Cylinder hydrotesting, also known as hydrostatic testing, is a non-destructive procedure used to verify the structural integrity, safety, and reliability of gas cylinders. This method detects leaks, corrosion, and structural weaknesses by subjecting the cylinder to high internal water pressure while enclosed in a test jacket. The process measures the total and permanent volumetric expansion by analyzing how much water is displaced during pressurization and after the pressure is released.

Visual inspections—both internal and external—are conducted as part of the evaluation, along with dead-ring tests for steel cylinders. Although we specialize in comprehensive hydrostatic stretch testing for most gas cylinders, we do not test disposable gas bottles or cylinders containing acetylene, carbon dioxide, liquid hydrocarbons, or any welded cylinders, regardless of their material of construction (MOC).

At Alchemie Gases & Chemicals Pvt. Ltd., we recommend regular hydrotesting of all other eligible gas cylinders to ensure they are safe for continued use. While the test itself is non-destructive, extreme pressure or pre-existing flaws (like micro-cracks) in the cylinder can lead to failure during testing. All hydrotests are conducted under strict, standardized procedures in line with government regulations.

We are certified to perform hydrotesting on cylinders manufactured as per standards set by the Petroleum and Explosives Safety Organisation (PESO), Government of India, including CO₂ fire extinguishers ranging from 1 to 68 liters in capacity.

According to PESO guidelines, high-pressure seamless gas cylinders must undergo hydrotesting every five years. However, cylinders used for toxic or compressed natural gases (CNG) are subject to stricter regulations and should be tested every two years or as specified by PESO.

Hydrotesting evaluates a cylinder's elasticity—its ability to return to original dimensions after being stressed during gas filling. Over time, elasticity can degrade, increasing the risk of failure. To ensure safe operation, cylinders are tested at a pressure 1.5 to 1.66 times their normal working pressure, depending on their design and material.

Regular testing helps determine whether the cylinder is safe for continued use or should be decommissioned due to permanent deformation or material fatigue.

The Water Jacket Method involves placing the gas cylinder in a sealed chamber (jacket) filled with water. As the cylinder is pressurized, it expands, displacing water into a calibrated glass tube. After the pressure is released, any permanent expansion is measured to evaluate the cylinder’s structural integrity. In the Proof Pressure Method, the cylinder is pressurized internally to check for wall thinning, minor leaks, or other structural defects. Unlike the water jacket method, this test does not measure expansion but ensures the cylinder can withstand a certain pressure without failure. Pneumatic Testing, on the other hand, uses compressed air or nitrogen instead of water. While it is useful in specific cases, this method requires extreme caution due to the high compressibility of gases, which can increase the risk factor if a failure occurs under pressure.