Repowering T-2, Woronoco's Low Flow Turbine

Woronoco Hydro is licensed by FERC for 2,700 kW, which includes two  450 kW Francis turbines, both abandoned in the 1980's.  Installed as low-flow turbines to operate in summer when flows in the Westfield River were too low to power T-3, the 1,800 kW turbine.  This turbine generates at about 1,650 kW without the 30" of flashboards that were omitted from the license when IPC renewed the FERC license in 2001. The existing plant utilizes less than the mean flow of the Westfield River.  So the project  would benefit by rehabilitation of the two 450 kW horizontal Francis units that have not operated since the early 1980's.

Woronoco Hydro has contracted Swift River Hydro Operations Company (SRHOCO) to rehab the two units. Both had seized tight with silt and rust during their idle years. Before beginning the job, SRHOCO had to build a stoplog gate to dewater the penstock to check the integrity of the butterfly gate on each pressure chamber and to determine whether the runners were sound enough to warrant rehabilitation.  The two Westinghouse generators tested well and new solid state exciters and switchgear were part of the proposed design. We start our picture report of T-2's rehabilitation, by showing you a panorama of the old powerhouse.

T-2's generator is located near the center of the photo with its pressure case behind the yellow ladder.

Currently, Woronoco Hydro plans to repower both turbines because the CT DPUC approved repowering of these two Woronoco units' as qualifying for Class I REC generation.  Also, MTC selected Woronoco Hydro's repowering project in Round 2 of the MGPP solicitation for 10-year REC contracts.  This contract will allow Woronoco to completely refinance its project, rebuild the four runners, reline the penstock, build a new substation, build an intake gate, and re-install flashboards on the dam to increase all three turbines' capacity.  The repowering project started in the fall in 2005 with installation of a new interconnection with WMECO next to the powerhouse and restoration of T-2 as the low flow unit.  Woronoco has begun analysis of the impact on the impoundment of restoring flashboards on the dam and will file it with the resource agencies and FERC.  A report of the recent smolt passage testing was sent to FERC in October 2005 and eel passage facilities will be installed this fall.  When the financing closed, Woronoco Hydro ordered the automatic intake gate constructed by Steel-Fab and new trashracks from SRHOCO. The penstock relining will be carried out in the fall of 2006. Then, in 2007, installation of an automatic trash rake and a rubber flap gate on the dam crest plus dredging of the gravel bar from the tailrace pool is planned.

We will streamline our description of the initial rehab of T-2 by annotating a picture story of the work's progress.  SRHOCO began by disassembling the generator, flywheel,  wicket gate control arm, sector gear, generator shaft bearing pedestal and finally the end of the pressure chamber. These components were stored in the laydown area of the station.

With the generator out of the way, the flywheel and bearings for the shaft must be removed.

Removing the coupling and fly wheel from the generator shaft.

End plate removed from the pressure chamber revealing the wicket gate case of one runner.

Lifting the camel back up over the gatecase and T-2 runners.

The first of two Leffel Francis turbines emerges in good condition, but wickets must all be replaced.

Pressure case is relined with 3/8" steel plate and between plate void is filled with special compound.

Preparing to drop into the draft tube to weld plate over holes. Note new welded steel lining of chamber.

Into the underworld with welding torch in hand.

T-2 runners cribbed up ready for trip to Chicopee Welding shop to be tempered.

                        (1)                                                        (2)                                                (3)

(1)  After welding to strengthen damaged blades, the turbine was treated with slippery Belzona coating.

(2)  New wicket gates were caste, machined and bronze bushings were pressed into place and aligned.

(3)  Bearing surfaces were polished and new bearing blocks cut and installed in the pressure case.

Recoated and like-new runners on lathe in SRHOCO's machine shop to turn bearing surfaces.

SRHOCO rigs the T stand back into the rebuilt and strengthened T-2 pressure case.

Reconditioned turbines being returned to the T-2 pressure chamber.

Swinging the camel's hump over the refurbished runner, to set it on the T-stand.

Putting the hump back on the camel leave too little room for comfort.

Threading the end plate bolt collar over the end of the turbine shaft

Mixing the special grout to be inserted between the new and old steel plates of the pressure case

Moving the goop into the powerhouse for lifting to pour into the funnels

How will be get the goop to settle?  Hit it with a sledgehammer and it will slump!

Fully reassembled, time to install run-or-river and exciter circuits before testing the new unit

Cutting loose the injection funnel for internal grout between two layers of pressure case

Button down the hatch to pressure case and prepare to fill the penstock

Finally turning slowly, Dave says it is too hot to touch; is this bearing heating up?

Ken says this bearing is cool at the back, tightened to much at the front end

Willy keeps it cool during the bearing's initial wearing-in of the new babbit surfaces.

The start up was a great success, but T-1 (left foreground) remains as the next challenge. SRHOCO's skills are demonstrated by the rehab of T-2, whose capacity tested out at 500 kW due to increased efficiency resulting from careful redesign in the shop.

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