ABSTRACT

The facility planning and design activity of large interstate pipeline systems is often asked to provide prompt estimates on the amount of incremental facilities required for a proposed expansion project. ANR has successfully implemented the concept of equivalent diameters in the development of spreadsheet models for steady state simulation of both mainline systems and distribution networks. Spreadsheet models are effective for quick analysis of looping versus horsepower expansions or preliminary design of new systems. This paper describes the structure and application of a spreadsheet model for facility planning of natural gas pipelines. Additional functions, such as optimization, expansion economics and functional macro's are also discussed.

INTRODUCTION

The purpose of this paper is to present a design tool to the facility planning engineer who has never used a spreadsheet model. For those engineers who may already be using a spreadsheet model, this paper is intended to provide ideas on other creative ways to utilize the basic simulation spreadsheet and to identify some of the potential application pitfalls. Sometimes facility planning can be as much of an art as it is a science. Qualitative analysis is often necessary in meeting management requests for information. Management rnay request that the engineer investigate up to three potential pipeline routes with five different design capacities. Added to this, the design engineer is faced with a number of other questions including what are the base design conditions, what are the expansion design conditions, how much loop versus compression, what size pipe and compressor units to consider, and comparative capital and O&M costs of pipe versus compression for each size considered. Development of a finite element analysis model is not necessary during the preliminary planning phase. Furthermore, due to time constraints, use of a finite element model may not be feasible. Spreadsheet models have proven to be very effective for this type of preliminary analysis. Spreadsheet models with proper tuning have also proven effective for existing static systems. Obviously, spreadsheet models cannot perform the same rigorous calculations as that of commercial simulation models. However, spreadsheet models follow the KISS (Keep It Simple Stupid) principle allowing an engineer to quickly understand what a model is doing while permitting easy modification. The concept of equivalent diameters simplifies the flow equation calculations permitting easy development of a spreadsheet simulation model. Spreadsheet models can be used for steady state simulation of both straight or "shotgun barrel" type mainlines and networked distribution systems.

BASIC EQUATIONS

The objective is to develop a model which is simple, flexible, and easy to use. Therefore, the model being presented here makes use of the simplified form of the AGA flow equation [II with further simplifying assumptions. The assumptions include:

  1. Use of equivalent diameter for flow calculations;

  2. yFully turbulent flow for determination of friction;

  3. No elevation effects;

  4. Isothermal flow; and

  5. Constant gas compressibility for the entire system.

Only the use of equivalent diameter is necessary to achieve the simple model presented here.

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