Why Do 150 Bar Oxygen Cylinders Have Different Test Pressures (225 Bar vs 250 Bar)?

Introduction

In the world of high-pressure gas cylinders, safety and reliability are always the top priorities. Many customers have noticed that although oxygen cylinders are commonly marked with a working pressure of 150 bar, the test pressure on the cylinder can be either 225 bar or 250 bar.

This difference often raises questions: Why are there two test pressures for the same working pressure?

Main Explanation

1. Safety Factors

• The test pressure is always higher than the working pressure to ensure cylinder safety.

• Depending on international standards, the test pressure is calculated using different safety factors:

• 1.5 × working pressure → 150 bar × 1.5 = 225 bar

• 1.66 × working pressure → 150 bar × 1.66 ≈ 250 bar

2. Different International Standards

• ISO 7866 / SS 448 (Singapore Standard): Test pressure usually set at 225 bar.

• DOT-3AL (US Standard): Requires a higher test pressure of 250 bar.

• Both standards are internationally recognized and ensure safety, but they use slightly different design philosophies.

3. Applications in Singapore

• Medical Oxygen Cylinders → Usually 225 bar (ISO/SS standards)

• Diving Cylinders → Sometimes 250 bar (higher safety margin)

• Industrial & Firefighting Oxygen Cylinders → May vary depending on the supplier, either 225 bar or 250 bar.

Conclusion

In summary, both 225 bar and 250 bar test pressures are safe and compliant. The difference simply reflects different international standards and design requirements.

At NANJING OCEAN, all our oxygen cylinders—whether tested at 225 bar or 250 bar—strictly follow international safety standards to guarantee reliability and user safety.