MT/T 668-2019 English PDF (MT/T668-2019)

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MT/T 668-2019: Steel cord fire resistant conveyor belting for coalmine
MT/T 668-2019
MT
COAL INDUSTRY STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 83.140.99; 53.040.20; 13.220.40
G 42
Replacing MT 668-2008
Steel cord fire resistant conveyor belting for coalmine
ISSUED ON. NOVEMBER 28, 2019
IMPLEMENTED ON. JUNE 01, 2020
Issued by. State Administration of Coal Mine Safety
Table of Contents
Foreword... 3
1 Scope... 6
2 Normative references... 6
3 Product categories, models, specifications... 7
4 Technical requirements... 9
5 Test methods... 16
6 Inspection rules... 20
7 Marking, packaging, storage, transportation... 23
Appendix A (Normative) Method for determination of bonding strength of covering
layer... 24
Appendix B (Normative) Determination method of bonding fatigue resistance of
dynamic steel wire core... 27
Appendix C (Normative) Determination method of rubber permeability... 29
Appendix D (Normative) Method for determination of dynamic durability of wire rope
joints... 31
Appendix E (Normative) Dimensions and technical requirements of fire resistant belt
joints... 36
Steel cord fire resistant conveyor belting for coalmine
1 Scope
This standard specifies the product classification, model, specifications, technical
requirements, test methods, inspection rules, marking, packaging, storage,
transportation of steel cord fire resistant conveyor beltings for coal mines (hereinafter
referred to as "fire resistant belts").
This standard applies to steel cord fire resistant conveyor beltings used in coal mines.
2 Normative references
The following documents are essential to the application of this document. For the dated
documents, only the versions with the dates indicated are applicable to this document;
for the undated documents, only the latest version (including all the amendments) is
applicable to this standard.
GB/T 528-2009 Rubber, vulcanized or thermoplastic - Determination of tensile
stress-strain properties
GB/T 3512 Rubber, vulcanized or thermoplastic - Accelerated ageing and heat
resistance tests - Air-oven method
GB/T 5752 Conveyor belts - Marking
GB/T 5753 Steel cord conveyor belts - Methods for the determination of total
thickness and cover thickness
GB/T 5754.2 Steel cord conveyor belts - Longitudinal traction test - Part 2.
Measurement of tensile strength
GB/T 5755 Steel cord conveyor belts - Cord-to-coating bond test - Initial test and
after thermal treatment
GB/T 7983 Conveyor belts - Transverse flexibility (troughability) - Test method
GB/T 9770-2013 Steel cord conveyor belts for general use
GB/T 9867 Rubber, vulcanized or thermoplastic - Determination of abrasion
resistance using a rotating cylindrical drum device
GB/T 12753 Steel wire ropes for conveyer belts
between the supplier and the buyer. If there is no agreement through negotiation, it shall
be governed by the provisions of Table 3 in GB/T 9770-2013.
4 Technical requirements
4.1 Appearance quality
4.1.1 The fire resistant belt shall not have edge waves.
4.1.2 When the depth of the exposed scar on the fire resistant belt is greater than 1 mm,
it shall be repaired (if the depth is not greater than 1 mm, it will not be repaired).
4.1.3 The total area of blisters and delamination on the fire-retardant belt's covering
layer shall not exceed 1600 cm2 per 100 m2; they shall be repaired and in good condition.
4.1.4 The cumulative length of the edge rubber sponges or torn off edge tape on both
sides of the fire resistant belt shall not exceed 8% of the belt length, which shall be
repaired and in good condition.
4.1.5 For every 100 m of fire resistant belt, no more than 5 places with a depth greater
than 1 mm shall be pressed with edge glue; they shall be repaired (those with a depth
not greater than 1 mm will not be repaired).
4.1.6 There shall be no exposed steel wire rope on the fire resistant belt.
4.2 Dimensions
4.2.1 Width deviation
The width limit deviation of the fire resistant belt shall comply with the provisions of
Table 1.
4.2.2 Covering layer thickness
The thickness of the covering layer of the fire resistant belt shall comply with the
requirements in Table 2.
joint tensile strength of the fire resistant belt shall not be less than 80% of the
longitudinal rated tensile strength of the belt.
4.11.4 For fire resistant belts of models above ST/S7500 (not included), the static joint
tensile strength of the fire resistant belt shall not be less than 75% of the longitudinal
rated tensile strength of the belt.
4.12 Dynamic joint durability
There is no damage to the fire resistant belt joint after 10000 cycles.
4.13 Surface resistance properties
The arithmetic average surface resistance of the two surfaces on the fire resistant belt
and the lower surface shall not be greater than 3.0 × 108 Ω.
4.14 Fire resistant properties
4.14.1 Roller friction performance
When the fire resistant belt is subjected to the roller friction test, flaming or flameless
combustion shall not occur in any part of the fire resistant belt; the surface temperature
of the roller shall not exceed 325 °C.
4.14.2 Blowtorch combustion performance
The fire resistant belt shall comply with the following requirements, after the alcohol
blowtorch combustion test.
a) For specimens with complete coverage, the arithmetic mean of the flaming
burning time and the arithmetic mean of the flameless burning time of the
specimen shall not be greater than 3.0 s, where the single value of flaming burning
time and flameless burning time of each specimen shall not be greater than 10.0
s;
b) For the test piece with the covering layer peeled off, the arithmetic mean value of
the flaming burning time and the arithmetic mean value of the flameless burning
time of the test piece shall not be greater than 5.0 s, where the single value of
flaming burning time and the flameless burning time of each test piece shall not
be greater than 15.0 s.
4.14.3 Propane tunnel combustion performance
If the fire resistant belt meets either of the following two requirements, the conveyor
belt is deemed to be qualified. The requirements are as follows.
a) The undamaged length of each specimen shall not be less than 600 mm;
b) The undamaged length shall not be less than 50 mm; the maximum average
temperature rise shall not be greater than 140 °C; the length of the belt loss shall
not be greater than 1250 mm.
A conveyor belt's propane tunnel burning test is deemed to have failed, when the test is
terminated prematurely, due to endangerment to people and equipment during the
burning process.
5 Test methods
5.1 Sample collection
Take samples, 24 h after the product is manufactured.
5.2 Appearance quality
Use visual inspection and measuring tools for inspection.
5.3 Dimensional measurements
5.3.1 Width measurement
Use a steel belt measure or steel ruler, which has a minimum resolution of not less than
1 mm, for measurement. Make 3 measurements in total. The longitudinal interval of
each measurement shall not be less than 0.5 m. Take the median value as the
measurement result.
5.3.2 Measurement of covering layer thickness
Follow the provisions of GB/T 5753.
5.3.3 Measurement of tear-resistant layer configuration
Follow the provisions of HG/T 3646.
5.4 Longitudinal tensile strength test
Follow the provisions of GB/T 5754.2.
5.5 Adhesion strength test
5.5.1 The bonding strength of the steel wire rope shall be carried out in accordance with
the provisions o...