With breathtaking terrain ranging from snow-capped mountains to lush lowland plains, New Zealand often is described as a paradise by those who have experienced its unique beauty. Approximately 2,000 kilometers east of Australia, across the Tasman Sea, New Zealand's isolated location and rich natural resources have fostered a self-reliant culture.
Unable to tap into the power generated by neighboring countries, New Zealand must locally produce the electricity to meet its consumer and industrial needs which, in 2001, was approximately 34.88 TWh. As the country's industrial sector continues to develop and the population continues to grow, so does the demand for electricity. In fact, even now, New Zealand's power generation capacity is continuously strained.
Tasked with keeping the supply side of this equation in proper balance is Genesis Energy, the country's largest provider of natural gas and electricity. By investing in new facilities and technology upgrades for existing facilities to increase capacity, Genesis is addressing the long-range needs of its island nation.However, that strategy doesn't address the challenge the energy provider currently faces. If a major interruption in production were to occur due to equipment failure at any one of its facilities, Genesis could be forced to purchase energy from other suppliers at the current spot price to make up the shortfall, putting the company at risk for financial penalties imposed by the system. Loss of a typical hydro unit could mean a loss in revenue of between $40,000 and $1,000,000 per day depending on the time of year and the spot price. As a result, maintaining power availability and optimizing the generation process is a core business goal. Through a reliability-centered maintenance (RCM) program supported by Rockwell Automation, Genesis can predict and prevent failures from occurring and extend the life of capital assets.
No room for error
One of three state-owned enterprises, Genesis supplies 20% of the country's electrical needs through a diverse electricity generation portfolio that includes Genesis' flagship thermal facility, the Huntly Power Station, five hydro power plants and various wind farms and cogeneration facilities at large industrial sites.With the majority of Genesis' output generated from Huntly Power Station and the hydro plants— some of which have been operating for more than 60 years—keeping these facilities properly maintained and operating at full capacity is key to achieving the company's business goals.
Huntly-With a current output capacity of 1,040 MW, Huntly is New Zealand's largest power station. The facility consists of four separate conventional boiler and steam turbine generation units, capable of burning coal, natural gas or a combination of the two. In 2005, the 22-year-old facility recorded 84% availability, but as the plant continues to age, higher levels of maintenance are anticipated to meet a sufficient level of production output. Recently installed on the same site is a 40 MW simple cycle gas turbine generator.
As part of its growth strategy, Genesis is building a high-efficiency combined-cycle gas turbine power plant that will increase production capacity at the site to 1,425 MW. It also is retrofitting the existing control and instrumentation system — which involves migrating one unit from analog to digital controls during the 2005/2006 shutdown and the remaining 3 units in the next three years.
Hydro-Approximately 60% of New Zealand's electricity is generated by hydro production. Within Genesis, the company's hydro generation capacity consists of five power plants operating from three remote sites within the country. Commissioned between 1923 and 1983, and with a production capacity of 498 MW, these plants continue to serve as a vital source of electricity for the country. Because of their geographic isolation, several of the hydro power plants are controlled and monitored from other locations.
Formulating a maintenance strategy
In 1999, when Genesis was formed out of the Electricity Corp of NZ,New Zealand was experiencing an energy surplus, so the need to prevent downtime wasn't as critical for Genesis. As a result, the majority of the company's maintenance efforts were focused on preventing major catastrophes. However, as demand changed in subsequent years, so did the role of maintenance. Today, across the organization, Genesis engineering and maintenance personnel are focused - around the clock - on ensuring maximum plant availability.
At Genesis, improving performance is not just the responsibility of the maintenance personnel but also engineers and operational staff. Employees work together to share information, prioritize activities and identify potential issues. As a result, the decisions they make have a greater impact on production capacity and performance.
Genesis is investing heavily in maintenance tools, technologies and personnel. For the greatest impact and return on investment, the company has adopted a maintenance strategy that seeks to maximize asset performance by applying the right activity to the right asset at the right stage in its lifecycle. Because maintenance activities can be tied directly to production output,Genesis' goal is to identify and plan for maintenance needs in a way that best optimizes production and extends equipment life.
