Non-Hermetic, Oil-Free Compression Solutions – A Reliable Approach to Reduce Life Cycle Costs for Compressor Applications

Abstract

Abstract Oil-free compression systems have been around for quite some time, but the benefits of the technology are usually not well understood. Furthermore, the issues that were experienced when magnetic bearings were originally introduced into oil and gas turbomachinery applications in the early 1980s has hindered the acceptance of oil-free technology by many operators, as they are seen as being less reliable than alternate, more conventional solutions. The advances in the technologies that are used today for this type of machinery, in combination with the ability of the original equipment manufacturer (OEM) to offer several levels of redundancy in the key components, have allowed these systems to reach very high levels of availability and reliability, making them ideally suited for critical rotating machinery applications. This technical paper is intended to provide a detailed discussion on the different technologies and options that are available from the OEM, and how they can be used as individual building blocks to adapt the compression train solution to the needs of a particular application. Some of the technologies that will be covered are: active magnetic bearings (AMB), high-speed electric motors and variable frequency drives (VFD). The paper will also provide information on how each of these technologies affects important aspects that are usually considered during the life cycle cost evaluation of the equipment. Some of these aspects are the capital expenditure required for the equipment, installation and commissioning activity requirements, overall power consumption during operation (including the potential reduction in the loss mechanisms that affect the performance of the compression train), reduction of maintenance cost and downtime, flexibility of the compression envelope, the extension of the time between required maintenance operations, and the extended life that can be achieved for critical components when they are protected from the harsh environment that may exist inside of the machine. The advantages that these systems offer from an environmental, health and safety perspective, and their ability to reduce the size and weight of the overall solution will also be covered. After the introduction of the different technologies, a case study is discussed to illustrate the reduced life cycle cost that can be achieved by the use of a compression train with higher overall efficiency, which provides greater operational flexibility due to the application of active magnetic bearings and speed control via VFDs. In addition, the paper covers other benefits that have been (or can be) achieved with the use of oil-free systems, when compared to other types of technology that may be considered for the same type of services. The technology solutions and evaluation methods presented in this paper can be considered by oil and gas operators and/or EPC companies when evaluating different types of rotating equipment alternatives for current and future projects.