CNG (Compressed Natural Gas) hydro testing refers to the process of testing the integrity and safety of CNG cylinders or tanks through hydrostatic pressure testing. CNG is a clean-burning alternative fuel that is used in vehicles and industrial applications. CNG cylinders store the gas under high pressure, and it's crucial to ensure their structural integrity to prevent leaks or failures that could lead to safety hazards.

Hydrostatic testing involves filling the CNG cylinder with water and subjecting it to a higher pressure than its normal operating pressure. This test helps to identify any weaknesses or defects in the cylinder's structure that might not be visible under normal circumstances. The cylinder's expansion and contraction under pressure, as well as any leaks or deformations, are carefully monitored during the test.