HGRD_Turbine_3_Inspection_Report_0001.pdf

HEADGATE ROCK UNIT # 3 INSPECTIONS

REPORT

DATE: 11/24/2021

Plant address (on the border between Arizona & California) is:

11850 Head-Gate Dam Rd Parker, AZ 85344

Turbine Manufacturer Allis-Chalmers/Voith Runner Diameter 5050mm Output 6.69 MW

CFS 6200

HP 9100

Head 15’

RPM 75

Date of Manufacture / Order 1986 In Service Date 1992

Generator Manufacturer Villaries

Voltage 4160V Output 7222KVA

RPM 75

Serial Number GH062 Date of Manufacture 1988

Other Relevant Machine Parameters

• Turbine has two (2) Mechanical Seals. One (1) upstream in the Stay Column, one (1) downstream where this style of unit typically has a Packing Box. Both Mechanical Seals are the Voith design. Sizes are 680 & 900mm. This is important as these have been a constant issue ever since commissioning. Changed at least every year on all three (3) machines.

• Governor is a Woodward 505H Cabinet

• Turbine Guide Bearing is a babbitted RENK 508mm design

• They do have tail water stop logs in place that they lower into place via their own Mobile

Crane

• The Intake has Radial Gates and stop logs.

• The Restoring Mechanism, Oil Head, Servomotor, Wicket Gate Shear Lever/Shear Pin and Slip-Joint Assembly are all the very same design as those on all of the Allis- Chalmers TUBE Turbines

• Both Generator Bearings were supplied by Waukesha

• The Villaries Generator also has a Woodward (Permanent Magnet Generator (PMG) at the very downstream end of the Generator

• The Brake Assembly is a Brake Disc mounted to the non-drive end of the Generator

Shaft with four (4) Brake Shoes, two (2) upstream of the disc, two (2) downstream. All in the lower quadrant of the disc.

Inspection Purpose of the trip was to investigate a recent (informed it was three (3) weeks ago) failure that they had on Unit 3. Most notably damage to the Generator Brakes/Brake Disc and breakage of four (4) Shear Pins on the Gate Mechanism. Our understanding is that the unit was shutting down and nearly off-line when this occurred. We are told that the unit ran for approximately five (5) hours after the Shear Pins had failed. The Brakes are/were activated at 15 rpm and the thinking is that they stay engaged throughout the failure.

Upon our arrival, the BIA had already done the following in the last few weeks:

• Replaced the broken Shear Pins (looking upstream, Arizona side, gates in the 3 – 6 o’clock positions)

• Drained and removed the top cap from the following bearings:

o Turbine Guide Bearing (Renk)

• Drive End Generator Bearing (Waukesha)

• Non-Drive End Combination Thrust/Guide) Bearing (Waukesha)

NOTE: the BIA had changed the Wicket Gate Bearings 031/014 on these same Gates in the last year.

Additional Findings

• Water passage – no signs of anything going through the machine

• Trash Rack – intact nothing removed

• Wicket Gates – appear intact, no damage from the failure or the fact they had rotated 360 degrees at some point.

• All Wicket Gate Shear Pins 031/008 are installed without the dye for detection of a failure

• Wicket Gate End Clearance, although not measured, looks sufficient visually

• Inner Bulb – noticeable markings to the Bulb that resulted from the four (4) broken Shear

• Pins allowing those Wicket Gates to rotate 360 degrees

• Discharge Ring Internal Surface – no evidence of blades hitting. Speed Ring area does show some erosion, to be expected after 28-29 years.

• Slip-Joint Assembly – leaking, BIA has assembled a temporary deflector

• Transition between Intake & Discharge Ring shows some erosion, coating removal, and maybe some cavitation.

• Draft Tube/Exit from Unit – nice shape, some spalling and a little coating removed

• Wicket Gate Seal Surfaces – look fine for the vintage.

• Runner Hub & Blades – some coating removed. No evidence of damage to Blades, gap between back of Runner Hub and Inner Barrel looked appropriate, and the Seal Retainer Covers looked in place.

• Runner Trunnion Seals – no signs of oil leaks or seepage.

• Collector Rings – worn, need machined & cleaned up. Would have a tough time getting brushes to seat well as is.

• Brush Rigging – good condition, very little carbon dust. Brushes worn, should be replaced.

• Brake Disc – damaged from extreme hear during the failure from the Brakes staying engaged for several hours.

*Note: these were all visual examination using familiarity of this type of machine as a guide for pass/fail type analysis. More in-depth analysis would certainly be warranted, but operation of the hydraulics would be necessary to perform further due diligence. Clearance requirements restricted hydraulic operation.

