FAA OSU Heat Release

(FAR 25.853 (a1); ASTM E906)

The OSU Rate of Heat Release Apparatus is used to expose aircraft interior cabin materials to an incident radiant heat flux of 35kW/m². This will determine if the material complies with FAR 25.853 [a1] requirements.

FTT OSU incorporates comprehensive safety features and is fully equipped to provide reliable test data for both FAA and ASTM tests. The apparatus, built in
accordance with Chapter 5 of the FAA Fire Test Handbook, is provided in four parts: test chamber, control unit, air distribution system and data acquisition and analysis system.

The heat release is measured by the temperature difference between the air entering and leaving the environment chamber by a thermopile with five hot and five cold Type K junctions.

OSU Main Unit

Test Chamber

Stainless steel insulated test chamber, with gasketed door and viewing window. The Test Chamber consists of:

Four silicon carbide elements Type LL 508mm by 16mm with nominal resistance 1.4 Ohms as a heat source with corrosion resistant stainless steel housing.
A reflector made from stainless steel is situated behind the elements.
In front of the elements, a truncated diamond shaped mask, constructed of stainless steel, this provides uniform heat flux density over the area occupied by the 151 × 151mm vertical sample.
Dual 110VAC transformers at 5.5kVA are provided for separate control of the upper and lower element pairs.
Wand Assembly for lighting the upper pilot and calibration burners.
Dual globar power controllers for ease of heat flux uniformity adjustment.
Upper pilot and lower pilot (with spark ignition) and calibration methane gas burners.
Thermopile for heat release rate measurement, with five hot thermocouple junctions in the chimney and five cold thermocouple junctions in the air chamber.

Air Distribution System

The air entering the apparatus is controlled to 2124° C (7075°F) and
set at approximately 0.04m³/s (85ft³/min) using an orifice meter.

The orifice meter comprises of a squared edged, circular plate orifice, 0.024 inch (0.5mm) thick, and is located in a circular pipe with a nominal diameter of 1.5 inch (38mm). There are two pressure measuring points located 1.5 inch (38mm) upstream and 0.75 inch (19mm) downstream of the orifice and connected to a mercury manometer. (Mercury not supplied)
The air entering the environmental chamber is distributed by an aluminium plate which has eight holes, and mounted at the base of the environmental chamber. A second plate having 120 evenly spaced holes is mounted 152mm above the aluminium plate.
The air supply manifold at the base of the pyramidal chimney section has 48 evenly spaced holes, resulting in an airflow of approximately three to one within the apparatus.

Specimen Holder and Drip Pan

Two specimen holders are provided with each OSU.
Each specimen holder and the drip pan are fabricated from stainless steel.
Each holder has two studs top and bottom which allows two wires to be attached vertically in front of the holder to secure the face of the specimen.

Control Unit

Standalone Control Unit housed in 19″ Rack, with flow control for both burners

Calibration Flow Rate Control

This is only used when a Calibration is required.
There are 5 latching push button switches which allow accurate control of calibration gas flow rates.
Under each flow control switch is a 10 turn potentiometer for fine adjustment of the calibration gas flow rates.

Lower Burner Ignition

Lower burner ignition button allows the gas to the lower and upper burners to flow.
In the event of a power failure the solenoid will automatically stop the flow of gas and hence extinguish any burner flames.
Five On/Off ball valves for controlling the Lower and Upper pilot burners and Calibration.
Four flow meters are fitted with needle valve adjustment for controlling the lower and upper pilot burner’s gas and air mixtures.

Calibration Heat Flux Meter

Two watercooled, heat flux sensors are supplied to measure the heat flux density at the centre and each corner.

Software

FTT offer a data acquisition and analysis standalone software package for the OSU that can be used either with our instrumentation or with existing equipment.

The OSU Apparatus is a sophisticated instrument, designed to make the calibration and use of the instrument user friendly. The OSUCalc software package acquires test data, assists with calibration routines and automatically generates test reports.

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