ML20148S634

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NPSH - Rept of Sulzer Bingham Pump
ML20148S634
Person / Time
Site: Monticello Xcel Energy icon.png
Issue date: 06/23/1997
From:
NORTHERN STATES POWER CO.
To:
Shared Package
ML20148S609 List:
References
12.5.487, NUDOCS 9707080277
Download: ML20148S634 (7)
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{{#Wiki_filter:-. SUZLER BINGHAJ PUMP Ref: E9710626. DOC Paga HYDRAUUC REPORT: 12.5.487 - NPSHR TECHNICAL REPORT 10 x 12 x 14.5 CVDS PUMPS FOR NORTHERN STATES POWER June 23.1997 01

SUBJECT:

NPSH - Report of SULZER BINGHAM PUMP (previously Bingham Pump Co.) Pump Sales. Order No. 270417/418 Pump Size: 10 x 12 x 14.5 CVDS Monticello (NSP) CORE SPRAY PUMPS Review and Analysis: by SBP HYDRAULICS GROUP: June 1997 / DLEI RL ltem 1. NPSH-Margin on Curve #26603/604 NPSPr shown on Curve No. 26603/604 represents a 1% Head-Drop per NPSH Test T-270417-A for Pump S.O. 270417. See CURVE #1(58374) of this report. Also, on CURVE

  1. 1(58374) are the NPSHr for 3% and 5% Head-Drop respectively. ALL DATA HAS BEEN NORMALIZED TO 3560 RPM.

Clarification:To clear-up confusion regarding suction specific speed "Nss". (Refer to Sheet No. 3 of calculation cover sheet by Northem States Power Company dated 04-18-97) Nos by definition is based on a 3% Head-Drop at the Best Efficiency Point. For a Double-Suction Impeller (CVDS-Style Pump) only 50% of this flow is used, since it is analogous to two (2) Single-Suction Impellers in parallel. ] N,, = N * [Q

    • '^* **

NPSHr.,,

  • 3 single suction impeller. For double suction or double entry impellers use 50% of this flow.

Where: Nss3s = SUCTION SPECIFIC SPEED at 3% Head-Drop, this is a nominal number, N = Rotative Speed in Revolution Per Minute (rpm); Q = Flow in USGPM at B.E.P. (0.5 Q for double-suction or double-entry impellers); NPSHr3%= Net Positive Suction Head required in feet based on 3% Head-Drop at B.E P. FOR THE " TESTED" MONTICELLO CORE SPRAY PUMPS, Nssasis: N,, = 3560

  • 44250/ 2m 14170, Note: This value is calculated on an actual test om data andis not the design Nss. which will be a different value based on the B.E.P. @

maximum diameter. Also this value has no tolerance and is subject to variance between pumping units, due to manufacturing processes. See values from CURVE

  1. 1(58374). The design Nss would < 14000 based on maximum diameter and including manufacturing and testing tolerances.

Comment By current standards, this is considered a "High-Nss" impeller design. Pumps of this design have a limited "perferredoperating range" outside of which increased vibration and internal re-circulation may take place. CURVE #1(58374) also identifies th3 recommended " continuous minimum flow" (greater than (2) two hours operation at this flow in a 24 hour-period). A second, intermittent, minimum flow is also identified. These values SULZER BINGHAM HQ Enaineenna E9710626. doc 9707000277 970702 PDR ADOCK 0500o263 P PDR

