A. Introduction
Vesconite Hilube was tested by an independent laboratory in Vancouver, Canada, in 2002. The purpose of the test was to evaluate the performance of self-lubricating Vesconite Hilube bushings for use in wicket gate applications in hydroelectric turbines.
B. Specification
The specification defines an accelerated wear, high loading oscillating test, simulating similar operations in hydro turbines. Bushings were tested under conditions representing the worst-case scenario for wicket gate operations.
These conditions included maximum design loading with impulse loading from passing turbine blades, plus small continuous oscillations to simulate governor hunting and/or built-in governor dithering to maintain motion of the gates.
C. Test Program
The test programme was divided into three sections: initial set test, creep test and accelerated wear test.
1. Initial Set and Creep
Before the accelerated wear test, the same bushing and sleeve are statically loaded to 3,300 psi (23 MPa). The shaft displacement relevant to the test block (wear) is continuously monitored. In the first four hours the shaft is rotated / oscillated ±5° from centre line at 0.1 Hz every five minutes. For the next twenty hours the shaft is rotated / oscillated the same amount, but every ten minutes. This period was used as the set and creep measurement phase for both wet and dry tests (straight test sleeves).
2. Accelerated Wear
After the set and creep phase tests, the accelerated wear tests begins. This applied radial load of 3,300 psi (23 MPa) has, in addition, a superimposed dynamic load of 1000 psi (7 MPa) at 2 Hz. The shaft is rotated at ± 1° from centre line, continuously, at 2 Hz. Every 15 minutes the radial dynamic load is paused and the shaft rotated at ± 15° at 0.1 Hz (10 seconds to complete the swing), with only the static radial load applied. This phase of the test runs for a minimum of 120 hours.
The wet test version is a repeat of this process, with the exception that the bushing/shaft assembly is placed in a distilled water environment.
D. Bushing Test Sleeves
- Diameter : 5.000 / 4.999 inches, 6.4 inches long
- Material : Heat treated 17-4 PH stainless steel
- Hardness : Mini Ra 0.4 micrometers (16 micro inches) or better
- Sleeve replacement : A new test sleeve was used for each testD. Bushing Test Sleeves
E. Bushing Design
Inside Diameter after installation: 5.026” (running clearance of 0.026”) Vesconite Hilube can be used at close clearances and close tolerances because of its excellent dimensional stability.
F. Test Results
The Vesconite Hilube bushings performed well with very little evidence of operating stress. There was no audible noise generated during the test. There was no indication of damage to the journals or damage to the bushings.
The dry test performed well with relatively low coefficients of friction and low wear rates – 0.173 mils/100 test hours (0.00439 mm/100 test hours). There was evidence of wear debris/ lubricant forming in the contact face and providing the desirable features of a self-lubricating bushing.
Dry Test Coefficient of Friction (Static): 0.131
Dry Test Coefficient of Friction (Dynamic): 0.110
Average Wear Rate: 0.173 mils/100 test hours
0.00439 mm/100 test hours
G. Conclusion
Vesconite Hilube performed exceptionally well in the stringent laboratory tests.
Vesconite Hilube has the following advantages in hydro-power applications:
- High design load carrying capacity whether wet or dry (4250 psi or 300 kg/cm2Â – highly loaded, for slow moving or oscillating applications)
- Exceptionally low friction with no stick-slip
- Dynamic friction goes as low as 0.08
- No water swell
- Longest life, low wear and low maintenance
- Cost effective
Vesconite Hilube is the long life, cost effective solution for many hydro applications, including:
- Pump bearings, wear rings and seal rings
- Sluice gate bearings and slides
- Trash rack bearings
- Control linkage bearings
- Wicket gate bearings – upper, middle and lower
- Segmented shaft seals
- Kaplan hub bearings
- Kaplan turbine bearings
Vesconite Hydro Case Studies
Other Industries
