GB/T 24648.1-2009Assessment of tractor reliability (English PDF)

1 Scope

This Part of GB/T 24648 specifies terms and definitions, fault classification and judgment rules, evaluation indicator system, evaluation method for assessment of tractor reliability as well as test methods for tractor reliability during use.

This Part is applicable to reliability assessment and evaluation of shaped tractor. Reliability assessment of prototype tractor may refer to this Part.

2 Normative references

The provisions in following documents become the provisions of this Part of GB/T 24648 through reference in this Part. For dated references, the subsequent amendments (excluding corrigendum) or revisions do not apply to this Part, however, parties who reach an agreement based on this Part are encouraged to study if the latest versions of these documents are applicable.

For undated references, the latest edition of the referenced document applies.

GB/T 3871.3, Agricultural tractors - Test procedures - Part 3: Power tests for power take-off (GB/T 3871.3-2006, ISO 789-1:1990, MOD)

GB/T 3871.4, Agricultural tractors - Test procedures - Part 4: Rear three-point linkage lifting capacity (GB/T 3871.4-2006, ISO 789-2:1993, MOD)

GB/T 3871.6, Agricultural tractors - Test procedures - Part 6: Determination of braking performance (GB/T 3871.6-2006, ISO 5697: 1982, Agricultural and forestry vehicles - Determination of Braking Performance, IDT)

GB/T 3871.12, Agricultural tractors - Test procedures - Part 12: Working tests

GB/T 6229, Test methods for walking tractors

GB/T 24648.2-2009, Reliability assessment of engineering and agricultural machine - Evaluation parameter system and failure classification code

3 Terms and definitions

For the purposes of this document, the following terms and definitions apply.

4 Fault classification and judgement rules

5 Evaluation indicator system

See formula (2) for mean interval time between faults.

Where, MTBF - Mean interval time between faults of tractor, in hours (h); tci - Timing end test time of the ith tractor to be tested, in hours (h); for tractor to be investigated, it is accumulated operating time, in hours (h); ra - Total number of faults (except minor faults) of tractors to be tested or investigated during use or test period (including during run-in and performance test).

If all tested tractors have no faults (except minor faults), it is specified to use to represent.

6 Evaluation methods

7 Use test methods

7.3.3 Put test prototype into normal use under actual conditions for use. It shall use and perform maintenance strictly according to provisions in user manual. All kinds of work quality shall meet agronomic requirements.

7.3.3.2 Total working time of test prototype is 1500h. It is 2x750h for tractor of which engine calibration power is greater than 18kW, 3x500h for rest tractors.

7.3.3.3 Work items for each test prototype: field work item (ploughing, hoeing, sowing, collecting) time of wheel tractor and walking tractor is not less than 70% of total operating time; transportation time is not more than 30%; fixed work is not allowed. For crawler tractor, all are field work, and fixed work is not allowed.

For forestry skidding tractor, all are skidding work. Work items and time proportion for tractors of other special uses are drafted and determined by referring to this Part.

7.3.3.4 During test process, it shall measure at any time hourly fuel consumption required to complete various works, so as to determine and adjust load degree of each test prototype. Average load factors for field work of wheel and walking tractors shall not be lower than 55% and 50%, respectively; transportation work is rated load mass. Average load factors for field work of crawler tractor shall not be less than 60%. Carrying capacity of forestry skidding tractor shall not be less than 80% of rated carrying capacity.

7.3.3.5 For all faults happened during use test (including run-in and performance tests), it shall record occurrence time, situation, cause analysis, repair work time in details. When necessary, it shall take photos and conduct physical and chemical analysis. For all faults, it shall, according to relevant provisions of Clause 4, determine their categories to which they belong and record them in Table A.6 and Table A.7.

