Session: DA-08-01: Fitness for Service Evaluations - 1

Paper Number: 84642

84642 - Impact of General and Local Metal Loss on the Api 579-1 Creep Residual Life 

Creep and corrosion are typical damage mechanisms of pressure components operated at high temperatures and they are frequently evaluated using the relevant sections of the API 579-1 standard. When a general or local metal loss is expected or assessed via NDE on a pressure equipment in the creep regime, the time-dependent corrosive phenomenon has a direct impact on the time and stress-dependent creep residual life and the two damage mechanisms are competing and reinforcing one another. For these cases, an API 579-1 Level 3 creep assessment shall necessarily take into account the metal loss induced by the corrosive environment to be effective in predicting the component residual life.

In this work, the impact of corrosion on the creep life evaluated according to API 579-1 and the Larson-Miller theory was evaluated for the special case of a low-alloy piping component exposed to both general and local metal loss with variable corrosion rates. A finite-element model was set-up incorporating the inelastic steady-state creep law, the API 579-1 time-fraction creep damage and the progressive metal loss due to general and local corrosion. A parametric analysis was finally carried out to investigate the role of corrosion rate, and the related, augmented stress field, on the overall API 579-1 creep damage.

Presenting Author: Lorenzo Scano Studio Scano Associato

Presenting Author Biography: Lorenzo Scano earned his M.S. and Ph.D. degrees in Mechanical Engineering from the University of Udine in 2002 and 2008. From 2003 to 2007 he worked in the field of metal constructions as a quality inspector and structural engineer. Since 2008 he is running his own consulting company Studio Scano Associato specialized in the PVP and FFS fields.

Authors:

Lorenzo Scano Studio Scano Associato
Francesco Piccini Studio Scano Associato