Tungsten carbide

Flammability

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

flammable solids

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

UN Manual of Tests and Criteria: Test N.1 (Test method for readily combustible solids)

Version / remarks:

The tests were performed per UN Manual of Tests and Criteria for Transportation of Dangerous Goods, Section 33, Classification Procedures, Test Methods and Criteria Relating to Class 4, Test N.1: Test Method for Readily Combustible Solids.

Principles of method if other than guideline:

The sixth revised edition of the UN Recommendations on the Transport of Dangerous Goods, Manual of Tests and Criteria clarifies that the “whole length of the sample” is to be taken as 100 mm: “Powders of metals or metal alloys should be classified when they can be ignited and the reaction spreads over the whole length (100 mm) of the sample in 10 minutes or less.”

GLP compliance:

not specified

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: Several manufacturers submitted samples for testing with Fisher particulate size between 0.21 to 1.43 µm

Key result

Test procedure:

burning rate test: preliminary screening test

Remarks:

FSSS: 0.21 microns

Burning time:

ca. 958 s

Key result

Test procedure:

burning rate test over 100 mm length

Remarks:

Avg= 775 sec; FSSS 0.36 microns

Burning time:

>= 607 - <= 967 s

Key result

Test procedure:

burning rate test over 100 mm length

Remarks:

Avg= 471 sec; FSSS: 0.52 microns

Burning time:

>= 392 - <= 605 s

Key result

Test procedure:

burning rate test over 100 mm length

Remarks:

Avg= 578 sec; FSSS 0.5 microns

Burning time:

>= 449 - <= 689 s

Interpretation of results:

study cannot be used for classification

Conclusions:

The situation with powders with particles sizes equal to or less than 0.52 µm is less clear as two samples with particles sizes of approximately 0.5 µm met the CLP Cat 2 criteria while two sample of particles sizes less than 0.5 µm did not. Therefore, this dataset is insufficient to draw firm conclusions regarding the flammability classification on tungsten carbide powders with particles size less than 0.58 µm.

Reference 2

Endpoint:

flammable solids

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

UN Manual of Tests and Criteria: Test N.1 (Test method for readily combustible solids)

Version / remarks:

The tests were performed per UN Manual of Tests and Criteria for Transportation of Dangerous Goods, Section 33, Classification Procedures, Test Methods and Criteria Relating to Class 4, Test N.1: Test Method for Readily Combustible Solids.

Principles of method if other than guideline:

The sixth revised edition of the UN Recommendations on the Transport of Dangerous Goods, Manual of Tests and Criteria clarifies that the “whole length of the sample” is to be taken as 100 mm: “Powders of metals or metal alloys should be classified when they can be ignited and the reaction spreads over the whole length (100 mm) of the sample in 10 minutes or less.”

GLP compliance:

not specified

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: Several manufacturers submitted samples for testing with Fisher particulate size between > 0.5 - 1.43 µm

Key result

Test procedure:

burning rate test: preliminary screening test

Remarks:

Avg= 783.5 sec; FSSS= 0.58 microns

Burning time:

>= 696 - <= 871 s

Remarks on result:

other: screening test for that sample was negative and the 100 mm burn rate measurements were not necessary as the sample was not readily combustible.

Key result

Test procedure:

burning rate test: preliminary screening test

Remarks:

Avg= 655 sec; FSSS= 0.62 microns

Burning time:

>= 632 - <= 678 s

Remarks on result:

other: screening test for that sample was negative and the 100 mm burn rate measurements were not necessary as the sample was not readily combustible.

Key result

Test procedure:

burning rate test: preliminary screening test

Remarks:

Avg= 1428 sec; FSSS= 0.64 microns

Burning time:

>= 1 205 - <= 1 651 s

Remarks on result:

other: screening test for that sample was negative and the 100 mm burn rate measurements were not necessary as the sample was not readily combustible.

