1

HNF-5480-FP

Nuclear Waste Cross Site Transfer Pump Operational Resonance Resolution

T. F. Kaiser Sulzer Pumps (US), Inc.

F. M. Hauck Flwr Federal Services

Data PuMlahd December 1999

To Ea Resentad at IF imamatlDnel Pump Usare Sympoaium Tams A&M Univeralty, TurbMnachinary Laboratory Houaton. TX March 6-9, 2000

Prepared for the U.S. Department of Energy Assistant Secretary for Environmental Management

Approved for Public Release; Further Dissemination Unlimited

SULZER BINGHAM i s a registered trademark o f Sulzer Bingham Pumps, Inc.

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LEGAL DISCLAIMER This rewrt was oreoered as an account of work soonsored by an kency of'the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, nor any of their contractors, subcontractors or their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy. completeness, or any third party's use or the results of such use 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, manufacturar, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof or its contractors or subcontractors. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

This report has been reproduced from the best available COPY.

Rlntsd in the United Statel of America

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ABSTRACT

Two single-volute, multi-stage centrifugal pumps are installec. at a nuclear waste transfer station operated by the Department of Energy in Hanford, Washington. The two parallel 100% pumps are Variable Frequency Drive operated and designed to transfer nuclear slurry from existing storage tanks into a collecting tank before vitrification-treatment to prepare for final storage.

Both units experienced high vibrations at l x synchronous speed after start- up at 2900 RPM (horizontal) and 3600 RPM (vertical) operating speed. Lateral rotordynamic analyses of pump and motor and a natural frequency analysis of the baseplate were performed to identify the root-cause(s) of the vibration problem. A motor rotor critical speed at approximately 2950 RPM and baseplate natural frequencies at 3000 RPM (horizontal) and 3500 RPM (vertical) operating speed were found.

The motor critical speed could not be changed. Therefore the effort focused on changes to the baseplate structure. Several design modifications have been analyzed with Finite Element Analysis. The only promising change consisted of loosening seven out of ten baseplate hold-down bolts. In the modified configuration, both calculated baseplate natural frequencies of concern dropped out of the pump’s continuous operating speed range.

After physically implementing this modification, the 2950 RPM resonance caused by the motor critical speed remained excessive on one unit. In order to achieve acceptable vibration levels, a small frequency range was excluded from continuous operation for this unit. The second pump did not need any changes other than the baseplate modifications.

The modification applied resulted in acceptable vibration levels.

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INTRODUCTION

INTRODUCTION

rrl 4

6

INTRODUCTION

Nuclear slurry cross-site transfer pump application at Department of Energy’s (DOE) Hanford site

Two horizontal single volute, 9 stage pumps in parallel arrangement (‘A’-pump and ‘B’-pump)

Variable Frequency Drive (VFD) operation (2600 RPM to 3600 RPM)

Pumps with unusual high pedestals (bleed-off at every cross-under)

All significant vibrations at lx synchronous speed

Both pumps showed the same phenomena. However, vibration levels on ‘Ahnit are higher than on ‘B’-unit.

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VIBRATION PROBLEM AFTER START-UP

I. Horizontal l x Bearing Housing Vibrations

3 cn \ 0.50 - .- Y

al U a c .- - E a 0.25 - Y a al n

Pump Outboard

Pump Inboard

- - Motor Inboard

--

0.00 ! I

2400 2600 2800 3000 3200 3400 3600

Operating speed [RPM]

All l x vibrations on pump are in phase 1 x vibrations on pump and motor are 180" out of phase Maximum: 0.636 ips at l x and 0.637 ips overall Resonance at approximately 49 Hz (2950 RPM) Motor vibrations indicate dynamic absorber effect

8

0.75 -

IT cn \

VIBRATION PROBLEM AFTER START-UP

Pump Outboard A - pump -- Pump Inboard

- Motor Inboard

11. Vertical l x Bearing Housing Vibrations

c 0.50 Q)

.- Y

3 c .- - E

2 0 0.25 - Y 0

0.00 I

2400 2600 2800 3000 3200 3400 3600

Operating speed [RPM]

All l x vibrations on pump are in phase Maximum: 0.399 ips at l x and 0.400 ips overall Resonance at approximately 60 Hz (3600 RPM) Motor vibrations indicate dynamic absorber effect

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DYNAMIC VIBRATION ABSORBER

A vibration absorber consists of an additional mass-spring system (m2, k2) attached to an existing resonant structure (m1, kl)

The individual natural frequencies of both systems are (nearly) equal

The resulting dynamic behavior shows two wide vibration peaks providing reduced vibration maxima

x2 Dynamic Absorber Effect t

Operating speed

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ROOT CAUSE IDENTIFICATION

I. Pump Lateral Rotordynamics

The calculated natural frequency of the 1'' lateral mode is, depending on speed, 33 to 44% above synchronous speed

The 1'' lateral mode is sufficiently damped, providing over 30% of critical damping ratio D

