An Alternative to API 14E Erosional Velocity Limits for Sand-Laden Fluids

Abstract

The current practice for eliminating erosional problems in piping systems is to limit the flow velocity (Ve) to that established by the recommended practice API RP 14E based on an empirical constant (C-factor) and the fluid mixture density (ρm) as follows: Ve=C/ρm. The API criterion is specified for clean service (noncorrosive and sand-free), and it is noted that the C-factor should be reduced if sand or corrosive conditions are present. The validity of the equation has been challenged on the basis that the API RP 14E limits on the C-factor can be very conservative for clean service and is not applicable for conditions when corrosion or sand are present. Extensive effort has been devoted to develop an alternative approach for establishing erosional velocity limits for sand-laden fluids. Unfortunately, none of these proposals have been adopted as a standard practice because of their complexity. This paper will review the results of these studies and proposes an alternative equation that is as simple as the API 14E equation. This alternative equation has the following form: Ve=SDρm/W. The value of the S-factor depends on the pipe geometry, i.e., bend, tee, contraction, expansion, etc. Using the units for mixture flow velocity (Ve) in m/s, fluid mixture density (ρm) in kg/m3, pipe diameter (D) in mm and sand production (W) in kg/day, the value of the S-factor is 0.05 for pipe bends. The accuracy of the proposed equation for predicting erosion in pipe bends for fluids containing sand is demonstrated by a comparison with several multi-phase flow loop tests that cover a broad range of liquid-gas ratios and sand concentrations. [S0195-0738(00)00202-8]