FIELD PERFORMANCE OF

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1 FELD PERFORMANCE OF EROSON RESSTANT MATERALS ON BOLER NDUCED DRAF' FAN BLADES TENNESSEE VALLEY AUTHORT!if KNGSTON FOSSL PLANT May 1993 Prepared by TENNESSEE VALLEY AUTHORTY RESOURCE GROUP RESEARCH AND DEVELOPMENT GENERATONS PROJECTS DEPARTMENT PRNCPAL NVESTGATORS 0. F. Karr, Mechanical Engineer Generation Projects Department Research and Development J. B. Brooks, Metallurgist Generation Projects Department Research and Development Ed Seay, Manager of Modifications Kingston Fossil Plant

2 DSCLAMER This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, make any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

3 DSCLAMER Portions of this document may be illegible in electronic image products. images are produced from the best available original document.

4 CONTENTS ntroduction... 1 Results Recommendations... 3 Erosion resistant material cost comparison... 4 Photographs of Conforma Clad WC200 test blades Photographs of Kinton Carbide test blades... 7 Photographs of ATC Metadur 11 test blades... 8 Photographs of Stoody test blades... 9 Sketch of Kingston fan blade with recommended coating Sketch showing Kingston fan blade fabrication details Erosion resistant material suppliers Fan design data for units

5 ' FELD PERFORMANCE OF EROSON RESSTANT MATERALS ON BOLER NDUCED DRAFT FAN BLADES TENNESSEE VALLEY AUTHORTY KNGSTON FOSSL PLANT MAY 1993 NTRODUCTON The!WA Kingston F o s s i l Power P l a n t has nine u n i t s and i s l o c a t e d near Kingston, Tennessee. U n i t s 1 through 4 have a r a t i n g of 148 MW and u n i t s 5 through 9 have a r a t i n g of 197 MW. Each u n i t has two induced d r a f t fans manufactured by Westinghouse E l e c t r i c Corp., S t u r t e v a n t Division. A table showing design d a t a f o r t h e induced d r a f t f a n s i s l o c a t e d on page 16 of t h i s r e p o r t. The f a n blade design d e t a i l s f o r u n i t s 5 through 9 are shown on pages 11 through 14. There i s a mechanical f l y ash c o l l e c t o r and a s m a l l electrostatic p r e c i p i t a t o r preceding t h e induced d r a f t f a n s i n t h e b o i l e r f l u e gas stream and a l a r g e, e f f i c i e n t e l e c t r o s t a t i c p r e c i p i t a t o r downstream of t h e s e fans. The steam generators and p u l v e r i z e r s w e r e supplied by Combustion Engineering. The average temperature of t h e f l u e gas i s about 340 degrees Fahrenheit f o r u n i t s 5 through 9. A l l induced d r a f t f a n s i n t h e b o i l e r f l u e gas stream experience erosion from f l y ash. When t h e p r e c i p i t a t o r s and f l y ash c o l l e c t o r s w e r e new t h e f a n blades would l a s t about t h r e e y e a r s before t h e y w e r e eroded s e v e r e l y and had to be replaced. Kingston P l a n t personnel say t h e f l y a s h c o l l e c t o r s are p r e s e n t l y i n need of major r e p a i r s ; t h e r e f o r e, t h e f a n blades are not expected t o l a s t as long as they d i d when t h e p l a n t was new. Between February 8, 1987 and August 25, 1989, Research and Development and Kingston performed a f i e l d t e a t on twelve d i f f e r e n t e r o s i o n r e s i s t a n t m a t e r i a l s. The r e s u l t s of t h i s t e s t w e r e published i n t h e TVA r e p o r t Number TVA/PBO/R&D-90/5 t i t l e d "Erosion R e s i s t a n t Material F i e l d T e s t Report, Kingston F o s s i l P l a n t Unit 9 "B" nduced D r a f t Fan Blades", dated August n t h e above test, chrome carbide weld overlays, vacuum bonded ceramic t i l e s, mechanically bonded coatings, and fused c o a t i n g s w e r e t e s t e d. The fused metallic coatings o f f e r e d t h e g r e a t e s t p r o t e c t i o n from f l y ash e r o s i o n and t h e mechanically bonded coatings o f f e r e d t h e least amount of p r o t e c t i o n. Many of t h e ceramic t i l e s came o f f e a r l y i n t h e test and permitted t h e blades t o erode severely. The chromium c a r b i d e and vanadium tungsten weld overlays eroded s e v e r e l y on t h e i n l e t edges of t h e blades. Stress cracks t h a t w e r e i n t h e weld overlays w e r e also deepened and widened by f l y ash erosion. The material t h a t performed b e s t was t h e Conforma Clad WC200 fused coating. This coating was made up of 69 t o 73% tungsten carbide, 15% chromium, 3.5% boron, less t h a n.1% carbon and t h e balance nickel. The WC200 coating performed b e t t e r t h a n t h e o t h e r coatings but it w a s a l s o more expensive than weld overlays. n t h e t h e s p r i n g of 1990 it w a s decided t o i n s t a l l t h e WC200 c o a t i n g on a f u l l set of blades i n one f a n (120 blades t o t a l ). n an e f f o r t t o minimize c o s t it w a s decided t o i n s t a l l t h e coating only on t h e area of t h e blades which experience severe erosion (see t h e photographs on page 5). The t o t a l c o s t of t h i s c o a t i n g was $12,000 f o r 120 blades ($100 p e r b l a d e ).

