- Author
-
Nakagawa, Y.
|
Komai, T.
|
Takahashi, M.
|
Kohno, M.
|
Yamao, S.
- Title
- Studies on Fire-Resistance Evaluation of Rubber Conveyor Belts With Fabric Skeletons. [With Revisions]
- Coporate
- National Institute for Resources and Environment, Tsukuba-Shi, Japan
- Report
-
NIRE No. 2; Thesis,
1992,
120 p.
- Keywords
-
belt conveyors
|
fabrics
|
fire resistance tests
|
coal mines
|
mine fires
|
rubber
|
evaluation
|
oxygen index test
|
flammability tests
|
thermogravimetric analysis
|
weight loss
- Identifiers
- flame tests; underground mines; JIS K 6324; drum friction test; belting materials; hot plate ignition test; laboratory-scale gallery fire test
- Abstract
- A fire which involves polymeric materials such as rubbers and/or plastics in a confined space might result in a serious disaster. From a viewpoint of fire safety mainly in underground mines, therefore, it is necessary to prevent the fires which involve such materials. Rubber conveyor belts, above all, are quite susceptible to underground mine fires, not only because they themselves are composed of combustible materials, but because most of them are installed over a long distance of underground haulageways. Fire-resistant conveyor belts are widely used particularly in underground coal mines, but a variety of safety standards or regulations on fire-resistance tests of conveyor belts exist in the world, probably due to difficulty in assessment of flammability properties of such composite polymeric materials. Thus experimental works on fire-resistance evaluation of such materials will contribute to improvement of the related standards and/or regulations. This thesis presents some investigative and experimental studies on flammability tests of rubber conveyor belts with fabric skeletons, and consists of eight chapters. Chapter 1 presents the significance, present situation and recent trend of the studies on fire-resistance evaluation of conveyor belts for use mainly in underground mines. The background, purpose and objectice of this research are also described in brief. Chapter 2 presents the method and results of two small-scale flame tests on six different rubber conveyor belt samples and discusses the problems in the fire-resistance evaluation by the results of the small-scale flame test as prescribed in JIS K 6324. In addition, a recommendation for improving this kind of test is also given. Chapter 3 presents the method and results of the oxygen index test on the rubber conveyor belt samples and discusses the effect of the sample width on the critical oxygen index to determine the adequate sample width for this test. In addition, the correlation between the critical oxygen index of belting composite and that of its cover or skeleton, and that between the critical oxygen index and the small-scale flame test results, were also discussed. Chapter 4 discusses some problems in a drum friction test for fire-resistance evaluation of rubber conveyor belts, comparing the drum friction test results on five different belt samples with some other flammability test results. In conclusion, fire resistance of belting materials themselves could not be adequately assessed by the drum friction test results, which could have some significance only when other combustible materials exist near the drive pulleys or idlers of belt conveyors. Chapter 5 presents the method and results of a hot plate ignition test on ten different rubber conveyor belt samples. Comparison of the results of the hot plate ignition test with those of some other laboratory-scale flammability tests has indicated that the "60 s ignition temperature" has a certain correlation with some flammability properties which reflect ease of ignition, whereas the "10 s ignition temperature" has a relatively good correlation with those which reflect surface ignitability and ease of flame propagation. This implies that both the "ignition temperatures" should be determined in order to assess their overall flammability properties. Chapter 6 presents some experiences in a laboratory-scale gallery fire test on nine different rubber conveyor belt samples. The test apparauts, procedure and results are described. For each belt sample, both the time to ignition and the flame propagation speed on both 60 mm and 90 mm wide specimens were determined for the upward airflow condition as well as for the horizontal one. The test results were compared with those of some other small-scale flammability tests, and in addition, some problems in the laboratory-scale gallery fire test were also discussed. Chapter 7 presents the thermogravimetric analysis on covers of the ten rubber conveyor belt samples. The TG-DTA curves on each sample, measured under the thermal range from room temperature to around 700 deg C are shown. The minimum temperatures at which the rapid weight loss of each sample in the airflow, i.e., a sign of combustion, begins to appear were determened through comparison of the TG-DTA data in the airflow with those in nitrogen gas flow. These temperature data were compared with the results of some other small-scale flammability tests. As a result, even the data of such a micro-scale flammability test were found to be somewhat consistent with the critical oxygen index of cover rubber of belting and with some "ignition temperature" in the hot plate ignition test. Chapter 8 concludes this thesis, describes some recommendations on the flammability evaluation requirements for fire-resistant rubber conveyor belts with fabric skeletons, and indicates some problems to be solved in the future.