Gas Leak Test Methods – Bubble, Pressure Decay & Helium Leak Testing

Published 2026-10-17 · Jinan Shangling Technology Co., Ltd.

A leak test verifies the seal integrity of pressure vessels, piping and valves before commissioning. Depending on sensitivity, three methods are commonly used: bubble testing, pressure decay testing and helium mass-spectrometer leak testing. This article explains each method and how to select the right pressurization equipment.

1. Three Leak Test Methods

1. Bubble test: pressurize the part with gas and submerge it in water – escaping bubbles reveal leak points; simple and reliable for low/medium pressure;
2. Pressure decay test: close the gas supply after pressurization and measure the pressure drop rate to quantify leakage; ideal for field and batch testing;
3. Helium leak test: use helium as a tracer gas with a mass-spectrometer leak detector; sensitivity down to 10^-9 Pa·m³/s, used for high-pressure, precision and vacuum systems.

2. Test Pressure & Acceptance Criteria

1. Pressure vessels: per ASME BPVC VIII and GB/T 150-2011, pneumatic leak testing is performed after the strength test at design pressure;
2. Piping: per ASME B31.3 / GB 50235-2010, leak testing at design pressure with soap-solution checks on flanges and welds;
3. Acceptance: stable pressure, no visible bubbles, detector reading within the allowable leak rate.

3. Selecting a Gas Booster for Leak Testing

1. Pressure range: cover the part design pressure; 10-35 MPa covers most applications, higher ratings for special high-pressure tests;
2. Media compatibility: air/nitrogen for general use; helium-compatible seals and oil-free construction for helium testing;
3. Control: auto stop at set pressure, automatic makeup to compensate leakage, pressure-curve recording for traceability;
4. Flow rate: larger volumes need higher charging flow – size by volume and target pressure.

4. Shangling Solution

Jinan Shangling Technology supplies air/nitrogen/helium booster pumps and complete leak test skids up to 100 MPa, oil-free, auto pressure-holding with recorded test curves, and custom designs per part. For more details, please call 18668913679 or email ljys@163.com.