6 Kinton Carbide installed tungsten carbide platelets on four test blades in another induced draft fan in the summer of The tungsten carbide platelets were silver soldered to the blades only in the area where the maximum amount of erosion was expected. Kinton Carbide estimated it would cost $16,680 ($139 per blade) to install tungsten carbide platelets on 120 blades similar to the four test blades. n February 1992 Applied Thermal Coatings, nc. (ATC) installed a coating, Metadur 111, consisting of 80% tungsten carbide, on 240 fan blades for a cost of $22,800 ($,95 per blade). One set of blades (120) were installed in the unit 5 "A" induced draft fan in March 1992 and one set in the unit 7 "A" induced draft fan in May The ATC Metadur 11 coating covered the same area of the blades the Conforma Clad WC200 and Kinton Carbide cladding covered. We learned from inspections of the Kinton Carbide and Conforma Clad test blades (see photographs on pages 5, 6, and 7) that we should, in the future, protect more area of the blades from erosion. Jim Weedman, District Manager of the Stoody/Thermadyne Welding Company, claimed the Stoody MG welding wire (60% tungsten carbide) would produce weld overlay that would be as resistant to solid particle erosion as the Conforma Clad and ATC coatings. The weld overlay could also be weld repaired in the field during a scheduled maintenance outage. After receiving a cost estimate from Consolidated which showed the Stoody weld overlay would cost less than the Conforma Clad WC200 and the ATC Metadur 11 coatings, Kingston and R&D decided to install Stoody weld overlay on a set of fan blades for a Kingston induced draft fan. These test blades were installed in a Kingston induced draft fan during the summer of During the fall of 1992, a set of fan blades with the Stoody weld overlay was installed in a Widows Creed unit 7 induced draft fan. RESULTS n April 1992 the blades with the WC200 Conforma Clad were inspected after being in operation for 20 months (see photographs on page 5). nspections of these blades indicated a need for cladding a greater area of the blade than was cladded. The area near the blade ear was eroded severely and was weld repaired with weld overlay. This fan was then placed in operation for about 10 more months before the blades were replaced. At the end of this operating period the blades were eroded so severely that two blades failed and were thrown from the fan rotor (see photographs on page 6). t appeared that during this 10 month operating period there was two or three times as much fly ash erosion of the blades as there was during the preceding 20 month operating period. This higher rate of erosion (4 to 6 times higher than normal) was caused by a decrease in the performance of the fly ash collectors preceding the induced draft fans. The blades with the Kinton Carbide cladding were eroded near the ear and directly behind the Tungsten Carbide cladding (see photographs on page 7). An inspection of these test blades again indicated that there was a need to protect more area of the blade. f more area of the blade is protected it appears the life of the blade could be tripled or quadrupled. Kinton Carbide quoted $44,400 to clad a set of blades (120 blades at $370 per blade) for a Kingston fan. This quotation included covering a larger area of the blades with tungsten carbide platelets than was covered on the four test blades.

