Definition(s)
PREN
Pitting resistance equivalent number.
Source: ISO 21457:2010, Petroleum and natural gas industries — Materials selection and corrosion control for oil and gas production systems, First Edition,September 2010. Global Standards
PREN (FPREN)
Number, developed to reflect and predict the pitting resistance of a stainless steel, based upon the proportions of Cr, Mo, W and N in the chemical composition of the alloy
NOTE 1 For the purposes of this International Standard, FPREN is calculated from Equation (1):
FPREN = wCr + 3,3(wMo + 0,5wW) + 16wN (1)
where
wCr is the percent (mass fraction) of chromium in the alloy;
wMo is the percent (mass fraction) of molybdenum in the alloy;
wW is the percent (mass fraction) of tungsten in the alloy;
wN is the percent (mass fraction) of nitrogen in the alloy.
NOTE 2 Adapted from ISO 15156-3:2009, definition 3.10, and ISO 15156-3:2009, 6.3.
Source: ISO 21457:2010, Petroleum and natural gas industries — Materials selection and corrosion control for oil and gas production systems, First Edition,September 2010. Global Standards
Pitting resistance equivalent number (PREN)
Number developed to reflect and predict the pitting resistance of a stainless steel, based on the proportions of Cr, Mo, W and N in the chemical composition of the alloy.
NOTE This number is based on observed resistance to pitting of CRAs in the presence of chlorides and oxygen, e.g. seawater, and is not directly indicative of the resistance to produced oil and gas environments.
FPREW = wCr + 3,3(wMo + 0,5wW) + 16wN
where
wCr is the mass fraction of chromium in the alloy, expressed as a percentage of the total composition;
wMo is the mass fraction of molybdenum in the alloy, expressed as a percentage of the total composition;
wW is the mass fraction of tungsten in the alloy, expressed as a percentage of the total composition;
wN is the mass fraction of nitrogen in the alloy, expressed as a percentage of the total composition.1
Source: API RP 17A Addendum 1, Design and Operation of Subsea Production Systems—General Requirements and Recommendations, December 2010. Global Standards