l Page Ref E9710826. Doc SULZER clNGHAM PUMP TECHNICAL REPORT HYDRAuuc REPORT: 12.5.487 - NPSHR }. 02 June 23.1997 10 x 12 x 14.5 CVDS Punes FOR NORTHERN STATES POWER i 1 were agreed on after the pumps were installed. Minimum flow values are based on Ns value of =14,000 along with a Ns of =1300 for the pump, and a and Nss3y,. The Nssas head value of 615 ft were used to determine the " minimum flow (s)" ) i Pump Specific Speed is approximately: 4 N,,= #*40/2 3560 V4250/2 H 615"" 4 siegt i Note: This is not at B.E.P. and maximum diameter impeller, but calculated from the l " trimmed" performance curve. Some references use Ns,n,, which would increase po the above value by a factor of 1.414 or the square root of 2 since the pump is a double suction design. The values for " minimum flow", in %, are taken from SBPI I Standard E31.68 and are guidelines used by SULZER BINGHAM in establishing a recommended minimum flow. i i Item 2. and 3.: NPSHa vs. Flow - Review of Cavitadon Report 12 x 14 x 14.5 CVDS, Pump S.O. 270425 dated May 15 & 16,1969 On Pump S.O. 270417 [10 x 12 x 14.5 cvos) a NPSH Test (T-270417-A) was performed. o l This test identifies NPSHr based on 0%,1%,3% and 5% Head-Drop in the range of { 4000 to 5300 GPM. The point of head collapse was not established. This is not I required for a NPSHr Test. A Cavitation Test is used to establish these values and is j a much longer and demanding test to conduct. { The Impeller in the 12 x 14 x 14.5 CVDS per S.O. 270419/426 are identical (except Trim-o Diamster) to the one in S.O. 270417/418, namely pattem #1213 CVDS-1. t ) The NPSHr tests base on 3% Head-Drop performed on S.O. 270425[12 x 14 x 14.5 o cvos) and S.O. 270417[10 x 12 x 14.5 cvDs] are identical in the flow regime of 4000 - 5300 GPM. On Curve #2(58375)the NPSHr3% values have been added in dotted line j from T-270425-2 in the flow ranges of 3500 to 4000 GPM and 5300 to 6000 GPM. 4 L o On Pump S.O. 270425[12 x 14 x 14.5 cvos) a Cavitation Test was performed. This test l was conducted on May 15 and 16 of 1969. Based on these tests the NPSHa at points of head collapse have been added on Curve #2(58375). ) it can be stated that the CORE SPRAY pumps for MONTICA 1 O (Pump S.O. 270417/418) will o j have the same NPSHr performance and the same expected cavitation flow j performance as Pump S.O. 270425, since they are of identical impeller design (same L pattem) and show identical NPSHr3% performances between 4000 and 5300 GPM..lds l notpossible toplotpump flow vs. NPSHa from initial value down to 20 feet. in onefaat j increments. Insufficient number of NPSHr data points were taken during referenced tests to demonstrate this. In addition no NPSHr - data below 4000 GPM and no j Cavitation Test data below 4000 GPM are available. l SULZER BINGHAM HQ Engineenna E9710626. doc 1

1 i CUZLER BINGHAM PUMP Ref; E9710626. doc Page HYDRAUUC REPORT: 12.5.487 - NPSHR TECHNICAL REPORT l 10 x 12 x 14.5 CVDS PuesPs Fom NORTHERN STATES POWER June 23.1997 03 ^ Curve #3(58376), generated from T-270417-A and T-270425-2 provides sufficient data to predict what will be happening to the pump when reduced NPSHa is encountered. l (

4. Item 3 is =pp!k=Me to the A1066iGII o ConESPRAYPt~.~s i

j lt has been confirmed that the Core Spray Pumps S.O. 270417/418[10 x 12 x 14.5 cvos] l l are hydraulically identical (same impeller pattern, same volute area, except trim diameter and pump l ] nozzle sizes) to the residual heat removal (RHR) pumps S.O. 270419/426[12 x 14 x 14.5 cvos). There will be some minor performance differences due to the size of the i suction and discharge nozzles. i

j The requested material comparison shows that both services use impellers made from f

ASTM A296. Gr. CA-15 (now replaced by ASTM A743 Gr. CA6NM). Both alloys have greater l l than 11% chrome with the CA6NM(13-4) being the easier grade to perform weld repair l on. l-Pump S.O. 270425 went through extensive cavitation testing for several hours without { } visible damage to the impeller, it can be wrmised that Pump S.O. 270417/418 will l experience similar wear to the impeller when operated for 10 minutes (following a LOCA) at NPSHa values 0.5 feet above head collapse value shown on Curve #2(58375) and l Curve #3(58376). u Additional Comments: I Despite the fact that the suction specific speed (Nss), based on tested 3% Head-Drop j [Nssa =14170], is high by current standards it should not imply that when properly applied these designs are " bad". However, it should be inferred you must know the 2 recommended operating parameters and ranges in which they should be used and the l duration of these periods. It is possible to design a new impeller with a higher Nssas (larger eye-dia, flatter suction vane angle of eye, well-rounded suction vane in;et profile with reduced ] thickness ) However, the minimum flow values would be increased over those shown on l CURVE #1(58374). In addition, the double-suction impeller would be designed with " staggered" pumping l vane configuration to reduce pulsation-and vibration levels (this is important for pumps l running at the higher rpm's). There will be no measureable impact on the suction side ofthe [ impellerfor thisfeature. The " net" impeller width at O.D. would be decreased to stay j with proper side-wall clearance to the volute, the vane discharge angle would be increased to stay with the same impeller outlet-area. A slower pump speed,1760 rpm, would reduce the NPSHr values, however the impeller diameter would need to be approximately double the current size to meet the same hydraulic conditions. This poses some interesting mechanical problems as well j as potential hydraulic problems when operating a low flows. 4 2 sUt.ZER BMGHARI HQ Engineenng E9710626. DOC --w-e n a ,-e--

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