Leak Detection Methods

It is reasonable to specify the tightness of systems and components by threshold values since absolute tightness cannot be achieved and is not necessary. 

The leakage rate in chemical engineering is expressed as amount of substance lost in a given period of time with the unit kg h .  

However often the leakage rate is defined as volume throughput in a period of time with the unit mbar 1 s (corresponds to cm s at 1 bar). 

To convert the amount of substance into throughput rate the equation of ideal gases is used  

Obviously the leakage rate Qpv depends on the temperature and molar mass of the leaking gas. Therefore in a statement of a leakage rate in volume throughput units the gas species, for example air or nitrogen and a reference temperature, for example 23 C must be stated additionally. 

---

Superfluid helium can pass easily through openings so small that they caimot be detected by conventional leak detection methods. Such leaks, permeable only to helium II, are called supedeaks. They can be a source of fmstrating difficulties in the constmction of apparatus for use with helium II. 

Le kDetection. Leak detection methods may be subclassified according to whether or not they are on the tank. On-tank leak detection systems operate immediately upon leakage. 

U.S. EPA, Straight Talk on Tanks Leak Detection Methods for Petroleum Underground Storage Tanks and Piping, EPA-510-B-05-001, U.S. EPA, Washington, 2005. 

EPA. 1987a. U.S. EPA evaluation of volumetric UST leak detection methods. In Proceedings of the 13th Annual Research Symposium, Cincinnati, OH, May 6-8,1987. Cincinnati, OH U.S. Environmental Protection Agency, 164-171. 

Compiled in Figure 5.2 are the nature and detection limits of frequently used leak detection methods. 

The detection of a test gas using mass spectrometers is far and away the most sensitive leak detection method and the one most widely used in industry. The MS leak detectors developed for this purpose make possible quantitative measurement of leak rates in a range extending aaoss many powers of ten (see Section 5.2) whereby the lower limit = 10 mbar l/s, thus making it possible to demonstrate the inherent gas permeability of solids where helium is used as the test gas. It is actually possible in principle to detect all gases using mass spectrometry. Of all the available options, the use of helium as a tracer gas has proved to be especially practical. The detection of helium using the mass spectrometer is absolutely ( ) unequivocal. Helium is chemically inert, non-explosive, non-toxic, is present in normal air in a concentration of only 5 ppm and is quite economical. Two types of mass spectrometer are used in commercially available MSLD s ... 

The UST must have a leak detection method that provides monitoring for leaks at least every 30 days. 

Several leak detection methods can be used with USTs. These methods are listed as follows and are illustrated in Figure 4-2. 

Some of the other leak detection methods explained earlier in this section are based on these techniques. Methods such as bagging parts of a vacuum system and filling the bagged parts with a probe gas are similar to the outside-in technique. However, it is not possible to quantify a leak with this approach. Alternatively, filling a container with gas and either submerging it in a liquid or covering it with a bubbling solution is similar to the detector-probe technique. 

Most helium leak detectors will not operate with pressures above lO"4 torr to 10 5 torr. At these greater pressures, the main element to the mass spectrometer will bum out. Fortunately most, if not all, helium leak detectors have various safety check mechanisms that automatically shut off the current to the main filament if the pressure goes above a set limit. So, you must depend on alternate leak detection methods, or use the detector-probe technique to discover large leaks. Once large leaks have been discovered and closed, you can concentrate on the smaller leaks that can be found with the tracer-probe technique. 

W. Fiszdon, Ad Hoc Liquid Spray Vacuum Leak Detection Method, Physics of... 

Thoroughly leak-test all equipment and fittings with Freon or other sensitive leak-detection methods. 

The leak detection methods described above for pressure leak testing also apply for vacuum leak testing. More sensitive methods use an easily detectable tracer gas. Excellent detailed reviews of leak testing and leak detection techniques are available elsewhere (315, 345). 

Sodium leak detection methods. Sodium metal leaking through a small craek in the component or piping wall in LMFR may drop off or flow out along the wall, producing aerosols as a result of its interaction with atmospheric oxygen and moisture. 

Major Applications Display device, photoresists, solar cells,inks, highlighters, rubber, lithium battery, petroleum products, leak detection method, decoder system, packaging materials, hair dyes, cosmetics, wound dressing materials, antitumor agent, determination of nucleic acids ... 

The ALMS detects leaks at specific locations or within specific components in the primary coolant system. This system uses accelerometers to detect the presence of a primary leak. The system follows, in part, the guidance identified in Regulatory Guide 1.45, as discussed in CESSAR-DC, Section 7.1.2.20. The system functions, theory of operation and description are given in CESSAR-DC, Section 7.7.1.6.2. Other leak detection methods employed in the System 80+ Standard Design are discussed in CESSAR-DC, Section 5.2.5. 

A review of the common leak detection methods in chemical engineering is given in Table 8.2. 

Table 8.2 Leak detection methods and their characteristics.

Helium pumping speed at test port litre/second (ls ) This pumping speed determines the detection limit together with the system pumps (see partial flow factor in the chapter about leak detection methods)... 

---