building and fire code officials.