Technical glossary

Guide to technical terms in industrial piping: materials, standards, units and components.

A

AISI 304 Materials: Austenitic stainless steel with 18% chromium and 8% nickel. Good corrosion resistance, ideal for general applications. Less resistant than AISI 316 in chloride environments.
AISI 316 / 316L Materials: Austenitic stainless steel with added molybdenum (2-3%). Superior corrosion resistance, especially in chloride environments. "L" suffix indicates low carbon (≤0.03%) for better weldability.
ANSI Standards: American National Standards Institute. US body that defines industrial standards, including flanges (ANSI B16.5) with pressure classes 150, 300, 600, 900, 1500, 2500.
ATEX Standards: European directive (ATmosphères EXplosibles) regulating equipment for potentially explosive atmospheres. ATEX valves are certified for use with flammable gases, vapours or dusts.

Bar Units: Pressure unit. 1 bar = 100,000 Pa = 0.987 atm ≈ 14.5 psi. Commonly used in European industry.

Cavitation Phenomena: Phenomenon where local liquid pressure drops below vapour pressure, forming bubbles that implode violently. Damages pump impellers and valve seats. Prevented by ensuring adequate NPSH.
Condensate Fluids: Water formed when steam gives up latent heat and returns to liquid state. Must be removed from steam systems via steam traps to maintain efficiency.

DN Units: Nominal Diameter (Diameter Nominal). Dimensionless number approximately indicating pipe internal diameter in mm. DN50 ≈ 50mm ≈ 2". Not a precise physical measurement.

EPDM Materials: Ethylene Propylene Diene Monomer. Elastomer with excellent resistance to steam, hot water, diluted acids and bases. Not suitable for mineral oils and hydrocarbons.

FDA Standards: Food and Drug Administration. FDA approval indicates materials are suitable for food contact. Required for components in food and pharmaceutical industries.
Flash steam Phenomena: Re-evaporation steam formed when high-pressure condensate passes to lower pressure. Part of the water evaporates instantly. Different from live steam, less energetic.
FPM / Viton® Materials: Fluoroelastomer with excellent chemical and high-temperature resistance (-20°C to +200°C). Ideal for oils, fuels, acids. Viton® is the DuPont trademark.

Kv / Kvs Units: Flow coefficient indicating m³/h of water at 15°C passing through a valve with 1 bar ΔP. Kvs is the value at fully open position. Essential for sizing.

NBR / Nitrile Materials: Nitrile rubber (acrylonitrile-butadiene). Good resistance to mineral oils, greases and fuels. Operating temp: -30°C to +100°C. Not suitable for ozone and polar solvents.
NPSH Units: Net Positive Suction Head. Energy available at pump suction expressed in metres of liquid column. Available NPSH must exceed required NPSH to avoid cavitation.

PN Units: Nominal Pressure. Number indicating maximum allowable pressure at 20°C in bar. PN16 = 16 bar at 20°C. Allowable pressure decreases with temperature.
PTFE / Teflon® Materials: Polytetrafluoroethylene. Polymer with exceptional chemical inertness (-200°C to +260°C). Used for gaskets, valve seats, linings. Low friction coefficient. Teflon® is DuPont trademark.

Raised Face (RF) Components: Flange face type with raised step where gasket sits. Most common standard. Better sealing than Flat Face due to higher gasket pressure.

Saturated steam Fluids: Steam in equilibrium with liquid water at same temperature. At 10 bar, saturation temperature is 180°C. Releases latent heat without changing temperature until fully condensed.
Steam trap Components: Automatic device that removes condensate from steam systems without losing live steam. Main types: mechanical (float, bucket), thermodynamic, thermostatic.

Water hammer Phenomena: Pressure spike caused by rapid valve closure or sudden pump stop. Can damage piping, valves and joints. Mitigated with slow-closing check valves or expansion tanks.

DN to inches conversion, PN to ANSI correspondence, saturated steam data.

In-depth articles on valve selection, maintenance and regulations.

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