ML19310A396
| ML19310A396 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 05/31/1980 |
| From: | Carey J, Seiber J DUQUESNE LIGHT CO. |
| To: | |
| Shared Package | |
| ML19310A394 | List: |
| References | |
| NUDOCS 8006110194 | |
| Download: ML19310A396 (7) | |
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DUQUESNE LIGHT COMPANY Power Stations Department Beaver Valley Power Station, Unit No. 1 4
Inspection Report Inside Recirculation Spray Pumps
. Prepared by:
1 J. 5. Sieber Approved by:
/
(/ Y J. Carey
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Date: May 31, 1980 l
80.06.110Af[i
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DUQUESNE LIGHT COMPANY Power Stations Department Beaver Valley Power Station, Unit No. 1 Inspection Report Inside Recirculation Spray Pumps I.
Summary and Conclusions The two Inside Recirculation Spray (IRS) pumps are vertical, dual stage pumps manufactured by Bingham Willamette Company with each being i
driven by a vertical shaft, 300 hp., 480 volts A.C. electric motor.
These pumps were disassembled, inspected, certain parts were renewed and the pumps were assembled during the period March through May 1980. The inspection of internal parts of the pumps showed moderate wear of the bowl bushings with minor wear of column and stuffing box bushings and insignificant wear of the shaft sleeves. There was no evidence of wear or interference of any other rotating parts against stationary parts. The examination of the~ operating history, initial operating conditions and the appearance of the pump parts leads to the conclusion that the bushing wear is attributable to abrasion caused when the pumps were used to flush the recirculation spray system.
The pumps were modified to reduce bushing caused by abrasive parcic<es in the pumpage.
Based upon the wea:
examination conducted and the repr?rs and modifications made, Duquesne Light Company considers the IRS pumps operable and fully capable of
. performing their design function.
4 II.
Description of Pumps i
The IRS pumps are two stage type J-VCR, Model 10X 18B, vertical pumps manufactured by Bingham Willamette Company. The pumps are driven by General Electric frams 6318-P20, 300 hp, 480 volts A.C. motors operating i
nominally at 1800 rpm. The pump column (i.e.: bottom of suction bell to the mounting flange is 14 feet 5 inches including the pump bowl assembly which is 48 inches long. The pump shaft 's a two piece shaft, each'section
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being approximately'9 feet in. length. The rotating parts are supportad radially by six carbon bushings; three of_which are located in the pump bowl assembly, two of which are contained in spiders mounted between the column sections and the remaining bushing located just below the stuffing.
box. The shaft is sleeved with type 440C chromed sleeves at each bushing Axial support of the pump shaft.is obtained from the thrust bearing.
area.
-located in the top of'the motor. 'The motor is coupled to the pump by an axially adjustable spacer and flange type coupling which acts as a solid unit when bolted'together. This coupling is designed with a spigot fit between: top flange and spacer and between spacer, adjusting collar and bottom flange.- The dimensional tolerances of the spigot fit arrangement are designed to prevent axial misalignment greater than 5 mills. During assembly, the coupling-is adjusted and bolted in place to achieve paral-1elism within 2 mills and concentricity of 0.5 mills.
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Beaver Valley Power Station, Unit No. 1
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Inspection Report Inside Recirculation Spray Pumps Page 2 i.
III.
Operating History The IRS pumps were used during the initial flush and preoperational test of the recirculation spray system. During this period (4/75 through j
12/75) the 1A pump was operated for approximately 29 hours3.356481e-4 days <br />0.00806 hours <br />4.794974e-5 weeks <br />1.10345e-5 months <br /> and 49 minutes, i
and the IB pump operated for 9 hours1.041667e-4 days <br />0.0025 hours <br />1.488095e-5 weeks <br />3.4245e-6 months <br /> and 49 minutes. The fluid being pump-ed at this time was flush water being drawn from a dammed up area of the containment sump. The pumps are operated " dry" for 30 seconds each month
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as required by an operational surveillance test.
IV.
Pump Distssembly and "As Found" Measurements Pump disassembly for inspection was performed us ng Corrective Main-tenance Procedures (CMP) 1-13RS-P-1A-1H and 2M, and 1-13RS-P-1B-1M and 2M.
t Basically, these procedures _ provide for the removal, disassembly, assembly and reinstallation of the pump, as well as measurement of the "as found" and "as left" condition.
a Because of limited space available at the location of the IRS pumps, disassembly and reassembly is performed while the pump is suspended vertically and is being withdrawn from the pump can. Because the' assembled pump is not laid on its side during any phase of the. maintenance procedure, the likelihood of bending the pump is remote.
The condition of the wear of the bushings was light to moderate rith I
the greatest wear exhibited by the bottom bowl bushing. Bushing w-ar was es'sentially uniform around the circumference of each bushing. A comparison of the "out of roundness" of the various bushings is given in Table I.
The minimal deviation between the "x" and "y" plane readings' clearly j
demonstrates the wear. pattern experienced was not caused by pump column misalignment or by a " whipping" pump shaf t during operation. The bottom I
bowl bushing exhibited moderate and uniform scoring or threading as by abrasive particles.
The shaft sleeves exhibited a polished and very lightly scored appearance. The "as found" dimensions of bushings and sleeves were as set forth in Table II.
As can be noted from Table II, both pumps exhibited substantially the same amount of journal wear in the sar. locations despite a difference in operating time of over a facuor of three for the two pumps.
