QC/T 798-2008 PDF in English
QC/T 798-2008 (QC/T798-2008, QCT 798-2008, QCT798-2008)
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Multi-layers plastic tubing for automotive fuel system
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QC/T 798-2008: PDF in English (QCT 798-2008) QC/T 798-2008
AUTOMOBILE INDUSTRY STANDARD
OF THE PEOPLE’S REPUBLIC OF CHINA
Multilayers plastic tubing for automotive fuel system
ISSUED ON: FEBRUARY 01, 2008
IMPLEMENTED ON: JULY 01, 2008
Issued by: Ministry of Industry and Information Technology of PRC
Annex:
Standard numbers, descriptions and dates coming into force of four automotive
industry standards
SN Standard number Standard description
Date coming into
force
1 QC/T 796-2008 Automotive fuel consumption labels July 1, 2008
2 QC/T 797-2008
Identification and marking of materials that are
fabricated into automotive plastic, rubber and
thermoplastic elastomer parts
July 1, 2008
3 QC/T 798-2008 Multi-layers plastic tubing for automotive fuel system July 1, 2008
4 QC/T 799-2008 Telescopic belt truck conveyer July 1, 2008
Table of Contents
Foreword ... 5
1 Scope ... 6
2 Normative references ... 6
3 Terms and definitions ... 6
4 Specification dimension ... 7
5 General requirements ... 8
6 Performance requirements ... 9
7 Test methods ... 10
8 Inspection rules ... 20
9 Markings and signs ... 21
10 Packaging, transportation, storage ... 22
Appendix A (Normative) Specifications for permeability resistance test ... 23
Multilayers plastic tubing for automotive fuel system
1 Scope
This standard specifies the dimensional specifications, appearance, technical
requirements, test methods, inspection rules, markings, packaging,
transportation, storage of multilayer plastic tubing for automotive fuel systems
(hereinafter referred to as multilayer tubing) and tube assemblies.
This standard is applicable to multilayer plastic fuel tubes which have a working
temperature between -40 °C and +115 °C (continuous use temperature shall
not exceed 90 °C) and maximum working pressure of not more than 0.7 MPa.
2 Normative references
The provisions in following documents become the provisions of this standard
through reference in this standard. For the dated references, the subsequent
amendments (excluding corrections) or revisions do not apply to this standard;
however, parties who reach an agreement based on this standard 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 528-1998 Determination of tensile stress-strain properties of
vulcanized rubber or thermoplastic rubber
GB/T 528-1998 Rubber, vulcanized or thermoplastic - Determination of
tensile stress-strain properties (ISO 527 -2: 1993 IDT)
GB/T 2828.1-2003 Sampling procedures for inspection by attributes - Part 1:
Sampling schemes indexed by acceptance quality limit (AQL) for lot-by-lot
inspection (ISO 2859-1:1999 IDT)
GB/T 2918-1998 Plastics - Standard atmospheres for conditioning and
testing (ISO 291:1997 IDT)
3 Terms and definitions
The following terms and definitions apply to this standard.
3.1
Multilayer plastic tubing
More than two layers of non-metallic plastic tubes which are made of
materials of different properties and different types, without connectors.
3.2
Tube assemblies
A combination of a multilayer tube and a tube joint which have a specified
length and shape.
4 Specification dimension
4.1 Structure
The multilayer tube is a multilayer structure which contains the wall-thickness
of the main body. The name of material is generally indicated on the drawing. If
specified, it shall identify each layer of all tube layers.
4.2 Dimensions and tolerances
Table 1 provides the dimensions and wall-thickness of various types of
multilayer tubes of this standard. The thickness and tolerance for each layer
may be determined by the manufacturer and the user through negotiation. The
dimensions and tolerances of the multilayer tube are indicated by mm.
4.3 Wall-thickness
Multilayer tubes of different sizes which are made by materials of different
grades have different wall-thicknesses. The minimum wall-thickness of a
straight tube which has a nominal diameter equal to 10 mm is 0.9 mm. The
larger the nominal diameter, the larger the wall-thickness. The requirements for
wall-thickness are as detailed in Table 1.
Note: Some of the following factors influence the choice of wall-thickness:
a) High burst-pressure requirements mean higher wall-thickness
requirements;
b) The thicker the wall-thickness, the greater the minimum bending radius.
6 Performance requirements
The performance requirements of the multilayer and/or multilayer tube
assembly shall comply with the requirements of Table 2.
Table 2 -- Performance requirements
No. Test items Unit Requirements Test methods
1 Burst-pressure
Burst-pressure at
room-temperature MPa
The minimum burst-pressure shall be greater than or equal
to 8 times the design working pressure in the system.
Before reaching to this pressure, the tube does not loose
and the assembly does not leak
7.3
Burst-pressure at
high-temperature MPa
The minimum burst-pressure shall be greater than or equal
to 3 times the design working pressure in the system.
