Reliability Digest, February 2015 27 Fault Diagnostic Opportunities for Solenoid Operated Valves using Physics-of-Failure Analysis N. Jordan Jameson* (jjameson@calce.umd.edu) Michael H. Azarian (mazarian@calce.umd.edu) Michael Pecht (pecht@calce.umd.edu) Center for Advanced Life Cycle Engineering University of Maryland College Park, MD Abstract—Solenoid operated valves are vital components in many process control systems. They are components that are often critical to safety. Solenoid valve degradation is difficult to detect in situ, leading to failures, which are often sudden and unexpected. This paper reviews some of the common causes of solenoid valve degradation, presents strategies that leverage these mechanisms to detect and diagnose faults before they lead to failure, and discusses research opportunities aimed at improving solenoid valve diagnostics and prognostics. Keywords-solenoid valve; diagnostics; electrical coil; fault detection I. INTRODUCTION The Transocean Deepwater Horizon disaster in 2010 was a major incident resulting in 11 lives lost and an estimated 4.9 million barrels of oil discharged into the Gulf of Mexico. Tests performed by Transocean Ltd. and Cameron International after the incident revealed that the coil of a solenoid valve failed to energize, suggesting an electrical coil fault. The investigation team found no evidence to suggest that this fault was a result of the incident. Rather, they concluded that the electrical fault(s) likely existed prior to the accident [1]. Had the solenoid valve been working properly, it could have yielded at least a partial closure of the blind shear rams, resulting in a far less serious incident. Solenoid operated valves (SOVs) are utilized to shut off, discharge, dose, allocate, or combine fluids. This action is accomplished by passing an electric current through a coiled wire, thereby producing a magnetic field, which magnetizes the plunger resulting in a position change. The position of the plunger controls the flow of the process fluid(s). SOVs are integral components of many systems. Their popularity is primarily due to their simple and rugged construction, and their inexpensive cost. Within the automotive industry, solenoid valves are used to achieve intelligent control in electro-pneumatic braking systems of motor vehicles [2], control in diesel fuel injection systems [3], [4], and the control of automobile transmissions [5]. In the process and nuclear industry, solenoid valves are used for process fulid control and in critical safety instrumented functions (SIF). Approximately 2–4% of all solenoid valves in a typical chemical plant are part of a SIF [6]. Moreover, safety valves are generally the most important components in the safety loop [7]. Thus, their reliability and availability are critical. Due to the pervasive use of SOVs in a variety of industries, interest continues to grow in estimating their health and remaining useful life (RUL). Understanding the underlying physics of their failure mechanisms can yield insight into the measurement techniques that may produce useful results for health estimation. This is referred to as the physics of failure (PoF) approach to diagnostics and prognostics. The first step in this process is to identify and analyze the hardware of the system. This yields an understanding of how the components connect and their functional relationships, which can be used in identifying loading conditions applied to system components. The loading conditions are a direct result of the life-cycle demands of the system. However, in a system where there is heavy interaction between the components, as seen in the SOV, life-cycle loads and demands can produce stresses that interact among the components. These stresses may be classified as mechanical, electrical, chemical, thermal, or environmental radiation. The presence of any particular load in the life-cycle depends on the specific application of the SOV. The next step is to perform a failure modes, mechanisms, and effects analysis (FMMEA) on the system. This, combined with a criticality analysis, is useful for identifying and prioritizing the failure mechanisms of the system. With an understanding of the failure mechanisms, a system can be designed to monitor key parameters in order to perform system diagnostics and prognostics. The purpose of this paper is to identify the critical components and failure mechanisms of the solenoid valve system, and then explore existing and potential methods of performing health diagnostics and prognostics. II. HARDWARE ANALYSIS Solenoid operated valves are used in many different operating environments and thus can have a variety of designs. The fundamental differences can usually be understood using the following terms: normally open versus