+ Acceptable pump lateral rotordynamics

1'' lateral mode of pump at 1560 RPM operating speed

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Spomd - 3560

O= 32.8 t F- 79.66 Hr

Spmed - 5560 F= 123.54 HX D- 32.1 X

1'' lateral mode of pump at 3560 RPM (top) and 5560 RPM (bottom) operating speed

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ROOT CAUSE IDENTIFICATION

11. Motor Lateral Rotordynamics

The calculated natural frequency of the 1'' lateral mode is at 49.4 Hz (2960 CPM)

+ First contributing cause for the resonance at 2950 RPM running speed

Speed = 3560 r p m

0 . 0 % D- E= 49.37 nz e-'

a

1'' lateral mode of motor at 3560 RPM operating speed

ROOT CAUSE IDENTIFICATION

111. Baseplate Structural Natural Frequencies

The baseplate design has been investigated for structural natural frequencies within the continuous operating speed range of the pump.

BASEPLATE NATURAL FREQUENCY ANALYSIS

S o l i d model ( s l i c e d view) O r 1 91 n a l Desj g n

2.25" p l a t e s

4 x b s 1 1 . 9 7 # s t r u c t u r a l t u b i n g

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ROOT CAUSE IDENTIFICATION

111. Baseplate Structural Natural Frequencies

BASEPLATE NATURAL FREQUENCY ANAL YSIS

F i n i t e E l e m e n t M o d e l O r 1 91 n a l D e s j g n

L u m p e d p u m p i n e r t i a /,

L u m p e d m o t o r i n e r t i a /

I M o t o r p e d e s t a l s B a s e p l a t e P u m p p e d e s t a l s

ROOT CAUSE IDENTIFICATION

111. Calculated Horizontal Baseplate Mode at 51.0 Hz (3060 CPM)

+ Second contributing cause for the resonance at 2950 RPM running speed

BASEPLATE NATURAL FREQUENCY ANALYSIS

H o r j z o n t a l m o d e a t 5 1 . 0 Hr (3060 CPM) O r i g i n a l d e s j g n

ANSYS 5.5.3 SEP 2 3 1999 15: 46 : ia NODAL SOLUTION STEP=1 SUB =5 TIME=50.982 USUM (AVG) RSYS=O Power GI ap h i c 5

E F A C E F l AVRES=Mat

SMX =.288951 DMX =.2as95i

0 - .02

.2

.22

. 2 6 0 .24 pJ .28 = . 3

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ROOT CAUSE IDENTIFICATION

111. Calculated Vertical Baseplate Mode at 58.2 Hz (3495 CPM)

j Explanation for 3600 RPM resonance

BASEPLATE NATURAL FREQUENCY ANAL YSIS

V e r t i c a l m o d e a t 58.2 HZ (3495 CPM)

( O r i g j n a l d e s j g n )

ANSYS 5.5.3 SEP 23 1999 15:32 : 40 NODAL S O L U T I O N STEP'1 SUB = 6 TIME=58.227 USUM (AYG) RSYS=O PowerGraphics E F A C E F l A Y R E S M e t DMX =.344621 SMX = .3 44 62 1

0 m ,023333 m ,046667

.07 ,093333

0 ,116667 0 .14

.163333 ,186667 .21 - ,233333 ,256667 0 .za ,303333 .326667 - .35

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CORRECTIVE MEASURES I. Balancing of Motor Rotor

11. Baseplate Modifications A number of baseplate design changes aimed at increased baseplate stiffness were investigated with Finite Element Analysis:

0 Side channels reinforced with gusset plates Side channels with increased # of hold-down

Increased number of hold-down bolts and bolts

reinforcement-plates welded to the pedestals

The calculated natural frequencies could not be moved out of the continuous operating speed range

Decreasing the baseplate stiffness by loosening seven out of ten hold-down bolts moved the baseplate natural frequencies of concern out of the continuous operating speed range:

Horizontal mode: From 51 Hz (3060 CPM) to 37 Hz (2220 CPM)

Vertical mode: From 58.2 Hz (3490 CPM) to 32 Hz (1920 CPM)

CORRECTIVE MEASURES

11. Modified Baseplate Design

Calculated horizontal mode at 37 Hz (2220 CPM)

BASEPLATE NATURAL FREQUENCY A N A L Y S I S

H o r i z n n t a l m o d e a t 3 7 . 0 Hz ( 2 2 2 0 CPM) ( M o d i E i e d d e s i g n )

RNSYS 5 . 5 . 3 SEP 2 4 1999 39 : 53 : 3 7 VODAL SOLUTION X E P = l SUB =5 FREQ=3 6.982

USUM I AVG) RSYS=O PowerGraphlcs EFACET=l AVRVRES=Mat DMX = . 3 3 8 6 5 6 SBX = . 3 3 8 6 5 6

0 . 0 2 3 3 3 3

- ,093333

. 1 4 , 1 6 3 3 3 3 .le6667 .21 . 2 3 3 3 3 3 . 2 5 6 6 6 7 0 . 2 8

u ,303333 , 3 2 6 6 6 7 - . 3 5

CORRECTIVE MEASURES

11. Modified Baseplate Design

Calculated vertical mode at 32 Hz (1920 CPM)

