9 Identification, Packaging, Transportation, and Storage

9.1 Safety Markings

Each gas spring product must be marked with safety markings in an obvious position.

9.2 Product Identification

Each gas spring product should be marked with the following information agreed upon by the supplier and the demander in an obvious position:
a) The trademark of the demander or the supplier;
b) Product code, model, or part number;
c) The name, code of the supplier, or the name of the demander;
d) Delivery date or production batch number.

9.3 Packaging Box Identification

The packaging box of the gas spring should be marked with the following information agreed upon by the supplier and the demander:
a) Product name, model, part number, order number, or barcode;
b) The name, code, or address of the supplier and the demander;
c) Quantity of products;
d) External dimensions, gross weight, and net weight;
e) Production date;
f) Markings such as “Beware of High Temperature” and “Handle with Care”.

9.4 Packaging

a) Each gas spring in the packaging box should be protected by flexible materials.
b) The gross weight of each box should not be greater than 30 kg.
c) A certificate of conformity stamped by the quality department should be included in the packaging box.
d) The material of the packaging box shall be agreed upon by the supplier and the demander.

9.5 Transportation

The gas springs are shipped according to the transportation method agreed upon by the supplier and the demander.

9.6 Storage

Gas spring products should be stored in a dry and well – ventilated warehouse, away from acids, alkalis, or other corrosive gases. Under normal storage conditions, there should be no rust on the coating or peeling of the paint within one year, and the attenuation of the nominal force should not be greater than 5%.

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).

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).

7. Test Methods

7.1 Dimensions and Appearance

• 7.1.1 Dimensions shall be inspected using special or universal measuring tools with a scale division value of not more than 0.5mm.
• 7.1.2 Appearance quality shall be inspected by visual observation.

7.2 Force Characteristicsd

• 7.2.1 Test Conditions: The test shall be carried out in an environment of . Before the test, the gas spring shall be kept in the extended state, and the piston rod shall not be pressed. The sample shall be placed in an environment of  for more than 2 hours. The test measurement speed is 400mm/min, and the force – measuring accuracy is not lower than 1%.
• 7.2.2 Test Methods: The test methods for force characteristics include dynamic tests and static tests. Dynamic test methods shall be used as much as possible.
  • 7.2.2.1 Dynamic Testing: Vertically clamp the piston rod of the gas spring upward on the testing machine. In the first cycle of starting the machine, record the unlocking force and start – up force. In the second cycle (when the gas spring has been stored for a long time, the number of cycles can be increased to three to five), record the extension and compression forces , , ,  at the force – taking point C, calculate the nominal force, dynamic friction force, and force ratio, and draw the force – displacement curve. At the same time, observe whether there is any jamming of the piston rod of the gas spring.
  • 7.2.2.2 Static Testing: Vertically clamp the piston rod of the gas spring upward on the testing machine. In the first cycle of starting the machine, record the unlocking force and start – up force. In the second cycle (when the gas spring has been stored for a long time, the number of cycles can be increased to three to five), record the extension and compression forces , , ,  at the force – taking point C, calculate the nominal force and force ratio, and draw the force – displacement curve. The residence time at the force – taking point C during static testing is [a certain time]. At the same time, observe whether there is any jamming of the piston rod of the gas spring.
  • 7.2.2.3 Detection of Locking Force:

a) Rigid Compression Locking Force: Vertically clamp the piston rod of the gas spring, which is locked in the fully extended state, downward on the testing machine. Compress the gas spring at a speed of 2 mm/min to make the piston rod displace 2 mm, and record the compression locking force value (applicable to the locking of Curve II). Or, vertically clamp the piston rod of the gas spring, which is locked in the fully extended state, downward on the testing machine. Start the testing machine, compress the gas spring at a speed of 2 mm/min, and when the locking force value reaches the agreed value, record the displacement of the piston rod (applicable to the locking of Curve I).
b) Rigid Tensile Locking Force: Vertically clamp the piston rod of the gas spring, which is locked in the fully compressed state, downward on the testing machine. Stretch the gas spring at a speed of 2 mm/min to make the piston rod displace 2 mm, and record the tensile locking force value (applicable to the locking of Curve II). Or, vertically clamp the piston rod of the gas spring, which is locked in the fully compressed state, downward on the testing machine. Start the testing machine, stretch the gas spring at a speed of 2 mm/min, and when the locking force value reaches the agreed value, record the displacement of the piston rod (applicable to the locking of Curve I).
c) Elastic Locking Force: To be agreed upon by the supplier and the demander.