In developing its maintenance strategy, the company sought to incorporate an optimum mix of predictive, preventive and reactive activities that corresponds to the criticality of the equipment, the failure modes and the costs associated with failure.Using a reliability-centered approach to maintenance, the type of maintenance activity is determined based on the overall impact and cost of downtime resulting from a failure. (During winter, the high demand period, there is virtually no spare generation capacity in New Zealand. Thus, the loss of a generator has an immediate consequence for the whole country. The generators must be available and reliable).
This strategy places an increased focus on using predictive and preventive techniques on core production assets and their supporting auxiliaries, many of which have 100 percent duplication but a failure increases the risk of production loss. On small low cost non critical plants, a run to fail approach can be adopted.
Within Genesis, a core group of engineers and maintenance personnel is intimately involved in the development and implementation of the company's maintenance strategy. Before any maintenance activities are determined, a team of Genesis engineers and maintenance personnel evaluate each phase and element of the production process at each of its facilities to determine the criticality and the probability of failure.Using a combination of technologies, including vibration and oil analysis, Genesis conducts an exhaustive evaluation of each piece of equipment.
The team looks at all potential failure modes to determine the risks for each, possible downtime costs, and potential safety concerns to outline failure scenarios. It then determines whether failure detection is possible and the types of technology necessary for detection. The most critical element of this risk assessment process is estimating the cost of failure, the replacement cost of the equipment, the potential damage to other equipment, and the financial ramifications of lost power generation.
The wide range of people involved helps ensure the team has a balanced perspective in terms of how they address and respond to different scenarios. This cross-team collaboration and input helps to balance decision making so that they consider both or immediate and short-term needs, as well as their long-term production requirements.
Once the assessment is completed, various points of data are inputted into a reliabilitycentered software program (available commercially and installed by Genesis) for more detailed analysis.
Predictive activities that measure the condition of equipment, such as vibration analysis, oil analysis and thermal imaging, represent nearly 60% of Genesis' overall maintenance activities. The predictive techniques are primarily focused at the Huntly Power Station, where approximately 400 pieces of equipment (mostly rotating equipment) are monitored, including boiler fans, boiler feed pumps and auxiliary generation units. At the hydro plants, predictive technology is used to monitor the main generators.
Before there was a great deal of unnecessary routine strip down (preventive) maintenance carried out, which is both a waste of resources and does not prevent failures. Today, the predictive tools allow Genesis to be more strategic and planned in its approach. The beauty of predictive maintenance is that the company is no longer caught napping when disaster is rapidly approaching. The value this technology provides is tremendous, particularly when the fault has the potential to reduce the generation capacity at a time when the spot price is high.
Solving the isolation issue
The remote location of the company's various hydro plants posed a unique challenge for the Genesis team. If a failure occurred at one of these plants, it could take up to six hours to drive to the location and assess the situation. In some cases, production at the facility could be down for days before the problem was corrected.
After reviewing all available options, the team determined that an online vibration monitoring and protection system would best meet Genesis' needs. More specifically, the monitoring system needed to be user-configurable and able to store data for post-event analysis. It also needed to be compact and easy to install and expand.
At first, the Genesis team didn't know if technology that could meet their specific condition monitoring requirements was even available. That was until they discussed what they needed with Colin Gracie, president of Inspyre Reliability Solutions, an independent sales engineer, who told the team about the unique capabilities of the Allen-Bradley XM Series monitoring and protection system.
Once team members were informed about the unique attributes of the XM system, they immediately saw the possibilities. Of particular interest to the team was the system's capacity to provide diagnostic protection and real-time data, as well as its ability to be easily integrated into the existing infrastructure.
Equally important in this case was the ability to monitor the equipment at various isolated locations. By connecting the equipment to a wide area network, the team would be able to analyze data from these remote plants and identify problems far in advance of a failure. As an added benefit, the time normally spent driving to the individual plants to gather vibration readings could be better used for other maintenance activities.
Installation of the XM Series on 13 generators at the company's five hydro power plants was scheduled to be completed in early 2006 . At the Huntly Power Station, the XM modules are monitoring 11 cooling tower fan drives, two 1.3 MW pump motors and the 40 MW gas turbine generator. The modules also will monitor the larger BOP (Balance of Plant) system on the plant's new 385 MW combined cycle gas turbine unit. Just on the hydro plant equipment alone, the system will collect more than 800 points of data in a fraction of the time to manually collect the information.
