Correlating Gas Leakage Rates to Fluid Ingress in Sensor Seals
Correlating gas leakage rates to liquid ingress requires deriving equivalent pore radius to confirm capillary entry pressure exceeds target hydrostatic head.
ISO 20485
Standardization Scope
International standards for non-destructive testing establish the general principles for gas leakage detection using tracer gas methods. This document, known as iso 20485, provides a framework for selecting the most appropriate gas and detection equipment for a specific application. It ensures that leak testing remains consistent across different industries and laboratories.
System Categorization
Methods are divided into those that measure the total leakage from an enclosure and those that locate individual leaks. The standard covers the use of helium, hydrogen, neon and other detectable gases that move easily through small defects. It defines how to prepare the specimen and how to handle the background signals that can obscure the results.
Instrument Qualification
Reliable data requires the mass spectrometer or electronic sensor to be calibrated against a reference leak of a known rate. This calibration must occur at the same temperature and pressure as the actual test. The standard specifies the frequency of these checks to ensure the drift in sensitivity does not lead to a false pass.
Technical Constraint
Application of these rules assumes the operator possesses a high level of training in vacuum technology and gas dynamics. It does not provide the specific pass or fail criteria for a component, as those limits are set by the design engineer. The standard stops at describing the technique and verifying the measurement, leaving the final quality decision to the manufacturer.
Because environmental noise and temperature fluctuations can influence the gas signal, the test area must be isolated from competing gas sources and thermal drafts.