A floating transfer system connected to a gas tanker
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Case Study: Equinor

By
David M Knutsen
and
Feb 8, 2021
4
minutes read time

ECONNECT Energy in partnership with Equinor conducted a physical wave operation to demonstrate the safe connection in waves, between the IQuay jettyless transfer system, La Santa Maria, to an Equinor-chartered gas carrier. The operation demonstrated the ability of the IQuay to withstand challenging weather without compromising safe and effective operations. The full-scale operation measured both the performance of the vacuum attachment system and the IQuay motion in waves, as well as a towing operation in significant swell.

The operation took place offshore Langesund (Såstein) in Southern Norway, an area known to have unforgiving weather conditions. On the day of the operation additional waves were produced by a passenger cruise ship.

Operation limitations (specific for the operation at Såstein):

Towing:

  • Wind: 14 m/s
  • Waves: Hs < 1.2 m
  • Current: < 0.4 m/s
  • 3 knots maximum towing speed

Connection:

  • Wind: 10 m/s
  • Waves: Hs < 0.8m, Tp < 6.0 sec
  • Current: < 0.4 m/s

Operation:

  • Wind: 12 m/s
  • Waves: Hs < 1.0m, Tp < 7.0 sec
  • Current: < 0.4 m/s

Wave Operation Procedure

Before departing from Skien Havneterminal, La Santa Maria underwent standard preparation procedures in addition to securing a wave measurement unit and a power generator. The IQuay approached the gas carrier through Langesundsfjorden and made contact at approximately 9:00am.

The operation was carefully orchestrated to make the IQuay the first point of contact with the oncoming wake as to fully test the integrity of the connection system (see below figure). La Santa Maria connected to the vessel without incident and manoeuvring the platform by tug in waves was without challenge.

set up for wave operation with floating transfer system
The operation was carefully orchestrated to make the UTS the first point of contact with the incoming waves.

The wave elevation at the platform’s horizontal centre of gravity was monitored and recorded. Data from the following was collected:

  • Platform motion (IQuay MRU)
  • Wave height
  • Vacuum forces
  • Attachment system motion envelope
  • Attachment system hydraulic pressure
  • Video of operation

Tug Towing Operation Procedure

As an adjunct to the wave operation, a towing simulation was also conducted. The IQuay was used for two methods of transport by tow in inclement weather, by line towing and by docking bollard “pushing.” The two simulations recorded the line and bollard loads based on a three hours of simulation with OrcaFlex 3D, non-linear large displacement software.

Towing calculations performed for:

  • 4.8m draft
  • 1.2m Hs head sea waves
  • 3 knots maximum towing speed
  • 2x10” 120m floating flexible pipes attached to platform

The forward tow bollards are intended to be used for towing when the tug docking station is not available or beneficial to use. An example would be to tow the platform from idle mooring to a sheltered location prior to a storm (see below figure).

towing setup for floating transfer system
The forward tow bollards are intended to be used for towing when the tug docking station is not available or beneficial to use.

The tug docking bollards are intended to be used during each operation. Pushing the platform out to- and back from- the LNGC (see below figure).

setup for tug towing floating transfer system
The tug docking bollards are intended to be used during normal operations.

Operational Results

The wave operation was a functional test of the vacuum system and a demonstration of the connection to a vessel in waves. The goal of the demonstration was to verify the performance of the vacuum attachment system and to verify the force and motion generated by the wave numerical model.

It was assumed that the IQuay would outperform fixed infrastructure to safely connect to waterborne vessels in significant weather, demonstrating the versatility of the IQuay platform.

The operation confirmed the ability of IQuay to safely operate while performing the following activities:

  • Berth tug to platform in waves,
  • Engage vacuum system in against the motion and force of waves,
  • Operate near maximum capacity for designed wave height.

The operational data and numerical results show that the numerical model can provide accurate but slightly conservative results.

The operational data showed that only 40% of the vacuum pad capacity was used in the tested time window, suggesting that the IQuay can withstand more significant weather without compromising the integrity of the connection. Additionally, the UTS proved to be resilient during towing (both during line towing and pushing) in significant swell.

Conclusions

The IQuay platform, La Santa Maria, performed better than expected with very gentle movements and interaction with the ship hull. Hook-up time, towing and tug operation were more efficient than originally anticipated. The wave operation demonstrated the IQuay platform’s ability to operate in arctic conditions in sub-zero temperatures. The operation proved that the IQuay can perform well in a variety of weather conditions at dock, during tow, during hookup and during operations.

The operation was performed according to schedule as a result of careful planning with local authorities and third-party surveyors. The approval process for the marine operation took less than four weeks to obtain, including permissions to conduct the operation in a nature reserve. Therefore, permits are obtained quickly with a jettyless transfer system.

In addition to previous permitting processes for the IQuay at various sites in Norway, it further proves the IQuay’s unique features with its limited interaction with local environment with high safety standards.

Parties included: Equinor as the LPG vessel operator, Brevik Shipping tug boat, Kysterverket (pilot), Cavotec (vacuum system), Connect LNG, Vessel Master, Norwegian Coastal Administration, Platform Crew, and the Solution Center.

Last updated:
Apr 20, 2021

This article is co-written by David M Knutsen and Danielle Murphy-Cannella.

Want to learn more?

Read more about jettyless LNG here

David M Knutsen

About

David M Knutsen

Chief Technology Officer
As co-founder, David has been instrumental in the development of the IQuay technology, from the very early concept development, to the production, operation and delivery of the first commercial unit. Today, he is responsible for Project Management and Operations at ECONNECT.

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