^ /

FLOW-INDUCED VIBRATION OF COMPONENT COOLING WATER

HEAT EXCHANGERS*

CONP-900617—1

^ DE90 003789

Y. S. Yeh and S. S. Chen**

Nuclear Engineering DepartmentTaiwan Power Company

Taiwan, Republic of China

**Materials and Components Technology DivisionArgonne National Laboratory

Argonne, Illinois USA

SUMMARY

This paper presents an evaluation of flow-induced vibration problems of

component cooling water heat exchangers in one of Taipower's nuclear power

stations. Specifically, it describes flow-induced vibration phenomena, tests to

identify the excitation mechanisms, measurement of response characteristics,

analyses to predict tube response and wear, various design alterations, and

modifications of the original design. Several unique features associated with the

heat exchangers are demonstrated, including energy-trapping modes, existence

of tube-support-plate (TSP)-inactive modes, and fluidelastic instability of TSP-

active and -inactive modes. On the basis of this evaluation, the difficulties and

future research needs for the evaluation of heat exchangers are identified.

* Paper to be submitted for presentation at the ASME Pressure Vessel and Piping

Conference, Nashville, Tennessee, June 17-21, 1990.

M A S T E R ^DISTRIBUTION OF THIS DOCUMENT IS UNLIMITED

The submitted manuscript has been authoredby a contractor of the U. S. Governmentunder contract No. W-31-109-ENG-38.Accordingly, the U. S. Government retains anonexclusive, royalty-free license to publishor reproduce the published form of thiscontribution, or allow others to do so, torU. S. Government purposes.

1. Introduction

The Maanshan Nuclear Power Station contains two trains of component

cooling-water (CCW) heat exchangers for each of two reactors. Trains A and B of

Unit 1 were placed in service in December 1982 and January 1983, respectively.

Tube leakage in both heat exchangers was discovered in March 1983, after only a

few months of operation. Damage was noticed at tube supports and midspan

regions. This was the beginning of a series of steps taken by Taiwan Power

Company (Taipower) to resolve the problem. A brief history is presented in

Table 1.

The CCW heat exchangers are one-pass, shell-and-tube heat exchangers

with sea water in the tube side and hot demineralized water in the shellside. A

schematic diagram of the heat exchanger is given in Fig. 1. Each exchanger

contains 3,488 tubes contained in a 66-in. (i.d.) circular cylindrical shell. The two

tube sheets are 1.75-in. aluminum-bronze plates, and two types of baffle plates are

0.625-in. carbon steel plates; four are segmental baffle plates with a single

horizontal cut, and ten are support plates with double horizontal cuts as shown in

Fig. 1.

A 36-in. (o.d.) circular impingement plate was installed at the inlet to

distribute the incoming flow to the first three passes. All heat exchanger tubes

are cupronickel with 0.75-in. o.d. and 0.049-in. wall thickness. The tubes are

arranged in a rotated triangular pattern with a pitch of 15/16-in.

2. Tube Damage

2.1 Initial Inspection

In March 1983, after a few months of operation, 14 tubes were found

damaged in Train A and 4 in Train B. All damaged tubes had flat spots

developing in the first and second baffle plates next to the inlet nozzle. These flat

spots are 6-24 inches long. A damaged tube in Train A developed a 4-in. long

crack along a 24-in. flat spot, and a damaged tube in Train B was severed at the

second support plate. All damaged tubes were located in the inlet area.

Apparently, the high flow velocity in the nozzle caused large tube motion that

resulted in tube damage. The flat spots were caused by tubes colliding with each

other.

In February 1984, the manufacturer of the CCW heat exchangers, Struthers-

Wells Corp. (SWC), completed initial modifications of both CCW heat exchangers

in Unit 1. The modifications included removing 420 tubes from each heat

exchanger. No damage inspection was performed when they were removed and

placed in groups in an open field.

In March 1984, the first five spans were inspected for flat spots between the

supports and ring-type markings at tube supports. If no damage was found in the

first five spans, the tube was considered undamaged. If damage was observed in

these five spans, inspection continued to the subsequent spans until no further

damage was found. Figure 2 shows the results of the damage inspection. Among

396 inspected tubes in Train A and 400 in Train B, 36 tubes in Train A and 28 in

Train B were damaged. Twenty tubes in Train A and 16 in Train B contained flat-

spot damage between the first two baffle plates.

2.2 Damage Inspection of Selected Tubes

In July 1984, 28 tubes from each heat exchanger in Unit 1 were selected for

evaluation of the extent and distribution of tube damage. Figure 3 shows the

location of the tubes selected from each heat exchanger. In contrast to the tubes

near the nozzle, most damage occurred at the supports and baffles. Only one tube

from Train A showed flat-spot damage. In general, most of the damage was in

the first three supports. However, several tubes showed damage only at the

middle supports, e.g., supports 5 through 9. This damage pattern shows that

tubes located in regions other than near the nozzle are also subjected to

unacceptable vibration.

