Panhandle Eastern Pipe line Company has developed a computer system that analyzes reciprocating gas compressor operation. The system is used by the Panhandle Engineering staff to:
produce conceptual compressor designs,
evaluate vendor Quotes, and
produce operating curve packages for both new and existing units.
The program is highly interactive and produces a variety of printed and graphic reports that summarize the compressor's operation over a variety of pressure conditions. The system solution technique is stable for any number of compression stages. The system has the ability to generate a sequence of adding clearance to the cylinders in such a way that the compressor is operated within 30% of rated load over a range of suction and discharge pressures.
Panhandle Eastern Corporation owns and operates over 900 reciprocating gas compressor units. These compressors are used in natural gas gathering field areas to compress gas from wellhead pressures to transmission line pressures and to maintain the relatively high pressures required throughout the main transmission pipeline system. The selection and operation of these compressors constitutes a major expense for Panhandle Eastern and the company is currently striving to reduce these expenditures. Panhandle Eastern frequently faces pipeline management decisions requiring the installation of a new compressor or the modification of an existing compressor. A great deal of information is required to assess and decide which of such compressor changes will result in the most efficient pipeline operation. The MIS and Technical Services Departments at Panhandle have developed a computer program, called MULTI-STAGE, designed to aid engineers in the process of defining, selecting, and operating reciprocating gas compressors as efficiently as possible. Automation of these engineering functions has resulted in significant cost savings as well as a reduction in the amount of time required to perform these tasks. The remainder of this paper provides an overview of the analysis process performed by Panhandle Eastern engineers during the selection and operation of reciprocating gas compressors. Automated portions of the analysis procedure consists of three phases:
determination of optimal compressor configuration,
assessment of compressor specifications, and
generation of unloading schedules and the production of compressor operation packages.
Each of these three processes has been described in the following pages. The discussions emphasize the kinds of problems facing the engineer, the approaches used to solve the problems, and the interaction between the computer program and the engineer performing the analysis.
Declining wellhead pressures dictate frequent compressor resizing or, in extreme cases, the installation of complete new booster stations to achieve main transmission line pressures (typically in excess of 600 PSIG). The installation of a new booster station will be used to illustrate the following discussion since such a problem requires a complete compressor analysis beginning with the development of initial performance and physical specifications, progressing through compressor evaluation and selection, to installation and the development of operating curves. Wellhead pressures at the selected location currently measure 15 PSIG.