Genesis Energy's predictive maintenance strategy targets most critical equipment to ensure optimal availability
With breathtaking terrain ranging from snowcapped mountains to lush lowland plains, New Zealand is often described as a paradise by those who have experienced its unique beauty. Located 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, New Zealand's power generation capacity is continuously strained by ever-increasing demand.
Tasked with keeping the supply side of this equation in proper balance is Genesis Energy, New Zealand'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 occurs 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 short fall and puts 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
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 percent 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 40MW simple cycle gas turbine generator
As part of its growth strategy, Genesis is building a high-efficiency combined-cycle gas turbine power plant, which will increase production capacity at the site to 1,425 MW. It is also 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 percent 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," explained Simon Hurricks, machine dynamics engineer, Genesis Energy. "We work together to share information, prioritize activities and identify potential issues. As a result, the decisions we 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, our goal is to identify and plan for maintenance needs in a way that best optimizes production and extends equipment life," said Hurricks.
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 so 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 % duplication but a failure increases the risk of production loss. On small low cost non critical plant a run to fail approach can be adopted.
Within Genesis, Hurricks is part of a core group of engineers and maintenance personnel 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 we have a balanced perspective in terms of how we address and respond to different scenarios," Hurricks said. "This cross-team collaboration and input helps to balance our decision making so that we're considering both or immediate and short-term needs, as well as our long-term production requirements."
Once the assessment is completed, various points of data are inputted into a reliability-centered software program (available commercially and installed by Genesis) for more detailed analysis.
Hurricks estimates that predictive activities that measure the condition of equipment, such as vibration analysis, oil analysis and thermal imaging, represent nearly 60 percent 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 lot of unnecessary routine strip down (preventive) maintenance carried out, which is both a waste of resources and does not prevent failures," said Hurricks, "Today, the predictive tools enable us to be more strategic and planned in our approach. The beauty of predictive maintenance is that you're 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 Issue of Isolation
The remote location of the company's various hydro plants posed a unique challenge for Hurricks and his 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 is corrected.
With more than 34 years of experience in the field, Hurricks has dedicated his career to understanding the science of predictive maintenance and is well-versed in the latest technologies and strategies for keeping a plant running at peak performance. After reviewing all available options, he 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, Hurricks wasn't sure if the technology was available that could meet his specific condition monitoring requirements. That was until he discussed what he needed with Colin Gracie, president of Inspyre Reliability Solutions, an independent sales engineer, who told him about the unique capabilities of the Allen-Bradley XM Series monitoring and protection system from Rockwell Automation.
"When I first heard about the unique attributes of the XM Series, I immediately saw the possibilities for the technology to address our needs," said Hurricks. "Of particular interest was its ability to provide diagnostic protection and real-time data, as well as its ability to be easily integrated into our existing infrastructure."
Equally important in this case is the ability to monitor the equipment from the various isolated locations. By connecting the equipment to a wide area network, Hurricks and his team would be able to analyze data from these remote plants and identify problems far in advance of a failure. And 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 is scheduled to be completed in early 2006 on 13 generators at the company's five hydro power plants. At the Huntly power stations, the XM modules are monitoring 11 cooling tower fan drives and two 1.3-MW pump motors and the 40 MW gas turbine generator.
The modules will also 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, the company replaced its analog network with a digital network, which allows for more cost effective remote analysis and allows Genesis to more 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 ten minutes for triggered data and every 24 hours for transient data.
However, just because a problem gets diagnosed, doesn't necessarily mean that there is a need for immediate action. The predictive technology enables Genesis to identify a potential failure before the problem affects productivity or performance of equipment. It can then 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. Hurricks 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 Genesis 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. Hurricks 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, we can more accurately target the work that needs to be done during the annual shutdown," said Hurricks. "With the trending data we collect, we can strategically go in and make the corrections or change out equipment. This allows us to make more effective use of our time during the shutdown."
With the reliability-centered approach to maintenance, Genesis has greatly reduced the amount of reactive maintenance performed. Today reactive maintenance represents only 10 percent of activities. For equipment not determined to have a high degree of criticality and low replacement costs, Genesis does not perform routine maintenance but 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, we have to prioritize our activities," explained Hurricks. "We've 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 we installed the 40 MW gas turbine unit, it unexpectedly tripped on high vibration" said Hurricks. "Since it was still under warranty, the manufacturer insisted that a full inspection, taking several days, was undertaken. While waiting, we decided to install the XM Series system as an informal test of the technology. Following the inspection which found no obvious problems, the machine was returned to service. The high vibration was still apparent. Looking at the spectra available from the XM120 it was immediately obvious that the high vibration was in fact a transducer fault. Further investigation showed that one of the vibration transducers had a broken connection and further more it was found that the transducers on the turbine were cross connected. If the XMs had been installed at the onset we would have saved several days of down time and paid for the XM installation"
As the XM Series continues to prove its value, Hurricks anticipates that there will be other opportunities to apply the technology through the company's various power plants. If early indications mean anything, the XM Series will prove to be a valuable tool in Genesis' highly effective predictive maintenance program. MT