Leak
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A leak is a way (usually an opening) for fluid to escape a container or fluid-containing system, such as a tank or a ship's hull, through which the contents of the container can escape or outside matter can enter the container. Leaks are usually unintended and therefore undesired. The word leak usually refers to a gradual loss; a sudden loss is usually called a spill.
The matter leaking in or out can be
Sometimes the word "leak" is used in a figurative sense. For example, in a news leak secret information becomes public.
According to ASTM D7053-17, water leakage is defined as the passage of (liquid) water through a material or system designed to prevent passage of water.
Types and possible causes
Types of leak openings include a puncture, gash, rust or other corrosion hole, very tiny pinhole leak (possibly in imperfect welds), crack or microcrack, or inadequate sealing between components or parts joined together. When there is a puncture, the size and shape of the leak can often be seen, but in many other cases, the size and shape of the leak opening may not be so obvious. In many cases, the location of a leak can be determined by seeing material drip out at a certain place, although the leak opening itself is not obvious. In some cases, it may be known or suspected there is a leak, but even the location of the leak is not known. Since leak openings are often irregular shapes or extended cracks, leaks are sometimes sized by the leakage rate, as in volume of fluid leaked per time, rather than the size of the opening.
Common types of leaks for many people include leaks in vehicle tires, which allows air to leak out and results in
system. Some of these vehicle fluids have different colors to help identify the type of leaking fluid.Batteries are at risk of leakage, because their operation inherently involves chemical corrosion. A
Water leaks occur when there is damage to the
Some industrial plants, especially
Leakage of air or other gas out of
A leak could even be inside a living body, such as a hole in the septum between heart ventricles causing an exchange of oxygenated and deoxygenated blood, or a fistula between bodily cavities such as between vagina and rectum.
There can be numerous causes of leaks. Leaks can occur from the outset even during
The pressure difference between both sides of the leak can affect the movement of material through the leak. Fluids will commonly move from the higher pressure side to the lower pressure side. The larger the pressure difference, the more leakage there will typically be. The fluid pressures on both sides include the
Testing
Containers, vessels, enclosures, or other fluid system are sometimes tested for leaks - to see if there is any leakage and to find where the leaks are so corrective action can be taken. There are several methods for
If submerging in water is not possible, then pressurization with air followed by covering the area to be tested with a soap solution is done to see if soap bubbles form, which indicate a leak. Other types of testing for gas leaks may involve testing for the outleaking gases with sensors which can detect that gas, for example - special sensing instruments for detecting natural gas. US federal safety law now requires natural gas companies to conduct testing for gas leaks upstream of their customer's gas meters. Where liquids are used, special color dyes may be added to help see the leakage. Other detectable substances in one of the liquids may be tested, such as saline to find a leak in a sea water system, or detectable substances may even be deliberately added to test for leakage.
Newly constructed, fabricated, or repaired systems or other vessels are sometimes tested to verify satisfactory production or repair. Plumbers often test for leaks after working on a water or other fluid system. A vessel or system is sometimes pressure tested by filling with air and the pressure monitored to see if it drops, indicating a leak. A very commonly used test after new construction or repair is a hydrostatic test, sometimes called a pressure test. In a hydrostatic test, a system is pressurized with water to look for a drop in pressure or to see where it leaks out. Helium testing may be done to detect for any very small leakage such as when testing certain diaphragm or bellows valves, made for high purity and utra high purity service, requiring low leak rate capability. Helium and hydrogen have very small molecules which can go through very small leaks.
Leak testing is part of the non-destructive test NDT portfolio that can be applied to a part to verify its conformity; depending on material, pressure, leak tightness specifications, different methods can be applied. International standards has been defined to assist in these choices. For example, BS EN 1779:1999; it applies to assessment of leak tightness by indication or measurement of gas leakage, but excludes hydrostatic, ultrasonic or electromagnetic methods. Other standards also apply:
- BS EN 13184:2001 Non-destructive testing. Leak testing. Pressure change process
- BS EN 13185:2001 Non-destructive testing. Leak testing. Tracer gasmethod
- BS EN 13192:2002 Non-destructive testing. Leak testing. Calibration of reference leaks for gases
In
Corrective action
In complex plants with multiple fluid systems, many interconnecting units holding fluids have isolation valves between them. If there is a leak in a unit, its isolation valves can be shut to "isolate" the unit from the rest of the plant.
Leaks are often repaired by plugging the leaking holes or using a patch to cover them. Leaking tires are often fixed this way. Leaking gaskets, seals, washers, or packing can be replaced. Use of welding, soldering, sealing, or gluing may be other ways to fix leaks. Sometimes, the most practical solution is to replace the leaking unit. Leaking water heaters are often replaced by home or building owners.
If there is a leak in one of the tubes of a
See also
- Explosion
- Fugitive emissions
- Non-revenue water
- Seal (mechanical)
References
- ^ Cheng, E. et al., Chemistry - A Modern View 2, Aristo-Wilson, Hong Kong, 2004