Fluorescent leak detection – this is how fluorescent leak detection works with industrial UV technology

In order for the fluorescent leak detection to work optimally, high-quality crack testing agents with outstanding fluorescence properties are required on the one hand, and state-of-the-art UV-LED lamp technologyon the other. This is the only way to carry out fluorescent leak detection efficiently and reliably and to reliably detect leaks.

In this article, we have compiled all relevant information on fluorescent leak detection (also called fluorescence leak detection) for industrial applications.

What is fluorescent leak detection or fluorescence leak detection?

Fluorescent industrial leak detection is a simple method often used in the field of NDT (Non-Destructive Material Testing) to safely and cheaply detect leaks in engines, engines, hydraulic systems, air conditioning systems and much more. to find and detect. UV leak detection with fluorescent dye is suitable in any liquid circuit of machines and systems.

On the one hand, existing cracks, leaks and exit points can be quickly identified with fluorescent leak detection, on the other hand, many companies also use UV leak detection to prevent machine failures, expensive repairs and damage. Oil and hydraulic leaks in particular are a major cost factor in large industrial plants, which can be integrated into the existing work processes in one quality with the relatively simple and inexpensive fluorescent leak detection, so that significant cost savings are possible.

Fluorescent leak detection works with dyes and pigments with fluorescence excitation, so that even the smallest cracks and leaks can be detected under UV lighting. The interaction of UV fluorescent dye, the appropriate UV lamp as well as the coordination between these aspects and the specific application determine how well, cheaply and safely the leak detection is possible.

How does fluorescent leak detection work?

The actual process of UV leak detection is quite simple:

1. Enter the fluorescent dye into the system (motor, plant,..)

2. Wait according to the specifications of your leak detection specialist / leak detection system manufacturer until the test equipment, fluorescent dyes or tracer pigments are properly distributed in the liquid circuit. The circulation times depend on the size of the liquid circuit, the leak detection dye used and much more.

3. Find leaks during leak detection: Check your system with a UV-LED lamp for leaks, cracks and other exit points. Fittings, valves, etc. are also possible causes of leakage.


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When is fluorescent leak detection used?

An undetected hairline crack in a hydraulic system or an undetected leak in an industrial engine and thus leaking oil can quickly lead to production coming to a standstill or unnoticed pollution of the environment with every drop of lost liquid and at the same time high costs arise in the company. This is exactly where fluorescence leak detection comes in, because it is safe, efficient and cost-effective.

Another focus for many companies is in the area of security. Occupational safety and sustainable production are becoming increasingly important and are increasingly in the focus of companies. The forward-looking and preventive use of fluorescent leak detection ensures that the products produced are cheaper and more sustainable and can also be marketed accordingly.

Fluorescent leak detection is therefore in most cases a worthwhile investment that pays off on its own.

But very important: Make sure that you have a well-coordinated leak detection system in use. Otherwise, a deceptive security can arise because there could be misinterpretations or leaks are not detected, even though you have established fluorescent leak detection in the company.

What equipment/equipment is needed for fluorescent leak detection?

The basic equipment for UV leak detection is fluorescent dye and a UV lamp. This makes fluorescent leak detection feasible. Note that it depends very much on the system to be investigated and the objective of leak detection, which dyes and which UV LED lamps you should buy.

UV lamp leak detection Area of application
: The size of the system to be serviced also plays a role. For example, with a small generator, leak detection can be carried out at regular intervals when the generator is not in operation. In a larger industrial plant, fluorescent leak detection is often a permanently implemented process. The leakage dye is continuously pumped into the system circuit to be tested using a special dosing system. The modern leak detection technology ensures a permanently constant circulation of the test equipment in the circuit, so that the system can be tested for leaks at all relevant points without manual intervention.

The professionalism of the system provider for leak detection and its expertise therefore ensures that you can make the right investment and thus achieve optimal results.

