# SPE Drilling & Completion Volume 21, Number 3, September 2006, pp. 212-215

SPE-89040-PA

### Surface-Roughness Design Values for Modern Pipes

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DOI  10.2118/89040-PA http://dx.doi.org/10.2118/89040-PA

### Citation

• Farshad, F.F. and Rieke, H.H. 2006. Surface-Roughness Design Values for Modern Pipes. SPE Drill & Compl21 (3): 212-215. SPE-89040-PA.

### Discipline Categories

• 1 Drilling and Completions

### Summary

The purpose of this paper is to present practicing engineers and scientists with a new means of estimating the absolute surface roughness values, ε, and relative roughness, ε/d, which are specific to modern pipes with specialized internal finishes. Our research thrust has developed new relative-roughness-design equations, values, and derived charts.

Currently, the friction-pressure losses in pipes are being evaluated by practicing engineers by use of Moody’s relative-roughness chart (Szilas 1975; Economides et al. 1994). Moody (1944) prepared a relative-roughness chart for a number of common piping materials. Relative roughness provides a simple means for estimating friction factors to be used in computing the friction-pressure losses in piping systems.

An accurate determination of the frictional fluid-pressure drop in pipes is required for design purposes. Currently, these newly developed pipes are used worldwide for various applications, and their surface-roughness values are needed to properly model the hydrodynamics (Farshad et al. 2001; Brown 1984).

Recently, Farshad and Rieke (2005) published a new relative-roughness chart for the modern manufactured oil-country tubular goods (OCTG). Moody did not provide equations for his relative-roughness chart. Equations are the foundation for establishing such correlation charts. In our research, a new set of nonlinear mathematical models was successfully regressed and developed to accurately describe the log/log relationship between pipe diameter and relative roughness.In this paper we provide a set of new equations for our charts. The new equations developed can be used directly in computer models and simulators for frictional pressure-drop calculations.

### Introduction

Today’s technology in surface engineering and pipe manufacturing has led to the introduction of modern pipes. In the past the selection of the material for the tubing was routine and basic, with most operators selecting carbon steel as a de facto standard (Craig 1993). Now, there is a drastic shift from the use of traditional carbon steel to pipes made with different alloys and internal surface finishing. For example, the increase in the use of Chrome (Cr13) tubing and internally plastic-coated pipes is because of their well-documented longevity (Farshad et al. 2000). Piping manufacturers, to mitigate the various problems associated with most operational phases of the chemical and petroleum industries, developed new alloyed pipes with different surface characteristics and specialized internal finishings (Arnold and Stewart 1986). Knowledge of the internal surface-roughness value, ε, is especially important economically in the design-optimization process of hydrocarbon production and pipeline systems. Surface roughness influences the pipe flow characteristics by creating unfavorable pressure and energy losses because of friction. Farshad and Pesacreta (2003)pointed out that reports on research of physical measurements, statistical analysis, and mathematical modeling of surface roughness in new pipes are still scarce in the technical literature. Current developments in profilometry and surface engineering have led to quick and accurate measurements of the internal surface roughness of a pipe. This is a very effective way of measuring and establishing the correct absolute surface roughness of these pipes. Additionally, uncertainty is reduced when estimating the friction factor necessary for calculating friction-pressure losses in modern manufactured pipes.

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### History

• Original manuscript received: 23 December 2004
• Revised manuscript received: 27 April 2006
• Manuscript approved: 28 April 2006
• Version of record: 20 September 2006