Fiber optic rotary joint bend stiffener buoyancy modulesomnisens.com/docs/CS-012(temp of umbilical...
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UMBILICAL CABLE TEMPERATURE MONITORING > Real time monitoring from FPSO through fiber optic rotary joint > Cable condition and thermal bottleneck detection and location Offshore Western Australia new pumps were installed on a certain field to improve the efficiency of oil recovery. These pumps required significant additional power leading to concern that the existing umbilical cable may overheat. The operator decided to monitor the umbilical’s operating temperature over a given period to see if the temperature reached the manufacturer’s maximum of 65ºC. Distributed Temperature Sensing (DTS), using the single mode optical fibers integrated within it provided the perfect solution to monitor the umbilical’s temperature all along its length. However, the presence of a fiber optic rotary joint (FORJ), wet-mate connectors, (WMC) and splices resulted in an optical loss of >17 dB, a loss which an OTDR could not measure because of back reflection peaks from the FORJ and J-plate of > -12 dB. Finding a DTS system capable of giving meaningful results with this level of attenuation was not easy. If there was any doubt that the umbilical could not safely handle the extra load, then a replacement higher-capacity umbilical would have to be purchased, with significant additional capital and operational costs. The Challenge Monitoring the temperature all along an umbilical using the integrated communication fibers as sensors. 1 Case study Bend stiffener Urethane protection Fiber optic rotary joint Buoyancy modules
Transcript of Fiber optic rotary joint bend stiffener buoyancy modulesomnisens.com/docs/CS-012(temp of umbilical...
Umbilical cabletemperatUre monitoring> real time monitoring from FpSo through fiber optic rotary joint> cable condition and thermal bottleneck detection and location
Offshore Western Australia new pumps were installed on a certain field to improve the efficiency of oil recovery. These pumps required significant additional power leading to concern that the existing umbilical cable may overheat. The operator decided to monitor the umbilical’s operating temperature over a given period to see if the temperature reached the manufacturer’s maximum of 65ºC. Distributed Temperature Sensing (DTS), using the single mode optical fibers integrated within it provided the perfect solution to monitor the umbilical’s temperature all along its length.
However, the presence of a fiber optic rotary joint (FORJ), wet-mate connectors, (WMC) and splices resulted in an optical loss of >17 dB, a loss which an OTDR could not
measure because of back reflection peaks from the FORJ and J-plate of > -12 dB.
Finding a DTS system capable of giving meaningful results with this level of attenuation was not easy. If there was any doubt that the umbilical could not safely handle the extra load, then a replacement higher-capacity umbilical would have to be purchased, with significant additional capital and operational costs.
the challenge
Monitoring the temperature all along an umbilical using the integrated communication fibers as sensors.
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case study
Bend stiffener
Urethane protection
Fiber optic rotary joint
Buoyancy modules
the SolutionBased on the powerful stimulated Brillouin scattering technique, Omnisens DTS allows temperature measure-ments to be made despite the attenuation. In addition, the staff at Omnisens includes both fiber optic and application specialists, on hand to help the offshore team make successful measurements during this challenging application.
The Omnisens system is capable of measuring up to 65 km with splice losses and fiber attenuation in excess of 14 dB (one way, 28 dB total loop). Thanks to this unique feature, the Omnisens system was selected as the only DTS capable of ensuring measurements between the turret and the umbilical termination unit despite the high optical loss.
the resultsThe temperature data obtained along the umbilical from the Omnisens system was recorded over a given period. During this time the umbilical was operated at maximum (for 20 days), minimum and intermediate power.
In the absence of a reference point (to provide an offset against which the temperature response could be calibrated), the measured temperature is given with a tolerance of ±3°C.
conclusionDespite the substantial optical loss and potential measurement difficulties, the Omnisens system was able to provide valuable information about the temperature behavior along the umbilical.
The temperature data showed:
• The maximum temperature, just over 50ºC, occurred along the first 50 m of the umbilical between the turret and the bend stiffener, when the umbilical was operated at full power.
• Even after operating at maximum power for 20 days, the temperature of the umbilical remained within the temperature limit of 65ºC.
• Where attachments were added to the umbilical (bend stiffener, buoyancy modules and bend restrictor) thetemperature was higher, albeit for perhaps different reasons.
The information provided by the Omnisens system enabled the costly purchase of a new umbilical to be avoided. The operator was satisfied that the umbilical had sufficient capacity to transmit power to the new pumps without exceeding its maximum temperature specification and could thus continue in service.
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The information provided by the Omnisens system enabled the costly purchase of a new umbilical to be avoided.
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Showing the temperature along the umbilical under full, medium and no load condition.
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Showing position of fiber optic cables within the umbilical.
Single fibers for sensing selected from fiber optic communication cables.
omnisens SaSwitzerlandT: +41 21 510 [email protected]
Bend stiffener
Urethane protection
Fiber optic rotary joint
Buoyancy modules
case study
