Since the early 2000’s singing risers phenomenon has been encountered. The so called Flow Induced Pulsations (FLIP) phenomenon occurs in dry gas risers (such as Gas Export lines) and may generate high tonal noises up to 110 dB but may also lead to high vibration of adjacent equipment leading to significant fatigue failure. This publication presents the recently developed model that aims at performing FLIP assessment for rough bore gas flexible pipes. The developed model provides the FLIP onset velocity and frequency for a given rough bore. It will also describe the main contributing factors such as the inner layer corrugation profile, the operating conditions (pressure, temperature and flow rate) and adjacent equipment’s acoustic reflection contributions. In addition, a Flow Induced Pulsation test carried out in 2003 to 2006 will be presented. Test outcomes will be compared to model presented in the first part. Finally, reliability of the model will be presented detailing benchmark with past tests and FLIP experienced on fields. To conclude, the model enables predictions and recommendations to avoid FLIP at an early stage prior to project execution.

Since the early 2000, Flow Induced Pulsations (FLIP) has been more and more encountered on platforms. This phenomenon generates high acoustic pressure pulsations that may cause noises up to one hundred and ten dB and significant fatigue stress levels in small piping either at topside or subsea equipment. The source of the phenomenon is inside of the flexible pipe but FLIP has no effect on it. Nevertheless, in case of FLIP experience companies may have to reduce their flow rate. Therefore, FLIP must be understood in order for the companies to avoid this constraint. In this frame, a FLIP test was performed with protagonists who are involved in the understanding of this phenomenon. The test was done in 2016 at CESAME Poitiers (France) in an eighteen meter-long and six-inch flexible pipe on an air open loop. The prototype was fully instrumented and pressures up to forty bars were tested and mass flow rates up to 6 kg.s−1 to reproduce the FLIP phenomenon. The test setup and signals analysis are presented in this paper. Moreover, FLIP onset velocities and frequencies are compared with TechnipFMC models. As a conclusion of this paper pressure influence for the six-inch tested on the FLIP initiation will be presented.

Large gas field developments are an important trend of the oil and gas industry and is likely to be reinforced in the next decades. For these developments, flexible pipes with larger Inner Diameter (ID) and high flow rates are more and more required. This paper presents solutions developed to improve flow assurance in gas flexible pipes by assessing and removing flow induced pulsations (FLIP) risk occurrence and optimizing the maximum allowable flow rate. This trend leads the industry to have a kind interest in FLIP free flowlines and risers as well as in flexible pipes with improved flow rates capacities for equivalent diameters. Beginning of the 2000’s smooth bore gas export flexible riser was a pioneered FLIP free solution which is now a well-known, field proven and recognized technology. In addition, the market and industry trend have led to develop a full panel of solutions to answer new market requirements: FLIP and pressure losses methodologies, appropriate selection of conventional carcass and smooth bore flexible pipes (smooth carcass & plastic smooth bore). This paper describes the different solutions to enhance the flow assurance of flexible pipes for gas applications (less pressure losses & FLIP proof) with different flexible pipes solutions. Then a focus is done on the development of a cost-effective solution applicable to all types of pipes: the smooth carcass. This new carcass is an incremental improvement of existing technology. The industrialization, prototype manufacturing, qualification program and technical performances obtained so far including FLIP aspect, pressure loss and global mechanical behavior are detailed. Results have demonstrated that the smooth carcass allows reducing the pressure losses compared to flexible pipe with standard carcasses and thus to optimize the fluids flow rates or to reduce the flexible pipe internal diameters. Complete API 17J qualification compliance is planned for end 2018 for both static and dynamic applications. Specific dedicated competencies and technologies were developed to answer market requirements of the new gas field developments. Furthermore, the development of smooth carcass will tackle the singing phenomenon on gas flexible lines, and provide an optimized solution for flow assurance improvement to oil and gas operators.

Since the beginning of the 21st century FLow-Induced Pulsations (FLIP) has been more and more experienced. The phenomenon is characterized by an acoustic wave that is created inside of the flexible pipe and that may lead to significant fatigue failure of the adjacent equipment. Flexible pipe integrity is not called into question regarding this phenomenon. In this context, a FLIP joint test involving TOTAL E&P, IRPHE (Institut de Recherche des Phenomenes Hors Equilibre) / CNRS (Centre National de la Recherche Scientifique), LMA (Laboratoire de Mecanique et d'Acoustique) / CNRS and TechnipFMC was conducted end of 2016 at CESAME Poitiers (France). The test was performed in a 6" internal diameter and 18-meter-long TechnipFMC flexible pipe. Both flow directions were tested to assess the influence of the rounded edges of the carcass. On the one hand, this paper presents the experimental test setup and the main results that came out of the test. On the other hand, this paper also presents the comparison between tests results and TechnipFMC analytical model outcome. Moreover, combining experiments and theoretical point of view enabled reproducing the phenomenon. A better understanding of the phenomenon will allow flexible pipes suppliers to propose mitigations or cancellation of FLIP to companies.