Advanced NDT

Leak Testing

Helium leak detection is used to locate and measure the size of leaks into or out of a system, vessel or containing device. The tracer gas, helium, is introduced to a test part that is connected to the leak detector. Helium is the best choice of tracer gas to find leaks for a number of reasons. It is non-toxic, inert, non-condensable, non-flammable and not normally present in the atmosphere at more than trace amounts (5 ppm). Due to its small atomic size, helium passes easily through leaks. The only molecule smaller than Helium is Hydrogen which is not inert. The helium leaking through the test part enters through the system and this partial pressure is measured and the results are displayed on a meter.

Helium leak detectors consists of the following components:

  • A spectrometer to detect the mass of helium

  • A vacuum system to maintain the pressure in the spectrometer

  • A mechanical pump to evacuate the part to be tested

  • Valves which enable the various stages of detection: evacuation, test & venting

  • An amplifier and readout instrumentation to monitor the output signal

  • Power supplies and controls

  • Fixturing that attaches the part to be tested to the detector

There are two main methods to leak test parts using helium: vacuum testing (outside-in) and pressure testing (Inside-out). The detection method should be selected based on the working conditions of the part to be tested. It is important to maintain the same pressure conditions during the test as will exist during the actual use of the part. Vacuum systems should be tested with a vacuum inside the chamber. A compressed air cylinder should be tested with high pressure inside the cylinder.

Vacuum box testing is a non destructive test used when trying to locate weld seam leaks. A vacuum box and a compressor create a high or low pressure vacuum while a detergent solution is applied to the test area. The detergent bubbles, making leaks visible within the created pressure envelope.

TTIS Ventures Private Limited uses Vacuum Box Testing to inspect

  • Lap welds, butt welds, and shell to annular welds

  • Piping systems and pressure vessels

  • Tank bottoms

  • ERW seamed pipe in pipelines

  • Objects on which a pressure differential can be created across the area to be examined

ADVANTAGES

  • Provides an immediate indication visual of the location of any leaks present

  • Can detect small leaks within a given area

LIMITATIONS

  • Size and orientation of any leaks will have to be analyzed with a secondary NDT method

  • For standard testing surface temperature of the test material must be between 5°C and 50°C.

Positive Material Identification (PMI)

Positive material identification is a cost-effective method for confirming general material types. While not as thorough as other chemical analysis methods, PMI is a great Non-Destructive option for confirming the alloy or type of large batches of material, testing finished components, re-certifying materials, and evaluating materials that cannot be destroyed, or shipped to a lab. Knowing the exact composition and grade of an alloy enables suppliers, plant workers, and other responsible parties to match alloy specifications that are chosen for their specific properties such as heat resistance, corrosion resistance, durability, etc. Having the right alloy in the right place is essential in places like petroleum refineries and chemical plants.
At TTIS Ventures Private Limited, we can detect a large range of metals and alloys, and routinely assist with large or on-site projects to ensure your materials meet the required specification and stand up to the demands of the environment.


Laboratory positive material identification services
TTIS Ventures Private Limited can perform PMI testing in our lab. Our experts can assist in identifying mixed batches of material, issuing alloy verification certifications and analyzing expensive or unique components without causing damage.


On-site PMI with portable XRF-analyzer
As part of our On-site Metallographic Analysis, Rapid Methodical Testing Private Limited offers on-site PMI with a portable XRF-analyzer for identification of medium and high alloyed metals, such as stainless steels, nickel alloys, and copper alloys. Our on-site PMI analysis services provide you with a rapid response to your material sorting requirements when shipping materials or parts to a laboratory is too slow or not possible.