ML20031D276
| ML20031D276 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 08/31/1981 |
| From: | ALLIS-CHALMERS CORP. |
| To: | |
| Shared Package | |
| ML20031D275 | List: |
| References | |
| ER-8102, NUDOCS 8110130202 | |
| Download: ML20031D276 (8) | |
Text
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AE.US-CHA8.MGERS POWEER BYSMW sw r
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ENGINEERING REPORT ER-8102 CRITICAL CRACK SIZES OF COMANCHE PEAK LP TURBINE DISKS i
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August,1981 l
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I FR711MiNMiY -
PROPRIETARY INFORMATION OF ALUS CHALMERS POWER SYSTEMS.INC.
Not to be reproduced, coped or disseminated wethout the express praor written consent of Alles Chalmers Pomr Systems. Inc.
l 8110130202 811005 PDR ADOCK 05000445
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ALL18-CHALMERS PCWVER SYSTEl% HIE,IIMC, i
ER-8102 (8/81) r 3
Critical Crack Evaluation Evaluations of the critical crack sizes a have been performed for disks #1 through c
- 5 of the four LP turbine flows of the Comanche Peak units under the following assumptions:
1.
The stress calculations for the disks of the Comanche Peak LP turbines are performed with a two-dimensional computer program.
Finite-element calcu-lations, however, are performed for each prototype disk to develop the basis for the two-dimensional computation.
2.
Calculations of the local stress concentrations at the keyways are based on finite-elenent computation. Jihis evaluation considers the plastic deformation in the vicinity of the keyway during the overspeed test at 125% rated speed. This plastic deformation has been utilized to define the stress distributions in the keyway vicinity at rated and 120% speed.
The resulting stresses are the basis for the evaluation of the stress intensity.
3 Evaluation of the relationships of the stress intensity versus the crack depth was performed by an analytic method utilizing the WESTERGAARD func-l l
tions or the integration method BETSY, both of which are computer pro-i grammed. The result is shown in Figure 1E81.137 indicating the high stress in the immediate vicinity of the keyway after the 25% overspeed test.
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can be seen that after reaching a peak at a depth of about one-half inch l
the stress decreases with increasing crack depth. The stress intensity, however, shows a sustained increase as the crack grows. While the above figure shows results of disk #5 for rated speed operation, all other disks yield similar resalts.
PREllMU!ARy l
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The fracture toughness was cale :ated in accordance with the method defined by ROLF & NOVAK from the yleid strength tests and the notch impact tests performed on the disk material. The maximum and minimum values shown in Figure IE81.159 are derived from tests on the Comanche Peak disks. The maximum values for disk #1 reflect the best results from all four #1 disks of the Comanche Peak 4-flow LP turbine. The minimum values are the lowest mechanical properties measured in any of the four #1 disks. The same method has been used for disks #2 through #5 It is of importance that the yield strength and notch impact tests were performed at 20*C (68'F) ambient temperature and some even at -20*C (N 7'F).
No corrections were performed for the actual operating temperature.
5 Shown in Figure 1E81.159 are the resultant critical crack sizes for the Comanche Peak LP turbine disks.
Minimum and maximum values are given for rated speed and 20% overspeed. The calculation assumes a crack shape with a crack length L which is four times larger than the critical crack depth (a = 1/4L). Minimum and maximum crack depths are derived from the minimum and maximum fracture toughness, respectively.
Calculations up to a crack depth of 3.94 in, were performed.
Critical crack depths in excess of 3.94 in. are tabulated as 3.94 in, cracks.
Critical crack depths were calculated and are listed for the keyway and hub vicinity of the disks.
Data to Assess Crack Growth i
For evaluating stress-corrosion cracking and crack growth risks, design features and manufacturing methods should be taken into consideration. The manu-facture and quality assurance for our disk-type rotors have been described in our PRELIMINARY l
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Al s se-CHAl MGM8 POWGM SYB'r&EM M r
3 The engineering report, ER-504, which includes the horizontal shrinking procedure.
lubricant used during the shrink-on process of the Comanche Peak disks was DAG156 purchased from the Deutsche Acheson GmbH in Ulm, West Germany.
The lubricant is a product of the U. S. Acheson Company in acco dance with the U. S. specification MIL-t-24131B.
It !3 a graphite-base lubricant with an isopropyl alcohol binder and specified solid substance of 3.3% i 0.5%.