Key result

Test procedure:

burning rate test: preliminary screening test

Remarks:

Avg=964.5 sec; FSSS=0.8 microns

Burning time:

>= 846 - <= 1 083 s

Remarks on result:

other: screening test for that sample was negative and the 100 mm burn rate measurements were not necessary as the sample was not readily combustible.

Key result

Test procedure:

burning rate test over 100 mm length

Remarks:

Avg=643 s; FSSS=1.02 microns, CLP Cat 2

Burning time:

> 509 - < 838 s

Remarks on result:

ambiguous

Key result

Test procedure:

burning rate test: preliminary screening test

Remarks:

Avg=726.5; FSS=1.04 microns

Burning time:

>= 634 - <= 819 s

Remarks on result:

other: screening test for that sample was negative and the 100 mm burn rate measurements were not necessary as the sample was not readily combustible.

Key result

Test procedure:

burning rate test: preliminary screening test

Remarks:

Avg=720.5;FSSS=1.22 microns

Burning time:

>= 653 - <= 788 s

Remarks on result:

other: screening test for that sample was negative and the 100 mm burn rate measurements were not necessary as the sample was not readily combustible.

Key result

Test procedure:

burning rate test over 100 mm length

Remarks:

Avg=952; FSSS=1.31 microns

Burning time:

>= 945 - <= 959 s

Remarks on result:

other: screening test for that sample was negative and the 100 mm burn rate measurements were not necessary as the sample was not readily combustible.

Key result

Test procedure:

burning rate test over 100 mm length

Remarks:

Avg=1457; FSSS 1.43 microns

Burning time:

>= 1 391 - <= 1 523 s

Remarks on result:

other: screening test for that sample was negative and the 100 mm burn rate measurements were not necessary as the sample was not readily combustible.

Interpretation of results:

not classified based on GHS criteria

Conclusions:

Although one sample with a reported particle size of 1.02 µm met the CLP Category 2, collectively, the weight of evidence indicates that tungsten carbide powders greater or equal to 0.58 µm in size are not Flammable Solids.

Description of key information

Several tungsten carbide metal powders were tested using the new recommended 100 mm testing train. A total of 15 tungsten carbide powder samples with a Fisher Sub Sieve Size (FSSS) ranging from 0.21 um to 1.43 um. The flammability tests were performed per UN Manual of Tests and Criteria for Transportation of Dangerous Goods, Section 33, Classification Procedures, Test Methods and Criteria Relating to Class 4,Test N.1: Test Method for Readily Combustible Solids.The scope of the laboratory’s accreditation (ISO/IEC 17025:2017) includes DOT 4.1 Ignitability and Burn Rate. 

One sample of particle size of 1.02 microns met the CLP Category 2 criteria, collectively, the weight of evidence indicates that tungsten carbide powders greater or equal to 0.58 microns in size are not Category 2 Flammable Solids. The situation with powders and particle sizes equal to or less than 0.52 microns is inconclusive. Therefore, it is insufficient to draw firm conclusions regarding the flammability classsification on tungsten carbide powders with particle sizes less than 0.58 microns.

Key value for chemical safety assessment

Flammability:

not classified

Justification for classification or non-classification

Although one sample with a reported particle size of 1.02 microns met the CLP Category 2 criteria, the weight of evidence indicates that tungsten carbide powders greater or equal to 0.58 microns in size are not Flammable Solids. The situation with powders and particle sizes equal to or less than 0.52 microns is less clear as two samples with partucle sizes of approximately 0.5 microns met the Category Cat 2 criteria while two samples of particle sizes less than 0.5 microns did not. As such, based on this study, some tungsten carbide particle sizes of approximately 0.5 microns fall into Category 2 (Packing Group III) and others are considered non-flammable powders as in general, they had a burning time of greater than 600 seconds. In summary:

- Tungsten carbide powders with a FSSS greater or equal than 0.58 microns are not flammable

- Tungsten carbide powders with s FSSS lower than 0.58 microns - Inconclusive