Flare Piping Material Selection for the Offshore Oil and Gas Industry

Abstract

released from a pressure relieve valve (PRV) [1,2]. A PRV installed on pressurized equipment (labeled "Protected System" in Fig. 1) releases the overpressure gas or fluid from the equipment to the flare system [3]. The combination of PRVs and flare systems plays an essential role in preventing overpressure scenarios inside the piping and equipment [4,5]. An overpressure scenario is defined as a situation in which the internal pressure within the piping and vessel exceeds the maximum allowable working pressure. Overpressure scenarios in plants have severe negative and even catastrophic consequences, such as damage to the piping and equipment, loss of asset, fire and explosion [6], and could can the release of toxic and flammable chemicals into the atmosphere or marine environment [7].Piping makes up the major part of flaring systems and is used to transport gases and liquids inside the system. Unwanted gases (and sometimes liquids) released from pressurized facilities through PRVs are collected and gathered in flare subheader piping and eventually released to the flare header piping [8]. The entire piping system, including the flare subsystem, should be designed with precision and care. Different causes can contribute to piping failure, such as corrosion and poor material selection, stresses and loads, and poor piping design and selection. Material failure and corrosion are known as the major and most important cause of piping failure. The offshore environment is highly corrosive due to its chloride content, and the continual splash of seawater against offshore platforms can cause failure of the material used for components and facilities such as piping [9, 10]. Piping material failure, both in general and specifically for flare lines, has severe negative consequences, such as loss of asset; loss of production because of plant shutdown; the possibility of human loss of life, especially if the service contains hydrogen sulfide; and health, safety and environment (HSE) problems such as environmental Abstract Optimal operation of offshore plants depends on the correct material selection for offshore piping systems. Flare systems, in particular, play a critical role in the safety of personnel in the plant. This study aims to determine the most suitable material for flare piping in order to prevent such failures in the future. In order to select the optimum piping material for flare systems, a systematic material selection process, called value engineering (VE), in conjunction with initial screening has been selected. Flare piping materials are selected according to six criteria: internal and external corrosion resistance, mechanical strength, cost, low-temperature resistance and availability. Using the VE method, the weight factor is determined by comparing each parameter pair-wise. A score is then calculated for each parameter for each material. For the flare system, five different types of material candidates were assessed in terms of performance. As a result, Inconel 625 was found to be the most suitable material f...