The same applies to fluorescent lamps with UV-LED technology. While I can check 2-3 valves on an engine block relatively well with a small UV flashlight, it becomes very inefficient when I have to examine large areas. Not only can leak users tire faster depending on the UV technology used, but also that leaks can be overlooked due to inhomogeneities in UV illumination is a factor that must be taken into account when choosing the right UV LED lamp.

For example, in the application of leak detection in the industrial sector, e.B. also in the aviation industry, larger UV floodlights are used to test engines, etc., which illuminate extremely homogeneously and thus work even more precisely in detection and fluorescence excitation.

In which application areas can fluorescent leak detection be used? (machinery, hydraulics, etc.)

The application of fluorescent leak detection is almost unlimited and the use of fluorescent dyes is very diverse in the most diverse industries:

  • Fluorescent leak detection for agricultural machinery, construction machinery, ships and aircraft
  • Leak detection with fluorescent dyes in forklifts, cranes, trucks, wheel loaders, excavators and much more.
  • Industrial leaks can be found in pumps, rollers, drills, etc.
  • Inspect hydraulic devices for leaks, e.B including cylinders, valves, seals, pumps, lifters, circuits
  • Inspect clutches, brakes, transmission, engine, turbine, screw connections with tracers (fluorescent powder) for leaks
  • Monitoring with fluorescent leak detection in lifting platforms, in the field of lubrication technology, in chassis, steering systems, drive technology but also in air conditioning systems
  • Checking UV powder with the black light flashlight in fuel systems, shock absorbers, generators, engines, cooling units, emergency power generators, engine units, drives and much more.

Of course, this list is not exhaustive, just as the application can be different for the same product. Some UV dyes, for example, can only be used in certain temperature ranges. The main goal of fluorescent leak detection methods is always that the fluorescent dye normally does not affect the host liquid at all or as little as possible. Circulation time may also be a selection criterion for certain leak detection applications. This is usually in the range of 5 to 45 minutes, but this is only a rough rule of thumb. The dye must be safely distributed throughout the system, as this is the only way to ensure reliable detection.


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What types of test equipment and dyes for fluorescent leak detection are there?

There are different methods for fluorescent leak detection, but this is mainly reflected in the type of products and dyes. In general, we recommend UV leak detection products of high quality with a corresponding fluorescence excitation, which enable easy detection during leak detection. The color of the oil or the hydraulic agent etc. which is to be monitored with the leak detection should of course stand out clearly from the contrast compared to the fluorescent test equipment. Again, the most important thing is the advice of a leakage specialist. Do not simply buy any leak detection products indiscriminately, but fall back on an individually tested, optimized leak detection system. It saves you a lot of money and effort in the long term and ensures a safe process for leakage detection.

Which causes can be combated and prevented particularly well with fluorescence leak detection?

Crack tests - example non-destructive crack testing train traffic, aviation etc.

Oil leaks at the industrial plant, agricultural machine loses gear oil, oil loss in excavators and construction site machines, oil leakage in industrial pipe systems, leakage in generators, leak in the air conditioning system,

Preventive measures of fluorescent leak detection: leak testing, oil dyeing to find hairline cracks, maintenance of hydraulic systems, lubrication / lubrication technology maintenance, prevention of machine failures, oil consumption, repair of engines and valves in the automotive industry and much more. as well as cracks/leaks find in the aviation industry for maintenance, repair and overhaul.

Which products and test equipment are available in the field of UV leak detection?

