Flow Induced Pulsations due to Flexible Risers

Belfroid, S.P.C.; Swindell, Rob; Kitney, Neil

doi:10.4043/otc-19904-ms

Cited by 6 publications

(6 citation statements)

References 1 publication

(1 reference statement)

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“…Small fractions of liquid are known to eliminate the singing, as was first reported for corrugated pipes by Belfroid (2009). Small fractions of liquid are known to eliminate the singing, as was first reported for corrugated pipes by Belfroid (2009).…”

Section: Mitigation Of Singing By Liquid Injectionmentioning

confidence: 68%

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Singing Mitigation in Corrugated Risers by Liquid Injection

Golliard¹,

Belfroid²,

Lunde

2015

Day 3 Thu, October 29, 2015

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In the last few decades, flexible risers have increasingly been used in the offshore oil and gas industry. In gas applications these risers can generate high amplitude tonal pressure fluctuations when the gas velocity reaches a threshold value. The resulting pressure fluctuations can then cause high vibration and cyclic stress levels in the associated topside and subsea pipe work. On a number of platforms, riser pulsations have led to serious limitations of the production capability and in at least one case to the fatigue failure of two small bore side branches, resulting into a shutdown of the platform for five months.An acoustic assessment can be performed to determine the risks of a flexible riser to be a source of Flow-Induced Pulsations (FIP) within its intended operating envelope. This assessment is based on models and methods to predict the onset velocity, pulsation frequency and amplitude and is based on actual field measurements on a number of different platforms and on research performed in collaboration with multiple operators and universities. Relevant inputs include the riser carcass geometry, operating conditions and the reflective characteristics of the topside and subsea piping.One critical parameters is the liquid content. The phenomenon is mainly observed in dry gas systems. At even low liquid fractions, corrugated risers are less prone to generate pulsations. A number of laboratory experiments have been performed to evaluate the singing suppression at different liquid loads for both horizontal as well as vertical (upward) flow. Finally, a field trial was executed by Statoil at an FPSO in the Norwegian Sea. One export riser showed singing tendencies. Due to the vibrations, a reduced production limit was set. A field measurement campaign was started to inject liquid into the export risers to provisionally increase production, while in the meantime permanent solutions were evaluated and installed.The mechanisms playing a role when liquid is present in corrugated pipe are reviewed in this paper: the cavities are (possibly partially) filled-up by the liquid, the boundary layers are modified by the added roughness of the wall, liquid droplets can interact with the acoustic waves. All these can reduce the source term and increase the acoustic losses in the pipe, therefore delaying or avoiding the singing.

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Section: Mitigation Of Singing By Liquid Injectionmentioning

confidence: 68%

“…Detailed results can be found in for instance Belfroid (2009), Swindell (2007), Nakiboglu (2011Nakiboglu ( , 2012aNakiboglu ( , 2012b, . Specifically, the frequency content, the onset velocity and amplitude of the pulsations are discussed.…”

Section: Introductionmentioning

confidence: 99%

Singing Mitigation in Corrugated Risers by Liquid Injection

Golliard¹,

Belfroid²,

Lunde

2015

Day 3 Thu, October 29, 2015

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“…Long flexible pipes necessary for conveying gas are corrugated on the inside and are known to exhibit strong sound levels of pure tones at some offshore installations. A study directly treating the singing riser problem was recently published by Belfroid et al 6 Using a simple experimental arrangement, the authors of the present communication found that the addition of a low frequency oscillation significantly influences the flow-excited whistling in a short corrugated pipe. Moreover, it was found that the whistling could be silenced or moved to higher frequencies, and also that the low frequency oscillation itself may excite whistling at the frequencies corresponding to the pipe's longitudinal modes.…”

Section: Introductionmentioning

confidence: 89%

Experimental study of the influence of low frequency flow modulation on the whistling behavior of a corrugated pipe

Kristiansen

Mattei

Pinhède

et al. 2011

The Journal of the Acoustical Society of America

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It is well known that airflow in a corrugated pipe can excite whistling at the frequencies of the pipe's longitudinal acoustic modes. This short contribution reports on the results of experiments where a low frequency, oscillating flow with velocity magnitudes of the same order as the airflow has been added. Depending on the oscillation strength, it has been found that this flow may silence the pipe or move the whistling to higher harmonics. It is also shown that the low frequency oscillation itself may excite higher frequency whistling sounds in the pipe.

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“…(2) Pressure of the bore fluids, and the hydrostatic pressure, externally and within the annulus (3) Extreme/ survival loading, influenced by e.g. vessel motions, metocean conditions, marine growth, soil conditions (4) Variable loading: fatigue (5) Product fluid composition and the partial pressures of harmful constituents (6) Corrosion, linked to a.o. (1), (2), (5) (7)…”

Section: !"#$%And'()*+and(%#mentioning

confidence: 99%

Integrity Management of Flexible Pipe: Chasing Failure Mechanisms

Out

2012

All Days

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Integrity management of flexible pipe has been a tenuous undertaking ever since flexible pipe was introduced, notwithstanding the substantial effort that has since been devoted to develop inspection and monitoring techniques. This is partly because flexible pipe as a composite structure has many failure processes and some of them are deeply buried. It is partly because the application boundaries are ever advancing and new failure modes manifest themselves. The paper examines some of the new failure mechanisms, such as those associated with gas applications at high pressure, temperature and velocity (erosion, Flow Induced Pulsations, PVDF applications near the design limits.) It further examines the current understanding of the risks that needs to be managed and what the means are to fulfill this task. These means start with standards and proper design specification, continue with the requirements of QA/ QC during manufacturing, monitoring and inspection during installation and finally during the service life. The safeguarding and monitoring methods and inspection techniques that significantly reduce the risk are discussed and so are the gaps that remain. Inspection only reduces the risk if the results can be interpreted well and the resulting course of action is clear. Corrosion and corrosion-fatigue of the steel reinforcing are highly uncertain processes, however. The consequences of this are treated. Finally, Life Time Extension (LTE) of flexible pipe is becoming topical. The paper addresses what should be demonstrated during LTE, what can be demonstrated and how any gaps should be addressed.

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Flow Induced Pulsations due to Flexible Risers

Cited by 6 publications

References 1 publication

Singing Mitigation in Corrugated Risers by Liquid Injection

Singing Mitigation in Corrugated Risers by Liquid Injection

Experimental study of the influence of low frequency flow modulation on the whistling behavior of a corrugated pipe

Integrity Management of Flexible Pipe: Chasing Failure Mechanisms

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