Keeping tabs on an ageing offshore valve population

Meg Chesshyre
Tuesday, January 5, 2010

Each major North Sea platform has in the region of 4000 valves ranging from safety relief valves and emergency shutdown valves through control valves and general isolation valves. Meg Chesshyre talks to specialist valve maintenance company Severn Unival about its rôle in helping to keep the North Sea's ageing infrastructure up to scratch.

Valve management, repair and maintenance are the highly specialised territory of UK firm Severn Unival, service arm of the Severn Glocon Group. The company is tasked with a high level of valve performance upgrading work, looking in particular at how well critical valves such as control and choke valves, are working and then upgrading them to suit new applications. About 85% of its work is oil and gas related, mostly in the North Sea, but increasingly today in the Middle East as well.

'We are 100% focused on improving the performance of our clients' platforms and our engineers understand the unique challenges of the offshore environment,' says Severn Unival executive director Colin Findlay. 'By taking a proactive, intelligence-led approach to valve maintenance and upgrade, we are able to make a considerable, positive impact on platform performance.'

When OE caught up with Findlay, the shutdown campaigns for 2009 had just been completed. The main offshore activity is from March through to end October, and Findlay reckons last year alone his company has done some 40,000 manhours of work offshore in the UK and Norwegian sectors of the North Sea. It is currently contracted to provide valve support on 17 platforms. Some 1200 safety relief valves have been recertified. Nonintrusive maintenance has been carried out on about 150 of the critical isolation valves. The company is also carrying out two major valve integrity surveys for clients with newly acquired assets.

Severn Unival has a workforce of 150, including 24 specialised valve application engineers and 36 field technicians. The valve application engineers provide analysis of condition and performance, and the solutions that are needed. The field technicians go offshore for anything from three to 20 days at a time, depending on work requirements.

According to Findlay, it is not just about physically having people in the field. 'We are contracted by many operators in the North Sea long-term to look after their valve populations,' he explains. 'We are working with them to plan their requirements. We are diagnosing the condition of the valves both from an integrity and a performance point of view and then we begin to develop appropriate campaigns for putting the guys into the field to do the work.'

With platform ageing, valve requirements change, adds Findlay. Well pressures change and fields such as Brent move from producing oil to producing gas. Over the last few years there have been significant asset sales by companies such as BP, ConocoPhillips and Shell to new entrants such as Talisman, CNR and TAQA. The new entrants in turn have different requirements from the platforms. They are trying to extend field life, and tie back new reserves. The new companies need to carry out condition and integrity surveys to establish that 25-30 year old platforms are safe and fit for purpose, and so that they can put in place an appropriate plan for upgrading and improvement.

Severn Unival's specialist subsidiary Design Paradigm analyses maintenance strategy once the integrity surveys have been carried out, finding answers to questions such as: Is the valve specification currently correct? Or, is the maintenance strategy that was written for those valves 10 years ago suitable for what is happening on the platform now? It also looks at the operators' spares inventory. Because of the age of the North Sea industry, there is a lot of inventory which really has no current application. It is important that companies have an inventory on the shelf which meets their current maintenance strategy, rather than a pile of spares that are actually of no value whatsoever, Findlay points out.

Fugitive emissions control is another key issue as environmental standards become more stringent. Severn Unival says it was well ahead of the game here, having developed a patented gland security system to prevent leakage about 10 years ago. This is now much more in demand by customers in the current climate, says Findlay, with online monitoring being applied on both linear and rotary motion valves to provide progressive early warning of gland seal performance change with time. 'The system can be used on valves of all sizes and pressure ratings with no change in the multi-function block dimensions or the connection sizes,' he explains.

Stressing the critical role of valves on any platform, Findlay declares: 'They are not the sexy end of the business. They do not get the same headlines as a compressor or a big turbine, but I can assure you that the valve population is a very serious business for the operators of the offshore platforms, and it is a major spend area. Valve management is a major component of the maintenance requirement and the integrity management of platforms. There are major valves, which if they don't work properly, put the whole platform at risk either from a safety or a production point of view.'

Findlay notes that the level of valve maintenance work is holding up despite the collapse in the oil price. Some of it is routine general maintenance, some of it is repair and upgrade work, and some of it is statutory. 'The operators are getting a bit tight on costs, but they are not cutting back on anything which is going to affect the integrity of the platform, or, of course the statutory work which has to continue regardless.' For routine maintenance customers are expecting a little more sophistication, with diagnostic analysis, to decide whether intrusive maintenance is required.

He expects the 2010 work level to be similar to 2009. OE

Categories: Europe Maintenance

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