  • UV dyes water- or oil-based: starting from the basis of the liquid cycle to be examined, the fluorescent dye must fit together from the chemical side. Water-based fluorescent dyes are therefore mostly used in the field of air conditioning systems, etc. Oil-based UV dyes are the most widely used, as they are especially necessary in the industrial sector of plants and machines.
  • Fluorescent dyes in different container sizes: starting with small sets and fluorescent dye vials for testing as a trial pack or for one-off applications, the UV leak detection dyes can also be ordered in larger containers such as e.B 5 liter canister or as large containers 20l, 60l, 200l barrels and even in 1,000l IBC tanks. In the industrial special area of industrial leak detection, call-off orders and special fillings (e.B. for simple, fast and safe dosing in series production) are also possible
  • Buy popular fluorescent liquid as UV dye and leak detection test equipment: in addition to the OIL-GLO series from Spectroline, there is also the SECU-CHEK series FS-818 SGB as a high-quality universal fluorescent dye directly from the manufacturer in Germany
  • Fluorescent pigments (tracer powder for leak detection): Leak detection Tracer or tracer powder for leak detection has slightly different properties than the usual fluorescent dyes and has optimal application possibilities depending on the area of application

What types of UV lamps for fluorescent leak detection are there and which properties should you pay particular attention to for the best possible test results?

Today’s UV technology offers a very wide range of UV LED luminaires. While you can get a black light lamp for hobby applications from just a few euros, you should definitely rely on reliable UV LED technology in the professional sector. Fluorescent dye reacts differently to different UV intensities and is also very dependent on the quality of the UV light for leak detection depending on the homogeneity of the illumination area and the intensity drop at the edge of the illumination range on peripheral vision. We have compiled some of the criteria for selecting the right UV flashlight for leak detection below.

UV flashlights for fluorescent leak detection

Leaks in areas of hard-to-reach industrial plants can be located very well with UV flashlights as leak detectors. On the one hand, the black light flashlights are handy and can be worn well on a belt or a bag, on the other hand, they are small and handy. However, you have to make compromises in the illumination range of the UV-LED flashlights, because the illumination range is relatively small.

UV-LED hand lamps for UV leak detection

The larger UV hand lamps for leak detection are still very handy and mobile. They combine the advantages of UV large-area luminaires with the manoeuvrability and usability of small flashlights. Another advantage of UV hand lamps is that they can often be held freely in the hand or temporarily fixed to a stand in order to have your hands free and to be able to carry out the leak detection as flexibly as possible.

UV-LED luminaire systems as a stationary system

Less often you see stationary UV floodlights in the product portfolio of leak detector suppliers. Even if stationary UV-LED luminaire systems for leak detection are not as widespread as the UV pocket lamps or UV hand lamps, depending on the specific application, they can be very useful and be the optimal solution for UV leak detection.

Blue light flashlights as an alternative to UV lamps for fluorescence excitation in leak detection and leak detection

In some cases, blue light flashlights are also used for leak detection, which are intended to help detect leaks. Although these have overall worse properties in terms of fluorescence excitation, they can be a good choice in less safety-critical applications. The advantage of a blue light lamp:it does not emit ultraviolet radiation (UV radiation) when it is switched on. This eliminates many requirements from the field of occupational safety (UV safety glasses EN170 etc.) but also the norms and standards, where especially with UV lamps are necessary, we can be largely bypassed. So if you have to check for leaks less often and the requirements of leak detection are generally lower than e.B. in the aviation industry, a blue light flashlight for leak detection can be a cheap and less expensive purchase.


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What are the ready-made leak detection kits for fluorescent leak detection?

Fluorescent leak detection does not necessarily have to be a particularly expensive initial investment. With the right leak detection set, you have directly the entire equipment and partly different fluorescent dyes to be able to take your first tests and steps in the leak detection.

A standard leak detection set for fluorescent leak detection usually includes

  • UV flashlight (black light lamp) or blue light lamp
  • UV fluorescent dye in different colors and different dosages, so that a leak detection test series can be carried out for the circulatory system to be tested
  • UV goggles
  • if necessary. Charger for the UV-LED lamp

How many cost savings can be achieved with fluorescent leak detection?

