Sunday, December 9, 2012

Newbuild offshore drilling rig tilts at Singapore Shipyard

Extracts from Straits Times 4th Dec2012

About 90 workers were injured when a jackup rig at Singapore Shipyard tilted to one side on Monday.
Among them, 22 were quite seriously injured and one was in a critical condition. The rest suffered minor injuries.

The accident happened at one of Singapore shipyard worksite at Tanjong Kling Road.
Preliminary findings showed that the three-legged jackup rig tilted to one side after the jack-up mechanism of one of the legs failed to work.

Officers from MOM's Occupational Safety and Health Inspectorate responded immediately and were investigating the accident on-site .

Thousands of workers were said to be working on the rig at the time of the accident, according to Chinese Shin Min Daily. Some workers said they heard loud bangs and some cables snapped.

According to the Chinese paper, some tried to escape by jumping off the rig into the sea. A worker who spoke to the evening daily said he decided to swim to safety because the gangway bridge linking the rig to the shore were crowded with workers.

Preliminary findings showed that the three-legged jackup rig tilted to one side after the jack-up mechanism of one of the legs failed to work.
A failed braking system might had caused the oil rig to tilt to one side. Providing an update on the incident to the media, the shipyard initial investigations showed the braking system on one of the movable legs of the rig had failed, causing the platform to slide down the leg on that side. Load tests run on the rig just a day before the accident had shown the three legs of the rig could bear a load of some 9000 tonnes each. The yard is now trying to stabilize the rig so that it can investigate the cause of the brake failure.
How Rig Tilted
Above Courtesy of Straits Times
Earlier, Singapore Minister for Manpower praised evacuation efforts at the yard, saying he was encouraged that all the workers on the rig had been evacuated within 20 minutes.

The new JU3000N design is the result of the combined development efforts of Jurong Shipyard, Noble and Friede and Goldman in creating an enlarged hull that will offer more operational benefits, including ergonomic and efficient accommodation layout, increased deck space and placement of equipment that will allow the crew to efficiently and safely carry out maintenance duties. On completion, the new rigs are capable of operating in waters of 400 feet and drilling depths of 30,000 feet.

The rigs are suitable for operations in many challenging environments, including high temperature areas such as the Middle East and in the North Sea.

General information about a typical offshore drilling jackup :-

The conventional jack-up design has three vertical legs, each leg normally being constructed of a triangular or square framework.

Jack-up basic design involves numerous choices and variables. Typically the most important variables may be listed as stated below.

Support Footing -

The legs of a jack-up are connected to structure necessary to transfer the loadings from the leg to the seafloor. This structure normally has the intended purpose to provide vertical support and moment restraint at the base of the legs. The structural arrangement of such footing may take the following listed forms;
-gravity based (steel or concrete),
-continuous foundation support, e.g. mat foundations
-individual leg footings, e.g. spudcans (with or without skirts).

Legs -

The legs of a jack-up unit are normally vertical, however, slant leg designs also exist. Design variables for jack-up legs may involve the following listed considerations ;

-number of legs
-global orientation and positioning of the legs
-frame structure or plate structure
-cross section shape and properties
-number of chords per leg
-configuration of bracings
-cross-sectional shape of chords
-unopposed, or opposed pinion racks
-type of nodes (e.g. welded or non-welded (e.g. forged) nodes)
-choice of grade of material, i.e. utilisation of extra high strength steel

Method of transferring loading from (and to) the deckbox to the legs

The method of transferring the loadings from (and to) the deckbox to the legs is critical to design of the jack-up. Typical design are ;

-utilisation and design of guides (e.g. with respect to ; number, positioning, flexibility, supporting length and plane(s), gaps, etc.)
-utilisation of braking system in gearing units
-support of braking units (e.g. fixed or floating systems)
-utilisation of chocking systems
-utilisation of holding and jacking pins and the support afforded by such.

Deckbox -

The deckbox is normally designed from stiffened panel elements. The shape of the deck structure may vary considerably from being triangular in basic format to rectangular and even octagonal. The corners of the deckbox may be square or they may be rounded. Units intended for drilling are normally provided with a cantilever at the aft end of the deckbox, however, even this solution is not without exception and units with drilling derricks positioned in the middle of the deckbox structure are not unknown.

Below are some news from the web as of 13th Dec 2012, that Dalian Shipbuilding Industry Corporation Offshore and Shanghai Waigaoqiao Shipbuilding have received notifications from F&G to stop work on the jacking systems of eight JU2000E units, according to news sources.  Work has been put on hold on six jack-ups being built at Dalian under contracts awarded by Norwegian rig giant Seadrill and Houston-based drilling start-up Prospector Offshore Drilling.  
CIMC Raffles is building two F&G JU2000E jack-ups, including one for new drilling start-up Varada HVR, but it has not received any correspondence from F&G to halt work on the units.

The jacks for the JU2000E are believed to be from South Korea manufacturer where the JU3000N are sourced from a Chinese supplier. All jacks ordered by Chinese yards are believed to be fabricated under the joint efforts of the South Korean manufacturer and Chinese yard operator ZPMC, which bought F&G for $125 million in 2010.

Below video downloaded with courtesy of youtube which shows typically the sequence of jacking the rig up and down to test the smooth functioning of jacking system.

Refer below links in my previous posts for more of drilling jack-up relevant information  :-

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