7 On February 8, 1993, a f t e r u n i t 5 a t t h e Kingston P l a n t had been i n operation f o r about 10 months, it w a s taken o u t of s e r v i c e. The t e s t blades i n t h e "A" induced d r a f t f a n with t h e ATC Metadur 11 c o a t i n g s w e r e replaced with blades made of conventional m a t e r i a l. The t e s t blades w e r e s e v e r e l y eroded i n t h e area near t h e blade e a r s where t h e r e w a s no c o a t i n g (see photographs on page 8 ). t appeared t h e ATC Metadur 11 c o a t i n g may t may p o s s i b l y t r i p l e d t h e l i f e of have doubled t h e l i f e of t h e s e blades. t h e blades i f more area of t h e blade i s covered with t h i s coating. The Kinton Carbide and Conforma Clad WC200 cladding caused an a c c e l e r a t e d rate of e r o s i o n i n t h e base metal near t h e edges of t h e cladding (see t h e photographs on pages 6 and 7 ). This w a s probably due t o t h e cladding t h i c k n e s s being a s t e p change from t h e base metal which caused t h e f l y ash t o c u t a p a t h (channel) down t h e edge of t h e cladding. The Metadur coating t h i c k n e s s t a p e r e d off a t i t s edges and d i d not cause t h i s channeling e f f e c t (see t h e photographs on page 8 ). RECOMMENDATONS t i s recommended t h a t t h e ATC Metadur 1 (50%tungsten c a r b i d e ) coating (0.040" t h i c k ) be i n s t a l l e d over t h e a r e a of t h e blades t h a t experience severe e r o s i o n (about 20% of t h e blade's concave s u r f a c e ) and t h e Metadur 11 (80%tungsten c a r b i d e ) coating (0.020" t h i c k ) be i n s t a l l e d over t h e Metadur 1 c o a t i n g i n t h e area experiencing m a x i m u m e r o s i o n ( a b o u t 6% of t h e blade's concave s u r f a c e ). This c o a t i n g arrangement is shown on page 10 and cost about $12,000 t o i n s t a l l on 120 blades of a Kingston f a n ($100 p e r blade). The Conforma Clad WC200 m a t e r i a l i s very erosion r e s i s t a n t and t h e r e f o r e should be r e t a i n e d i n t h e f u t u r e a s an a l t e r n a t e method f o r e r o s i o n p r o t e c t i o n. The c o s t f o r i n s t a l l i n g t h e Conforma Clad WC200 c o a t i n g over 120 blades of a Kingston f a n i s $18,480 ($154 p e r b l a d e ). The above c o s t i s f o r i n s t a l l i n g a coating (0.030" t h i c k ) over t h e area of t h e blades shown on t h e sketch on page 10. f t h e Stoody weld overlay proves t o be s a t i s f a c t o r y it may be considered an a l t e r n a t e method of p r o t e c t i n g t h e f a n blades from f l y ash erosion. A t t h e time of t h i s r e p o r t, t h e test blades w i t h t h e Stoody weld overlay had not been inspected. The c o s t f o r i n s t a l l i n g t h e Stoody on 120 blades of a Kingston f a n w a s $13,024 ($ p e r b l a d e ). t is expected t h a t t h i s price could be reduced i n t h e f u t u r e with l o w e r cost M G welding w i r e. The Kinton Carbide tungsten carbide material i s very r e s i s t a n t t o f l y ash erosion but it i s t h e highest c o s t blade p r o t e c t i o n t e s t e d. Kinton Carbide estimates it would c o s t $370 p e r blade t o provide s a t i s f a c t o r y p r o t e c t i o n from f l y ash erosion. This c o s t includes covering about 76 square inches of t h e blade with.0625 inch t h i c k tungsten carbide platelets. -3- ~