As part of the upgrade, Genesis replaced its analog network with a digital network that allows for more cost effective remote analysis— as well as the ability for the company to easily expand to more plants using only one server and database. A server installed at the Huntly facility communicates to the XM modules via a wide-area network. The data in the modules is downloaded according to a programmed schedule–every five minutes for normal data (within specifically defined parameters), every 10 minutes for triggered data and every 24 hours for transient data.
Just because a problem gets diagnosed, however, doesn't necessarily mean that there is a need for immediate action. The predictive technology lets Genesis identify a potential failure before the problem affects productivity or performance of equipment. It then can track progression of the fault and schedule the repair or replacement when it is convenient.
As part of its maintenance strategy, Genesis also performs preventive maintenance on a time-based or convenience basis depending on the type of equipment, performance specifications and operating conditions.
Genesis uses traditional predictive maintenance techniques—vibration and oil analysis, thermal imaging and ultra-sound signature analysis—to monitor various parameters on a preventive basis. These tools complement the predictive maintenance tools that the Genesis maintenance team employs.
For example, oil analysis checks the percentage of metal in the oil used to lubricate gearbox bearings—a symptom of metal fatigue or excessive wear. If metal is reported in the oil, maintenance can more closely monitor and trend equipment operation to determine the root cause and take corrective action before affecting production. Genesis uses thermal imaging to detect hot spots in rotating equipment and ultrasound monitoring to detect changes from the norm, which would trigger the need for closer analysis.
Using a combination of predictive and preventative maintenance, Genesis maintenance team members can more accurately target the work that needs to be done during the annual shutdown.With the trending data they collect, they can strategically go in and make the corrections or change out equipment. This allows them to make more effective use of their time during the shutdown.
Through its reliability-centered approach to maintenance, Genesis has greatly reduced the amount of reactive maintenance performed. Today, reactive maintenance represents only 10% of activities. For equipment not determined to have a high degree of criticality and low replacement costs, Genesis does not perform routine maintenance; instead, it simply replaces or repairs the equipment when obvious problems occur.
With 70 maintenance personnel covering six major energy production facilities, along with numerous cogeneration facilities at industrial sites scattered across the region,Genesis has to prioritize its activities. Team members have calculated that the capital expense of replacing non-critical equipment when it fails is evenly balanced against the cost of implementing a predictive or preventive program for this equipment.
Even before the company's latest predictive equipment was completely installed, the XM Series modules demonstrated their ability to quickly detect and diagnose equipment failures.
Shortly after Genesis installed the 40 MW gas turbine unit, the equipment unexpectedly tripped on high vibration. Since it was still under warranty, the manufacturer insisted that a full inspection be conducted. That meant several days.While they waited, maintenance team members decided to install the XM Series system as an informal test of the technology. Following the inspection (which found no obvious problems), the turbine was returned to service.But, the high vibration was still apparent. Looking at the spectra available from the XM120, though, it was quite clear that the high vibration was, in fact, due to a transducer fault. Further investigation showed that one of the vibration transducers had a broken connection and furthermore it was found that the transducers on the turbine were cross-connected. If the XMs had been installed at the onset, the team would have saved several days of downtime—which, in turn,would have paid for the XM installation.
As the XM Series continues to prove its value, Genesis anticipates that there will be other opportunities to apply the technology through the company's various power plants. If early indications mean anything, it should prove to be a valuable tool in Genesis' predictive maintenance program—as well as in the growth of New Zealand.
Simon Hurricks has worked for Genesis Energy and its predecessors (NZED and ECNZ) for 34 years, and has specialized in vibration analysis and balancing for 28. Based at the Huntly Power Station for 25 years as a machine dynamics engineer responsible for condition monitoring, including vibration analysis and balancing, he also has carried out vibration analysis and balancing at many other hydro installations across New Zealand.Hurricks is a member and the current treasurer of the Vibrations Association of New Zealand, as well as a regular presenter at the organization's annual conferences. MT