by Super User

What Is Leak Detection and how Thomas Plumbers can help you.

Leak detection is a control method used to identify, monitor, and measure the unintentional entry or escape of fluids and gases, usually from pressurized systems or into empty enclosures. Leaks can move from the inside of a component or machine into the outside, or penetrate from the outside in, due to differences in pressure between two regions. Most leak detectors are primarily responsible for locating the leak, determining the extent or rate of leakage, and keeping track of increases or decreases in leakage. Leak detection is highly important in industrial systems that rely on sensitive components or equipment with the potential for being damaged by external contaminants. 

Environmental concerns and the rising value of some manufactured products have made leak management a vital concern. A product’s quality and the safety level involved in its production can be greatly influenced by leak detection effectiveness. Leak detectors often reduce overall manufacturing costs by decreasing the need for repairing or reworking products. Leak testing and detection are implemented to prevent material or energy loss, improve a manufacturing system’s reliability, and reduce the risk of environmental contamination. 

Leak Detection Terminology

In order to understand the principles of leak detection methods, it is necessary become familiar with the terms used in the process. A leak itself is defined as the passage through which a gas or fluid escapes, leakage refers to the fluid escaping, and leak rate is the amount of fluid or gas passing through the leak over a unit of time and under a specific set of conditions. The minimum detectable leak is the smallest passage or flaw that can be detected in a leaking system, while the minimum detectable leak rate is the lowest rate of escape that can be identified and measured. Minimum detection levels are used to determine the sensitivity of a leak detector, but these values are often influenced by variables such as operating pressure and temperature.

Types of Leaks

There are generally two types of leaks that can occur in an industrial setting. A “real leak” is a localized source of outflow, such as a simple hole, that provides a direct passage through which material escapes. A real leak can be in the form of a crack, a tube, or a flawed opening. These kinds of leaks often expand over time and they may change due to fluctuations in temperature and pressure. A distributed leak is a specific type of real leak caused by fluid permeating an extended barrier, which involves the diffusion of fluid particles through a porous solid. A “virtual leak” is the second basic type of industrial leak, and it occurs due to the gradual desorption of gas from a surface or gas escaping from sealed containers in a vacuum system. Vacuum systems sometimes have both real and virtual leaks occurring at the same time.

Selecting a Leak Detection Method

There are several factors that may influence a leak detector’s effectiveness for a given application. Some of the major considerations in selecting a leak detection method include the size of the potential leak, the physical specifications of the system, the type of tracer fluid being used, and the purpose of the detection device (whether it is intended to detect, locate, or measure). These factors can affect leak detector selections in a number of ways:

  • Large Leaks: If the leakage amount is too large, the leak detector can malfunction, making it important for the instrument and detection method to have a working range suitable for the problem. When a detector moves to full scale and cannot be reset unless it is removed from the leak, it has probably become swamped from excess leakage.


  • Small Leaks: A smaller-sized leak may not register on a detection device because it is below the instrument’s operational range, making it difficult to find and repair. If a detector records zero leakage, this does not necessarily mean there is no leakage present, as the reading may be inaccurate due to the leak’s size. The parameters for a detection device should be determined according to minimum detectable leakage and maximum leak rate.


  • System and Tracer-Fluid Features: If a gas or liquid tracer-fluid is used to track the movement of material, it is important for the tracer to be non-reactive to the system’s components so that it does not interfere with operational performance. Gases with a small molecular size and a high diffusion rate, such as helium, tend to be effective in these circumstances.


  • Leak Location: If the purpose of the detection unit is to locate and pinpoint a leak, probes or portable detectors may be needed to scan the surface of the fluid passage. In vacuum systems, a tracer fluid can be effective for spotting the position of a leak, while pressure systems may be better served by bubble detectors, liquid penetrators, and chemical indicators.

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