IN-SITU METALLOGRAPHY
Field metallographic procedures are performed “on location” or in the “field” on components that are too large to bring to the metallographic laboratory. Generally, these components are still being used in service or must be returned to service and cannot be destructively sectioned or physically altered. Field Metallography is also called in situ Metallography and it is sometimes called non-destructive Metallography.
The major application areas are power plants, petroleum and natural gas pipelines, and welding quality inspection for metal constructions…etc.
In situ metallographic work must be performed on-site without damaging the components. This means that portable metallographic instruments for grinding, polishing, and etching procedures are required.
We also Sell: In - situ Metallography Kits & Consumables
POSITIVE MATERIAL IDENTIFICATION (PMI)
Positive Material Identification (PMI) also referred as Material Verification, is an NDT method used to identify metal alloy element compositions with a portable x-ray fluorescence alloy analyser.
PMI is performed on ferrous and non-ferrous metallic materials including welds, weld overlays, castings, forgings, valves and components, pipe, fittings, machined parts, pressure vessels, structural steel, and on components requiring certification to NACE MR0175.
Surface preparation and cleanliness are essential when performing PMI, as the depth of penetration for element analysis is minimal. Analysers have a margin of error for element composition in low percentages that may vary depending on the activity of the equipment's radioactive source. PMI analysers are limited to identifying only those alloys that are listed in the manufacturer's analyser library, and should not be performed on material in excess of 200°F unless specialized equipment and techniques are used. X-ray fluorescence analysers are unable to detect carbon, sulphur and phosphorus.
OPTICAL EMISSION SPECTROSCOPY
Portable optical emission spectroscopy (OES),also known as Spark Testing, is a method of positive material identification (PMI). History shows numerous industrial incidents have occurred as a result of the inadvertent substitution of materials in piping systems, fittings, flanges, gaskets, bolting materials and other components. OES techniques can be implemented as a stand-alone program or as part of an API 578 Program to identify potentially rogue materials in high-risk systems to prevent catastrophic failures
What Is OES?
OES involves applying electrical energy in the form of an arc generated between the electrode and metal sample in an argon atmosphere, where vaporized atoms are brought to a high energy state and light is emitted. The excited atoms and ions have a characteristic emission spectral line for each element. The light channels through photo multiplying detectors which measure the presence and intensity of each element of the spectrum to perform a quantitative analysis of the elements. A wide range of elements can be detected using this method of chemical analysis
Post Weld Heat Treatment
Welding is an essential part of operating and maintaining assets in the petroleum (upstream, midstream, downstream) and chemical processing industries. While it has many useful applications, the welding process can inadvertently weaken equipment by imparting residual stresses into a material, leading to reduced material properties.
In order to ensure the material strength of a part is retained after welding, a process known as Post Weld Heat Treatment (PWHT) is regularly performed. PWHT can be used to reduce residual stresses, as a method of hardness control, or even to enhance material strength.