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GB/T 24648.1-2009: PDF in English (GBT 24648.1-2009)

GB/T 24648.1-2009
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 65.060.10
T 60
Assessment of tractor reliability
ISSUED ON: NOVEMBER 15, 2009
IMPLEMENTED ON: MAY 01, 2010
Issued by: General Administration of Quality Supervision, Inspection and
Quarantine;
Standardization Administration of the People's Republic of
China.
Table of Contents
Foreword ... 3 
1 Scope ... 4 
2 Normative references ... 4 
3 Terms and definitions ... 4 
4 Fault classification and judgement rules ... 6 
5 Evaluation indicator system ... 8 
6 Evaluation methods ... 11 
7 Use test methods ... 12 
Annex A (Informative) Tractor test summary ... 18 
Annex B (informative) Examples of tractor faults ... 26 
Assessment of tractor reliability
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.
3.1 operating time
The time for a product to complete various defined functions. For tractor,
operating time includes tractor load operation time, turning time at turn-row and
conversion time for tractor’s null operation (5h null operation time is converted
to 1h working time), but excluding tractor running-in time, performance test time
and engine idle time.
3.2 fault correction time
The time required from fault is found to product function is recovered, that is,
the sum of fault diagnosis time, repair time and commissioning time, but
excluding time delayed by human or natural factors.
3.3 maintenance time
The operating time required to complete maintenance specified in user manual.
It includes shift maintenance and time spent on maintenance at all levels, but
excluding time delayed by human or natural factors.
3.4 fault
All phenomena that a product or its component cannot perform its specified
functions or performance indicators are deteriorated beyond specified range
(see 2.2 in GB/T 24648.2-2009).
For example, parts damage, wear overrun, weld cracking, paint peeling, loose
fasteners, sign off and difficulty in starting, power reduction, fuel consumption
increase, slow rise and other phenomena that exceed specified values.
3.5 inherent weakness fault
Under specified conditions of use, the fault that is caused by defect inherent in
product itself.
For example, excessive deformation, fracture, early wear and fatigue of parts,
abnormal corrosion and aging, loosening or failure of fasteners, performance
degradation, and "three leaks" (see 2.3 in GB/T 24648.2-2009).
3.6 secondary fault
The fault of other parts of product that is directly or indirectly caused by fault of
some part of product, or the derived fault caused by inherent weakness fault.
For example, when engine is broken due to broken connecting rod bolts and
damages of a series of parts such as connecting rods, bushings, pistons and
cylinders, broken connecting rod bolts shall be inherent weakness fault, and
damages of a series of parts shall be secondary fault (see 2.4 in GB/T 24648.2-
2009).
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.
5.4 Mean interval time between downtime faults
See formula (3) for mean interval time between downtime faults.
Where,
DTMTBF - Mean interval time between downtime faults of tractor, in hours (h);
rd - Total number of downtime faults (i.e., fatal faults and severe 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.
5.5 Trouble-free comprehensive score
Within specified test time, if one of tractors to be tested has fatal fault, this type
of tractor shall fail in trouble-free comprehensive score. Its Q value shall not be
calculated.
For tractor to be tested that has no fatal fault, its trouble-free comprehensive
score is calculated according to formula (4):
or total cost of troubleshooting of this type of tractor (including replacement and
repair costs) during test period specified in 7.3.3.2, in RMB;
Ct - Unit price of this type of tractor, in RMB.
6 Evaluation methods
6.1 Data sources
Sources that are used to evaluate tractor reliability may come from the following
three aspects.
6.1.1 Use test
According provisions of Clause 7, perform reliability test, combing with
production use.
6.1.2 Laboratory or test site reliability test
According to method specified in relevant standard, perform reliability test in
laboratory or on test site where conditions are controllable. However, equivalent
relationship between such test time and actual use time of user shall be known
in advance.
6.1.3 User survey
Conduct sample surveys or full follow-up surveys among users to obtain
reliability data for actual use of tractor.
6.2 Fault determination
For all faults of tractor, according to provisions of Clause 4, determine the nature
of each fault and its category one by one, which are used as basis to calculate
relevant indicators.
6.3 Marking methods for indicator
Marking format for tractor’s reliability indicators is specified as follows:
Indicator code = indicator value (data source)
For example: reliability indicators for tractor of which ××× type engine calibration
power is less than 18kW are as follows:
MTTFF=150h (3×500h use test)
MTBF=250h (3×500h use test)
load specified in user manual. Lifting time is the time used when lower
suspension point rises from the lowest point to the highest point when throttle
is fully open.
7.3.2.3 Brake test
According to provisions of GB/T 3871.6, measure maximum average
deceleration speed of cold braking.
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.
7.3.3.1 Record test situation of each test prototype in details according to Table
A.5.
7.3.3.2 Total working time of test prototype is 1500h. It is 2×750h for tractor of
which engine calibration power is greater than 18kW, 3×500h 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
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/(k
W·h)]
Pd/kW ne/(r/min) Gt/(kg/h)
gd/[g/(k
W·h)]
Pd/kW ne/(r/min) Gt/(kg/h)
gd/[g/(k
W·h)]
Be
for
e t
es
1)
Ma
xim
um
po
we
r o
ca
libr
ati
on
sp
ee
2)
85
of
ite
1)
tor
qu
3)
75
of
ite
2)
tor
qu
4)
50
of
ite
2)
tor
qu
5)
25
of
ite
2)
tor
qu
6)
No
loa
d - -
Av
era
ge
- - -
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
Note:
Recorder: Reviewer: Participant:
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
/ %
Gear
Gear
Gear
Gear
Gear
Average load coefficient of field work/%
Field work time as a percentage of total time /%
Recorder: Reviewer: Participant:
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)
Recorder: Reviewer: Participant:
Annex B
(informative)
Examples of tractor faults
B.1 General parts are in accordance with provisions of Table B.1.
Table B.1
No. Name Fault mode Situation description Category
1 Body, rack, walking equipment Breaking, disengaging I
2 Internal parts of body Damaged or invalid II
3 Important parts and components outside body
Damaged or
invalid II
4 General parts outside body Damaged or invalid III
5 Important fasteners outside body Multiple damage
Fastener bolt strength of 8.8
or more, nut of 8 or more,
causing connection failure
II
6 Important fasteners outside body
Individually
damaged or
loosened multiple
times
No connection failure III
7 General fasteners outside body Damaged or detached No connection failure IV
8 Part joint surface Serious “three leaks”
Exclude by disassembling
and replacement II
9 Part joint surface “Three leaks”
Exclude by not
disassembling and
replacement
III
10 Part joint surface Leakage Wet IV
11 Warning sign or seal Falling off III
12 Non-warning sign Falling off IV
13 Surface paint wax and electroplated coating
Large pieces of
flakes III
14 Surface paint wax and electroplated coating Falling off IV
15 Non-essential plastic parts Cracks IV
16 Butter mouth Damaged or detached IV
......
 
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.