Maximum values of specified compositions within the solid substance are:
Ash 0.75%
Fluorine 20 PPM Chlorine 200 PPM Sulfur 200 PPM Lead 150 PPM The shrunk-on disk and the locking pin design are depicted in Figure 1E81.160 indicating that only the disk center, about 60% of the disk hub width, provides the actual shrink fit. The locking pins and their keyways are actually aside from the shrink fit, providing a shrink fit area without any stress concentration.
Five locking pins are provided equally spaced at the circumference of the disks' exhaust sides. After the disks are shrunk on, the 20mm keyways for the ? locking pins are drilled into the shafts and disks. To eliminate high stress concentrations at the bottom ends of these keyway bores, large radial relief grooves have been machined in both the disks and shafts, as shown in Detail A of Figure 1E81.160. The large-radius relief grooves not only minimize the stress concentration at the keyway bottom ends but also provide an area without shrink stresses in the keyway vicinity.
PREL!MINARY J
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ER-8102 (8/81)
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To assess stress-corrosion of the Comanche Peak LP turbine disks, it is im-portant to note that we have inspected nuclear turbine disks in the past s.ithout finding a single disk crack.
For the performance of stress-corrosion crack-growth evaluations, the following 1
temperatures are the values calculated as the expected steady-state metal tempera-tures at the shaft-to-disk shrink fit during operation of the Comanche Peak unit with rated steam conditions:
Disk 1 Admission / Exhaust 356*F/284"F Disk 2 Admission / Exhaust 284*F/225*F Disk 3 Admission / Exhaust 225*F/192"F I
Disk 4 Admission / Exhaust 192*F/158*F Disk 5 Admission / Exhaust 158 F/167*F a
l Attachments:
Drawings:
1E81.137 1E81.159 1E81.160 I
PREL!fA! NARY- }
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REVISION Stress 6 4
/ g/ W b
C d
e Stress Intensity K g
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s 25 Crack Depth a(in.)
Ej8~8l Keyway b* z H Diameter 0.79 in.
PREllf.1? NARY l
STRESS AND STRESS INTENSITY VERSUS CRACK DEPTH IN Z",7"Ok7,'0". m KEYWAY VICINITY OF NUCLEAR LP TURBINE I
DISK #5 AT RATED SPEED 1E81.137 l
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O Tangential Stresses at Disk Hubs for Various Speeds in Ksl:
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l Disk #1 Disk #2 Disk #3 Disk #4 Disk #5 b
Zero Speed 60.5 61.9 56.1 61.3 59.3 lC Rated Speed 76.4 80.0 71.8 79.3 77.3 M
1.2 X Rated Speed 83.4 88.0 78.7 87.2 85.1 l0f Fracture Toughness Min. and Max. Values I
from Measurements on all Comanche Peak #1 and 2 LP Turbine Disks in Ksi/Iii:
Value Disk #1 Disk #2 Disk #3 Disk #4 Disk #5 Min.
171 173 202 173 176 Max.
223 224 227 215 213 Critical Crack Depths a at the Keyways for c
Min. and Max. Values of Fracture Toughness in inches:
Min./ Max. Value Disk #1 Disk #2 Disk #3 Disk #4 Disk #5 Rated Speed 1.50/3.15 1.42/2.87 2.91/3.94 1.46/2.64 1.61/2.72 p
1.2 X Rated Speed 1.18/2.48 1.10/2.20 2.28/3.15 1.14/2.05 1.22/2.09 II S i
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E. } ; g Critical Crack Depths a at the Disk Hubs for c
l g$ il; Min. and Max. Values of Fracture Toughness in inches:
Eh_!!f Min./ Max. Value Disk #1 Disk #2 Disk #3 Disk #4 Disk #5 3, o B
Rated Speed 1.93/3.35 1.81/3.07 3.07/3.94 1.85/2.87 2.05/2.99
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1.2 X Rated Speed 1.65/2.80 1.50/2.52 2.56/3.23 1.57/2.44 1.69/2.48 I
5 2n kN Eik PRELIMiriARY CRITICAL CRACK SIZES a u = -c~^==a
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OF COMANCHE PEAK LP TURBINE DISKS 1E81.159 I
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Radius:
R10 = 0.39 in.
R22.5 = 0.89 in.
Diameter:
R390N 20 = 0.79 in.
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