What is a leak?

A leak is the result of a fault or flaw in the wall of an object which is capable of passing gases or liquids from one side of the wall to the other. This flaw can be due to a hole, porosity, a permeable element, incorrect assembly or any other manufacturing error. Every mechanical object has such imperfections – there is no such thing as an “absolutely leak tight” object. Leak tightness refers to the in service requirements of a final assembly, a specific system, or a respective component that must not leak liquid or has a defined maximum gas leak requirement.

Examples for mechanical leaks

Criteria for leak-tightness have to be defined and quantified on an individual basis for the respective needs. Media transport through the wall can be described with a “leakage rate”. It is defined as the throughput of a specific fluid which passes through a leak under specific conditions. Driving effects of media transfer can be pressure gradient or concentration difference across the wall.

Adsorption, Absoption, Desorption, Permeation, Leakage

The impacts of a leak can be very diverse. A leaky water tap in a private household is just an annoyance with little consequences for function, environment, or waste of energy. However, if it is discovered that a water provider in a big city loses 26 % of drinking water in his pipe network (which is a real scenario) then this is a massive waste of resources and money which has to be addressed. Discovering water droplets in a water-tight wrist watch is a quality issue and requires that you read the time through water bubbles formed.

Magnitudes of leak size and leakage rate

Penetration of water into the igniter or gas generator of a car’s airbag can lead to serious malfunctions and may cost lives. Massive leaks may also be the cause of the release of corrosive or toxic substances into the atmosphere. One of the most severe incidents after failure of a seal was the Space Shuttle Challenger disaster in January 1986. Leaks can result in malfunctions or reduced lifetime of many technical products. A leaking product can also reflect badly on the manufacturer and his capability to produce a quality product.