What the Standard Demands: A Fire That Follows the Curve

Under the GB 9978 series of standards, the temperature rise inside the test furnace must strictly follow a defined time-temperature curve:

T − T₀ = 345 lg(8t + 1)

This means temperature climbs extremely fast early on — pushing past 800 °C within just a few minutes — then gradually levels off toward a stable range around 1200 °C. Beyond temperature, furnace pressure is tightly specified too: 15 ± 5 Pa five minutes into the test, tightening to 17 ± 3 Pa at the ten-minute mark.

If either parameter drifts, the entire test result becomes questionable: did the component actually fail because its fire resistance fell short — or did it “burn through” early simply because the furnace’s own temperature curve wasn’t compliant? That is a very hard distinction to untangle after the fact. For third-party testing labs and component manufacturers alike, curve-control precision is now weighed as heavily as raw furnace size or maximum temperature.

NH-XL: Built for Curve Precision and Sustained High Heat

The BRT NH-XL Vertical Fire Resistance Test Furnace was designed from the ground up to meet exactly this demanding standard.

High-temperature furnace construction

• Metal frame with a baked-enamel steel-plate outer shell
• Furnace body and roof built on a lightweight high-alumina fiber suspended structure lined with zirconium-fiber wool block modules
• Floor constructed with the same zirconium-fiber wool block-module configuration — a design that both withstands sustained high heat and keeps the temperature curve under tighter control

Precise, automated combustion control

• Runs on natural gas or LPG with 8 burners operating on proportional combustion
• Automatic furnace-pressure control and automatic temperature regulation
• The entire temperature curve is managed through a programmed sequence with computer-aided operation — barely requiring anyone to sit there manually adjusting parameters
• Maximum operating temperature of 1300 °C

Large test space with external specimen mounting

• Effective internal test space of 3.0 m × 3.0 m × 1.2 m — large enough for standard-sized fire partition walls, doors, windows and valves
• Specimens mount externally, keeping loading and unloading relatively straightforward and reducing downtime between tests

Complete failure-mode judgment

The furnace covers both core failure modes of fire resistance testing — integrity and thermal insulation:

• Insulation failure: mean temperature rise on the unexposed face exceeding 140 °C above the initial value, or any single point exceeding 180 °C
• Integrity failure: cracking or penetration of the specimen

Broad test coverage for a stronger ROI

The NH-XL maps onto a wide set of related standards — GB/T 9978, GB/T 7633, GB/T 38252, GB 16809, GB 12955 and GB/T 23449–23451 — covering fire partition walls, doors, windows, roller shutters, check valves and oil-fume exhaust dampers. For third-party testing laboratories, the broader a single unit’s testing coverage, the better the return on that investment.

Who Needs the NH-XL Fire Resistance Test Furnace?

• Manufacturers of fire-protection building components — for factory-gate quality control; falling short on fire-resistance data can mean a product never clears the factory gate
• Third-party fire testing laboratories — where the precision of the furnace’s temperature curve and pressure control determines directly whether a test report can withstand review and regulatory audit
• Research institutes and certification bodies working with fire doors, fire partitions, fire windows, roller shutters and fire dampers

FAQ

What is a fire resistance test furnace? A fire resistance test furnace is a piece of fire testing equipment that reproduces the standard time-temperature curve of a real fire — reaching over 800 °C within minutes and stabilizing around 1200 °C — to test whether building elements such as fire doors, fire partition walls, windows and fire dampers maintain their integrity and thermal insulation for the required fire-resistance period.

What is the ISO 834 / GB 9978 time-temperature curve? The standard fire curve follows the formula T − T₀ = 345 lg(8t + 1): temperature rises extremely fast in the first minutes, passes 800 °C, then gradually levels off toward a stable range around 1200 °C. The furnace must follow this curve closely or the test result is considered unreliable.

What does a 120-minute fire resistance rating mean? A 120-minute fire-resistance rating (or fire-resistance limit) means the tested component maintained both integrity and thermal insulation — no cracking or penetration, and unexposed-face temperature rise within limits — for the full 120 minutes of furnace testing.

What is the difference between integrity and insulation in fire testing? Integrity failure means the specimen cracked or was penetrated by fire; insulation failure means the unexposed face exceeded the allowable temperature rise (mean >140 °C or any single point >180 °C). Both are judged during fire resistance tests of doors, partitions and dampers.

Which products can the NH-XL furnace test? The NH-XL tests fire partition walls, fire doors, fire windows, roller shutters, check valves and oil-fume exhaust dampers, covering standards including GB/T 9978, GB/T 7633, GB/T 38252, GB 16809, GB 12955 and GB/T 23449–23451.

Get a Quote

Need a reliable fire resistance test furnace for fire door certification or building element fire testing? Contact Shenyang Baoruitong Automation Equipment Co., Ltd. today for the NH-XL datasheet, test procedure guidance and a customized quotation. Every BRT instrument is backed by a 1-year warranty, installation guidance, operation training and long-term after-sales support.

Email: info@brt-test.com | WhatsApp: +86 15604057553 | Web: www.brt-test.com