From the damage inspection, several general conclusions can be made:

• Excessive flow-induced vibrations were noted in both Trains A and B.

• Tube-to-tube impacts appear between the first two baffles.

• Damage at supports occurs in various regions of the tube array and at

different axial locations.

It is apparent that the original design of the heat exchanger is inadequate

from the standpoint of flow-induced vibration. The mechanism causing such

large tube vibration is due to fluidelastic instability.

3. Vibration Tests of CCW Heat Exchangers by Bechtel Group, Inc.

3.1 Phase-1 Tests

Two modifications were made in accordance with the manufacturer's

recommendations after the initial report of tube damage: (1) removing 420 tubes

from each train. [One hundred fourteen removed tubes were not replaced and the

holes were left in the baffles; supports and tube sheets were plugged. The rest of

the tubes were replaced by BWG 12 tubes (0.75-in. o.d. and 0.109-in. wall

thickness.)]; and (2) replacing the original impingement plate at the inlet (a 36-in.

diameter, 3/8-in. thick stainless steel plate welded to tie bars and a support plate)

by a flow deflector. Bechtel Group, Inc. performed tests on the modified heat

exchanger [1].

Eighteen tubes were selected for measurement. Two accelerometers were

embedded in each pod and inserted inside the selected tubes to measure tube

accelerations in two perpendicular directions at midspans. Three additional

accelerometers were placed on the outside shell.

After properly checking all accelerometers, flow tests were performed at a

series of flow rates, varying from zero to the rated flow of 127,000 gpm. A 14-

channel FM-type recorder was used to store the accelerations.

Analysis of the data includes time-domain data, frequency spectra, and

vibration amplitude.

3.1.1 Time-Domain Data

The data on acceleration-time plots revealed that

• Low-level background vibration of about 0.25 g peak-to-peak existed at

zero flow due to other equipment.

• Tube accelerations increased with flow velocity, reaching a magnitude

of 10 g peak-to-peak (p-p) at 127,000 gpm.

• Impact signrls were noted for flow above 7,000 gpm.

• The impact signals, occurring right at the peak of the vibration

waveform, indicate a direct impact at the accelerometer pod location.

In addition, the accelerations were doubly integrated to obtain tube

displacements. Figure 4 shows the tube displacements (p-p) as a function of flow

rate for nine tubes.

3.1.2 Frequency Spactra

Typical frequency spectra are shown in Fig. 5. The following general

characteristics are noted:

• Tube responses at low flow rate are broadband, indicating that the

excitation is turbulent buffeting.

• As the flow velocity increases, the major frequencies are located in two

regions, i.e., at 21-24 and 26-32 Hz.

3.1.3 Monitoring of SheU Vibration

Three shell accelerometers were installed on the external surface of the heat

exchanger to supplement the internally mounted accelerometers. At 6,000 gpm,

faint impact sounds could be heard at the first baffle location. At 7,000 gpm,

clean, but still faint, impact sounds could be heard at the second support and first

baffle. At 8,000 gpm, sound intensities increased noticeably. At 12,000 gpm, the

impact sounds became more frequent and much stronger.

The heat exchanger was tested again with the flow deflector rotated 180

degrees. The objective was to obtain vibration response under a new shellside

inlet condition. The test was conducted in February 1984 with flow rates at 7,000,

10,000, and 12,000 gpm. Tube responses were comparable with those of the

original test. However, the flow deflector did change the details of tube response.

3.1.4 Conclusions and Recommendations

When the shellside flow rate exceeded 7,000 gpm, the modified CCW heat

exchanger experienced severe tube vibration. Some of the tubes are subjected to

fiuidelastic instability at the rated flow of 12,700 gpm. The modifications

recommended by the manufacturer are inadequate. Meanwhile, it is

recommended that the following steps be taken before a final resolution of the

problem is reached.

8

• Operate the heat exchangers at flow rates not to exceed 6,000 gpm

whenever possible.

• Implement a surveillance program to detect leakage and inspect tube

damage before final modification.

• Investigate measures to resolve the problem, (e.g., improve flow velocity

distribution by adding inlet and outlet nozzles, and increase tube natural

frequencies by adding tube supports, in particular, in the inlet and outlet

regions.

• Evaluate the feasibility of replacing the existing units with a better

design.

3.2 Phase-2 Tests

Additional modifications to the heat exchangers were made as a result of the

Phase-1 tests. The modifications included staking the bottom 14 tube rows in

Bays 1, 2, and 3, and installing perforated plates in Bays 2 and 3. Two large cuts

were made to implement these modifications in June 1984.

