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How Does NGC Testing Services Stack Up?

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Jul 14, 2021 by Bob Menchetti

Testing Services Update | August 2021

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“How Does NGC Testing Services Stack Up?” references the fact that we stack up as one of the best testing laboratories, but it also refers to the multiple stacks of prebuilt test floors we store in our acoustical laboratory. Later in this newsletter, we will discuss why this is good news for our customers. 

We will also discuss our laboratory’s wind load test capabilities. Since we are entering hurricane season, we have included a wind speed-pressure chart that correlates wind load test pressures in PSF (pounds per square foot) to actual wind speeds and hurricane category storms. 

In addition, a very important test method in terms of fire safety, and perhaps the greatest volume test we conduct, ASTM E84 utilizes the 25-foot long Steiner Tunnel to determine the flame spread and smoke development of surface materials. We discuss this test and provide how the reported flame spread and smoke-developed indices are calculated. Typically, building codes require all interior finish materials to be evaluated by this test method. 

Finally, the basis of a testing laboratory’s all-important accreditation, including our own, is ISO/IEC 17025. The most recent 2017 version of ISO/IEC 17025 includes significant changes from the previous 2005 version, including more stringent requirements in evaluating the accuracy of test results, assessing risks and opportunities, and added insurance of impartiality. We will outline these changes in this newsletter as well.

Please keep us in mind for your next test project. Experience firsthand how NGC Testing Services stacks up.

FOCUS ON:  Wind Testing

Wind Speed Intensity Chart
Click to view the full chart

We have the capabilities to test exterior building products and systems such as exterior finishes, sheathing, windows, doors, and curtain walls under wind load conditions.

With hurricane weather on the horizon, we thought we would share some facts about wind-based hazards. At NGC Testing Services, we duplicate some of these wind loads through ASTM E330 to see how building assemblies and materials resist damage from high winds. The adjacent table gives examples of wind and pressure rates and the havoc wind can create.

The Saffir-Simpson Hurricane Wind Scale, for example, estimates potential hurricane damage based on sustained wind speed, with a rating of 1 to 5 (5 being severe catastrophe likely). We also test for air leakage (ASTM E283) and water penetration (ASTM E331) under high wind loads. For more information contact us today.

Calculating Flame Spread and Smoke Developed

Flame Spread Testing Tunnel
Steiner Tunnel at NGC Testing Services

ASTM E84 Standard Test Method for Surface Burning Characteristics of Building Materials

How is “flame spread” measured and calculated? Through the 25-foot-long Steiner Tunnel test furnace windows, we observe the distance traveled by the flame front and plot it (in feet) versus time. We then calculate the resulting time-distance curve's total area (AT), ignoring any flame front recession.

If the calculated total area is less than or equal to 97.5 feet per minute, the flame spread value is 0.515 times the total area (FS = 0.515 * AT). If the calculated total area is greater than 97.5 feet per minute, the flame spread value is 4,900, divided by the difference of 195 minus the total area (FS = 4900/(195-AT)). For reporting, the calculated flame spread value is rounded to the nearest multiple of 5.

How is “smoke developed” measured and calculated? Throughout the 10-minute test, percent light absorption data is collected from a photocell located in the exhaust duct of the test furnace. This data is plotted versus time and we calculate the total area (ATS) under the resulting time-light absorption curve. We divide this calculated area by the area under the time-light absorption curve for heptane (AH), which is determined from calibration of the test furnace, and multiply the result by 100 (SD = (ATS/AH) * 100).

For reporting, the calculated smoke-developed value is rounded to the nearest multiple of 5, unless it is greater than 200, then it is rounded to the nearest 50. The performance of the material is compared with that of fiber-cement board and heptane, which have been arbitrarily established as 0 and 100, respectively.

ISO/IEC 17025:2017

The ISO/IEC 17025 standard serves as the basis of our testing laboratory’s accreditations, including NVLAP and IAS. The standard specifies the requirements to demonstrate our testing laboratory’s competence in performing the myriad of the tests we conduct for our partners.

The most recent version of the ISO/IEC 17025 standard, published in 2017, has a few significant changes from the now outdated 2005 version. The 2017 version is more performance-based and less procedure-based, with a new focus on competence, impartiality, confidentiality, and consistency of operations. This new focus provides our clients with added confidence in our laboratory’s ability to consistently deliver valid and reliable results.

The new version of the standard also takes on a more risk-based approach, putting it in greater alignment with an ISO 9001 management system. Laboratories are now required to consider both risks and opportunities associated with their activities and take appropriate action. Risks to impartiality must also be considered and, if identified, they must be minimized or eliminated.

Another change in the 2017 version involves the use of an appropriate decision rule when establishing conformity. Laboratories must document and state its decision rule and apply it when determining if a test result conforms to a specification or standard. When applied, the decision rule must account for the measurement uncertainty of the result and consider the level of risk (such as false accept and false reject) before stating conformity.

Lastly, the 2017 version of the standard recognizes the major changes in information technology that have occurred since 2005. Accordingly, the newer version of the standard has provisions for electronic-based processes, reports, and records.

NGC Testing Services is in full compliance with this more stringent 2017 version of the ISO/IEC 17025 standard.

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Acoustical Floor-Ceiling Test Assemblies

NGC Testing Services is known for our stacks of prebuilt floor-ceiling assemblies throughout the industry and acoustical community. We have over 50 assemblies and counting, many of which are conventional concrete or wood structure assemblies kept permanently in stock, while others are our customers’ proprietary designs held for exclusive use for their future testing programs. We are continually constructing new assemblies.

Once we test your custom-built assemblies, we can store them on-site and repeatedly test them with new floor toppings or with ceiling design changes, as needed. An overhead crane shuffles the stacks of 12’ x 16’ assemblies, inserting the next assembly to be tested into our two-story test chambers. Any construction and/or required curing takes place outside the test chambers and the assembly is then craned into place when ready for testing. 

This unique capability allows us to test multiple assemblies in a single day. This translates to faster turnaround and lower costs for IIC, STC, and Delta IIC tests compared to other laboratories since, in many instances, the base assembly does not need to be constructed. In addition to acoustical floor-ceiling assemblies, we have other stacks here as well: stacks of fire test frames, stacks of test samples, stacks of construction, and other common materials that we stock for our customers’ use in our 53,000 square foot - high bay laboratory facility.

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