Short communication Failure analysis of PSV springs of 17-4PH stainless steel S.S.M. Tavares a, * , J.M. Pardal a , L. Menezes a , C.A.B. Menezes b , C. D’Ávila b a Universidade Federal Fluminense – Departamento de Engenharia Mecânica, Rua Passo da Pátria, 156 – CEP 24210-240 Niterói, Rio de Janeiro, Brazil b Petróleo Brasileiro – UN-Rio – Av. Presidente Vargas, 3131, sala 1704 – CEP 20210-030 Rio de Janeiro, Brazil article info Article history: Received 27 October 2008 Accepted 6 December 2008 Available online 14 December 2008 Keywords: Hydrogen embrittlement 17-4PH steel Intergranular cracking 1. Introduction Pressure safety valve (PSV) is one of safety devices in oil and gas production facilities, which ensure that pipes, valves, fittings, and pressure vessels are never subjected to pressures higher than their design pressure. From the definition of API 520 standard [1], a safety valve is a spring loaded pressure relief valve actuated by the static pressure upstream of the valve and characterized by rapid opening or pop action. A safety valve is normally used with compressible fluids. In the present work two failures of PSV springs working in the same conditions in off-shore oil platforms were investi- gated. Fig. 1a and b shows the fractured springs before disassembling and cutting. Springs were named ‘‘A” and ‘‘B”. Spring A show secondary cracks while spring B presents only one crack which resulted in the fracture at an angle of about 45 o . 2. Methodology of failure analysis The methodology of the failure analysis is described as follows: – Chemical analysis by plasma spectroscopy. – Examination of the fractures with stereo-microscope. – Microstructural analysis of the material of the springs. The samples were prepared by mechanical grinding in emery papers and polishing in diamond paste. Villelas etching (90 ml H 2 O + 10 ml HCl + 4 g picric acid) was used to reveal the microstructure. – Hardness measurements in samples collected near the cracks location. – Observation of the cracking surfaces in the scanning electron microscope operating in the secondary electron mode. The surfaces were cleaned with Clark’s solution before observation to remove corrosion products. 1350-6307/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.engfailanal.2008.12.003 * Corresponding author. Tel.: +55 21 26295584; fax: +55 21 26295368. E-mail address: ssmtavares@terra.com.br (S.S.M. Tavares). Engineering Failure Analysis 16 (2009) 1757–1764 Contents lists available at ScienceDirect Engineering Failure Analysis journal homepage: www.elsevier.com/locate/engfailanal