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How best to repair the world’s aging pipelines?
Paul Hughes, Global Subsea Market Leader at Hydratight, explains how organisations have an obligation to maintain their aging pipelines and how they can best go about achieving leak free pipelines, in the env i ronmentally sensitive subsea environment. A Chartered Engineer with 10 years experience in the subsea engineering field, Paul discusses the advantages of using mechanical connectors for pipeline repair.

There is no escaping the fact that many of the subsea pipelines around the world are reaching the end of their natural life. Indeed, some are probably already working beyond this point. The majority were brought in to service in the 1970s in places like Europe’s North Sea and the ‘Mumbai High’ fields in India, and as such will need more rigorous maintenance in the coming years. The Nor th Sea, and more recently ‘Mumbai High’, have seen a rapid expansion of oil and gas extraction activities, due mainly to demand for oil and gas having risen significantly as consumer habits altered and the incomes of the world’s population rose. It is estimated that around 25 per cent of subsea pipelines are now operating beyond their intended lifespan. This createsa number of problems for the industry. Firstly, there will become an increasing need for a larger propor tion of budgets to be spent on maintenance, which naturally cuts into bottom lines.

Secondly, in light of a number of high profile incidents, political and environmental pressure has grown on organisations to ensure that they maintain pipelines and joint integrity. The industry needs to ensure that incidents like this don’t happen again, in order to repair its badly tarnished image in some quarters of the mainstream media.

Finally, it is worth noting the cost implications of an unscheduled shutdown. These can run into millions of dollars in lost production time per day if a platform is taken out of action for any period of time, meaning that a leaking pipeline cannot be ignored until routine maintenance checks are carried out.

It is likely therefore that at sites across the world many pipeline repairs will have to take place in the coming years. But, the big question is; how should these repairs be done?

As a rule it would normally be suggested that in shallow water welding would be the way to go when tackling a repair. This is not always the case, with some people within the industry subscribing to the view that pipelines can be wrapped with repair clamps, composites and epoxy materials. In our experience though, this kind of repair should be limited to smaller, more localised repair jobs. Surprisingly to me, welding still remains the principal method used by most organisations for repairs in deeper water. At depths of up to a couple of hundred meters it is usually relatively simple to arrange for divers to come and carry out work, but beyond this problems start to arise.

However beyond that the equation suddenly becomes significantly more complex. The need for hyperbaric chambers, specialised rigs and the fact that due to a number of factors repairs rarely have the longevity of the original fitting, mean that financial and speed advantages of welding suddenly don’t seem so great. So what is the solution?

We believe that now, and in the future, more and more pipeline repair work will be done using mechanical connectors. Indeed, since Mumbai High has been actively explored, mechanical connectors have become an increasingly popular tie-in method.

Mechanical connectors are by no means a new technology. They have been in use since the 1920s, however for a number of reasons, ranging from sealing problems and issues with materials, which included inflammable elements, they were largely obsolete by the 1970s.

However since the end of the 1980s the situation has changed significantly and much work has been done to improve both systems and sealing materials, making connectors a real alternative to traditional welding methods.

Organisations such as our own, have led the field in graphite sealing systems, which overcome many of the fire-safe and shelf-life disadvantages of the polymer and elastomeric seals previously used. Indeed there has been almost a development of an industr y within an industry, specialising in mechanical connectors.

Even up until the turn of the last century many engineering papers were dismissive of the use of mechanical connectors. Often citing a belief that they weren’t as durable as welds, and that the mechanical systems used for installation were not accurate enough to ensure that further damage wasn’t done whilst installing them, many in the industry were rather mistrusting of the technology. Welding seemed to be the ‘chosen son’ in terms of method of repair, and although attitudes are gradually shifting, there are still elements within the industry that seem unwilling to shift from this paradigm.

In reality, many connector systems, through well over 15 years of painstaking research now offer a number of benefits, that welding cannot; particularly in deep-water exploration sites. Systems available now offer strength and safety benefits, above those offered by welding and in every case less damaging to the metal structure of the joint, and which are far more placement-tolerant.

Modern diverless connection methods for welding or mechanical connection use the same highly-accurate systems. These were not available 15 years ago, and have given rise to increased confidence in the application of connectors. It is not in the interest of anyone in the industry to jeopardise safety, and as an organisation we know this from our conversations with other businesses working in the field. But is it possible for mechanical systems do the work of typical welded ones?

Yes. In our own experience and through rigorous product testing of our own range, it is certified in place of welds (DNV, Lloyds, API, ABS, ROK) on pipes up to 42 inches in diameter and on pressure ratings up to ANSI Class 2500. We have also shown that we can create a joint at least as strong as a weld. We can only speak about our own product, but its designed connection life is at least 30 years. Over the years we have installed approaching 2,500 connectors around the world in the past 2 decades, many of them diverless, and they have a 100 per cent leak-free record.

Do mechanical connector soffer advantages over welding? In many instances they do. The benefits of welding are only really apparent at lower depths. Mechanical connectors require no welding, which means no specially trained divers; they cannot introduce the common problems of welds, including contamination and the requirement for pre and post weld treatments and inspection. Indeed, pressure testing is made significantly easier by using connectors, with all of our connectors having pressure-test facilities built in.

Other major advantages include the negation of the need for specialised machining and preparation tools or careful shaping of the joint, and most importantly, complex requirements such as hyperbaric chambers are not required to install them.

Mechanical connectors, fitted diverless on largediamete rlines, do admitte d l y re q u i re heav y placement and alignment rigs, but this would be the same when using welding as a method too. In practical terms, it could be argued a weld rig requires greater accuracy, as the need for bringing pipes together within a millimeter of each other is apparent, and they must be held in this position until the weld has cooled. Mechanical connectors have much wider installation tolerance and as soon as the system is tensioned, the connection is at full strength.

Mechanical connector systems offer a range of elements - pipe-to-pipe connectors, pipe-to-flange connectors, riser connectors, subsea and topside connectors, end caps and special tees amongst many more, to cater for all manner of emergencies and repairs that may arise.

A number of organisations also now routinely hold mechanical connectors in storage, for use as and when emergencies occur. Connectors can also be used on lines that need to be connected and then disconnected, which is another advantage of using them, as they can be reused a number of times.

There has been a lot of talk within the industry about the usage of mechanical connectors to tie longer welded lines together, by staging them at intervals along sections of pipeline. Our own experience suggests that the usage of connectors is particularly cost effective when fields are over 100km out to sea. This is due to the complexities associated with organising manpower and the sheer logistical nightmare that such a welding operation can involve.

An example of what is achievable from our own operations with modern connectors comes from using one of our products on a Nor th Sea gas platform. The estimated welding time for four twoinch flange adaptors was 50 hours, added to around 240 estimated hours for another five 12in couplings and one flange adaptor. Whilst a very experienced welding team may have been able to reduce this time, by using connectors the work was completed in 70 hours, and with fewer personnel. Each hour that a platform is down costs money, and by reducing the down time, connectors helped the organisation in question limit their losses.

Whilst welding will invariably still play a significant role in the future of the pipeline repair industry, undoubtedly the case for the use of mechanical connectors is growing ever stronger as operators look to improve profitability and more importantly safety on platforms.