Outages | Improving performance
Two views of outage culture1 June 2012
Valve service contracts tend to follow the main trends of power station servicing: contracted out in Europe but performed in-house in the USA.
Outage management is handled differently within the US and European power markets, with two alternative approaches typically being adopted by power plant operators. In Europe, plants are handed over to an external maintenance and service provider for outage management and shutdown. During the agreed service period, the external supplier will be responsible for all aspects of the shutdown from on-site maintenance, to more complex service work offsite and preparation for handover and re-commissioning of the facility. The European model has proved successful at recent outage management projects completed in Germany, Switzerland, Belgium and the Netherlands.
For example, Tyco Valves & Controls completed a €1.5 million service contract in November 2011, encompassing a major shutdown service package at Electrabel’s Doel nuclear power stations, near Antwerp, Belgium. SABO, together with Sempell, both Tyco brands, completed shutdowns at all four Doel sites, including the 1000MW Doel 3 and 4. The four Doel sites provide around 30 per cent of Belgium’s energy demand, so efficiency of service was a key requirement.
The scheduled shutdown lasted three weeks and involved 40 SABO/Sempell technicians servicing over 300 valves as part of the primary and secondary circuit. This included service work to pressurizer main steam safety valves, injection valves and pump protection safety relief valves within the primary circuit. Turbine control valves (quick-acting turbine and pump gate valves) were maintained in the secondary circuit.
SABO has been a preferred supplier for Electrabel for more than 15 years. This was the first time that SABO and Sempell have collaborated. Both brands met Electrabel’s requirements for international certification, including EMAS (Environmental Management and Audit Scheme) and ISO 14001. The Electrabel contract is likely to reach €2 million this year, with major shutdowns every two years and minor shutdowns annually.
In the US there is a preference for plant operators to handle the outage management process themselves. For nuclear power facilities, refuelling outages are planned carefully and scheduled according to each individual plant, typically every 18 months. Due to mergers and acquisitions within the US nuclear power market, workforce consolidation has enabled plant operators to move technicians around different locations, with additional support from subcontractors.
The differences in outage management practices between the US and Europe are largely driven by regulatory and political policies. For nuclear equipment and components, MRO facilities in the US require permission to handle contaminated materials. Some states ban any nuclear materials from crossing its borders, which makes offsite repair and servicing difficult. Preventative maintenance is essential and plant operators often know exactly what work needs to be carried out before conducting any outage. In the US, the current trend is for increased validation and product testing. ASME Section III requires rigorous testing for main steam safety valves and with Gen III reactors operating at higher temperatures and pressures, manufacturers must stringently test their products before they can be installed.
ASME testing in the US requires each valve to be tested under operating conditions with pipeline media at the correct pressure to mimic flow and functional testing as part of standards such as QME-1. This approach is not required in Europe and many plants will only test the opening and closing of the valve in the ambient environment rather than on the specific service fluid using test facilities that mimic in-service conditions.
Both the US and European models for outage management strategy have developed over time and are now well established. Recent changes in the way plant operators approach outage management has been driven by regulatory reactions to external events, such as the events at Fukushima which have led to increased scrutiny on safety. This focus affects the outage and the testing of critical equipment and has already resulted in renewed interest in nuclear safety valve testing criteria, for example in France with the introduction of seismic testing on valves.
In 2010 Tyco Valves & Controls invested $25 million in the opening of its Advanced Nuclear Testing & Development facility in Mansfield, Massachusetts, one of the largest testing facilities of this type in the world. The facility tests a range of products which are manufactured on-site, including main steam safety valves, pressurizer safety valves and other pressure relief valves. Advanced technology includes a range of test loop facilities that can test the full line of pressure relief products and other equipment on steam, air and liquid utilizing qualified measurement and supporting Quality Assurance (QA) programs.
Tyco recently expanded its Mansfield capability with improvements to the existing test boiler fleet and steam flow loop, including the addition of a new 2250 psig (155 Barg), 350 horsepower boiler. This additional expansion enables the business to mimic the severe operations conditions in the new Gen III nuclear power plants.
This article was first published in the May 2012 issue of Nuclear Engineering InternationalRelated ArticlesSempell expands nuclear valve factory