Before reaching to this pressure, the tube does not loose
and the assembly does not leak
7.4
2 Bending performance
Minimum bending
radius mm Meet the requirements of Table 3
7.5 Anti-bending deformation - The steel ball can pass it freely
Burst pressure after
bending MPa
The minimum burst-pressure shall be greater than or equal
to 8 times the design working pressure in the system
Resistance
to zinc
chloride
Appearance - Multilayer tube or tube end shall be free of cracks
7.6 Burst-pressure at
room-temperature MPa
The minimum burst-pressure shall be greater than or equal
to 75% of the burst-pressure at room-temperature
Impact
performance
at low-
temperature
Appearance - The surface is free of cracks
7.7 Burst-pressure at
room-temperature MPa
The minimum burst-pressure shall be greater than or equal
to 75% of the burst-pressure at room-temperature
Resistance
to
permeability
Permeability g/m•d
OD ≤ 10 mm < 0.05
7.8
10 mm < OD ≤ 18 mm < 0.15
Change rate of
length - -1% ~ +1%
Burst-pressure at
room-temperature MPa
Meet the requirements of the burst test pressure at room-
temperature
Yield stress
Extruding direction
N/mm2
≥ 24
7.9
Perpendicular
direction ≥ 25
Elongation
at break
Extruding direction
≥ 170
Perpendicular
direction ≥ 170
7 Resistance to fuel
Appearance - The surface is free of cracks
7.10 Impact at low-
temperature - The surface is free of cracks
7.3.3.1 At the ambient temperature of 23 °C ± 2 °C, carry out the test. The
internal test medium of the multilayer tube is liquid. Block one end of the
specimen. Connect the other end to the burst pressure testing machine. Then
at the rate of 7 MPa/min ± 1 MPa/min, increase pressure to the multilayer tube,
until it bursts. Record the maximum pressure during the test period. Use the
minimum value of the five specimens as the test result.
7.3.3.2 If the tubing/connection fails before reaching the burst-pressure, discard
the test data. If necessary, it may use the existing tubing connections plus the
auxiliary fixtures, to ensure that the test is carried out effectively.
7.3.3.3 The minimum burst-pressure of all specimens shall be greater than or
equal to 8 times the design working pressure in the system. If the design
working pressure is not known, record the measured burst-pressure, which can
be used to compare with the requirements in application state. The end user
shall discuss establishing the maximum pressure Pmax in the system when the
multilayer tube is in the use state.
7.4 Burst-pressure at high-temperature
7.4.1 Specimen: Five tube assemblies which have a length of 300 mm between
the tubes.
7.4.2 Test device: Burst-pressure testing machine.
7.4.3 Test procedure:
7.4.3.1 After the state conditioning, the specimen shall be kept at 115 °C for 0.5
h ~ 1 h and then tested according to the test procedure of 7.3.3.
Note: The liquid used in this burst pressure test shall also be at the same
temperature.
7.4.3.2 The minimum burst-pressure of all specimens shall be greater than or
equal to 3 times the design working pressure in the multilayer tube system. The
end user shall discuss establishing a maximum pressure value, to allow the
multilayer tube to deliver a particular liquid or is possible in a vapor system.
The recommended minimum burst-pressure at high-temperature is: Not less
than 1.286 MPa for the high-pressure liquid fuel line; not less than 0.143 MPa
for the low-pressure liquid fuel line; not less than 0. 057 MPa for the fuel vapor
tube.
7.5 Bending performance
7.5.1 Determination of the minimum bending radius.
7.5.1.1 Calculation of the minimum bending radius: Table 3 gives the empirical
products;
b) After formal production, where there are large changes in structure,
materials, processes that may affect the product’s performance;
c) When the production is restored after long-term suspension;
d) For products manufactured in batches or mass, not less than once a year;
e) When the exit-factory inspection result is significantly different from the
previous type inspection result;
f) When the national quality supervision agency proposes the requirements
for type inspection.
8.4.2 Sampling:
The multilayer tubes of the same specification which are continuously produced
at the same production site, by the same raw material, equipment and process
are considered as a batch. The products to be type inspected shall be taken
from the same batch of products that have passed the exit-factory inspection.
The sampling plan shall be agreed by the supplier and the buyer.
8.4.3 The items of type inspection are all items as specified in clauses 5 and 6.
8.5 Determination of qualification
Use the test method as specified in this standard to carry out inspection. Based
on the test results and technical requirements, make quality determination
against the product. If there is one disqualified item, it allows to double the
number of products to repeat testing for this item. If it is still disqualified, this
batch of products are disqualified. If it fails to reach the requirements, randomly
take double number of samples to re-inspect this item. If it is still disqualified,
this batch of products is disqualified.
9 Markings and signs
9.1 Markings on multilayer tube
The markings on the multilayer tube shall be clear and firm, which shall not
impair the performance of the multilayer tube and the function of the connecting
elements. The spacing between markings shall not exceed 300 mm. The
information of the marking on the multilayer tube shall have at least the following:
a) This standard number;
b) Specifications of multilayer tube; nominal diameter (OD) and wall-
Appendix A
(Normative)
Specifications for permeability resistance test
A.1 General
This Appendix specifies test equipment, methods and procedures, calculation
formulas and reports for the permeability resistance of multilayer tubes.
A.2 Test equipment
- Gas analyzer;
- Explosion-proof drying oven;
- Burst pressure testing machine;
- Liquid circulation test machine;
- Vernier calipers (0 -500 mm/0.02 mm), etc.
A.3 Test conditions
A.3.1 Test medium: test liquid (90% volume of high-quality lead-free gasoline +
10% volume of ethanol).
A.3.2 Test conditions:
- Test environment: temperature: 23 °C ± 2 °C, relative humidity: 50% ± 10%;
- Relative working pressure: 0.35 MPa ± 0.01 MPa;
- Test medium’s temperature: 40 °C ± 2 °C;
- Flow rate: 30 L/h ± 5 L/h;
A.3.3 Burst-pressure test: The internal medium of the specimen is water (23 °C
± 2 °C). The specimen is placed in an explosion-proof drying box which has an
ambient temperature of 100 °C ± 5 °C.
A.4 Test procedure
A.4.1 The connection diagram of permeability resistance test is as shown in
Figure A.1. Connect the specimen to the connector. Measure the length
between the two connectors or the length between the two markings on the part
assembly (the length between the markings is at least 500 mm). Record it as
......
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.
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