7.3 Extension Speed

7.3.1 Test Conditions

The test is carried out in an environment of 20°C ± 2°C. Before the test, the sample should be placed in an environment of 20°C ± 2°C for more than 2 hours, and the scale division value of the timer should not be greater than 1/100 s.

7.3.2 Test Method

Vertically clamp the piston rod of the gas spring downward on the testing machine. Start the testing machine, lock the gas spring in the fully compressed position, and then quickly open the control valve to allow the piston rod to extend freely. Measure the extension time t and the extended stroke S, and calculate the extension speed (average speed)  according to the following formula:

where:

• S is the stroke, with the unit of millimeter (mm);
• t is the extension time, with the unit of second (s).

7.4 Sealing Performance

Lock the gas spring in the compressed state, measure the extended length of the piston rod, store it at room temperature for 24 hours, and then measure the extended length of the piston rod again.

7.5 High and Low Temperature Resistance Performance

Put the gas spring into a low – temperature test chamber at -30°C ± 2°C and keep it for 48 hours. After taking it out, place it in a high – temperature test chamber at 60°C ± 5°C and keep it for 48 hours. Take out the gas spring, test its force characteristics according to 7.2, and calculate the attenuation of the nominal force  and the locking force .

7.6 Cycle Life

Clamp the piston rod of the gas spring, which has passed the high and low temperature test, downward on a testing machine equipped with an oil – collecting device. Conduct a cycle life test at a frequency of 6 times/min to 12 times/min. During the entire test process, the temperature of the gas spring cylinder barrel should not be higher than 50°C. After 40,000 cycles, test the force characteristics and the locking force  according to 7.2, and calculate the attenuation of the nominal force , the dynamic friction force , and the locking force . Test the stroke of the piston rod according to 7.1.1 and calculate its variation. Weigh the amount of oil leakage on an electronic scale with an accuracy of not less than 0.01 g.

7.7 Tensile Resistance Performance

Fix the gas spring in the extended state on the testing machine, load it at a speed of 1 mm/min to 2 mm/min according to the values specified in Table 3, keep it for 3 minutes, and after unloading, test the force characteristics according to 7.2 or make observations.

7.8 Corrosion Resistance Test

The corrosion resistance test of the gas spring is carried out in accordance with the provisions of GB/T 1771 or GB/T 10125.

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).

6. Technical Requirements

Products shall meet the requirements of this standard and be manufactured in accordance with the product drawings and technical documents confirmed by both the supplier and the demander. The materials and coatings used in product manufacturing shall comply with the safety and environmental protection regulations of the application area.

6.1 Dimensions and Appearance Quality

• 6.1.1 The ratio  shall not be less than [a certain value]. The piston rod diameter and stroke of the gas spring shall be selected according to [relevant standards]. Special requirements shall be agreed upon by the supplier and the demander.
• 6.1.2 The dimensional tolerance of the extended length of the gas spring shall comply with the IT16 – level accuracy regulations in GB/T 1800.1.
• 6.1.3 The coating on the piston rod of the gas spring shall be uniform, and the surface shall be smooth and free from defects such as scars, blisters, peeling, pitting, pinholes, and nodules.
• 6.1.4 The coatings on other exposed parts except the piston rod shall be uniform and free from defects such as red rust, peeling, blisters, roughness, and uncoated areas (except for process holes and holes smaller than 1mm).
• 6.1.5 The quality of the paint coating on the gas spring cylinder barrel shall comply with the regulations of QC/T 484. The paint coating shall be uniform, free from exposed bases, obvious pitting, and severe sagging, and may have a slight “orange peel” effect.

6.2 Force Characteristics

• For gas springs with a specified force greater than 100N, the force value shall be determined in integer multiples of 50N. There shall be no jamming during the compression and extension processes of the gas spring.
• 6.2.1 The specified force value  and friction force : The limit deviation of the specified force value and the dynamic friction force shall comply with the regulations in Table 2. Special requirements can be agreed upon by the supplier and the demander.
• 6.2.2 Unlocking force : The unlocking force of the gas spring shall be agreed upon by the supplier and the demander according to customer requirements.
• 6.2.3 Start – up force : The start – up force of the gas spring shall be less than .
• 6.2.4 Force ratio : The force ratio of the gas spring shall be agreed upon by the supplier and the demander according to the usage conditions.
• 6.2.5 Locking force : For rigid – locking gas springs, when the displacement of the piston rod is not more than 2mm, the compression locking force shall be greater than . The locking force of elastic – locking gas springs, the tensile locking force of rigid – locking gas springs, and special requirements shall be agreed upon by the supplier and the demander.

6.3 Extension Speed 

The extension speed  of the gas spring shall be between 40mm/s and 200mm/s. Special requirements shall be agreed upon by the supplier and the demander.

6.4 Sealing Performance

When the gas spring is locked at any position and stored at room temperature for 24 hours, its stroke shall not change.

6.5 High and Low Temperature Resistance Performance

After the gas spring is stored at high and low temperatures, the attenuation of its nominal force  and locking force  shall not be more than 5%.

6.6 Cycle Life

After the gas spring has undergone the high and low temperature performance test, it shall be subjected to [a certain number of] cycle life tests ( shall be tested according to the actual stroke; when , it shall be tested according to [the specified stroke]). After the test, the total attenuation of its nominal force  and locking force  shall not be more than [the specified value]. The dynamic friction force shall comply with the regulations in Table 2, and the amount of oil leakage shall be less than 0.5g. The change in the piston rod stroke shall be agreed upon by the supplier and the demander.

6.7 Tensile Resistance Performance

The tensile resistance performance of gas spring products shall comply with the regulations in Table 3.

6.8 Corrosion Resistance Performance

• 6.8.1 After 72 – hour neutral salt spray testing, the gas spring shall be free from blisters, peeling, and corrosion defects; the threads at the rod ends and pipe ends, as well as the hole openings, shall not have blisters or peeling.
• 6.8.2 After 48 – hour neutral salt spray testing, the hard – chromium – plated piston rod shall be free from blisters, peeling, and corrosion defects on its rod body; the rod – end threads and hole openings shall not have blisters or peeling.
• 6.8.3 The corrosion resistance performance of other exposed parts shall comply with the regulations of the corresponding coatings in QC/T 625.
• Special requirements shall be agreed upon by the supplier and the demander.

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).

4. Types

4.1 Shape and Force – Displacement Curve

The external shape and force – displacement curve of the gas spring are shown in Figure 1.

4.2 Types and Codes of Gas Spring Connectors

The types and codes of gas spring connectors are shown in Figure 2. Other connection types shall be agreed upon by the supplier and the demander.

5. Marking

5.1 Marking Method

The marking of a gas spring consists of a code, piston rod diameter (which may not be marked), cylinder barrel outer diameter (which may not be marked), stroke, extended length, and specified force value. The regulations are as follows:

Where:

• “KQ” is the code for lockable gas springs;
• “” represents the piston rod diameter and cylinder barrel outer diameter (if not marked, this part can be omitted);
• “” represents the stroke;
• “” represents the extended length;
• “F\times\times\times\times” represents the specified force value.

5.2 Marking Examples

• Example 1: For a lockable gas spring with a piston rod diameter of 10mm, a cylinder barrel outer diameter of 27mm, a stroke of 60mm, an extended length of 260mm, and a nominal force of 350N.
  Marking: KQ10/27 – 60 – 260Fa350 or KQ60 – 260Fa350
• Example 2: For a lockable gas spring with a piston rod diameter of 10mm, a cylinder barrel outer diameter of 27mm, a stroke of 30mm, an extended length of 150mm, and a minimum extension force of 600N.
  Marking: KQ10/27 – 30 – 150F1600 or KQ30 – 150F1600

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).