• The first bay was staked at midspan and the second and third bays were

staked at the 1/3 and 2/3 points of each span. Staking strips of carbon

steel with a width of 0.75-in. and a thickness of 60 mils were wedged

horizontally between adjacent tube rows.

• A plate, 43 x 45 x 3/8 inches, with 3/8-in. diameter holes on a 13/16-in.

staggered pitch, resulting in 19% open area, was installed in Bajr 2.

• Two perforated plates were installed in Bays 2 and 3; a top plate

contained 1/2-in. diameter holes on a 1-in. staggered pitch (22% open

area) and a bottom plate contained 7/16-in. diameter holes on a 1-in.

staggered pitch (17% open area). All plates were stainless steel sheets

3/8-in. thick.

The Phase-2 vibration tests were a continuation of the Phase-1 test. The test

procedure, instrumentation, and data analysis are the same as those in Phase 1.

Accelerometers used for Phase 1 were used, to the extent feasible, for Phase 2

tests. Twenty-eight additional acceleronieters were procured for Phase 2 [2].

To guide the selection of suitable locations for installing accelerometers, and

to assist the interpretation of test results, natural frequencies of selected tubes

were calculated.

The test results were summarized as follows:

• Tube impact signals are noted at high flow velocity.

• Response of the unstaked tubes in the frequency range of 20 to 55 Hz was

excited at flow rates of 6,100 gpm and above. The only tube that was

instrumented and staked detected prominent tube response at 129 Hz.

• The largest tube motion was about 15 mils.

10

Tube vibration amplitudes increase with increasing shell side flow velocity.

At the maximum flow rate of 12,700 gpm, the peak acceleration amplitude was

about 1.2 g, which was considerably lower than the 15 g in Phase-1 tests. The

maximum tube displacement was about 30 mils, peak to peak; tube collision at

midspan is unlikely. Impacts were noted for flow over 9,000 gpm. Tube wear is

still possible, and the long-term effect is uncertain. Under the described

conditions, it is recommended that flow rate be restricted to 9,000 gpm, a rigorous

surveillance and maintenance program be implemented, and sources be located

for replacement heat exchangers.

After the Phase-2 test, Taipower decided to replace two CCW heat exchangers

with a new design, and modify the other two trains. The new design has a 15-in.

tube span and it is not expected to have any flow-induced vibration problems. The

other two trains were modified as follows by Taiwan Machinery Manufacturing

Corp. (TMMC) on the basis of a recommendation of a French consulting firm:

• The inlet region was changed from the original three passes to seven

passes.

• The outer shell diameter was increased.

The modified heat exchanger is shown in Fig. 6 After completion of the

modification by TMMC, flow tests were conducted by Loutech Taiwan, Inc. [3].

11

4. Analysis and Vibration Tests of Modified Heat Exchangers

4.1 Tests by Loutech Taiwan, Inc.

To verify the severity of vibration and structural integrity, Loutech Taiwan,

Inc., performed a flow test in September 1988. Twenty-five tubes were

instrumented with two accelerometers each to measure the accelerations in two

perpendicular directions. The instrumented tubes and the fisial locations are

given in Fig. 7.

Four types of plots were obtained from the data from each accelerometer:

• Overall tube displacement versus time: the peak amplitudes at each of

147 time intervals within 110 seconds.

• Average spectra of tube displacements: average spectra for 0 to 147 Hz.

• Peakhold spectra: the peaks of all spectra from 0 to 147 Hz.

• Frequency spectra versus time: frequency spectra of different tubes as

function of time.

Figure 8 shows typical average frequency spectra for a series of flow rates

and Figs. 9 and 10 show the frequency spectra as a function of time.

One method to determine the response characteristics and the critical flow

velocity is to plot tube displacement as a function of flow rate. The most frequently

12

used tube response is the rms value of *abe response (acceleration, velocity, or

displacement). Loutech did not provide rms values of tube displacements.

Alternatively, the peak values are presented. Figures 11 to 13 show the peak tube

displacements as a function of flow rate in logarithmic scale for selected tubes,

where H and V are used to indicate horizontal and vertical components

respectively.

4.2 Natural Frequencies: ISP-active and-inactive Modes

The natural frequencies of the tubes are very important for the interpretation

of tube response data. A free-vibration analysis was performed for different cases.

