"Online" Monitoring of Reciprocating Compressors Alberto Guilherme Fagundes Schirmer  Mechanical Engineer. Senior Maintenance & Reliability Engineer at Dresser-Rand Company, Houston, TX. Nelmo Furtado Fernandes Chemical Engineer. Senior Process Engineer at PETROBRAS Gabriel Passos Refinery, Betim. MG, Brazil. José Eduardo De Caux Maintenance Technician. Technical Consultant at PETROBRAS Gabriel Passos Refinery, Betim, MG, Brazil. ABSTRACT Continuous monitoring of critical rotating machinery is widely accepted by users of strictly rotating machinery such as centrifugal and screw compressors. However, continuous monitoring of reciprocating machinery such as compressors and internal combustion engines has not achieved the same level of acceptance. Significant progress has been achieved recently in narrowing this “acceptance gap.” This paper describes the pilot installation of a RECON C-GUARD monitoring system on a Worthington BDC-2 reciprocating compressor at PETROBRAS Gabriel Passos Refinery in Betim, MG, Brazil. This system, developed by Windrock Inc. Technology and marketed exclusively by Dresser-Rand, is the first system of its kind ever installed in Brazil. This paper also includes basic theory of Reciprocating Compressor Dynamic Analysis using practical examples of common compressor defects diagnosis. The results of the pilot project at Gabriel Passos Refinery are assessed regarding both process and refinery profitability improvements. 1. Introduction Worldwide installed reciprocating compressor horsepower is approximately three times that of centrifugal compressors and maintenance costs of reciprocating compressors are approximately three and a half times greater than those for centrifugal compressors [1]. Large reciprocating machinery users such as gas transmission and storage companies in the United States and Europe use condition-based maintenance. This maintenance strategy allows not only cost reduction by reducing the number of maintenance interventions to only those actually needed, but also provides efficiency improvements through dynamic analysis of the equipment as well. Condition-based maintenance has become more prevalent in refineries and petrochemical plants because of the critical nature of these machines as plant capacity increases to the point that compressors previously spared are now pressed into full-time service. Achieving higher reliability requires continuous monitoring of the reciprocating compressors. Reciprocating compressor dynamic analysis is based on the interpretation of deviation of its operating parameters from ideal conditions. Parameters to be analyzed include cylinder internal pressures, volumes, temperatures, phase, vibrations and rod drop. The analysis also includes calculated parameters such as power, efficiency, rod loads and losses. Continuous online monitoring of reciprocating compressors through dynamic analysis allows malfunction diagnosis, improving the time and cost to repair and provides continuous protection from catastrophic events such as rod or cylinder rupture.