ASTM F1959:2024b

• Ablation, n-in arc testing, a physical response evidenced by significant erosion or the formation of one or more large holes in a layer of a multilayer system.
• Eab: The incident energy in a multilayer system that results in a 50% probability of the physical ablation response.
• The arc index is expressed in cal/cm2 and is derived from the determined ATPV or EBT value (in the case where a material system has a fracture response below the ATPV value) or the nominal arc limit. It can be expressed in ATPV, EBT or ARLim.
• ATPV: Incident energy in a material or a multilayer system of materials that results in a 50% probability that sufficient heat transfer is expected through the sample under test to cause the occurrence of a second-degree skin burn according to the Stoll curve5, kJ/m2 [cal/cm2].
• The sample is considered to be fractured when a hole is at least 1.6 cm2 [0.5 in2] or at least 2.5 cm [1.0 in2] in size.] in any dimension. In multilayer samples of fire-resistant materials, all layers must be broken to meet the definition.
• EBT: The incident energy in a material or system of materials that results in a 50% probability of opening, J/cm2 (cal/cm2).
• ARLim: The arc rating indicates the maximum thermal energy protection that has been assigned to the product according to the manufacturer’s specifications after verification by testing or detection limits of the analytical method. The value assigned from the dataset of all samples will be less than the Stoll curve and without breaking.
• Heat flux, n: the thermal intensity indicated by the amount of energy transmitted divided by the surface area and time kW/m2 [cal ⁄cm2s].
• Incident energy (Ei), n: total thermal energy received at the surface of the panel as a direct result of an electric arc.
• Stoll curve5: An empirical model of second-degree skin burns, also known as the Stoll response.
• Nominal Weight: Theoretical Weight (g/m2)
• Current weight: Sample weight before washing and after conditioning according to D1776/D1776M (g/m2)
• Weight tested: Test weight of the sample used to generate the arc index (g/m2)
• Target arc weight: Measured weight for a specific sample expressed in g/m2 used to generate the arc classification according to F1959/F1959M
• Mixed zone: Range of incident energies, which can be positive or negative to predict second-degree burns or ruptures. The low value of the range starts with the lowest incident energy, indicating a positive result, and the high value of the range is the highest incident energy, indicating a negative result

This test method determines the response of heat transport through a material, fabric, or fabric system when exposed to the thermal energy of an electric arc. This heat transport response is evaluated against the Stoll curve.

During this procedure, the amount of thermal energy transferred by the material under test is measured during and after exposure to an electric arc.

The performance of the material for this procedure is determined from the amount of heat transferred through and through the material under test.

The heat transfer data determined by this test method form the basis for the classification of the material’s arc.

The arc index determined by this test method is the amount of energy that predicts a 50% probability of second-degree burn, determined by the Stoll curve or rupture (if the tissue shows that it breaks before the skin burn prediction is reached). It can also be expressed in ARLim depending on the limitations of the testing device or the performance of the tissues. The ARLim can be a reduced limit set by the manufacturer:

The reaction of the material should be described in more detail by recording the observed effects of arcing exposure on the samples.

This method specifies the standards for performing the test under controlled laboratory conditions. Different exposure conditions can have great potential for different results. If different conditions are used, these must be documented in the final report.

The test device will consist of 3 panels of 2 sensors, a power bus and electrodes, monitoring sensors, a power supply, a test controller and a data acquisition system

1. Sensor:
2. The calorimeter must be constructed with copper with a purity greater than 99.9% electrical grade. The copper disc must be 1.6±0.1 mm thick, 40±0.1 mm in diameter and 18±1 g in weight. These parameters must be measured to determine the actual response coefficient of each calorimeter to be used in the heat capacity calculation.
3. Type K thermocouple (NiCr-NiAl) with welded tip and a cross-sectional area of 0.05 mm2. This thermocouple will be located inside the hole in the copper disk. The hole will be made in the center of the disc at a depth of 1.3±0.1 mm. The tip should be exposed inside the copper disc. The thermocouple wires separate at the exit of the copper disc. (see Figure 1).

C. The insulating material shall have a conductivity of less than 0.23 W/mK at a maximum temperature of 500 °C.

2. Sensor Panel:

A. Each panel will consist of two sensors, a fabric support frame, an insulating panel, a fabric retention system, and two sensors for monitoring.
B. The insulation board must measure 20×55±1.3 cm. It must be heat-resistant and have a thermal conductivity of less than 0.30 W/mK at a maximum temperature of 200 °C.
C. Both sensors will be inserted into the front panel in a vertical line (see image).

D. To prevent damage to the insulation surrounding the copper disc, a refractory foil with a maximum thickness of 3 mm can be used.
E. The exposed surface of the calorimeters should be painted with a thin layer of matt black spray paint with an emissivity of >0.9.
F. Each sensor panel will have 4 clamps to hold the sample. Each clamp should be applied between 4.4 and 6.7 N to ensure that the material is secured.

