DIAMOND NDT INSPECTION SERVICES PRIVATE LIMITED

LPI is based upon capillary action, where surface tension fluid low penetrates into clean and dry surface-breaking discontinuities. Penetrant may be applied to the test component by dipping, spraying, or brushing. After adequate penetration time has been allowed, the excess penetrant is removed, and a developer is applied. The developer helps to draw penetrant out of the flaw where a visible indication becomes visible to the inspector. Inspection is performed under ultraviolet or white light, depending upon the type of dye used - fluorescent or nonfluorescent (visible).

Liquid penetrant inspection is a widely applied and low-cost inspection method used to locate surface-breaking defects in all non-porous materials (metals, plastics, or ceramics). Penetrant may be applied to all non-ferrous materials, but for inspection of ferrous components magnetic particle inspection is preferred for its subsurface detection capability. LPI is used to detect casting and forging defects, cracks, and leaks in new products, and fatigue cracks on in-service components.

Applications:

Liquid penetrant inspection (LPI) is one of the most widely used non-destructive evaluation (NDE) methods. Its popularity can be attributed to two main factors: its relative ease of use and its flexibility. LPI can be used to inspect almost any material provided that its surface is not extremely rough or porous. Materials that are commonly inspected using LPI include the following:

• Metals (aluminium, copper, steel, titanium, etc.)
  
• Glass
• Many ceramic materials
• Rubber
• Plastics

Ultrasonic thickness gauging is a widely used non-destructive test technique for measuring the thickness of a material from one side. It is fast, reliable, and versatile, and unlike a micro meter or calliper it requires access to only one side of the test piece.

Virtually any common engineering material can be measured ultrasonically. Ultrasonic thickness gages can be set up for metals, plastics, composites, fiberglass, ceramics, and glass. On-line or in-process measurement of extruded plastics and rolled metal is often possible, as is measurement of individual layers or coatings in multilayer fabrications. Liquid levels and biological samples can also be measured. Ultrasonic gauging is always completely non-destructive, with no cutting or sectioning required.

The three most common formats are known in the NDT world as A-scan, B-scan and C-scan presentations. Each presentation mode provides a different way of looking at and evaluating the region of material being inspected.

Some of the advantages of ultrasonic thickness gauging:

• Non-destructive technique
  
• Does not require access to both sides of the sample
• Can be engineered to cope with coatings, linings, etc.
• Good accuracy (0.1 mm and less) can be achieved using standard timing techniques.
• Can be easily deployed, does not require laboratory conditions.
• EMAT can conduct thickness measurements through corrosion and other surface coatings on metals.
• No need to remove the coating of the metal.

Conventional hardness testers, like Rockwell, Brinell or Vickers machines, require the test piece be brought to the testing device; but this is not always possible. Portable testing devices have been developed that permit in-situ hardness measurements thus offering quick and economical supplements to conventional, stationary testing machines.

This paper explains the basic principles of both test methods and compares, using examples from the practical field, the application possibilities of both methods. The subjects critically discussed are the factors of influence on hardness testing, such as surface preparation or the wall thickness of parts to be tested.

The Through Diamond Technique. This optical mobile hardness tester measures, for the first time, real Vickers hardness under load. One popular device measures the frequency shift of a resonating rod with a Vickers- diamond tip, which occurs when the diamond penetrates into the test material by applying a specific test load. The frequency shift is evaluated and electronically converted to a hardness value displayed on the LCD