David Wayne Gandy

US Patent:

6364971, Apr 2, 2002

Filed:

Jan 20, 2000

Appl. No.:

09/487931

Inventors:

David Wayne Gandy - New London NC
Gregory Frederick - Harrisburg NC
Jan T. Stover - Travelers Rest SC
Ramaswamy Viswanathan - Saratoga CA

Assignee:

Electric Power Research Institute - Palo Alto CA

International Classification:

B23K 2634

US Classification:

148525, 21912164, 228228

Abstract:

A method of repairing a metallic member, such as a superalloy turbine blade, includes the step of preparing the blade by stripping the protective coatings from the blade. The blade is then pre-conditioned for welding by a first hot isostatic process. Once the blade conditioning sequence is complete, the blade is welded using a laser welding technique and by adding weld fillers to the weld area. After the welding step, the blade is sealed by a second hot isostatic process treatment performed at conditions similar to the first hot isostatic process. The blade is finally prepared for re-entry into service.

US Patent:

6596957, Jul 22, 2003

Filed:

Nov 16, 2001

Appl. No.:

09/991216

Inventors:

David Wayne Gandy - Concord NC
James William Hales - Harrison TN
Kent K. Coleman - Concord NC
Gregory J. Frederick - Harrisburg NC
Richard M. Tilley - Harrisburg NC

Assignee:

Electric Power Research Institute, Inc. - Palo Alto CA

International Classification:

B23K 3102

US Classification:

219 61, 21912511, 228119, 29890031

Abstract:

A method, an apparatus ( ), and a prefabricated replacement tube ( ) are provided for repairing a defect ( ) in a tube ( ), such as in a waterwall ( ). In the method, a replacement tube ( ) is prefabricated having a wall ( ), a central opening ( ) extending through a portion thereof, and a predetermined length. A length of the tube ( ), including the defect ( ), equal to the predetermined length is removed. The replacement tube ( ) is positioned between stubs ( ) of the tube ( ), and a rotatable torch ( ) of an automated welding apparatus ( ) inserted through the opening ( ) to align with a joint between an end ( ) of the replacement tube and a stub ( ). The torch ( ) is rotated to join it to the stub ( ) along the entire joint. The torch ( ) is then removed, turned 180 degrees, and reinserted to weld the remaining joint. Optionally, the replacement tube ( ) is held in position before welding by slip rings ( ) which are slid down to cover the joints.

US Patent:

6673169, Jan 6, 2004

Filed:

Apr 1, 2002

Appl. No.:

10/115204

Inventors:

David Wayne Gandy - New London NC
Gregory J. Frederick - Harrisburg NC
Jan T. Stover - Travelers Rest SC
Ramaswamy Viswanathan - Saratoga CA

Assignee:

Electric Power Research Institute, Inc. - Palo Alto CA

International Classification:

B23K 1002

US Classification:

148524, 148525, 228119

Abstract:

A method of repairing a metallic component, such as a superalloy turbine blade or turbine nozzle, includes the step of preparing the component by stripping the protective coatings from the component. The component is then pre-conditioned for welding by a first hot isostatic process. Once the conditioning sequence is complete, the component is welded using any of a number of welding techniques and by adding weld fillers to the weld area. After the welding step, the component is sealed by a second hot isostatic process treatment performed at conditions similar to the first hot isostatic process. The component is finally prepared for re-entry into service.

US Patent:

6884959, Apr 26, 2005

Filed:

Sep 7, 2001

Appl. No.:

09/949472

Inventors:

David Wayne Gandy - Concord NC, US
James William Hales - Harrison TN, US
Roger Allen Swain - Harrisburg NC, US
James Franklin Turner - Signal Mountain TN, US
Ramaswamy Viswanathan - Saratoga CA, US

Assignee:

Electric Power Research Institute, Inc. - Palo Alto CA

International Classification:

B23K009/04
B23K009/18
B23K009/12

US Classification:

219 7614, 219 7321

Abstract:

This invention relates to a method and apparatus for controlling the composition of a weld. More particularly it relates to welding using an electric circuit, thereby creating a weld puddle, and adding at least one filler that is electrically independent from the electric circuit to the weld puddle at a controllable rate to obtain a target weld composition. The filler can be added to the extent limited by practical weld puddle geometry and, thus, the method and apparatus also facilitate increased weld deposition rates.

