Technical Blog

Carbon steel buttweld fittings used in buried pipeline service — cross-country gas and oil transmission lines, buried water mains, district heating…

Flow-accelerated corrosion (FAC) is the mechanism responsible for a number of catastrophic pipe failures in power plant and process steam systems…

Amine gas treating — the process of removing H₂S and CO₂ from refinery or natural gas streams using alkanolamines (monoethanolamine MEA, diethanolamine…

CrMo alloy steel pipe fittings (P11, P22, P5, P91, P92) undergo post-weld heat treatment (PWHT) to temper the martensite or bainite microstructure formed…

CrMo alloy steel pipe fittings (P11, P22, P5, P9, P91, P92) in high-temperature service — power plant steam systems, refinery heater circuits, hydrogen…

Creep is the time-dependent plastic deformation of metal under sustained stress at elevated temperature — and it is the dominant life-limiting failure mode…

Decarburisation is the loss of carbon from the surface of a steel fitting by chemical reaction with the surrounding atmosphere. In high-temperature…

A flanged joint between a pipe fitting and connecting pipe relies on bolt preload to compress the gasket and maintain a seal. The bolt load applied during…

When 316L fails in chloride service, two upgrade paths are available: high-molybdenum austenitic stainless grades such as 254 SMO (EN 1.4547) or AL-6XN…

Austenitic stainless steel pipe fittings — particularly 304L (UNS S30403, EN 1.4307) and 316L (UNS S31603, EN 1.4404) — are the standard materials for…

Austenitic stainless steel pipe fittings are manufactured by hot or cold forming — pressing, extrusion, or rolling — from flat plate or tubular blank…

Caustic stress corrosion cracking (caustic SCC, also called caustic embrittlement) is a failure mode in carbon and low-alloy steel exposed to sodium…

Concentrated sodium hydroxide (caustic soda, NaOH) attacks austenitic stainless steel through a stress corrosion cracking mechanism that is distinct from…

Chloride stress corrosion cracking (Cl⁻ SCC) is one of the most consequential failure modes for austenitic stainless steel pipe fittings. The cracking is…

Chloride ions are the primary enemy of stainless steel passivity. Above specific chloride concentration and temperature thresholds, 316L stainless pits…

Cobalt-base alloys — commercially known under the Stellite (Kennametal) and Tribaloy (Kennametal) trade names — are the highest-performance wear and…

Corrosion under insulation (CUI) is one of the most widespread and costly integrity threats in process plant — it has been identified as the single largest…

Crevice corrosion is localised attack that initiates in occluded spaces — under gaskets, inside socket weld crevices, at flange faces, under insulation…

Crevice corrosion is a localised corrosion attack that initiates within confined spaces — gasket faces, bolt holes, lap joints, socket weld annuli — where…

Delta ferrite (δ-ferrite) is a BCC iron-chromium phase that forms in austenitic stainless steel weld metal during solidification and is retained in the…

Duplex stainless steel pipe fittings (2205, 2507) are increasingly specified for offshore oil and gas piping in sour service — produced water handling, gas…

Duplex stainless steel pipe fittings (2205, 2507, LDX 2101) owe their properties to a carefully balanced ferritic-austenitic microstructure. This…

Erosion-corrosion is the accelerated degradation of a pipe fitting caused by the combined action of mechanical erosion (from particle impact or…

Erosion-corrosion is the combined attack of mechanical erosion (from particulate or high-velocity flow) and corrosion acting synergistically at the pipe…

Bellows expansion joints absorb thermal growth, vibration, and equipment movement in piping systems where loop or offset flexibility is impractical. They…

Ferritic stainless steels (Types 405, 409, 430, 444) have a body-centred cubic (BCC) crystal structure at all temperatures, unlike austenitic grades which…

Alloy 825 (UNS N08825) and Alloy 625 (UNS N06625) are both nickel-iron-chromium alloys with molybdenum additions that provide broad corrosion resistance in…

A chlor-alkali plant electrolyses brine to produce three co-products simultaneously: wet chlorine gas, sodium hydroxide (caustic soda) solution, and…

Copper-nickel alloys — 90/10 (90% Cu, 10% Ni, UNS C70600) and 70/30 (70% Cu, 30% Ni, UNS C71500) — are the standard materials for seawater piping and pipe…

When flue gas from sulphur-bearing fuels cools below the sulphuric acid dew point — typically 120–160°C depending on SO₃ concentration — concentrated H₂SO₄…

Hydrofluoric acid (HF) service is one of the most specialised and hazardous applications for pipe fittings. HF alkylation units — used in refineries to…

Acoustic-induced vibration (AIV) is a fatigue failure mechanism in pipe fittings and piping downstream of high-pressure-drop gas-service components…

Acoustic-induced vibration (AIV) is the fatigue failure mechanism that has caused small-bore pipe connection failures at high-pressure gas relief valves…

AD 2000-Merkblatt (Arbeitsgemeinschaft Druckbehälter — Pressure Vessel Committee) is a German technical rules series for pressure equipment design…

Not all pipe fittings are buttweld fittings. ASME B16.11 covers forged socket weld and threaded fittings — a completely different product family from B16.9…

Long radius (LR) elbows to ASME B16.9 — with a centre-to-end dimension equal to 1.5 times the nominal pipe size — are the default for the vast majority of…

ASME B31.3 Process Piping Code classifies piping by fluid service category. Most engineers are familiar with normal fluid service, but Category D…

Preheat — heating the pipe fitting and adjacent pipe before welding — is the primary control for preventing cold cracking (hydrogen-assisted HAZ cracking)…

A fitting that passes material certification can still fail in service or cause fabrication problems if it is dimensionally out of tolerance. Centre-to-end…

Fatigue failure — crack initiation and propagation under cyclic stress — is the dominant failure mechanism for piping connections in reciprocating…