PODx heading control case study - Gall Thomson

PODx heading control case study

Successful FPSO heading control operation with PODx

Project overview

In December 2020, Gall Thomson manufactured and supplied a bespoke Quick Release Mooring PODx (Powered Offshore Disconnect) for an FPSO heading control application in Europe to ALP Maritime Services specialist in the field of Ocean Towing, Offshore Positioning and Mooring of Floating Platforms, Heavy Transport and Salvage operations.

PODx is a quick mooring release system that can be retrofitted between two shackles for temporary or permanent use.

Challenges

  • Short timeline to manufacture and supply a 250Tons load PODx with HPU (push-button emergency release power unit), control lines and shackles.
  • Short timeline for development of all engineering documentation for safe PODx use on this specific heading control application.
  • Use of compact H-link to go through narrow fairlead.
  • Retrofit of PODx to be undertaken without affecting FPSO production.

This FPSO operator in Europe required heading control assistance during maintenance operations. The Anchor Handling Tug specialist ALP Maritime Services was contracted to support this heading control operation and saw the need to use a mooring disconnection device should an emergency arise.

There was a short timeline to install a proven quick release mooring device on a temporary basis on an existing FPSO vessel with limited deck space. The FPSO fairlead was also too small to accommodate a 250Tons shackle following a quick release mooring activation.

Solution

Release options available:

Option 1: Traditional Quick Release Hooks

The requirement for a temporary application on the bow of the FPSO meant that a traditional quick release hook would not have been a quick and viable economical solution. There are also technical drawbacks with welding a large device on a producing FPSO without impact on the offtake schedule and safety.

Option 2: SMIT bracket and sledgehammer use in emergency situations

SMIT brackets are useful points for rigging to connect mooring lines/towing chains for offshore commissioning, heading control and towage operations.

In certain FPSO operations, SMIT brackets can be used for station keeping and heading control operations.

Typical SMIT manual operated towing bracket design as defined by OCIMF

gall thomson smit bracket

Due to its simple design, the SMIT bracket enables quick chain connection and disconnection and has been used for emergency towing.

Due to the convenience of being in the location where mooring activity is concentrated, the SMIT bracket has been wrongly associated with emergency chain disconnection.

To release the chafing chain from the SMIT bracket, an operative must manually drive the securing pin out of the SMIT bracket with a sledgehammer.

This can be unpredictable and potentially unsafe in emergency situations.

Option 3: Powered Offshore Disconnect (PODx)

PODx is composed of two blocks assembled with a reusable release bolt which is activated by a bespoke compact HPU. PODx can be retrofitted using standard shackles and does not require permanent welding on the vessel deck.


mooring emergency release closed mooring emergency release activated
PODx in set (closed) position PODx in activated (open) position

Typical installation of a PODx for an FPSO Heading Control application:

PODx application

The optimum solution

In this FPSO application and based on safety and operational criteria, PODx was supplied with a compact link to ensure smooth emergency ejection through the fairlead.


podx with shackles podx shackle and compact link
PODx with standard shackles PODx with shackle and compact link

Comparison
Quick Release Hook SMIT Bracket PODx
Commisioning on vessel deck NA
Ease of retrofitting NA
Safety
Operation
Cost
Deck space required

KEY

Safe/easy operationally/low cost

Medium

Not safe

 

Result

A PODx specified to 250Tons load was manufactured and supplied in four weeks and retrofitted on the FPSO deck within days. The Anchor Handling Tugs are now performing the Heading Control operation safely; in line with OCIMF FPSO Heading Control Guidelines


To download a copy of OCIMF FPSO heading control guidelines visit:

OCIMF FPSO heading control guidelines