The cost of a leak depends on the size of the leakage, the pressure/speed at which it leaks and the price of the leaking liquid. The cost savings in leak detection therefore vary greatly. Here is an example of the cost savings that can be achieved through fluorescent leak detection:

A crack of only 0.5mm in size in a hydraulic system of an industrial plant, for example, can lead to a loss of about 50 liters of hydraulic fluid per hour. This can already be several hundred to thousands of euros in costs if such a leakage is not noticed. The cost savings in professional leak detection are one important effect, the other is sustainability.

Topic sustainability and environmental friendliness or environmental compatibility in fluorescent leak detection, in particular the fluorescent dyes used. What is there to consider?

The topic of sustainability in fluorescent leak detection, but also environmental compatibility and environmental friendliness in leak detection are increasingly in demand. What distinguishes sustainable and environmentally friendly as well as environmentally friendly test equipment, fluorescent dyes and UV-LED lamps?

Chemical composition of the products: Fluorescent dye for leak detection should, if possible, not contain solvents and be able to degrade organically, so there is no danger to the soil and nature should any leak detection dye enter the soil.

Environmental compatibility and occupational safety in leak detection: Industrual UV dyes for leak detection should not be harmful to health or should be harmful to health as little as possible. The corresponding safety data sheets list in detail for each leakage dye what needs to be considered at work and what protective measures should be taken.

Sustainable and environmentally friendly UV lamps: Meanwhile, you should always prefer a UV-LED lamp to a mercury vapor lamp as a UV leak detector. On the one hand, this is due to the fact that no mercury and also significantly less environmentally harmful substances have to be installed in UV LED lamps. On the other hand, the power and thus energy absorption of a UV LED luminaire is significantly lower than with mercury vapour lamps. Anyone who attaches particular importance to the topic of sustainability and environmental compatibility of UV lamps should take a closer look at the UV lamps from SECU-CHEK, because they offer the so-called ECO mode depending on the model. This ensures that the UV lamps for leak detection intuitively switch off when they are not being tested. This saves valuable energy and also ensures that the UV luminaire does not receive unnecessarily many operating hours and thus the lamps etc. have to be replaced less frequently than with conventional UV LED lamps from other manufacturers.

Where can I find and inquire about manufacturers of test equipment and UV lamps for fluorescent leak detection?

Of course, you can make your request for fluorescent leak detection directly here on

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Furthermore, providers from the field of NDT (Non-Destructive Material Testing) and English NDT (Non-Destructive Testing) are also geared towards fluorescence leak detection. Less often, pure manufacturers of UV flashlights or UV-LED hand lamps or black light lamps can also directly offer the right overall package including leak detection dye. But also under terms such as flluorescent leak detection, flluorescent leak detection, leak detection systems, leak detection test, leak detection test, leak test, leak test, leak search, leak detector or leakage detection you can find the right providers.


What are the patents for fluorescent leak detection?

Under Google Patents there is the patent US6165384A “Full spectrum fluorescent dye composition for the optimization of leak detection processes”, which translates as follows:

Full-spectrum fluorescent dye composition to optimize leak detection processes

A fluorescent dye composition is provided to be enclosed in a liquid for leak detection applications that responds to a wide range of UVA, blue and UVA blue light sources. The composition comprises a mixture of a perylene dye, a naphthalimide dye and a hydrocarbon-based fluid, wherein the combination of the perylene dye, the naphthalimide dye and the hydrocarbon-based fluid is miscible with the fluid. It also provides a fluorescent dye composition that is effective for all automotive work fluids, including heavy lubricants and transmission fluids, synthetic lubricants and combustion oils, coolants, liquid and gaseous fuels, and hydraulic fluids. A fluorescent dye composition is also provided, which contains only a combination of perylene dye and naphthalimide dye.

Field of invention
This invention generally relates to the field of leak detection by illumination of fluorescent material and in particular to fluorescent dye compositions used in leak detection (leak detection).

Background of the invention

Fluorescent additives provide an excellent leak detection technique for determining the leakage point of an operating fluid from a working system. Operating fluids such as lubricants, hydraulic fluids, heat transfer fluids and coolants are treated with a dye additive that fluoresces when illuminated with appropriate ultraviolet or visible blue light.

