Hydro Electric Turbines & Valve

Periodically, all hydroelectric turbines require a major overhaul. The extent of the work required during an overhaul will depend a great deal on operating conditions such as water quality and how the unit was loaded. Our experience can be an asset to your organization for your shutdown. In order for the overhaul to proceed smoothly and to accomplish all the work required, planning should start well before the overhaul starts. Based on the inspection of the unit and on the discussions during the scheduling meeting, a list of required materials, tools, and services should be made. Bender U.S. can help with this planning and will do so in advance of your turnaround typically free of charge. We recommend utilizing our experience because we guarantee that we can save you time and money. The specifications for materials and tools required for the overhaul should be prepared as well as "Statements of Work". Bender U.S. has experience reworking worn or damaged turbine components as well as designing and manufacturing replacement most components.

It is helpful to obtain reports of previous overhauls since they can prevent the same mistake from being made twice and may provide tips that can expedite the overhaul procedure. The maintenance files may also provide names of sources for parts and materials.

 

Turbine runner: Check each bucket carefully for cavitation damage and cracks. If possible, use die penetrant or other nondestructive test to check for cracks. Compare seal ring clearance readings with design clearances. Bender has several large vertical mills which can be utilized to inspect runouts, concentricity, and skim cut runner as needed to repair areas as needed.

Wear Rings: Bender manufacturers wear rings up to 18 feet in diameter for replacement on Francis and Kaplan type runners. Bender U.S. has access to affordable Ring Rolling mills in the United States and Mexico with a proven track record for providing high quality rough rings for the both the upper and lower head cover as well as the runner.

Wicket gates: If sealing surfaces are uneven or damaged, they should be repaired by welding and machining back to drawing dimensions. The heel and toe sides of the gate should both be measured when checking the top and bottom clearances. If journals are worn at the bushing areas as they typically are Bender U.S. can thermal spray these areas with several coatings to aid resize them. Chroming is also an option however with current advances in thermal spray coatings the cost can be competitive as well as quicker thereby reducing the outage window. Bender U.S. has manufacturer’s representative agreements with an overseas casting plant used by Alstom power and others to cast new wicket gates. At our Los Angeles factory we can finish machine these components and prepare them for installation into the reconditioned turbine.  

 Wear Plates: Check condition of facing plates looking for any galling or wear from contact with the wicket gates. If the facing plates are severely damaged, they will require replacement or resurfacing. It is advised that whenever replacing wear plates that you rough the plates in preparation of the turnaround and do not finish them to original print dimension so that some wear can be made up in this area. In addition the breakaway cap screw holes should not be cut until the old plates can be removed and used as guides for location the true coordinate position. It is likely that the prints provided by the manufacturer are manufacturing drawings and are not the exact location of actual patch bolts in the plates. Bender U.S. can aid in the inspection of these plates using coordinate mapping technology and transfer such coordinates to CAD software for drilling of patch bolt holes.

Wicket gate operating linkage and Pins: Bender U.S. can assist with the dimensional inspection of these components and advise on the appropriate replacement parts and industry standard repairs. During the design phase of the project Bender U.S. will make sample breakaway pins and link pins to be destructively tested to determine compliance with OEM and industry standards. This is a critical step to ensure the parts give as required to avoid damage to the turbine and creating a hazardous condition.

Wicket Gate Bushings: Bender U.S. is an authorized distributor of Oiles America lubeless wicket gate bushings. Please contact us to coordinate a presentation on the advantages of using Oiles for your turbines. It is common place to replace lubed bushings during an overhaul to reduce pollution by grease into the water supply. Many options are available these days and not all lubeless bushings are created equal so be careful in your selection. Our experience both onsite and in the shop can prevent the reordering of costly components due to dimensional problems. Remember to figure the line boring of wicket gate bores into your planning so as to avoid under sizing your replacement parts.

Other Services: Packing box fabrication, Shift ring sleeve fabrication, shift ring surface and bore resizing, turbine shaft machining, fusion Babbitting of guide and main bearing, thrust plates, thrust collar grinding and others. Please call to discuss our shop and field service capabilities.

Valve Services:

Bender U.S. has experience overhauling all types of valves that are used in municipal water systems and on hydro-electric projects. Rather than replacing your valves we can repair them at a fraction of the cost (typically 1/3 to 1./2) to like new condition. We recommend this approach with all valves greater than 36” in diameter. We offer the following services:

 

·         Seat Ring Manufacturing

·         Valve body mating surface restoration

·         Weld overlays on worn areas

·         Shaft thermal spray / chroming services

 

·         Complete Turnkey Overhauls

·         Onsite removal and installation

·         Field Machining of Mating Flange Faces

·         Shop Hydro and Mechanical Testing

 

·         Replacement bushings

·         Rubber seat replacement

·         Blasting, Coating, and Lead Abatement

 

Types of Valves: