Everything You Need To Know To Find The Best Ndt Uv LED Lamp

With regulatory exemptions for NDT expiring in recent years and advancements in LED technology and manufacturing, high-intensity LED UV-A light sources are now the go-to solution for NDT professionals.

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While flexibility is one of the main advantages to LED technology brings to NDT, it also means more details are required to specify the right performance for nondestructive testing. For a lamp to be useful in fluorescent penetrant or magnetic particle inspection, many factors must be considered.

1. Peak Wavelength & Emission Spectrum

Peak wavelength is the most important factor when selecting an LED lamp for fluorescent inspection.

When the formulas for penetrants and magnetic particle materials were created, the default UV-A source was mercury-vapor, which produce a single UV-A peak at 365.4 nm, the elemental emission line of mercury. Therefore, all fluorescent penetrants and magnetic particle materials are tuned to fluoresce under UV-A at 365 nm.

With LEDs, the peak wavelength is variable and depends on the individual LEDs used when the UV lamp is manufactured. To make sure that an LED UV-A lamp produces fluorescence in penetrants and magnetic particle materials, the LEDs must have a peak wavelength within the range 360-370 nm.

It is also important to consider the UV-A emission spectrum since the UV-A emission of an LED is much wider than that produced by mercury-vapor. At the tail end the spectrum includes some emission in the visible light range above 400 nm which can be observed as a deep violet glare from the lamp. Fluorescent penetrant and magnetic particle inspections are performed in a dark environment to increase contrast, and visible light contamination will degrade the inspection. For inspections to aerospace specifications, like ASTM E, Nadcap AC and Rolls-Royce RRES , this deep violet glare is not acceptable. For that reason, any lamp used for aerospace inspection, such as the EV, must include a UV-A pass filter to block visible emission.

Read more about why ASTM E requires a UV-A pass filter.

2. Beam Profile & Working Distance

With LED lamps, you are not limited to a single configuration to perform all NDT inspections. Lamps can be designed for specific applications and uses.

Lamps designed for close-up inspection will have a focused intense spot, but a small beam area. The beam area of an LED UV-A lamp is the measure of how much surface is above the minimum 1,000 µW/cm2 irradiance required for inspection. To achieve a wide beam area, an array of LEDs is needed.

However, if an array is used too close to the inspection surface, patterns of bright and dim spots will result. This is the trade-off between working distance and beam area. 

Lamps with a small beam area are useful for inspecting tight areas like holes, weld joints, and internal surfaces. But when used on large structures, a small beam can create &#;tunnel vision&#; where the inspector is focused on a single area and indications just outside of the beam area can easily be missed.

A lamp with a large beam area will provide UV-A irradiation to the area peripheral to the inspection. This allows the inspector to quickly locate and identify fluorescent indications in the peripheral area for closer inspection.

The working distance of an LED UV-A lamp is the minimum distance required to provide even coverage.

When placed very close to a surface, individual LEDs in an array will project separate beams with dim areas in between. Such uneven coverage degrades the quality of the inspection, and could lead to missed indications. But as the lamp is moved away from the surface, the beams from individual LEDs will merge into a smooth, even profile.

Inspection should only be performed when the lamp is positioned farther than minimum working distance.

Check out Magnaflux's range of LED UV lamps for nondestructive testing.

3. Power Supply

Working at low voltage, an LED UV-A lamp can operate on battery power for several hours. This makes the lamp very portable, and field inspections become quick and simple.

However, there is a concern with battery-powered lamps because LED intensity is directly related to supply voltage and current. As a battery is used, the voltage and current drops, giving a characteristic discharge curve. With an LED UV-A lamp, this can result in decreasing intensity over time, eventually dropping below the minimum 1,000 µW/cm2 requirements.

Advanced lamps incorporate constant-current circuits that monitor the battery discharge. These lamps will automatically turn off if they are not able to maintain 1,000 µW/cm2 minimum intensity. Knowing the type of battery and the discharge curve is important to ensure quality inspections with battery-powered LED UV lamps.

4. Certification Requirements

Different industries have different inspection requirements and tolerances.

The aerospace NDT industry, including fluorescent penetrant and magnetic particle inspections, have high level specifications on all aspects of the process. After five years of study, the aerospace requirements for LED UV-A lamps were established in ASTM E. This standard provides baseline performance for lamp manufacturers to meet for use with fluorescent inspections.

An LED UV-A lamp that is certified by the manufacturer to ASTM E, like the EV hand-held UV lamp, is acceptable for use by all aerospace primes and OEMs, and meets Nadcap audit criteria. However, these requirements only apply to lamps used for final aerospace inspection. Lamps used elsewhere in the process, such as penetrant wash or rinse stations, typically do not require full ASTM E certification.

Are you interested in learning more about Ndt Uv LED Lamp? Contact us today to secure an expert consultation!

For non-aerospace industries like welding, energy, pipeline or field inspection, there are fewer certification requirements. More rugged industrial inspections are often done in less-than-ideal conditions so more intense UV-A is needed to make fluorescent indications visible. However, research has shown UV-A intensities above 10,000 µW/cm2 at 15 inches / 38 cm can cause fading of fluorescent dyes and pigments.

An LED lamp for industrial applications, like the newly released EV dual-light UV lamp, should include a manufacturer&#;s certificate of conformance that includes the maximum UV-A intensity, regulated below 10,000 µW/cm2.  The certificate should also include peak wavelength within the range of 360-370 nm to ensure the lamp has the proper emission spectrum to induce fluorescence.

Learn about our Stationary LED UV Lamp for NDT Inspections.

LED lamps are a valuable advancement to nondestructive testing by providing greater flexibility in design and application, and improved safety. However, there are many considerations to choosing the right LED UV-A lamp for use in fluorescent inspection. Factors such as emission spectrum, beam area and power supply must be considered when using LED lamps. Certification requirements are also a consideration for aerospace and other high-spec industries.

By carefully considering their testing needs before investing in a LED UV lamp, NDT professionals can be confident they are getting the right tool to help make their fluorescent penetrant testing and magnetic particle inspections faster and more efficient. 

EV
Hand-held LED UV Lamp EV
Hand-held, Dual-light LED UV Lamp ST700
Stationary Inspection LED UV Lamp Part Number

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Description UV-A Pass filter eliminates deep violet glare and provides highest inspection contrast High UV-A intensity gives bright fluorescent indications, and wide-angle white light mode prevents glare Broad and even coverage in both UV-A and white light modes, and full inspection intensity

Published April 18,

When selecting the UV lamps it is important to know what features to look for in a lamp. A quality lamp will create the best illumination for the appropriate application when paired with fluorescent dye.

(1) Peak Wavelength

The most important consideration for a UV-A lamp is its peak wavelength. In former times, Mercury&#;s elemental emission line was used in the formulation of testing products and produces fluorescence under UV-A lighting at 365 nm. Therefore, an inspection lamp needs to achieve a peak wavelength between 360-370 nm.

(2)Beam Area

If the lamp produces too wide or too focused beam for its specific application, results will be skewed and inconsistent. Always pay attention to the recommended working distance and select a lamp that produces the correct coverage for the part or component to be inspected. Furthermore, choose a lamp without hot-spots in the beam profile, as this can lead to a sort of &#;tunnel vision&#; whereby irradiated areas outside of the focus area are not inspected properly.

(3)Power Supply

For portable, handheld lamps, power supply is a critical concern since the device&#;s LED intensity will diminish proportional to the voltage and current. Requirements stipulate that 1,000 μW/cm2 is the bare minimum intensity, so ensure that your desired lamp is capable of exceeding this minimum intensity during daily use.

(4)International Standards

Requirements and tolerances for NDT with UV-A lamps depends on the industry and the application, and a quality lamp should meet international standards for NDT methods. Industries such as aerospace manufacturing have much higher standards, so they&#;ve produced requirements for UV-A testing with ASTM E. A product that meet this standard will naturally get nearly any job done to this high standard.

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Post time: Sep-27-