Basic Principle
Hydrostatic testing uses water (or oil) as the test medium; pneumatic testing uses air or nitrogen. Both pressurize the component to a specified test pressure and hold for a defined time to check for leaks or deformation.
Safety Comparison
The critical safety difference is energy storage. Water is nearly incompressible — if the component fails, the energy release is small and the crack does not propagate violently. Gas is compressible — a failure releases stored energy rapidly, which can cause explosive fragmentation.
Rule of thumb: use hydrostatic testing whenever possible. Use pneumatic testing only when the component cannot be filled with liquid (e.g., it must stay dry), and then with appropriate shielding.
SUNCENTER Equipment
SUNCENTER manufactures both hydrostatic test benches (water/oil medium, up to 600 MPa [TBC]) and pneumatic leak test equipment (air/N2 medium). For safety-critical validation, we recommend hydrostatic testing as the primary method.