Hydrates are crystallized, compact, porous and rather light mass, similar to compressed snow. They are made of water, hydrocarbons, H2S and CO2. Unlike ice, hydrates have an unusual characteristic: they form at a temperature that is above water freezing point . For instance, they can form at 20 °C at particular pressures. When they are exposed to air, they dissolve chugging and fizzing because of the gas that is more or less slowly freed according to the surrounding temperature. When they are lit in the air, they can slowly and completely burn, until they leave a small residue of water. … Continue reading What is Hydrates?

The qualification of welding procedures is necessary to ensure that the selected welding parameters can produce sound welds and complying with project specification.  Qualification typically involves a combination of destructive and nondestructive testing (DT and NDT).  When a particular code, such as AWS D1.1 or ASME Section IX is used, the code will indicate the type and numbers of tests necessary in order to qualify the welding procedure. But incase of you are not required to follow specific codes or standards, it is advisable that you do some kind of testing if you are developing a new procedure.  Many fabricators … Continue reading How to qualify a Welding Procedure

What is Porosity in Welding? Porosity is a type of weld-defect that specifically refers to the entrapment of external gases within a welded joint, most commonly oxygen. As the molten metal of a weld cools and solidifies, the external gas will either enter in a weld and become trapped internally thus creating cavities or it will be forced out of the weld leaving behind visible holes, gas-mark, or pits, or crater pipe on the surface of the weld. The presence of porosity can severely affect the overall integrity and strength of the weld meaning, that a porosity-contaminated weld will nearly always be … Continue reading Weld porosity, herringbone, wormhole, crater pipe

High Temperature Hydrogen Attack (HTHA) is one of the Damage Mechanisms that affects Hydrogen service Steel equipment which exists mainly at Refineries, Methanol and Ammonia plants . HTHA occurs at elevated temperatures with Hydrogen service. HTHA vulnerability for equipment depends on three major factors, namely, Metallurgy type (composition), operating temperature and Hydrogen partial pressure. HTHA is mostly found in equipment made from Carbon Steel as well as Carbon ½ Mo. Damage mechanism· HTHA can occur in hydrogen atmosphere at elevated temperatures (at least 400 °F or 204 °C) and a hydrogen partial pressure of pH2 > 3.45 bar.· Thermal dissociation … Continue reading Nelson curves and HTHA damage