Turboexpander redesign concepts and economics

Turboexpanders are mostly custom designed to the existing process conditions. Over time, however, process gas conditions often change. Minor variation in the gas composition, flow, pressure, and temperature may shift the turboexpander operating point from the optimal point to a sub-optimal point. Such a shift, in spite of minor numerical deviations, may cause a sharp drop in turboexpander performance may be harmful to the mechanical integrity of turboexpander. In this paper the authors describe an effective method of off-design evaluation for machine performance in general and turboexpander compressor units in particular. Application of the slide-rule and the software package that have been developed to assist the clients will also be discussed. The economics of turboexpander redesign investment are also discussed