Today, we are going to discuss about the special sizing criteria for mixed phase (two-phase) piping inside an oil and gas facility. Usually, we could easily meet two-phase pipe at the flowline from the production well, inlet of two phase or three phase separator, and downstream of control valve.
(1) Erosional Velocity Criteria
in a mixed phase / two-phase fluid service, one of the most common widely use limit is erosional velocity as defined in API RP 14E [1]. This limit is defined by following equation:
In order to ensure safety operation of two-phase fluid pipe, the velocity should be limited below this API RP 14E erosional limit criteria.
(2) Fluid Pattern Criteria
Beside of velocity criteria, the two-phase fluid pattern is also critical and has to be checked.
 |
| Figure 6 - Two phase flow pattern inside horizontal pipe (Quiben, 2005) [2] |
 |
| Figure 7 - Two phase flow pattern inside vertical pipe (De Kerret et al., 2016) [3] |
Typically, the engineer will try to avoid the "Slug" flow pattern since this regime shall be closely checked using pipe-stress analysis and will need a special pipe support. This stress analysis is usually done by piping engineering discipline.
One of the most practical way to check the two-phase fluid pattern is using Aziz's Map (for vertical pipe) [4] and Baker's Map (for horizontal pipe) [5]. Fluid pattern will depend on superficial velocity for gas and liquid phase that is calculated from the pipe diameter and fluid flow for each phase (gas & liquid).
 |
| Figure 8 - Aziz's Map (Aziz et al., 1972) [4] |
 |
| Figure 9 - Baker's Map (Baker, 1958) [5] |
Hopefully this brief article could give you a little bit knowledge about how to choose the adequate pipe size for a mixed fluid phase service . See you on the next thread :)
References:
[1] API RP 14E : Recommended Practice for Design and Installation of Offshore Production Platform Piping Systems” (American Petroleum Institute, 1991).
[2] Quibén, Jesús. (2005). Experimental and analytical study of two-phase pressure drops during evaporation in horizontal tubes. 10.5075/epfl-thesis-3337.
[3] De Kerret, Francois & Benito, I. & Béguin, C. & Pelletier, Dominique & Etienne, Stéphane. (2016). Two-phase flow pattern recognition in a varying section based on void fraction and pressure measurements. IOP Conference Series: Earth and Environmental Science. 49. 052015. 10.1088/1755-1315/49/5/052015.
[4] K. Aziz, G. W. Govier, and M. Fogarasi, “Pressure drop in wells producing oil and gas,” Journal of Canadian Petroleum Technology, vol. 11, no. 03, 1972.
[5] O.Baker, Oil and Gas Journal, Nov. 10, 1958, p. 156
Latest update : 17 July 2020
Comments
Post a Comment