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Turbine Lubrication Systems Small changes can make a big difference in water quality Éric Auger, Eng. May 19, 2011
Turbine Lubrication Systems Small changes can make a big difference in water quality
Éric Auger, Eng.
May 19, 2011
INTRODUCTION
• Hydroelectric turbines have many moving parts that required lubrication.
• Traditional lubrication systems are based on the use of oil and grease.
• Even if cleanup is done regularly, grease and oil accumulation can never be completely eliminated.
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INTRODUCTION (cont’d)
• Alternative solutions exist:– Biodegradable greases.– Grease management and distribution.– Replacement of grease lubrication by self-
lubricating bushings.
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INTRODUCTION (cont’d)
• Other general opportunities:– Taking care of oil leaks in different systems.– Hydrostatic water guide bearings.– Oil free Kaplan runners.– Water based high pressure units when the
head is available.
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What are turbine and generator units and how their systems have an impact on water quality?
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General Layout of a Typical Power Station
From web page: http://nothingnerdy.wikispaces.com/HYDROELECTRIC+POWER+-+William
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What are turbine and generator units and how their systems have an impact on water quality? (cont’d)
From Lirycs Search Website
Present Situation – Grease Based Systems
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Turbine lubrication systems can have up to 140 application points that can operate up to four times a day.
These application points apply grease mainly to the following systems:
Present Situation – Grease Based Systems (cont’d)
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• the pins for the servomotor links; (1 & 2)• the horizontal and vertical pads on which
the operating ring slides; (3 & 4)• the pins for the wicket gate links and
levers; (5)• the upper guide and thrust bearing of the
wicket gate; (6)• the intermediate guide bearing of the
wicket gate; (7)• the lower guide bearing of the wicket
gate; (8)
Improving on the Present Situation – Biodegradable Grease
• The simplest modification available to a hydroelectric powerhouse owner is the use of biodegradable grease.
• Modification basically consists in changing the barrels of traditional grease for biodegradable barrels and adjusting the distribution system to the new grease specifications.
• Tribospec-Biospec GRL is an example of biodegradable grease. This non-toxic grease has a biodegradable index superior to 97%. By comparison, traditional greases have indexes in the 20% to 30% range.
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Improving on the Present Situation – Grease Management and Distribution (cont’d)
• The grease management system generally controls consumption by using elapsed time and/or unit start/stop cycles to determine when to apply grease.
• Older systems tend to be mechanically timed and therefore can not detect long periods of inactivity and multiple start/stop cycles in a short period of time.
• New technologies and growing knowledge of the grease requirements of hydro turbines have paved the way for newer systems that can better manage grease distribution.
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Improving on the Present Situation – Grease Management and Distribution (cont’d)
• Grease is distributed to the appropriated lubrication points via a network of pipes and distributors.
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Improving on the Present Situation – Grease Management and Distribution (cont’d)
• Some application points require considerably more grease than others, such as the wicket gate intermediate and lower bearings that are constantly degreased by the water flow.
• Instead of using a single circuit, a grease system with multiple distribution circuits can provide just the right amount of grease to the right application points at the right time.
• The relocation of a single distribution point from an external circuit to an internal circuit has, in certain cases, provided a 75% reduction of grease accumulation in the units head cover.
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Improving on the Present Situation – Replacement of Grease Lubrication by Self-Lubricating Bushings
• Interventions on the units which can partially or completely eliminate grease based lubrication systems are also possible.
• A planned major overhaul of the unit provides a good opportunity to install self-lubricating bushings with little impact on the overhaul cost.
• If a major overhaul can not be justified due to its high cost and associated production losses, an alternative solution is to partially replace the greased bushings by self-lubricating ones.
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Improving on the Present Situation – Replacement of Grease Lubrication by Self-Lubricating Bushings (cont’d)
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Improving on the Present Situation – Replacement of Grease Lubrication by Self-Lubricating Bushings
• Wicket gate and servomotor links are generally easily accessible. These parts can be disassembled in the turbine pit, removed through the pit access door and sent to the workshop for the installation of self-lubricating bushings.
• The replacement of the operating rings wear and sliding pads requires lifting the ring until the pads are accessible.
• Upper and lower wicket bearings are accessible only if they are mounted in removable tubes.
• More than 80% of grease application points can be replaced by self-lubricating bushings.
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Improving on the Present Situation – Replacement of Grease Lubrication by Self-Lubricating Bushings(cont’d)
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Self-lubricating bushings started being installed in hydroelectric units in the mid-1980s. Widespread acceptance of their ability to replace greased bushings was not until the mid-1990s. Many companies now produce a wide variety of these bearings.
ORKOT TXMM self lubricating bearings
Improving on the Present Situation – Replacement of Grease Lubrication by Self-Lubricating Bushings(cont’d)
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In any case, before undertaking such work, a feasibility study is required to ensure that replacement is possible.
Other opportunities for Improving the Environmental Footprint of a Unit
• Other parts or components where self-lubricating bearings can be installed:– Spiral case door hinges.– Draft tube door hinges.– Servomotors and main bearings of the spherical or
butterfly turbine inlet valve.
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Other opportunities for Improving the Environmental Footprint of a Unit (cont’d)
• Other possible sources of water contamination that simple interventions can eliminate, include:– Oil leaks from the hydraulic cylinders.– Oil leaks from the guide bearings.– Oil leaks from the generator breaks.– Oil leaks from the oil piping.
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Other opportunities for Improving the Environmental Footprint of a Unit (cont’d)
• A green technology offered by some turbine manufacturers is water based (hydrostatic) turbine guide bearings. The pressurized water from the penstock is used to maintain a water film for the lubrication and cooling instead of an oil film.
• Another technology developed and implemented in the last 5 to 10 years replaces the oil in Kaplan runners with water. Self-lubricating bearings are then installed to support the blades of the runner. This greatly reduces the amount of oil in close proximity with the water passage and therefore the risk of leakage into the river.
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EXPERIENCE
• AECOM has already completed feasibility studies for work the four units on Manic-5PA powerhouse in Quebec, Canada. The Client has chosen to replace the existing lubrication management and distribution system by a completely new design which has the ability of easily adjusting the lubrication frequency of the various circuits.
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EXPERIENCE (cont’d)
• This summer, AECOM will conduct the detailed engineering which will allow his Client, Hydro-Québec, to undertake work associated with the partial replacement of traditional bronze bearings, as described above. The detailed engineering will be conducted over a period of six months and work will be performed on the unit by Hydro-Québec’s maintenance staff.
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