7/23/2019 Nelson Curve - Model for Predicting Hydrogen Attack

1/2

-

Stress Engineering Services (Europe) Limited

HomeClient industriesClient issuesServices andproductsMissionLatest newsContact us

Phone:

+44 (0) 1243 778231

Models for predicting hydrogen attack

Component: Pressure parts, fabricated from low-alloysteels, operating in hydrogen service atelevated temperatures

Situation: The susceptibility of such components to hydrogen attack is currentlydetermined by reference to the 'Nelson curves' (API RP541)

These material-specific curves provide a go / no-go criterion based on

temperature and hydrogen partial pressure For most materials they do not contain any time-dependence, and are thus

subject to periodic revision based on accumulating service experience in theindustry

Objective: To provide a secure basis for determining the susceptibility to hydrogen attackApproach: Analysis of the current Nelson curves, and the underlying data where available,

in terms of accepted models of solubility and diffusion Calculation of theoretical curves based on solubility and diffusion models

Benefits: A significant step towards understanding the basis of the Nelson curves A provisional theoretical form of the Nelson curves with time dependence

included A reasonable correlation between the model and recent service experience of

failures under conditions below the current published limits

Page 1 of 2Models for predicting hydrogen attack

23/12/2010http://www.seseurope.com/htm/industries/petrochemical/PVPcase/pvpnelson.htm

7/23/2019 Nelson Curve - Model for Predicting Hydrogen Attack

2/2

Publication: Brear, J.M. and Church, J.M., Technical basis for API Publication RP941 (Nelson Curves), Third IntConf Engineering Structural Integrity Assessment, Cambridge, September 1996

See more case studies: Pressure vessels and piping Remaining life prediction

Petrochemical and refining SES Europe Home Page

Page 2 of 2Models for predicting hydrogen attack

23/12/2010http://www.seseurope.com/htm/industries/petrochemical/PVPcase/pvpnelson.htm