Neil Ritchie explains a recent overhaul of the 1980s era Relay Logic Solver monitoring system at the Māui Production Station.
IT MAY BE THE most expensive ‘brain transplant’ in the world – yet the surgery did not involve any neurosurgeons or other medical staff. Instead, an American multinational corporation provided the new ‘brain’ and a team of highly skilled professionals performed the ‘transplant’ while the ‘patient’ was still alive.
We are talking about Māui gas field operator Shell Todd Oil Services (STOS) getting rid of an old manual monitoring system and replacing it with the latest automated digital equipment over an eight-month period, with the help of the American Emerson Group and Australasian energy, resource and process industries giant WorleyParsons.
And the operation did not happen offshore, on either the Māui A or B platforms. Rather it was at the onshore processing plant at Oaonui, officially known as the Māui Production Station (MPS), which receives and processes all the raw natural gas produced from the Taranaki field.
Originally, the MPS used a 1980s’ Relay Logic Solver system to monitor the transportation of the raw gas stream ashore via a pipeline from the Māui A platform, the processing of that gas, separating out the condensate (the light oil associated with gas production) and making sure the refined gas was up to specification for reticulation around the North Island. If any anomalies were identified then the system implemented an immediate and automatic stop if deemed necessary.
But with the worldwide advent of sophisticated digital systems, the field’s owners Shell Exploration NZ, Todd Energy, and Austrian company OMV realised that a total systems digital transplant was necessary, according to maintenance engineering and project delivery manager, Kerry Williamson.
“Although the [old] system was very reliable, a decision was made to overhaul it, to a fully digital approach.
“Parts of the 1980s system were becoming obsolete and the system was complex to modify as it was hardwired as opposed to programmable,” says Williamson.
And the Māui partners decided they wanted a new digital distributed control system (DCS) that would integrate seamlessly into the now 36-year-old MPS plant. They investigated and found the best answer to be the Emerson DeltaV SIS Automatic Shutdown System from Emerson Process Management, part of the American multinational corporation headquartered in Ferguson, Missouri.
According to Emerson Process Management, its modern DeltaV SIS process safety system, whether standalone or integrated with a control system, helps reliably protect all sorts of process and control system assets, improving process availability. Safety integrity is increased by continuously monitoring the ability of sensors, logic solvers, and final elements to perform on demand, with faults diagnosed before they cause spurious plant trips.
Initially the DeltaV system was going to be installed at the MPS during a planned full field shutdown in 2014. But then a decision was made not to proceed with the implementation of the new system during that planned shutdown, meaning innovative approaches were needed to undertake the switch while working with a live producing field.
So, after some successful and safe demonstrations, the change took place step by step over a period of eight months using STOS maintenance, engineering and projects team members, three of them full time.
“After many months of careful planning and analysis, it was retrofitted to seamlessly integrate into the mature Māui facilities while production continued. This was a complex project and one which was completed safely and with no interruption to production,” recalls Williamson.
“It proved to be a seamless shift to the modern technology with no HSE incidents, minimal downtime and no impact on production delivery.”
He adds that the new DCS is technologically advanced due to its safe and reliable safeguarding functions, and meets the high requirements of the international standards of the International Electrotechnical Commission (IEC) – specifically the IEC 61508 standard for functional safety. Functional safety is the detection of potentially dangerous conditions, resulting in the activation of protective or corrective devices or mechanisms to prevent hazardous events arising or providing mitigation to reduce the consequences of any hazardous events.
“Part of this requirement is to manage the system over its entire lifecycle using competent, qualified individuals,” says Williamson.
“Engineers are competent in managing the system to international standards because of rigorous training and ongoing assessment requirements.
“The [new] system provides more comprehensive information to the operator, allowing this staff member to have more context, which in turns avoids an unnecessary shutdown and fulfils market expectations. This includes comprehensive data to constantly analyse how it is performing and to identify further opportunities for improvement.
“An integrated team consisting of operations, engineering, maintenance and project delivery professionals worked hard to deliver this project to a high standard in a way that maximised the value it brought to the business. A highlight was a flawless transition from design to construction, testing, cut over and hand over to operations.”
Williamson also says the new digital system constantly measures how the production system is operating. If it detects an anomaly starting to occur, it will immediately shut down the production station, using a predetermined sequence of steps.
An example would be if a pump’s production levels were dropping.
“This safety system detects and isolates it … then when the pump is operating as normal, again the system detects this and will allow a restart and re-integration of the pump back into the broader production model.
“This is a technologically advanced safety system and this is the first time in New Zealand that this version of the Emerson DeltaV system has been retrofitted into an existing plant.
“These sorts of projects rely on our Taranaki staff upskilling and are about bringing the latest technology to our business.
“The end result [of this upgrade] is a world-class automatic shutdown system that exceeds industry standards. Our focus remains the ongoing reliability of Māui and this project was another piece of that puzzle.”
STOS completed the multimillion-dollar transformational project earlier in 2015. And the upgrade means the MPS should last until the very last drop of condensate and the very last petajoule of gas have been economically extracted from the aging field – which may not be until the 2020s, perhaps even the 2030s.