The National Fire Protection Association Standard for the Inspection, Testing and Maintenance of Water-Based Fire Protection Systems (NFPA 25) details recommended practices to prevent system failure and ensure fast and effective response in a fire emergency. Most of the recommended tasks are performed at the facility, where the system is located, either by the building owner or a qualified contractor.
However, in addition to these onsite tests, there are also recommendations to send a sample of a system component to a laboratory for testing. Here is a description of those tests that must be performed offsite at a recognized testing laboratory.
Automatic sprinkler testing
NFPA 25 – Section 5.3.1 “Where required by this section, sample sprinklers shall be submitted to a recognized testing laboratory acceptable to the authority having jurisdiction for field service testing.”
The reason for this testing is to ensure that older sprinklers in a system will operate as intended in a fire. The standard allows for either 1) replacement of all of the sprinklers in the system or 2) one-percent of the sprinklers in a system, or a minimum of 4, shall be sent to a laboratory for testing. Table 1, details the required frequency of this testing. Sprinklers manufactured prior to 1920 must be replaced and are not subject to testing.
Sprinklers sent into a laboratory for testing are exposed to a plunge oven in order to determine the response time of the sprinkler when exposed to a defined temperature and air velocity. The acceptable response time is based on a response time index (RTI). For example, standard response sprinklers are defined as having an RTI value between 80 (meters-seconds)1/2 and 350 (meters-seconds)1/2, a fast response sprinkler must have an RTI less than 50 (meters-seconds)1/2.
The plunge oven circulates air at a specified temperature and velocity. The sprinkler, connected to 5 psi of air pressure, is “plunged” into the oven at which time a stopwatch is activated. When the sprinkler releases, the pressure drops and the timer stops. This time to release is used to calculate the RTI.
Automatic water mist nozzle testing
NFPA 25 – Section 126.96.36.199 “Where required by this section, sample automatic water mist nozzles shall be submitted to a recognized testing laboratory acceptable to the authority having jurisdiction for functional testing.”
The testing requirement for automatic water mist nozzles is similar to automatic sprinklers. They are required to be replaced or tested after 20-years in service and every 10-years thereafter. However, water mist nozzles exposed to harsh environments are to be replaced or tested every 5 years. The testing of automatic water mist nozzles is also carried out in the plunge oven.
Diesel fuel testing
NFPA 25 Section 188.8.131.52 “Diesel fuel shall be tested for degradation no less than annually.”
NFPA 25 requires an ASTM oxidation stability test be done to ensure continued fuel performance. Oxidation stability covers two important physical properties of diesel oil – thermal stability and storage stability. Storage stability considers environmental factors such as humidity, sunlight, microbes, temperature, etc. While thermal stability is the tendency to generate gum and solid deposits at elevated temperatures.
Firefighting foam concentrate testing
NFPA 25 Section Table 184.108.40.206 “Summary of Foam Water Sprinkler System Inspection, Testing and Maintenance. Foam Concentrate Samples Annually 11.2.9”
NFPA 25 Section 11.2.9 “Samples shall be submitted with the manufacturer’s recommended sampling procedures.”
The physical properties of foam concentrate can be tested to determine whether the foam has changed physically since the time of manufacture. Properties such as refractive index, pH, density and viscosity are key properties that should remain stable over time. If these properties have changed significantly, it can indicate the foam has been inadvertently diluted with water, contaminated by some other compound, or that it is breaking down over time and may not perform effectively.
The viscosity of a concentrate sample is measured using a Brookfield® Viscometer. Samples can have a higher viscosity because a polymer is added to the formulation to allow the foam to function on polar solvents, such as ethanol. Ensuring the viscosity of the foam concentrate sample falls within the specified range, indicates the polymer is at the appropriate level in the formulation and that the concentrate will extinguish polar solvent fires. Additionally, the viscosity is important to ensuring the concentrate will proportion at the correct concentration. If the viscosity of a concentrate rises significantly over time, it may no longer proportion acceptably.
Foam proportioning is another test required annually by NFPA 25. This test can be performed in the field using a refractometer or a conductivity meter. However, if it is not feasible to measure the concentration of the foam solution in the field, samples can be sent to a laboratory where often times a more accurate result can be obtained.
Performance properties of a foam concentrate can also be tested in a laboratory setting. Performance properties can include the foam expansion, 25% drain time, surface tension, spreading coefficient and burnback performance.
As foam ages, the expansion can decrease—this is more likely if the foam concentrate is stored incorrectly. If the expansion decreases below a critical value, the majority of the foam will sink below the surface of the flammable liquid, making extinguishment unlikely.
By testing foam annually, and tracking both the physical and performance properties of the concentrate, the effectiveness of the foam in a real fire situation can be assured.
Things to consider
When looking for a laboratory to send sprinkler system components for testing, there are several things to consider:
- Find a laboratory that focuses on NFPA 25 testing to ensure the testing in completed as outlined in the standard.
- Consider the turnaround time for the testing. A quicker turnaround time ensures you get an answer back quickly regarding the condition of your fire protection system component. For contractors, a quick turnaround time allows you to bill for the service and get paid for the service more quickly.
- Some laboratories provide kits to make it easier for you to test. Kits often contain sample jars, boxes, shipping labels, etc. These kits make it easier for you to take the samples and ship them off to a laboratory for testing.
- Check with the authority having jurisdiction to make sure the laboratory is acceptable to them.
- Laboratories with certifications such as ISO-9001, are audited annually by an outside company and are more likely to provide accurate results.
- Price is always a consideration when choosing a vendor. Make sure to consider the entire cost of the sampling – packaging and shipping costs are sometimes included in the price. Shipping can be significant when sending samples.
Most contractors and building owners are familiar with the testing that must be completed onsite on either a weekly, monthly, yearly or other periodic basis. However, there are also testing that must be completed by either replacing the system component or sending in a sample to a laboratory for testing. Examples of this type of testing are automatic sprinkler testing, automatic water spray nozzle testing, fire pump diesel fuel testing and firefighting foam concentrate testing. By performing both the onsite requirements, in addition to the offsite laboratory testing, the likelihood of the system operating correctly during a fire can be increased considerably.
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