Vast experience and the latest technology ensure that ChainCo is certainly not the weakest link for operators and rig owners requiring a rapid and thorough chain inspection service
The addition to ChainCo’s equipment inventory in recent months of three new mobile chain inspection units and a mobile stud press unit has significantly boosted the company’s service capabilities and reinforced its position as the world leader in mooring chain inspection, repair and maintenance.
The company now has seven mobile units strategically located around the world, which is part of the reason behind the company’s success, according to managing director Alan Duncan. “ChainCo’s reputation is based on its ability to respond rapidly to requests for help from clients, and to supply them with highly experienced people and sufficient inspection capacity to carry out work within tight time frames,” he says. “A good example of this is the way we recently mobilised two complete inspection spreads and four inspection squads to Malta at short notice to inspect 8500 m of chain for a customer. We were able to complete the job in just five days.”
Floating production and storage vessels
ChainCo’s mobile stud press unit, the only one of its kind in the industry, was built with floating production and storage vessel mooring chains in mind. In the past, these have been designed for the life of the vessel, perhaps as long as 25 years. As these moorings are often oversized to allow for some wear and corrosion, there has not been much emphasis on inspecting them. However, the position is changing and there are increasing calls for regular inspection of these mooring systems. The reason is the growing number of failures that are coming to light; there have been numerous reports of single chain failures in the North Sea alone over the past two years.
Ideally, chain inspection would be carried out offshore, which presents quite a challenge. Fly-by camera inspections using remotely operated vehicles are possible, but magnetic particle inspection requires the chain to be taken out of the water and placed on the back of a boat. Even then, pressing loose studs in chain that may be up to 140 mm in diameter has hitherto been impossible. In the past, this was outside the range of existing mobile chain inspection units.
The new mobile stud press unit changes all this. It has been designed to press the largest chains on the market, and can be easily transported offshore in a standard open-top shipping container. Now, operators can inspect and repress the studs of the largest chains offshore on the deck of an anchor-handling vessel, thus saving huge amounts of time and money.
In the short time that the unit has been available, it has been used offshore to repress the studs on chains belonging to two permanently moored production facilities in the North Sea.
ChainCo inspected approximately 21,000 m of chain during 2008 in 11 countries around the world using mobile inspection units. Most of the chain belonged to semisubmersible drilling rigs, which commonly have eight moorings, each typically around 1400 m long. The diameter of the steel bar used to form the links is normally between 76 and 84 mm.
The shipping and offshore industry classification societies require that the chains used to moor structures of this kind are normally inspected every five years. This is largely because of the wear and tear on the chain caused by the frequent relocation of these structures, and the critical nature of the drilling operations that they support.
The inspection process begins by laying out the chain on the ground or the back deck of a boat for cleaning using ultra-high-pressure water jets. It is then closely visually examined before being fed through the ChainCo unit, where it undergoes dimensional checks and magnetic particle inspection to detect any cracks or weld defects. Any loose studs are also picked up at this stage. The chain is then passed through a press where the offending studs are tightened.
ChainCo currently has inspection units in Angola, Canada, Namibia, Singapore, South Africa, the UK and the USA : though this is a situation that could change rapidly. A team of three or four experienced operators and DN V-certified inspectors man the units, which have their own power generators and can, therefore, work independently.