MT/T 681-1997 in English

1 Scope
This standard specifies the technical requirements, inspection contents, requirements and method for reducer for belt conveyor for coal mining.
This standard is applicable to reducer for belt conveyor for coal mining
2 Normative References
The involved provisions in the following standard will become the provisions by quoting by this standard. When published, all the shown versions are valid. All the standards will be modified, and all parties using this standard shall discuss the possibility of using the latest version.
GB/T 3077-88 Technical Specification of Alloy Structure Steels
GB/T 3323-87 Methods for Radiographic Inspection and Classification of Radiographs for Fusion Welded Butt Joints in Steel
GB/T 3768-83 "Determination of Sound Power Levels of Noise Sources-Survey Method"
GB/T 9439-88 Grey iron castings
GB/T 10095-88 Accuracy of involute cylindrical gears
GB/T 11365-89 Accuracy of bevel and hypoid gears
GB/T 1168-89 Cleanliness for gear drive units
MT/T 101-93 Inspecting specification for gearbox of chain conveyors
ZB J19 004-88 Reduction cylindrical gear units
ZB J19 005-88 Load test method for reduction cylindrical gear units
ZB J19 009-88 General specification for reduction cylindrical gear units
ZB J19 026-90 Safety Regulations in Coal Mine for gearboxes for transportation machinery (92 edition)

3 Technical Requirements
3.1 Service conditions
3.1.1 Reducer shall meet the requirements of this standard and shall be manufactured according to the approved drawing and documents of established procedure.
3.1.2 The working ambient temperature of reducer is -10~+40℃; where the ambient temperature is lower than 0℃, lubricating oil shall be preheated correspondingly.
3.1.3 The working conditions of reducer shall meet the requirements of "Safety Regulations in Coal Mine".
3.2 Service life
The service life reducer shall not be less than 20 000 h, and bearing shall not be less than 5 000h.
3.3 Sealing performance
Reducer shall be free from oil leakage, and no dirt and water shall seep into reducer.
3.4 Mechanical efficiency
Under rated load, when the oil temperature of reducer reaches thermal equilibrium temperature, or the oil temperature of the reducer using internal water for cooling is 75℃±5°C, the hard tooth surface of reducer is adopted for transmission, and the transmission efficiency of each level is not less than 0.98; Soft tooth surface transmission: the transmission efficiency of each level is not less than 0.965.
3.5 Machine body and cover
3.5.1 Box may use casting or welding part. Where casting is used, it mechanical performance shall not be lower than HT 200 in GB/T 9439.
3.5.2 Casting machine body and cover shall be free from casting defects such as slag inclusion, shrinkage cavity, looseness and crack.
3.5.3 The welded joints of welding part shall reach the requirements of Grade I in GB/T 3323.
3.5.4 Aging treatment shall be carried out for casting machine body and cover, while annealing treatment shall be carried out for welding machine body and cover.
3.5.5 Box shall be carried out with leakage test before assembly, and shall be free from oil leakage.
3.5.6 The contact fit of joint surface shall be inspected under free combination state of machine body and cover, 0.05 mm shall not be able to wedge into.
3.5.7 After mould assembling of machine body and cover, the edge shall be parallel and level, the mutual dislocation quantity of each edge shall not be larger than 2mm.

Contents
Foreword
1 Scope
2 Normative References
3 Technical Requirements
4 Test Method
5 Inspection Rules
6 Marking, Packing, Transportation and Storage