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"As fonnd" journal and shaft run out' measured at ten positions along-the shaft and at each of the five sleeves was well within the allowable 5 mills in 10 feet for-the shaft and 1.5 mills TIR for the sleeves. The bottom'five bushings and the bottom sleeve.were replaced on the lA pump and 3
th( bottom four bushings were replaced on the'1B pump. There was no indi-cation.of wear or: interference on'any other moving or stationary part and-wear rings were within "new" specifications.
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L Beaver Valley Power Station, Unit No. 1 Inspection Report Inside Recirculation Spray Pumps Page 3 Pump Assembly and Installation Assembly and reinstallation of the IRS pumps were performed in accord-ance with detailed, approved plant mafatenance procedures and specifications.
New bushings were pressed into bearing positions and dimensions verified to be within specifications as noted above.
Shaft concentricity was verified to be within specifications by runout measurements taken at 15 positions along each shaft.
Each pump was assembled, while being suspended vertically, from the bowl upward, taking care during assembly to maintain alignment of the two columns and associated bearings.
Bolted joints in the pump column were bolted by using a special, two-pass-alternate tightening sequence designed to maintain the straightness of the pump. Match marks were used to assure that parts were reassembled in the "as found" relationship to one another.
This care was exercised to maintain the " straightness" of the pump reflected by the "as found" condition of the column bushings.
Pump to drive motor alignment was accomplished by adjustment of the drive motor until the horizontal and vertical runouts were within the required 2 mill tolerance. Parallelism between the pump shaft and the motor shaft was verified to be within 1/2 mill. On pumps as short as these pumps, the alignment procedures employed provide adequate alignment for satis-factory long term operation.
Exotic alignment methods are not required for satisfactory pump operation except for those pumps which are excep-tionally long and of relatively flex 1 ole construction.
The coupling was assembled efter alignment to provide proper axial clearance of the impeller.
Proper runout of the pump shaft was verified after the coupling was made.
The top bearing spider was bolted to the column flange'after the pump / driver alignment was fixed.
VI.
Discussion of the "As Found" Condition The most significant finding during the inspection was the wear exhibited by the bottom bushings of both pumps. The similarity of the
. wear of both pumps, despite different operating times, suggests that this initial wear was not progressing as operating time increased. The scored nature of the wear suggested that it was cauced by abrasive particles encountered during the initial flush. The monthly " dry" starts used to verify pump operability could easily.have contributed to scoring of the bottom bushing. Concentricity of the wear pattern observed in the bushings indicates that no side load was present at any bearing point during opera-tion.
The wear pattern observed does not suggest that the wear was the result of any hydraulically excited vibration. The configuration of the pump can and st ction flow path leads to the conclusion that side loads on the pump column will not occur due to suction flow.
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Beaver Valley Power Station, Unit No. 1 Inspection Report Inside Recirculation Spray Pumps Page 4 VI.
Discussion of the "As Found" Condition (continued)
It is a misconception to assume that an increase in bushing clearance automatically means that a pump is not reliable.
If the bushings were the only support for the rotating element of the pump, then any increase in bushing clearance greater than the running clearance of other rotating parts would cause wear at these other clearance points.
No wear or other evidence of interference was evident in the pu.1ps at Beaver Valley. A vertical diffuser bowl pump is supported not otly by the bushings but also by the hydro-dynamic centering effect of the case and impeller rings. Because of its verticle suspension, no side loads are developed which would cause impeller ring to cause clearances to increase.
The dimensional data and observation of wear were discussed with representatives of the pump manufacturer, and it was recommended that the pump be modified to eliminate the bushing flush line betweea the second-stage discharge and the first stage bushings. This flush line forces second stage discharge pumpage to be pumped between the bottom and second bushings, thus causing any entrained particles to be forced through the bushing / sleeve clearance.
This modification is designed to equalize the wear rate for all bowl bushings and to reduce the amount of particles in the fluid between sleeve and bushing. Therefore, this modification was made to the pumps.
The pump manufacturer further stated that the effect of abrasive particle wear would be less during continuous pump operation than start-stop operation because abrasive particles would settle out in low velocity portions of the system, not in the pump bushings.
VII.
Conclusion In conclusion, there was no evidence to support the hypothesis that the wear observed wns caused by hydraulic induced vibration, side loads of
.any type, by misalignment of the pump bowls, columns, bearings, shafts, couplings or motor by any natural or forced vibration of the pump shaft or column nor by any condition of out-of-plumbness of the pump or motor.
The wear pattern observed was clearly caused by abrasive particles in the pumpage.
The observed wear pattern was distinctly different than the wear observed in the LHSI pumps at Beaver Valley in that the severe threading of the bushings was indicative of abrasion as opposed to excessive radial loading.
The pump was modified to reduce bushing wear from abrasive particles and all worn parts were replaced. Based upon.the examination conducted, Duquesne Light Company considers the pumps operable, reliable and fully capable of performing their intended function.
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g Table II "As Found" Dimensions of IRP Bearings Specification 1A Pump 1B Pump New New Bearing Specification Specification As Found*
As Found*
As Found*
As Found*
Position Bushing Sleeve Bushing Sleeve Bushing Sleeve Top 6 (Stuffing 3.00711 3.00011 3.007 2.9975 3.0085 2.999 Box) 5 (Column) 3.00711 3.00011 3.007 2.999 3.004 2.999 4 (Column) 3.00711 3.00011 3.0065 2.9995 3.0055 2.999 3 (Bowl) 3.00711 3.00011 3.012 2.999 3.0195 2.999 2 (Bowl) 3.00711 3.00011 3.024 3.013
}
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2.998 1 (Bowl) 3.00711 3.00011 3.0745 3.065 Bottom
- Each measurement reported herein is the measurement representing the greatest wear of two measurements taken at 90' planes on each bushing and four measurements on each journal sleeve.
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