Hydro Case Studies

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

1. Diameter : 5.000 / 4.999 inches, 6.4 inches long
2. Material : Heat treated 17-4 PH stainless steel
3. Hardness : Mini Ra 0.4 micrometers (16 micro inches) or better
4. 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/cm2 – 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

Two significant Argentinian hydroelectric projects have chosen Vesconite: Central Los Quiroga and Planta Hidroeléctrica Cabra Corral-Salta. Vesconite Hilube replaced bronze wicket gate bushings in 2009 at Central Los Quiroga. The results were very satisfactory, the bushings were reported to still be like new in discussions held in 2019. In addition, five turbines at Planta Hidroeléctrica Cabra Corral-Salta were fitted with Vesconite Hilube in 2011 and were reported to be operating without any problems in 2019.

Twenty Vesconite Hilube staves were provided for Drop 4, Unit 2, of GE Hydro’s Imperial Irrigation Project. The Imperial Irrigation District is community owned and provides irrigation water in the south-eastern portion of California’s desert. The housing diameter was 700 mm, shaft diameter 572 mm and the bearing length 940 mm. The Vesconite Hilube replaced rubber staves.

A 5-wing Kaplan wheel turbine that was supplied to Haapakosken Tehdas Oy in 2007 included a Vesconite Hilube bearing with an outside diameter of 225mm, inside diameter of 180mm, and a length of 300mm. The Kaplan turbine provided electricity for this Finnish integrated power plant and iron works, including power-intensive foundry. This old ironworks environment was owned in 2021 by Haapakoski Ruukki and protected by the Finnish National Board of Antiquities. The turbine (including the Hilube bearing) is still working. The electricity is used for the small needs of Haapakoski Ruukki and the rest is sold out to the general net.

After a long testing campaign, where a series of self-lubricating products were tested in the Centre de Technology in Grenoble, France, Vesconite Hilube was approved for Alstom turbines, in wicket gates, connecting rods, servomotors, radial and axial segments. This approval is valid worldwide.

The basic results and testing conditions are as follows:

Supplier: Grafimec Bearings Systems – Brazil
Material tested: Vesconite Hilube
Size of bushings: 95 x 80 x 60 mm
Testing conditions:
Test: dry
Temperature: room
Tests duration: 1.800.000 cycles
Specific load: 20 MPa
Speed: 15 mm/s

Results:
Wear: ≤0,1 mm
Dynamic friction coefficient: <0,12 

Argentina – A hydropower plant fitted its turbine with Vesconite Hilube turbine bearings in 2007. The original oil-film main-guide bearings used in the turbine ran the risk of water contamination. Vesconite Hilube proved itself as a superior alternative – hard-wearing, non-water absorbing and self-lubricating. Downtime and maintenance was significantly reduced, with resultant cost-savings.

USA – Vesconite Hilube has been the preferred choice for the pressure relief valves (PRVs) at the Hoover Dam. Originally designed in the 1930s, the PRV’s divert water around the turbines when flow to the turbines needs to be stopped. Vesconite Hilube was selected to replace the existing cast iron parts, which had oxidised and seized, preventing the valve from functioning. Vesconite Hilube has proved to the ideal material for this application, due to its self-lubricating, hard-wearing, corrosion-free and low slip stick features.

USA – The link-arms and change ring controlling the wicket gates on America’s Hoover Dam demanded a maintenance-free self-lubricating bush. The specific bush is subjected to considerable force and has a knock-on effect on the wicket gate system, which ultimately controls waterflow to the dam’s turbines. Vesconite Hilube was supplied, machined and fitted, and has performed flawlessly for the past seven years.

Canada – A manufacturer of small-scale hydroelectric plants required a hard-wearing bushing material for its wicket gates – aerofoil-shaped blades that control water flow to the hydroelectric turbines. A central shaft runs through the wicket gate and three bushings assist in their rotation. For the past 10 years, the company has successfully fitted Vesconite Hilube bushes to these critical parts, thanks to Vesconite Hilube’s low friction co-efficient, self-lubricating properties and negligible water absorption.