8 Inspection Rules

8.1 Defects

If a gas spring does not meet the technical requirements specified in the product technical standard and product drawings, it constitutes a defect. Defects are classified according to their severity as follows:
a) A – Critical defect;
b) B – Major defect;
c) C – Minor defect.
The defect items are shown in Table 4.

8.2 Sampling Methods

8.2.1 Inspection Lot

a) The inspection lot must consist of qualified gas spring products, with 280 gas springs as one inspection lot. If the number of products is greater than 280, the inspectors shall arbitrarily divide them into several inspection lots of 280 products each, and then randomly agree on one inspection lot as the sampling object.
b) If the number of products is less than 280, it is not suitable to be sampled as an inspection lot. Instead, inventory products should be selected for sampling, or the corresponding code letter and sample should be found in Table 1 of GB/T 2828.1 according to the actual quantity.

8.2.2 Sample Selection

a) For non – destructive inspection items, a common sample is used. If the number of products is greater than 150, according to the general inspection level I specified in GB/T 2828.1, with the sample size code letter E, and the normal inspection single sampling plan, 13 gas springs are sampled. If the number of products is not greater than 150, the sample is selected according to 8.2.1 b).
b) The high and low temperature resistance performance, cycle life, tensile resistance performance, and corrosion resistance performance tests are destructive tests and belong to type test items. During inspection, according to the special inspection level S – 1 specified in GB/T 2828.1, with the sample size code letter B, and the normal inspection single sampling plan, one group of samples is used for the force characteristics, high and low temperature resistance performance, cycle life, and tensile resistance performance tests, and another group of samples is used for the corrosion resistance performance test. Three gas springs are sampled for each group.

8.2.3 Acceptable Quality Limit (AQL) and Acceptance Number (Ac)

The acceptable quality limit for A – class defect items and B – class defect items is 4.0, and the acceptance number is 0.
The acceptable quality limit for C – class defect items is 6.5. When the code letter is E, the acceptance number is 2; when the code letter is D, the acceptance number is 1.

8.2.4 According to the stability of product quality, the transfer can be made among normal inspection, reduced inspection, and tightened inspection in accordance with the transfer rules of GB/T 2828.1. During reduced inspection, with the general inspection level I and the sample size code letter E, according to the reduced inspection single sampling plan, 5 gas spring samples are sampled. When the sample size code letters are D and B, 3 and 2 gas springs are sampled respectively. During tightened inspection, the sampling quantity is the same as that in 8.2.2.

8.3 Inspection Classification

Product inspection is divided into factory inspection and type inspection.

8.3.1 Factory Inspection

All products must undergo a final inspection before delivery. The inspection items are shown in Table 5.

8.3.2 Type Inspection

Type inspection is generally required in the following cases:
a) When a new product is developed or an old product is transferred to production and needs to be finalized;
b) When there are significant changes in the product design, structure, materials, or manufacturing process;
c) When there are significant changes in the equipment and personnel of key processes;
d) After a certain period of normal production of a series of products;
e) When a major quality problem occurs in the product;
f) When the product resumes production after being out of production for more than one year;
g) When there is a significant difference between the results of factory inspection and the previous type inspection;
h) When the national quality supervision agency requires a type inspection.
The type tests in cases d) and h) are carried out according to 8.2. Other type inspections are carried out in accordance with the provisions of GB/T 2829. Six gas springs are sampled, divided into 3 groups with 2 gas springs in each group, and inspected according to Table 6.

Technical Specification for Lockable Gas Springs (English version of national strandard, initiated by LeiYan Gas Springs), proposed and prepared by SAC/TC 235 (National Technical Committee 235 on Spring of Standardization Administration of China).