Summary: no smoking gun was found. Possibilities are:

1. Something came through the water passage. There was no evidence to support this theory, but it can’t be ruled out.

2. Wicket Gate Mechanism Operation. Improper Wicket Gate Bearing replacement could result in problems with the leakage, adjustment, closure, etc…

3. An isolated Shear Pin fails from fatigue/old age. It is plausible and has happened in the past, that one Shear Pin fails or experiences fatigue which causes the Gate Arm/Shear Lever relationship to fail. When this does happen, it is not uncommon for that Wicket Gate to hit adjacent Wicket Gates and cause multiple failures. But there is no evidence of the Wicket Gates coming in contact with each other.

4. Rework all shear pin mechanisms ensure smooth and concise operations. Test to factory intended tolerances. Ensure Governor analogs are accurate to gates and blades.

Action Plan (to return unit to service)

• Remove PMG & Brake Disc, send Brake Disc to shop for clean-up machining

• Remove Turbine Guide Bearing, Thrust Bearing, and both Generator Guide Bearings.

Send to shop for inspection/recommendations. Flush all lines, reservoirs, etc… to same.

• Partially Disassemble both Mechanical Seals to insure they weren’t damaged

• Remove Collector Rings, send out for inspection/repair

• Energize Wicket Gate Servomotor and do the following:

o stroke the gates multiple times while visually examining the water passage and gate mechanism o measure stroke length and squeeze at the Servomotor Rod o measure & record open & close timing

• Readjust Gate Closure & Gate End Clearance

• Replace the remaining Shear Pins

• Check Generator Air Gap

• Fix the oil leakage from the Oil Head & Restoring Mechanism

• Clean debris from the Water Passage

• Reinstitute dye in Shear Pins for future detection

• With the machine dewatered, stroke the Runner Blades, measure the following:

o Stroke length, compare to drawing o Stroke angle, measured at Trunnion o measure & record open & close timing via marks on the Trunnion Seal Cover

Plates o Transfer those marks to the Restoring Rod area

• Take a sample of the oil in the Runner Hub. Reports are that it typically has a green hue to it when removed, no evidence of water, and no metal/bronze/brass particles. It would be good to confirm after an event like just experienced.

• Flush the entire lube systems.

Other Possibilities to Improve Function and reduce maintenance costs

• This inspection revealed a requirement that the mechanics had to remove and replace the

Voith IP seals multiple times per year. This is an industry known issue and to Replace factory seals with a conventional Packing Box to replace the Mechanical Seals on the Draft Tube Flange is the recommend repair. This will eliminate the need to repair the seals yearly or biannually. This would be a huge savings for the owner. Packing Box for other TUBE Turbines looks like below:

Work Details and Images

Down Stream braking disc has groves needs turned to smooth finish.

Placement Brake pad Dimensions for replacement

Brake Caliper reflects extreme heat evaluate internal damage and retraction springs

Brakes disc pads are 8x12 only 5 inches of pad is contacting the disc. Remove disc turn for full pad contact to disc. Evaluate warpage of the disc shows signs of excessive heat.

Brake Caliper replace pads x 8 evaluate pressure cups and rebuild as required. Replace all retraction springs

Thrust Barring Name Plate Data

Braking Disc Calipers Removed Remove disc and send for resurfacing

Right Side Upper Guide Barring has Babbit shavings in the oil well. Lift Barring evaluate oil journals and flush. Reseat barring shim to factory tolerances. Gaskets are showing sign of aging.

Recommend re-gasketing

Generator 3 Name Plante Data

Left Side Upper Guide Barring has Babbit shavings in the oil well. Lift Barring evaluate oil journals and flush. Reseat barring, shim to factory tolerances

Last repairs by CA/US Brake San Diago CA

Brake pad damage replace x 8

Disc Pad damage replace x 8

Upstream babbit mate barring deign information #

Thrust Barring Babbit damage Remove and send out for inspection and or Babbit Repairs

Thrust barring design information.

Guide barring well. Barring Babbit Materials in the well. Each well on each barring has contamination

Barring Serial #

Guide Barring has ware and heat discoloration. Remove send out for evaluation of damage due to heat. Oil Geraniols may have blockage from contaminated revisor. Flush the oiler system remove contamination throughout the system.

Collector Ring Remove and send out for Machining surfaces back to Factory tolerances. Balance ring and reinstall. Replace all brushes and springs.

Collector ring remove and send for resurfacing

Collector ring remove resurface rebalance replace