Lawrenceburg HP Non-Return Valve Cracking

Lawrenceburg HP Non-Return Valve Cracking
and Review of Plant Start up Procedures
D. Buzza
American Electric Power
8/4/14
HP non-return valve is located within the boiler proper
HP Non-Return
Valve
HRSG HP
SH Outlet
HP Non-Return Valve
Guide
ribs
Cracking in body
located near bottom
and top of
downstream rib
Overall View of Installed Non-Return Valve
Only the valve body is shown. The hand wheel, yoke, stem, bonnet and disk have all
been removed.
Side View of installed valve
Top View
Top View - Looking into bonnet nozzle
Top View – Looking into bonnet nozzle
Seat
Guide
ribs
for
piston
Body cracking is
at top and
bottom of
downstream
guide rib.
Cracking at Bottom and Top of Downstream Guide Rib, Looking
from Above, Unit 1 HP NRV
toe
Flow
toe
Bottom
DS Guide
Rib
Cracks
Top
Close up of Bottom Cracking, Unit 1 HP NRV
Toe
Flow
Toe
Cracks
DS Guide
Rib
Close up Bottom Cracking, Unit 4 HP NRV
Flow
Cracks in the body
at bottom of rib
Guide rib
Cracks in seat
Close up of Bottom Cracking, Unit 2 HP NRV
DS Guide Rib
Cracks
Valve Seat
Close up of Top Cracking, Unit 2 HP NRV
Cracks
Flow is into the
page
DS Guide
Rib
Flow is into the
page
Close up of Top Cracking, Unit 3 HP NRV
(looking at under side)
Guide
Crack
Close up of Seat Cracking (Unit 3 HP NRV)
Body
Cracks
Seat Cracks
Body Crack Depth by Phase Array – Unit 4
Minimum diameter of flow passage = 8.625”
Valve minimum wall thickness per ASME B16.34 = 3.041”
Crack depth = 0.338”
Crack is within the valve
crotch
Crack depth = 0.495”
Actual Wall =
5.4”
Good Material = 4.905”
Min Wall =
3.041”
Response from Valve Manufacturer
• Root cause of cracking is thermal fatigue during plant
temperature transients (start-up, shutdown). The guide rib is
heating / cooling faster than the valve body.
• Cracks found in every one of their C12A Y pattern stop valves
that have been inspected. So far, +100 have been inspected
of over 300 installed. All valves were shipped between 1998 –
2012.
• Solution is to install new valve body with rib cut loose at the
bottom to allow thermal expansion of the rib.
• No clear response on the seat stellite cracking.
Measured Valve Body Thickness
(Minimum Wall = 3.04”)
Body Contour
Edwards
Atwood &
Morrill
Pacific
HP Non Return Valve Specification
Lawrenceburg
Waterford
Size, in
12
16
Type
Y-globe stop check
Y-globe stop check
Pressure Class
2500
2500
Material
A217 C12A
A217 C12A
Current Valve Min Wall, inch
3.04
3.64
Current Valve Wt, lb
4600
7010
Current Valve Cv
2200
3200
Operating Flow, klb/hr unfired
433 at 1055F, 1348 psia
417 at 1055F, 1243 psia
Operating Flow, klb/hr fired
646 at 1049F, 1971 psia
657 at 1055F, 1930 psia
Actuator
Manual w/ gear drive
Manual w/ gear drive
Equalizer
With downstream
With downstream
Comparison of Valves - Lawrenceburg
Original-Edwards
New –
Edwards
Attwood & Morrill
Crane Pacific
Velan
End to End, in
41
same
43
41
41
Cv
2200
same
2620
2650
2350
Guides
4 w/ 1 in flow path
Same, but flow
path not attached
at bottom
3 w/ 1 in flow path
3, none in flow
path
4 w/ 1 in flow path
Body Contour
3.38 min
3.92 ave
6.35 max
same
Contoured,
dimensions are
confidential
Contoured, 3.25
min, 3.81-4.19
max
proprietary
Weight, lbs
4600
same
6000
4745
5100
History w/ CC
plants (self
reported)
+300, 3”-20”
installed w/ 100
cracked
Working to
improve
+30 installed w/ 1
cracked at rib
133, 8”-24”
installed w/ no
cracks
150, 3”-28”
installed w/ 1
cracked at seat
Seat HF cracking
(self reported)
Cracking
Working to
improve
Proven procedures
Proven procedures
Second part of solution is to
reduce thermal stresses during
plant start-up / shutdown / load
changes
Lawrenceburg Unit 2 Cold Startup after 13 Days Offline
HP T increases from 115F
to 919F in 18 minutes
(45F/min).
HP Steam T, F
Temperature, F
GT Exhaust T, F
GT Start
GT Ignition &
ramp to 38 MW
GT ramp to
spinning reserve
(17MW)
Lawrenceburg Unit 4 Warm Startup after 2.5 Days Offline
Temperature, F
HP T increases from 229F
to 900F in 18 minutes
(37F/min).
GT Start
GT Ignition &
GT ramp 38MW
ramp to 24 MW
GT Exhaust T, F
HP Steam T, F
Waterford Unit 1 Cold Startup after 13 Days Offline
GT Exhaust T, F
Temperature, F
HP T increases from 212F
to 841F in 23 minutes
(27F/min).
GT Start
GT Ignition &
ramp to spinning
reserve (17MW)
GT ramp
to 38 MW
HP Steam T, F
Waterford Unit 1 Warm Startup after 2 Days Offline
Temperature, F
HP T increases from 341F
to 866F in 19 minutes
(28F/min).
GT Start
GT Ignition &
ramp to spinning
reserve (17MW)
GT ramp
to 38 MW
GT Exhaust T, F
HP Steam T, F
EPRI HP Superheater Header Life Predictions for Combined Cycle
Hot Start / Shutdowns (Report 1015464)
Start –up / Shutdown
Procedure
(GT exhaust T hold / HP
steam temp ramp rate)
Minimum Cycles to SH
Header Cracking (Thermal
Fatigue only)
Mimimum Cycles to SH
Header Cracking (Severe
Creep Fatigue Interaction)
900F hold, no ramp (Wfd)
269
27
700F hold, 35F/ min ramp
626
63
700F hold , 12F / min ramp
3,393
339
900F hold, no ramp (Wfd)
5,010
501
700F hold, 35F/ min ramp
49,410
4,491
700F hold , 12F / min ramp
>10^5
>10^4
2.5 inch thick SH Header
1.2 inch thick SH Header
SH Header Thickness: LWB = 1.5”, WFD = 2.5”
Recommended Startup Changes
• Drain condensate from SH drains at GT start. To drain the RH
drains at GT start, the RH section should be pressurized with
the HP let down valve.
• Utilize GT exhaust gas temperature matching mode. After GT
reaches spinning reserve, change GT control mode to exhaust
gas temperature matching with a 700F set point. Hold 700F
for 15 minutes to soak the HRSG and complete condensate
removal from HP and RH SH sections.
• After soak, then ramp HP steam temperature at 12F/min by
ramping GT exhaust gas temperature. Once exhaust gas
temperature reaches 1100F, then switch GT control mode to
load / speed.

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