Fluorescence is generally understood as a property that allows certain materials to absorb light energy and emit visible light with a longer wavelength than the absorbed light. According to the generally accepted theory, electrons in fluorescent materials are excited when illuminated by light energy of a particular wavelength, and light energy of a longer wavelength is emitted by these materials when the electrons return to the unexcited or ground state. The specific excitation and radiation wavelengths are characteristic of the respective fluorescent materials. The apparent brightness of the luminescence of a fluorescent material depends on the wavelength emitted by the material and the intensity of the incident radiation that excites the material. For example, a fluorescent dye whose excitation peak is at a certain wavelength can quickly emit greatly reduced luminescence when the wavelength of the incident light deviates from the excitation peak, and loses the ability to fluoresce if the incident light does not have enough energy within the specific excitation range.

The visibility of the fluorescence reaction is greatly increased when the intensity of the other visible light is reduced so that the fluorescence reaction is not masked or washed out by other light. Thus, ultraviolet/blue leak detector lamps directed at an operating system containing a fluorescent dye reacting to UV/blue under otherwise dark conditions show leaks that glow against the dark background.

The most commonly used UV/blue fluorescent leak detection dyes today are either perylene-based fluorescent compounds or naphthalimide-based fluorescent compounds. Perylene dyes produce an intense yellow fluorescence reaction when exposed to incident radiation in a band of the electromagnetic spectrum that spans the long-wave ultraviolet (UV-A) wavelength range of about 315 nm to about 400 nm, with a strong peak between about 340 to 375 nm. Long-wave ultraviolet is also known as “black light” because it covers a small portion of the visual violet range. Naphthalimide dyes fluoresce bright green when exposed to incident radiation of visible violet/blue light. The visible violet/blue range ranges from about 400 nm to about 480 nm within the electromagnetic spectrum. Both perylene and naphthalimide dyes are suitable for leak detection in oil-based working fluids or liquids in which oil is miscible.
The various inspection lamps used to illuminate the exterior of the liquid-containing parts of the operating system can be divided into three general types according to the emission wavelength: (a) UV filters (see 1 ), (b) UV/BLUE glass filter (Fig. 2) and (3) wide-spectrum UV blue thin-film filters (Fig. 3).
The UV filter lamps emit long-wave ultraviolet light, which provides optimal energy for use with the periylene dyes. These high-intensity/narrowband UV lamps also emit enough energy in the wider excitation band of naphthalimide dyes to produce a fluorescent reaction. However, these high-intensity lamps tend to be larger than those used to provide visible light and can be cumbersome in situations where the working space is very limited.
The lower intensity lamps with UV/BLUE glass filters for visible violet/blue illumination are ideal for use with the naphthalimide dyes whose excitation peak is in this wavelength band. These lamps can make the perylene dyes fluoresce, even if only weakly. These lamps are also typically less expensive and more compact than high-intensity lamps.