3. Panel layout:

The panels must have a separation of 120º depending on the image

4. Structural box: It will have a diameter of between 2.0 and 2.5 m, made of conductive tubes and a height of at least 3 m.
5. Electrodes: stainless steel rods with a diameter of 19 mm
6. Fuse: It is consumed during the test. It is formed by a copper cable with a diameter of less than 0.5 mm.
7. Power supply: It must allow the discharge of an electric arc with an alternating current of 8±0.5 kA of 1s with a duration of 60 or 50 Hz
8. Data acquisition system: It must record the voltage, current, and outputs of the calorimeter.

A. The data corresponding to the temperature wave must be acquired at a speed of 100 samples/s for each calorimeter, being able to record temperatures up to 500ºC with a variability of ±2% and a resolution of 0.1ºC for energy calculation.

• Weigh a conditioned sample according to option C D3776/D3776M for specification F1506
• Perform 3 washes of the fabric according to AATCC 1-2021: 3, IV, Aiii
• It will only dry once.
• Before performing the test, the samples must be conditioned at 25±8ºC with a relative humidity of 50±20% for 1 hour.
• To determine the weight of the sample, cut a circle 3.8 to 7.6 cm in diameter with a cookie cutter. Make at least 3 samples of the same sample distributed throughout the fabric.
• Weigh the circles with an analytical balance of 0.001 g accuracy.

1. GENERAL METHOD

•  Initial temperature of the sensors before ignition 15-35ºC
• Parameters: 8±0.5 kA; 305±5 mm electrode spacing; Sensors in position 1 for an expected arc value of up to 55 cal/cm2 or in position 2 for values greater than 40 cal/cm2.
• The duration of the arc must be variable to produce the required series of exposures.
• The specimen must be attached to the panel without stretching it so as to allow the specimen to contract during the test.

DETERMINATION OF THE ATPV

• 3 samples of the same fabric will be determined, one for each sensor panel.
• At least one set of 7 tests shall be performed within the incident energy range to be tested by increasing or decreasing the arc duration. This series of shots is distributed as follows: at least 3 points with a negative SCD, at least 3 points with a non-negative SCD.
• At least 10 points must be between ±20% of the final ATPV. All points are valid unless the calorimeter exceeds 500ºC, there is a malfunction of the equipment, or if the sample assembly fails.
• If the samples are broken, they are considered valid points for the calculation of the ATPV. In the event that there are 2 or more ruptures with energies less than 20% higher than the ATPV determination, evaluate the fracture response. In this case, more than 7 samples will be required.

1. DETERMINATION OF THE EBT:

• The dataset will be distributed as follows: at least 3 points must be below the lower limit of the mixed area; at least 3 points must be below the upper limit of the opening mixed upper area
• At least 10 data points must be within the range of ±20% of the final EBT.
• If you don’t have enough data depending on the settings, run additional tests.

1. ARLim ARK CLASSIFICATION LIMIT:
   It can occur in the following cases:

1. 1. This limit may be chosen by the manufacturer for a variety of reasons for any system below the EBT or ATPV determined above.
   2. When the device has a limit of 100cal/cm2
   3. According to the manufacturer’s request

• -Determination of time 0-Tracking panel sensor response. This is determined shortly before, during, and 30 seconds after exposure to electric arcs.

  -Calculate the value of the monitored incident energy by applying the incident energy correction factor

  -Determination of second-degree skin burns. The thermal energy of each panel is compared to the empirical model of the Stoll curve.

  -Determination of ATPV values: a minimum of 20 panel measurements is used to calculate the ATPV.

  -Determination Ett: the value of 1 is assigned to each panel that has a case and 0 in case of no case. Use logistic regression to determine the curve and y-intercept to calculate the 50% probability of material failure.

• Name of the laboratory performing the test
• Identification of the test report
• Date of test and issuance of report
• Name of manufacturer, producer or contractor
• Amend the standard and explain any deviations from it
• Sample Description
  • Producer
  • Unique identification number for each layer or system
  • Layer placement order with the outer layer first
  • Fabric construction, including the fiber content of the material per layer
  • For each layer, the actual weight according to F1506, the weight of the fabric tested and the nominal weight of the fabric according to the manufacturer.
  • Color of each layer
  • Pre-treatment of the tested sample
  • Assay results, including Arc, ATPV, EBT, ARLim results.
  • Table with results
  • Subjective Material Evaluation
  • Logistic Regression Curve Graph
  • Photographs of samples analyzed before and after the test
  • Detailed Trial Records
  • Graphs of individual arc voltage, current, and calorimetric response
  • Video and photographs of all tests performed

• Arc ratings ≤ 10 cal/cm2 will be reported with an accuracy of 0.1 cal/cm2. Nominal values greater than 10 cal/cm2 must be accurately stated 1 cal/cm2
  • ImARLim may be reported in addition to ATPV and/or EBT.