7.3.3.6 In test, general fault and severe fault shall be excluded before test is continued. In the event of any major damage caused by non-essential causes, organization in charge of test may negotiate with entrusting party before it selects another prototype for testing. If test is a sampling test, it must be reported to entrusting authority for approval before standby prototype can be […]

Annex B (informative) Examples of tractor faults

A Annex A (Informative) Tractor test summary

Where, Qso - Total workload to complete a work, in hectares (ha) or tons kilometers (t.km); Qs - Shift workload to complete a work, in hectares (ha) or tons kilometers (t.km).

d) Average productivity Respectively collect according to work category. Average productivity is calculated according to formula (10).

Where, qsp - Average productivity of tractor to complete a work, in hectares per hour (ha/h) or tons kilometers per hour [(t.km)/h]; ts - Shift operating time to complete a work [see formula (11)], in hours (h).

e) Average hourly fuel consumption See formula (12) for average hourly fuel consumption.

Where, Gtp - Average hourly fuel consumption of tractor to complete a work, in kilograms per hour (kg/h); Gs - Total fuel consumption of tractor to complete a work, in kilograms (kg); Gfk - Idling hourly fuel consumption of tractor engine, in kilograms per hour (kg/h).

f) Average unit workload fuel consumption See formula (13) for average unit workload fuel consumption.

Table A.2 -- PTO shaft (engine bench) test results. Tractor model _________ Manufacturer ______ Engine model ___ Test site _________ Inspection basis _______________ Test date: before test _________ after test _______ Average atmospheric conditions during test: Before use test: temperature _____°C Air pressure _____kPa Relative humidity _____% After use test: temperature _______°C Air pressure ______kPa Relative humidity ____% Highest temperature during test: Before use test: cooling water _____°C Lubricating oil _____°C Fuel ____°C Intake ___°C After use test: cooling water ______°C Lubricating oil ___°C Fuel _____°C Intake _____°C Number of test prototype 1 2 3 Performance parameter Pd/kW ne/(r/min) Gt/(kg/h) gd/[g/(kW.h)]

Table A.5 - Use test shifts of tractor reliability. Tractor model ______________ Prototype No. __________ Test date ________________ Work name _________ Soil type and vegetation (or road) conditions ________________ Work situation: working depth ______cm working width ____cm or loading mass _______t Workload of this shift: working area __________ha Transportation load _________ t.km Fuel consumption of this shift: fuel ____kg Engine oil ___kg Chassis lubricant ________kg Work content Start time End time Duration / h min Work gear Downtime / min Null operating time / min Idling time / min Total Maintenance time of this shift __ h __min Fault repair time ___ h ___min Tractor working time __h ___min

Table A.6 -- Registration of use test faults of tractor reliability. Tractor model ________ Manufacturer ________ Prototype No. _____ Test date _______ Fault appearance date _______________ Work name _________________________ Accumulated operating time of tractor _________________ h List of parts damaged in this fault: Name No. of piece Number of pieces Accumulated operating time of each part / h Exit-factory unit price of this part / RMB Description of fault phenomenon and its influence degree (with photo) Fault cause and its physical and chemical test results: Troubleshooting method: Fault category _______________ Fault repair time _________h Repair cost______ RMB

Table A.9 - Comprehensive collection of user test of tractor reliability. Tractor model __________ Manufacturer ___________ Test start and end date ______ Test prototype No. 1 2 3 Accumulated operating time / h Accumulated idling time / h Accumulated maintenance time / h Accumulated repair time / h Accumulated fuel consumption / kg Fuel Lubricating oil Engine Chassis Accumulated workload Field / ha Transport / (t.km) Average hourly fuel consumption / (kg / h) Field Transport Average unit workload fuel consumption Field / (kg/ha) Transport / [kg/(t.km)] Operating-time proportion of each gear / % Average load coefficient of field work/% Field work time as a percentage of total time /%

Table A.10 -- Evaluation results of tractor reliability. Tractor model ____ Manufacturer _______ Test start and end date _______ Accumulated number of faults (times): No. of test prototype 1 2 3 Total Fatal fault Severe fault General fault Minor fault Total Reliability indicators MTTFF= h ( h use test) MTBF= h ( h use test) DTMTBF= h ( h use test) Q= h ( h use test) PWC= h ( h use test)