GB/T 7825-2017Road vehicles -- Spark-plugs -- Test methods and requirements (English PDF)

3.1 General Principles

The test of spark plugs shall comply with the following stipulations.

---If there are no specific stipulations, all tests of spark plugs shall be conducted

under normal temperature (23 +/- 5) °C and normal humidity (65 +/- 20) %.

---Type inspection items and samples of spark plugs shall comply with the test

sequence and requirements stipulated in Table 1.

---Exit-factory inspection items and samples of spark plugs shall comply with the

test sequence and requirements stipulated in Table 2; or the customers'

requirements.

---Each test in Table 1 and Table 2 shall start from new products that have not

been used; tests shall be conducted from the top to the bottom in accordance

with the mark "".

---Please refer to Appendix A for the inspection rules.

Table 2 -- Spark Plug Exit-factory Inspection Sequence Table

3.2 General Characteristics

3.2.1 Test method

Conduct the method of visual inspection to inspect the characteristics indicated in 3.2.2.

The method of visual inspection refers to the inspection with naked eyes (normal vision

and color discrimination ability) at the most comfortable visual inspection distance

under suitable lighting conditions.

3.2.2 Requirements

3.2.2.1 External sealing washer shall manifest no notches or obvious damages;

corresponding dimensions shall comply with the requirements stipulated by the

manufacturers or the customers.

3.2.2.2 Heat chamber shall be clean; there shall be no foreign substances.

3.2.2.3 Central electrode and side electrode shall be in the right position.

3.2.2.4 No visible corrosion is allowed on the shell. Thread shall manifest no burrs or

damages (which can be determined by whether threaded ring can freely pass through).

The fixation with insulator shall be reliable and manifest no abnormalities.

3.2.2.5 Insulator shall be smooth and consistent; there shall be no abnormalities like

fracture, crack or impact scar.

3.2.2.6 The marking shall be distinct and consistent; it shall also comply with the

requirements stipulated by the manufacturers or the customers.

Test Items Clause Test Quantity (PCS)

Sample No.

General

Characteristics

Dimension

Resistance Value

Thermal Sealing

Performance

Bending Strength

Wiring Screw Tensile

Load

Adopt an exclusive tensile test device; along the axial direction, gradually increase

tensile force at the rate of less than 500 N/s to pull the wiring screw of the spark plug.

3.4.2.2 Requirements

After bearing 980 N of tensile load (low-seat spark plug bears 400 N of tensile load),

the wiring screw shall manifest no abnormalities in all parts.

3.4.3 Bending strength

3.4.3.1 Test method

Adopt the maximum installation torque stipulated in GB/T 6791 to install the spark plug

on a suitable test bench. Within the range of 5 mm from the ends of the insulator,

impose vertical force, which acts on the axial direction of the insulator; the speed of

the force shall be less than 10 mm/min.

3.4.3.2 Requirements

Spark plug shall be able to bear 15 Nm of bending moment at the minimum and shall

not be damaged.

3.4.4 Vibration test

3.4.4.1 Test method

In accordance with the torque stipulated in relevant national standards, install spark

plug on a standard vibration test bench. Parameters of the vibration test shall satisfy.

---Frequency range. 50 Hz ~ 500 Hz, sinusoidal signal;

---Sweep rate. 1 frequency multiplication/min;

---Vibration acceleration. 30 g (294 m/s2);

---Vibration direction. axial direction and radial direction of spark plug;

---Duration. 8 h in each direction.

3.4.4.2 Requirements

After the test, the spark plug shall manifest no abnormalities; it shall pass the

subsequent tests stipulated in Table 1.

3.5 Thermal Sealing Performance

3.5.1 Test method

In accordance with the installation torque stipulated in Table 4, install spark plug on a

Appendix A

(Normative)

Inspection Rules

A.1 Spark plugs shall pass the inspection conducted by the manufacturer's inspection

department before exiting factory; they shall also be attached with a product quality

certificate.

A.2 Spark plugs shall be inspected by batch. It shall be guaranteed that each batch of

spark plugs are the same model of products continuously manufactured through the

same techniques.

A.3 The inspection of spark plugs is divided into exit-factory inspection and type

inspection.

A.4 In exit-factory inspection, random sampling test shall be implemented in

accordance with the stipulation in Table 2. The criterion of determination is zero defect.

A.5 Type inspection shall be conducted in accordance with the items and sequence

stipulated in Table 1; it shall also comply with the requirements in this Standard. Under

the following circumstances, type inspection shall be conducted.

---Type inspection shall be conducted at least once every three years on each

series of products in normal production.

---In the type approval stage of new products.

---When there are significant changes in the structure, raw materials, ingredients

and techniques of previous products.

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