BASEPL ATE NATURAL FREQUENCV ANAL YSlS

V e r t i c a l m o d e a t 32 .0 Hz 11920 CPMI ( M o d i E i e d d e s i g n )

ANSYS 5 . 5 . 3 SEP 2 4 1999 0 9 : 4 3 : 2 1 NODAL SOLUTION S T E P = l S U B =4 FREQ=3 1 . 9 5 6

USUM (A'JG) RSYS=O PowerGraphics EFACET=l AVRES=Mat DMX = . 3 0 6 2 3 3 SMX = . 3 0 6 2 3 3

0 - . 0 2

I 3 .I I 3 .12

0 .2 0 . 22

. 0 4

. 0 6

.08

,14

.16

.18

. 2 4 0 . 2 6

. 2 8 - . 3

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VIBRATION LEVELS AFTER MODIFICATIONS

I. Horizontal l x Bearing Housing Vibrations

Pump Outboard -- Pump Inboard

%T Motor Inboard

iaaa 2000 2200 2400 2600 2000 3000 3200 3400 3600

Operating speed [RPM]

Structural resonance eliminated; motor-rotor critical speed situation remained unchanged

Elimination of one resonance source also eliminated the dynamic vibration absorber effect + motor vibrations at approximately 2950 RPM increased

Maximum l x vibration on B-unit: 0.2 ips

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0.75 -

- 8 \ 0.50 - - L

8 - ir - E 0.25 -

Y 8 n

0.00

VIBRATION LEVELS AFTER MODIFICATIONS (11)

A - pump Pump Outboard

Pump Inboard -. -. -. - . Motor Inboard

--

c

, t --,

Excessive vibration levels at operating speeds close to 3600 RPM are now acceptable

0 Maximum lx vibration on B-unit: 0.1 ips

111. Lock-Out of Operating Speed Range A-unit: Based on the test results, the 2820 to 2970 RPM speed range be excluded from continuous operation

B-unit: No additional changes

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CONCLUSIONS Both units run with acceptable vibration levels after applying the described modifkations. The applicable bearing housing vibration limits are 0.3 ips overall and 0.2 ips filtered (API 610 7th edition, Paragraph 2.8.4)

Variable Frequency Drive operated motors with a first rotor critical speed below 60 Hz are likely to cause resonance problems in the lower operating speed range

Baseplate natural frequencies of pump applications with unusually high pedestals need to be analyzed in the design phase

Operating the pumps with only three hold- down bolts tightened is acceptable. These bolts are located at opposite corners of the baseplate. The pump is primarily held by the piping and the loosened bolts are still in place, preventing the equipment from growing out of alignment in the horizontal direction.

INFORMATION CLEARANCE FORM

A. Information Cabgory

] Abr$ ld 0 Journal Art!&

] Summary 0 Intarn& 3 VlwalAld 0 SORmm

] Full Paper 0 Report

8. DoWment Number HNF-5480-FP C. TIue NUCLEAR WASTE CROSS SITE TRANSFER PUMP

OPERATIONAL RESONANCE RESOLUTION

COurWl

Pmgmm

3. Relenmaeln the lnformatlon are Appkd Technology @No O Y e e

Export Contmlbd lnformatlon @No ()Yes

Title of Journal 0. Complete for a Presentation

5. IS Inbrmatbn mquirlng submlasbn to OSTI? @ NO 0 Yea

IfYE. uc- and B6R-

@ PuMic 0 Lirnlted

7. Charge Code j j r n ~ m o 2 2 1

th teo fconhmnm March 6-9, 2000 4 cw/state Houston, TX

\MI1 Information bn P u b l l h d in Proceedings? O N 0 @Yea 6. \MI1 Material be Handed Out? 0 No @ Yes

d h q , AuthorIRequeator Reapondble Manager

'.M. Hauck A.W. Bjorkedal Print and Sign)

RevkWN Yes Prinl Slgnature PuMlcY/N (If N, complete J:

General Counml J.T. Curtis

(Prlnt and Slgn) .

o n m o f w e r M I A m i m D.D. Miller DOE-RL B.J. HarD

other J.R. Collins

Other J.L. Henderson

If lnformatlon Indudee Sendtive Inbrmatbn and la not to b-s released to the Public Indicate caIegory below 2 Applkd Technology 0 Proladed CRADA

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3 Abstract 0 Journal Artlcle 7 Summary 0 Internet 7 Visual Aid 0 sonware

3 Full Paper 0 Report

gother CASE STUDY

6. DocumenlNumber' HNF-448O-FP C. TMe

NUCLEAR WASTE CROSS SITE TRANSFER PUMP OPERATIONAL RESONANCE RESOLUTION

', D. Internet Address

:. Requlred lnformatbn 1. Isdocument potentially Claurined? @No O Y e s (MANDATORY)

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d. Trademdrkr? @No O Y e s lf.tea*. Identltf In Document.

@ No 0 Yes .1

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