8 $/SQUARE NCH 6 FAN BLADE PROTECTON COST 5 f KNTON ATC 111 wc200 M AT E R AL ATC KF-FAN -4-

9 UNLT-5 "B" NDUCED DRAFT' FAN BLADES Test period: June to February Condition of the Conforma Clad WC200 Tungsten Carbide coating after operating about 20 months. The coating protected the fan blades from erosion except for a small area at the edge of the blade where the coating is starting to come off, There is also an unprotected area at the side of the blade that eroded and was weld repaired. The cost of this coating was $12,000 for 120 Kingston fan blades 100 Der bl

10 ...-.-_. UNT-5 '%'' NDUCED DRA3FT FAN BLADES Test period: June 24, 1990 to February 8, 1993 Condition of the Conforma Clad WC200 Tungsten Carbide coating and fan blade base metal after operating about 30 months. The coating protected the fan blades from erosion in the area it is installed except for an area of severe erosion near the inlet edge. The coating cost: $12,000 for 120 blades ($100 per blade). -6-

11 UNT-7 "B'l NDUCED DRAFT FAN BLADES Test period: September 29, 1990 to April 24, 1992 Two fan blades withkinton Carbide Tungsten Carbide platelets after operating about 19 months. The Tungsten Carbide protected the blades from erosion in the areas it was installed. Some Tungsten Carbide platelets came off the inlet edge of the four test blades. The unprotected area of the blade downstream from the Tungsten Carbide eroded severely (it eroded through the first layer of the 3/8" thick steel blade at the points shown by the arrows). Cost: $16,680 for 120 blades ($139 per blade). -7-

12 UNT-5 "A" NDUCED DRAFT FAN BLADES Test period: April 12, 1992 to February 8, 1993 Condition of the ATC Metadur 11 80% Tungsten Carbide coating and fan blade base metal after operating about 10 months at 4 to 6 times the normal erosion rate. The coating reduced solid particle erosion and made the blade last about twice as long as it would have lasted without the coating. The coating cost: $11,400 for 120 blades ($95 per blade). -8-

13 UNT-7 'B" NDUCED DRAFT FAN FAN BLADE EROSON PROBLEM A fan blade before it was placed in service with a 60% Tungsten Carbide weld overlay on the area that experiences fly ash erosion. Two layers of weld overlay are installed on the area that experiences severe erosion. The weld overlay is made from 1/16 inch diameter Stoody mig welding wire. The contractor was Consolidated Metal Services, nc. The cost was $13,024 for 120 blades ($109 per blade) for a Kingston fan and $17,572 for 128 blades ($137 per blade) for a Widows Creek unit-7 fan. Test S t a r t : June 19,

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19 EROSON RESSTANT MATERAL SUPPLlERs Conforma Clad Michael D. Reeder Regional Sales Manager W. Alameda Pkw. Suite 200 Lakewood, Colorado (303) Fax: (303) Customer Service: (812) Fax: (812) Consolidated Metal Services, nc. Jim Wilbanks (615) Vice President/General Manager Fax: (615) E. 10th St. P. 0. Box 568 Chattanooga, Tennessee Applied Thermal Coatings, nc. Harley A. Grant (615) President Fax: (615) Rossville Boulevard (Rear) Chattanooga, Tennessee Kinton Carbide Gilmer Supply Company Harry U. Gilmer Sales Representative P.O. Box 1104 Birmingham, Alabama (205) Fax: (205) Whispering Pines Circle Hoover, Alabama

20 FAN DESGN DATA UNTS 5-9 NumberofnducedDraftFans...2 nduceddraftfantype...16mvd Fanratedcapacity(CFM)...400,000 Rated static pressure attest block (inches of water) Fan Speed (,M)...~