US Patent:

7371988, May 13, 2008

Filed:

Oct 22, 2004

Appl. No.:

10/972249

Inventors:

Kent K. Coleman - Concord NC, US
David Wayne Gandy - Concord NC, US
Ramaswamy Viswanathan - Saratoga CA, US

Assignee:

Electric Power Research Institute, Inc. - Palo Alto CA

International Classification:

B23K 9/067

US Classification:

219 50, 228230, 228232, 2282481, 148521

Abstract:

In one embodiment, the present invention provides a method for welding together two metal pieces, comprising buttering a surface of a first metal piece with a first nickel-based filler metal at a thickness sufficient to isolate a heat-affected zone in the first metal piece from subsequent welding; heat-treating at least the heat-affected zone in the first metal piece; buttering a surface of a second metal piece with a second nickel-based filler metal having the same composition as the first nickel-based filler metal and at a thickness sufficient to isolate a heat-affected zone in the second metal piece from subsequent welding; heat-treating at least the heat-affected zone in the second metal piece; and welding the heat-treated first buttered surface to the heat-treated second buttered surface with a third nickel-based filler metal having the same composition as the first and second nickel-based filler metals.

US Patent:

7484651, Feb 3, 2009

Filed:

Oct 22, 2004

Appl. No.:

10/972247

Inventors:

David Wayne Gandy - Concord NC, US
Gregory J. Frederick - Harrisburg NC, US
Andrew McGehee - Harrisburg NC, US

Assignee:

Electric Power Research Institute, Inc. - Palo Alto CA

International Classification:

B23K 20/00

US Classification:

228193, 228128, 228119

Abstract:

Accordingly, the present invention provides a method for joining metallic members, which can be used to join component sub-assemblies. Further, the present invention provides a method for repairing a component by replacing a damaged portion and re-inserting a replacement section. In general, the present invention provides in one embodiment a method for joining metallic members comprising: preparing a surface of a first metallic member, thereby providing an oxide-free surface; preparing a surface of a second metallic member, thereby providing an oxide-free surface; applying pressure to the first and second metallic members, thereby forcing the surface of the first metallic member and the surface of the second metallic member together and forming a joint area; sealing an outer edge of the joint area; and subjecting the members to a hot isostatic process operation.

US Patent:

7547859, Jun 16, 2009

Filed:

Feb 28, 2006

Appl. No.:

11/364604

Inventors:

David Wayne Gandy - Concord NC, US
Greg Frederick - Harrisburg NC, US
Kent Coleman - Concord NC, US

Assignee:

Electric Power Research Institute, Inc. - Palo Alto CA

International Classification:

B23K 31/00
B23K 9/28
B23K 37/02
B23H 9/00

US Classification:

219 61, 2940207, 29890031, 219 6917, 219 692

Abstract:

A method for repairing a heat recovery steam generator (HSRG) header to tube attachment damage, includes providing an access window in the header opposite the damaged header to tube attachment location; removing the header to tube attachment damage; inserting a tapered stub tube into a header penetration centered axially immediately over the tube; effecting a profile weld between the header and the tapered stub tube at the header penetration from the inside surface of the header; welding the tapered stub tube to the existing tube through the header inside diameter; welding shut the access window; and completing a post weld heat treatment of all the welds.

US Patent:

7562807, Jul 21, 2009

Filed:

May 5, 2004

Appl. No.:

10/839863

Inventors:

Kent K. Coleman - Concord NC, US
David Wayne Gandy - Concord NC, US
Ramaswamy Viswanathan - Saratoga CA, US

Assignee:

Electric Power Research Institute - Palo Alto CA

International Classification:

B23K 35/00
C22C 19/05

US Classification:

22826241, 420442, 420452, 420453

Abstract:

Accordingly, the present invention provides a weld filler composition for joining different alloy steel pieces with substantially different chromium content, such as joining low alloy ferritic steel to high alloy ferritic steel, low alloy ferritic steel to austenitic stainless steel, or high alloy ferritic steel to austenitic stainless steel, and a method using the same. In one embodiment, the present invention provides a composition for a weld filler comprising nickel, iron, and chromium, which collectively comprise at least 50% by weight of the weld filler; niobium, carbon, manganese, molybdenum, and silicon, which collectively comprise no more than 50% by weight of the weld filler, and a niobium to carbon ratio of approximately 20 or less.