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 selected for manufacturing products shall comply with the safety and environmental protection regulations of the application area.

6.1 Dimensions and Appearance Quality

• 6.1.1 The ratio of D₂/D₁ shall not be less than 1. The diameter and stroke of the gas spring piston rod shall be selected in accordance with GB/T 2348 and GB/T 2349. Special requirements shall be agreed upon by the supplier and the demander.
• 6.1.2 The tolerance of the extended length of the gas spring shall comply with the IT16 accuracy level specified 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, without 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, without defects such as red rust, peeling, blisters, roughness, and missing plating (except for process holes and holes smaller than 1 mm).
• 6.1.5 The paint coating on the gas spring cylinder shall comply with the provisions of QC/T 484. The paint coating shall be uniform, without exposed substrate, obvious pitting, or serious sagging.

6.2 Force Characteristics

For gas springs with a specified force greater than 100 N, the force value shall be determined in integer multiples of 50 N. There shall be no jamming or obvious jitter during the compression and extension processes of the gas spring.

• 6.2.1 Specified Force F× and Dynamic Friction Force F,
  The limit deviation of the specified force value and the dynamic friction force shall comply with the provisions of Table 2. In case of special needs, it shall be agreed upon by the supplier and the demander.
  | Specified Force Value (N) | Limit Deviation of Specified Force Value (N) | Maximum Dynamic Friction Force F, (N) |
  |—|—|—|
  | ≤100 | ±5 | 25 |
  | 101 – 200 | +20 – 10 | 30 |
  | 201 – 400 | +30 – 15 | 40 |
  | 401 – 600 | +40 – 20 | 60 |
  | 601 – 800 | +50 – 25 | 80 |
  | 801 – 1000 | +60 – 30 | 100 |
  | 1001 – 1200 | +70 – 35 | 130 |
  | >1200 | +80 – 40 | 150 |
• 6.2.2 Start – up Force F₀
  The start – up force of the gas spring shall be less than 1.5F₃.
• 6.2.3 Force Ratio
  The force ratio of the gas spring shall be agreed upon by the supplier and the demander according to the usage situation.
• 6.2.4 Liquid Damper Part
  The length of the liquid damper part of the gas spring shall be agreed upon by the supplier and the demander according to the load situation.

6.3 Extension Speed

The extension speed of the gas spring shall be between 50 mm/s and 350 mm/s. In case of special needs, it shall be agreed upon by the supplier and the demander.

6.4 High and Low Temperature Resistance Performance

After the gas spring is stored at a high temperature of 110°C and then undergoes two high – low temperature cycle tests at – 40°C and 80°C, it shall not fail, and the attenuation of its nominal force F. shall not be greater than 5%.

6.5 Cycle Life

• 6.5.1 Normal Temperature Cycle Life
  After the gas spring undergoes high – low temperature tests, it shall undergo a cycle life test of 25,000 times (when the stroke ≤ 200 mm, the actual stroke shall be used; when the stroke > 200 mm, a stroke of 200 mm shall be used). After the test, the total attenuation of its nominal force F. shall not be greater than 13%, the dynamic friction force shall comply with the provisions of Table 2, and the amount of oil brought out shall be less than 0.5 g.
• 6.5.2 Environmental Cycle Life
  For gas springs used in harsh environments, after 1,000 high – low temperature dynamic cycle life tests at – 40°C and 1,000 tests at 80°C, the attenuation of their nominal force F. shall not be greater than 5%. After the gas springs undergo high – low temperature dynamic cycle life tests, they shall then undergo a normal temperature cycle life test of 18,000 times (when the stroke ≤ 200 mm, the actual stroke shall be used; when the stroke > 200 mm, a stroke of 200 mm shall be used). After the test, the total attenuation of their nominal force F. shall not be greater than 13%, the dynamic friction force shall comply with the provisions of Table 2, and the amount of oil brought out shall be less than 0.5 g.
  Note 1: 6.5.1 and 6.5.2 are not required simultaneously.
  Note 2: When 6.5.2 is required, 6.4 shall not be required.

6.6 Tensile Resistance Performance

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

6.7 Corrosion Resistance Performance

• 6.7.1 After a 96 – hour neutral salt spray test, the gas spring shall have no blisters, peeling, or corrosion defects; the threads at the rod end and tube end and the hole openings shall have no blisters or peeling.
• 6.7.2 After a 48 – hour neutral salt spray test, the hard – chrome – plated piston rod shall have no blisters, peeling, or corrosion defects on its rod body; the threads at the rod end and the hole openings shall have no blisters or peeling.
• 6.7.3 The corrosion resistance performance of other exposed parts shall comply with the provisions of the corresponding coatings in QC/T 625. In case of special needs, it shall be agreed upon by the supplier and the demander.

Technical Specification for Compression 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).