Water Lubricated Guide Bearings
What is the function?
To steady and align the rotating generator shaft. The main guide bearing is submerged below the waterline while the generator shaft rides on a hydrodynamic water layer trapped between the shaft and the bearing. Increased velocity has a positive effect on the load carrying capacity of the bearing because the minimum clearance gap increases when velocity is increased.
What are the typical types of turbine designs?
There are several designs, but the most common are Bulb Turbine, Pelton Wheel Turbine, Francis Turbine, Pelton Turbine
What are the types/designs of turbine guide bearings?
Staves, Bearing Blocks, Full Formed and Split Bearings (with or without water grooves). Here in the picture, we show a Stave Bearings installed in a split horizontal unit.
Bearing Design
First, analyze which sliding material can be economically employed. Orkot? TLMM is a low friction, low cost choice. We also have Orkot? TXMM, this material has lower friction and is more abrasive resistant than Orkot? TLMM.
Second, calculate bearing overall dimensions and basic data of water supply. With water flow determined, calculate flow area and design ID grooves. Ascertain the installed fit with clearances and tolerances. We can help you with the design.
Third, determine a method to fix the bearing into the housing. There are several options we can use, Freeze fit using Liquid Nitrogen (LN?), Mechanical fastening or two part epoxy adhesives, contact us for recommended adhesives.
Fail Safe methods to insure long life of the bearing
First, ensure that there is adequate water flow for cooling and lubrication - as a general rule, we recommend a minimum water flow of 0.18 liters per minute per mm of shaft diameter (1.21 US gallons per minute per inch of shaft diameter)
Second, monitor the cooling water temperature at the top of the bearing (water inlet) and at the outlet of the bearing. If the outlet temperature raises more than ten degrees over the inlet temperature, a cooling flow problem is indicated, and the unit should be shut down for evaluation.
Orkot? experience in developing and applying plastic bearings goes back to 1954. Orkot? has been tested by PowerTech Labs and approved by the US Army Corps of Engineers (USACE) for use in Hydro applications. Stated by the USACE, Orkot? TXMM was one of the first materials tested back in the 1990’s and has been installed in more Corps turbines than any other material. It has performed well and is one of our favorites.
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