The third type is the relatively new wide-spectrum lamps, which use thin-film filters to allow a significant amount of visible violet to blue light to pass through, as well as long-wave ultraviolet light. These lamps are the most versatile, as they can be used effectively with both periylene and naphthalimide fluorescent dyes, providing intense lighting even in a compact form. However, since they are relatively new, fewer of these lamps are in use than the other types.
The sensitivity of the human eye to low-intensity light is greatest at wavelengths between about 540-570 nm (yellow-green). Perylene dyes emit an intense but narrowband fluorescence reaction that has a main intensity peak between about 520 and 550 and a smaller peak between about 560 and 580. Thus, the color of the perylene fluorescence reaction is close to this wavelength range that the human eye is most sensitive, and the perylene dyes show a more intense fluorescence than that of naphthalimide dyes. Under ideal conditions in clean, clear liquids, periylene dyes provide superior fluorescence than naphthalimides.
What the leak tester sees, however, is the combination of the fluorescence of the dye and any natural fluorescence of the liquid. This combination can “wash out” the apparent brightness. Many of the lubricants to which fluorescent dyes are applied for leak detection have a natural fluorescence reaction to UV/visible blue light. These liquids may also have a color or be contaminated with impurities that can mask the fluorescence reaction of the leak detection dye. The combination of a natural fluorescence of host fluids and the presence of impurities (such as dirt or combustion residues) can mask the fluorescence reaction of a periylene dye.
Naphthalimide dyes emit a broad fluorescence response with an intensity peak between about 480-520 nm. The naphthalimide dyes do not fluoresce as brilliantly as the perylenes, but the green fluorescence of a naphthalimide dye is not so noticeably reduced by the natural fluorescence of a host liquid.
The majority of fluorescent leak detection dyes currently marketed for use in oil-based working fluids or in liquids in which oil is soluble use perylene-based dye materials. These dyes are used in lubrication systems, fuel systems, transmission fluids and hydraulic fluids. Naphthalimide dyes are mainly used in applications in some air conditioning and cooling systems where polyol ester or polyalkylene glycol-based lubricants with R-134a or similar coolants are used.

Typical automotive fluids cover a wide range of physical properties and include air conditioning coolant, engine lubricating oil, transmission fluid, brake fluid, power steering fluid, radiator coolant, diesel oil and gasoline. In an auto repair shop, where diagnostic leak detection is usually performed using fluorescent dyes on both air conditioners and other liquid systems, only one inspection lamp is generally available for leak detection purposes. This light source may not be optimal or even not effective overall on the dye in the target liquid.
It would be desirable to have a fluorescent dye for the different types of working fluids that is effective when used with one of the available inspection lamps. It would also be desirable to have a dye that is effective in all automotive work fluids.
An objective of this invention is therefore to create mixed dye compositions of perylene and naphthalimide dye in different proportions to produce effective dyes for certain liquids with a considerable fluorescence reaction to illumination by the entire range of inspection lamps. Another goal is to create a single general purpose mix that is satisfactory for all vehicle fluids and all inspection lights.

Summary of the invention (fluorescent leak detection)
In its general aspect, the invention is a fluorescent dye composition for the leak detection of working fluids, wherein the composition comprises a mixture of a perylene dye, a naphthalimide dye and a hydrocarbon, wherein the combination of the perylene dye, the naphthalimide dye and the hydrocarbons are miscible with the working liquids.
In its more limited aspects, the invention is a fluorescent dye composition tailored to the physical and chemical properties of a working fluid.
In another aspect, the invention is a fluorescent dye composition that is effective for all automotive work fluids, including heavy lubricants and transmission fluids, synthetic lubricants and combustion oils, coolants, liquid and gaseous fuels, and hydraulic fluids.

Source: Patent US6165384A

I have questions about fluorescent leak detection or need a special solution or an individual system for leak detection. Where can I get advice for UV leak detection that is optimally tailored to my application?

Depending on the individual test situation, some hurdles and challenges have to be mastered in order to achieve optimal industrial leak detection with fluorescent dye. As an expert and full-service provider with more than 20 years of experience, you are always in good hands with us.

You will receive careful advice and support in the implementation of the testing process free of charge. In this way, you can be sure that all relevant norms and standards for fluorescent leak detection are adhered to and that you have an efficient, cost-effective and easy-to-implement testing process that results in reliable detections.

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Fluorescent leak detector – on-site testing with inexpensive fluorescence sample dosages

Fluorescence excitation with UV lamps, especially state-of-the-art UV LED technology: Let us demonstrate the advantages of the extremely homogeneous illumination of the H1 UV LED lamp.

Fluorescence test equipment and fluorescent dyes based on oil and water: wide range of leak detection dyes for all areas of application

Equipment and equipment for fluorescent leak detection: RIL-CHEMIE as a full-range supplier offers everything from A to Z for leak detection and leak detection

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