Guidelines for a Motor driven Centrifugal Compressor Package Specification
A centrifugal compressor package is a critical equipment in the hydrocarbon processing industry that requires intensive capital investment. Therefore, proper specification of the compressor package for the intended service becomes imperative in the early stages of design of a project. This article aims to provide some insight into the various process design related aspects of a centrifugal compressor package specification.
Firstly, the points that need to be considered in establishing the basis of design of the compressor package are discussed, with the key points being precise identification of the battery limit points, flow rates and conditions at the battery limit, design codes for compliance, number of trains, thermodynamic model for the compression package, design flow rate and rated flow rate, hydrate issues etc. Subsequently, the various philosophies that need to be factored into the design such as design margins, operating / start-up / shutdown philosophy ,etc. are discussed. This will be followed by various considerations that need to be looked into in carrying out the heat and mass balance for the compression package.
Factors that need to be considered pertaining to interfaces on the process and utility side, battery limit points and conditions, scope of supply of the package and utility data are discussed. Specific design considerations that the compressor package vendor needs to take into account such as deciding on the number of stages, basis for choosing the design speed and establishing the motor rating, basis for sustained and stable operation at the rated flow, etc. are also dealt with.
A list of documents that need to be attached with the specification is provided and particularly the points that need to be considered when making the preliminary P&ID that is to be sent to the compressor vendor are also discussed. Any specific points that the vendor needs to revert on, either at bid stage or after order placement are addressed.
The article also touches upon the process related terms of guarantee that need to be given by the compressor vendor. The documents that the vendor needs to supply along with the bid are also listed.
Engineering companies have their standard format for centrifugal compressor specifications. However, the essence of this article lies in sharing the experience gained from working on compressor packages and feeding back the lessons learnt into this article, with the aim of minimising re-work, cost and schedule implications..
The article endeavors to provide a cogent step-by-step framework of guidelines for the specification process, which comes predominantly from past experience, which may not be readily available in standard literature. Hence, it is intended to be a guide for best practice.