Lubricants can help increase productivity and reduce total cost of ownership for turbines, transformers and stationary engines, writes Marcelo Goldberg
Globally, the demand for power is increasing, driven by a growing population, mass urbanization, and rapid industrialization of nations like China and India.
The consequence for those in the business of power generation, transmission and distribution is a need to achieve greater productivity and reliability in a challenging climate of stricter environmental targets, severe penalties for supply interruptions, tighter budgets and tougher operating conditions.
Many companies are already well aware that reducing Total Cost of Ownership (TCO) over the lifetime of machinery is key to extracting the best possible value from the investment.
However, the impact of lubrication on TCO is too often underestimated.
According to an international industry study commissioned by Shell Lubricants, the savings opportunity is recognized but undervalued. Some 58 per cent of companies recognize that lubricant selection can help reduce costs by 5 per cent or more, but fewer than one in ten (8 per cent) realize that the impact of lubrication could be up to six times greater.
|Selecting the right lubricant is a critical first step
In general, the cost of lubricants accounts for less than 5 per cent of a power generation company’s total operational expenditure. Yet lubrication can deliver significant business value through improved system efficiency, reliable equipment protection and longer oil and equipment life.
When considering the potential savings, the definition we use for TCO includes costs related to lost production resulting from equipment downtime.
To quantify the cost saving potential, let’s look at an example from the wind power sector. Wind turbine insurance company GCube Renewable Energy Insurance reported that there are around 1200 incidents of gearbox failure each year among the 175,000 geared turbines in operation worldwide.
Some 76 per cent of these breakdowns are related to bearing failure, and the insurance claims commonly range between $200,000 and $300,000.
By helping protect bearings against wear and guard against premature failure, lubrication has the potential to deliver huge cost savings. There are two key elements to seizing this opportunity. The first is selecting the right lubricant; the second is effective lubrication management.
Whether it’s a turbine, transformer or stationary engine, every piece of power generation machinery or transmission/distribution transformer made by different OEMs has its own specific oil requirements.
OEMs define the minimum requirements for lubricants, but for critical equipment, lubricants that exceed – rather than simply meet – these standards can prove a worthwhile investment.
For any piece of equipment, the design characteristics, how it is fuelled, its operational parameters and the surrounding environment all pose different challenges for lubrication.
Below are some of the industry’s primary applications and examples of specific lubrication challenges. In all cases, selecting the right lubricant is a critical first step in improving productivity and realizing significant TCO savings.
|Modern turbine oils must cope with stress
Today’s power generation turbines are working under more demanding conditions than ever – from continuous 24/7 running to frequent stop-start, cyclic operation in order to accommodate fluctuating renewable power generation.
Modern turbine oils must be able to cope with increased stress and considerable operational challenges, including: reduced downtime, extended oil drain intervals, higher temperatures and loads, frequent change of load, stop-and-start operations and greater output power, but with a lubricant reservoir that is the same size or smaller, imposing more rapid cycle times on the lubricant with a consequent need for excellent surface properties.
They must also help enhance system reliability and efficiency by preventing metal-to-metal contact and controlling valve sticking during startup and shutdown; cooling rotating parts quickly to prevent oil degradation and the formation of oil insoluble deposits; and protecting against wear and corrosion of the main bearings and system components.
Wind power is playing an increasingly prominent role in today’s global energy mix. Industry projections suggest that existing installed capacity will double by the end of 2019.
The past decade has seen vast increases in size and capacity of both onshore and offshore wind turbines. Tower heights now commonly reach 80–120 metres, rotor diameters average 95 metres or more, and average output capacity has increased to 1.96 MW, or 3.6 MW for offshore. In addition, 27 per cent of wind turbines installed in 2014 use direct drive technology, and this trend is growing. All of this poses a number of challenges for lubrication:
• Increasing turbine blade lengths lead to increasing loads and vibration on bearings, which can cause increased wear;
• Turbines are often located in extreme climates – lubricants must be able to perform efficiently in spite of freezing winters or, at the other extreme, very high ambient temperatures and frequent sandstorms;
• For turbines located offshore or in coastal environments, protecting bearings against corrosion by seawater is vital. In addition, the lubricant must resist the formation of harmful deposits and retain its wear protection properties when contaminated with water;
• The high flow rate for gear oils in a wind turbine gearbox (in cases of 200 L/min or more) means that the oil has little time in the sump to release any entrained air. As such, gear oils need to be designed with low foaming tendency.
The average age of a power transformer in many countries is around 30 years or older and many companies are operating equipment close to or beyond its original recommended lifespan due to the high capital cost involved in replacing a unit. Stresses on lubricants have increased:
• Many transformers frequently operate under overload, with larger voltages to improve transmission efficiencies and higher power:weight or power:volume ratios to reduce manufacturing and installation costs;
• This means transformer oils must work effectively for longer and in higher temperatures;
• They must also protect against copper corrosion, paper degradation and premature oil aging.
|Lubricant samples for testing
While the latest engines, such as natural gas engines, deliver greater efficiency, they pose challenges for the lubricant.
The use of non-conventional fuels – such as landfill, biogas or sewage gas – in stationary power generation engines also poses challenges for lubrication:
• Key among these is the increased risk of ash deposit buildup in the combustion chamber due to siloxanes, and corrosion resulting from the presence of halogenic compounds and acidic elements in the gas. Higher levels of oxidation and nitration products also significantly increase the acid stress and can shorten the oil’s life;
• Lubricants need to protect the engine and extend equipment life by neutralizing acids produced during combustion or by the oxidation and nitration of the oil itself. Lubricants should have a low ash content to minimize deposit buildup;
• A balance between ash level and performance has to be made to ensure system efficiency is not compromised. Ash content needs to be sufficiently high to manage alkalinity reserve depletion, but not so high that it can lead to wear and deposits.
By selecting a high performing oil or grease, power sector companies can realize TCO savings that reach far beyond any savings related to the price of the oil or grease itself.
Selecting a less effective lubricant rarely results in immediate equipment failure, but can lead to increased maintenance expenses over time and, in the event of disruptions from unplanned downtime, heavy financial penalties.
These mounting costs can be far greater than the savings from selecting a lower price lubricant.
In contrast, a high quality lubricant that keeps equipment clean of deposits, retains good miscibility (the ability to mix compatibly with other liquids) and effectively protects against wear and corrosion can help extend equipment life, reduce frequency of breakdown and increase equipment availability. This could significantly decrease spend on spare parts and maintenance.
Even the best product cannot perform effectively if it does not reach the right surfaces at the right time, in the right amount, without being contaminated or degraded.
Effective lubrication management is vital to unlock potential TCO savings. It helps deliver value from improved productivity and reductions in lubricant consumption, maintenance and operating costs.
Modern power plant operators will continue to demand three things from an oil or grease: improved system efficiency, reliable equipment protection, and longer oil and equipment life. With pressure on the power industry higher than ever, for many companies the demands of today often supersede the challenges of tomorrow.
Marcelo Goldberg is Shell Lubricants’ Global Sector Manager for Power. www.shell.com/lubricants