CCW heat exchanger tubes, fixed to the tube sheets at the two ends, were

supported by 14 tube-support plates (TSP), see Fig. 14. To facilitate assembly and

relative motion caused by thermal expansion, holes in the TSP were made larger

than the tube diameters. It is not uncommon for tube holes to be drilled 0.4 to

0.8 mm larger than the outside diameter of the tubes. In this case, the magnitude

of the clearance was not known. Owing to the clearance, TSP? may not provide

support in some cases. Therefore, there are two types of modes: TSP-active and

TSP-inactive

Current design practices consider the heat exchanger tubes to be simply

supported, without clearances, at the TSPs. For small clearances, this

assumption is expected to be applicable; the tube will respond as a continuous

beam supported by all TSPs, and anti-nodes of all modes do not appear at the

TSPs. This type of mode is called "TSP-active." Studies show that this

assumption is indeed applicable if the clearance is small [4-7], although there are

13

some variations of resonant frequencies. With this assumption, the simple beam

theory can be used to predict tube natural frequencies, as well as tube responses to

different excitations.

When the clearance is relatively large, the tube will rattle inside some of the

TSP holes for small-amplitude oscillations. This type of mode, in which some

TSPs do not provide effective supports, is called "TSP-inactive.:i

For intermediate clearances, the tube response will depend strongly on the

excitation amplitude. For low excitations, the tube will vibrate within the

clearance gap (TSP-inactive modes). For large excitations, the tube will be in

contact with all TSPs most of the time (TSP-active modes). In reality, the tube

response will be composed of both TSP-active and TSP-inactive modes.

A typical CCW heat exchanger tube was analyzed for the TSP-active and

-inactive modes. Table 2 shows the natural frequencies of TSP-active and -inactive

modes for different cases. The characteristics of Tube BWG 12, presented in this

paper, are similar to those of Tube BWG 18 except that the natural frequencies of

Tube BWG 18 are a little lower. As an example, the natural frequencies of TSP-

active modes of two tubes are compared in Table 3. The difference in natural

frequencies of the two tubes for the TSP-active mode is small; this is also true for

TSP-inactive modes.

Two different situations are considered for TSP-inactive modes: a particular

TSP, such as TSP 2, being inactive, and two TSPs, such as TSPs 2 and 4, being,

inactive.

14

Figure 14 shows the tube and all TSPs. The TSP-active modes are given in

Fig. 15 for the first five modes. The results agree well with those obtained by

Bechtel [2]. Figure 16 shows the first five modes when TSP 2 is inactive, and Fig.

17 shows the first two modes when two TSPs are inactive.

Among the TSP-inactive modes, some of the modes are dominant in specific

spans; these modes are called energy-trapping modes [8]. For example, Fig. 18

shows the lowest TSP-inactive modes for different cases. These modes are the

most important ones when one TSP is inactive.

43 Tube Response Characteristics

Among the information that is most important for the interpretation of the

daca is the natural frequency of the tubes. Based on the results presented in Table

2 and Figs. 15-18, we can construct frequency bands for tube BWG 12, as shown in

Fig. 19. These frequency bands are plotted on the assumption that only one

support is inactive. Experimental data show that those modes associated with

more than two inactive supports are not significant. Two types of frequency

bands, passing and stopping, can be constructed. Within a passing band, waves

can propagate freely through each tube support; however, within a stopping band,

waves will be attenuated as they travel from one support to the next. All natural

frequencies are in the passing bands only. In a stopping band, since no natural

frequencies exist within that frequency range, tube response will be very small.

Figure 19 shows the approximate boundaries of the first two stopping and passing

bands:

First Stopping Band 0 - 9.5 Hz

15

First Passing Band 9.5 - 73 Hz

Second Stopping Band 73 - 95 Hz

Second Passing Band 95 - 176 Hz

The first passing band is approximately between 9.5 and 73 Hz; therefore, the

dominant tube response is expected to be in this frequency range. In addition, the

first TSP-active mode is at 23.9 Hz; any frequencies below this are the energy-

trapping modes associated with TSP-inactive modes. The first two stopping bands

are approximately between 0 and 9.5 Hz and 73 and 95 Hz; in these two frequency

bands, we expect that the tube response will be very small.

Based on the experimental data and analytical results, some general

observations can be made.

TSP-inactive modes contribute significantly to tube response. It can be seen

from the frequency spectra that TSP-inactive modes, whose frequencies are lower

than that of the first TSP-active mode of approximately 23 Hz, contribute

significantly to the response.

Some of the tubes are subjected to fiuidelastic instability of TSP-inactive

modes. For example, let us consider Tube 11C. The frequency spectra for Tube

11C are given in Fig. 8 for various flow rates. When the flow rate is increased

from 10,000 gpm to 145,000 gpm, the contribution of TSP-inactive modes increases;

at 14,000 and 14,500 gpm, TSP-inactive modes are dominant. Furthermore, Fig.

13 shows that the slope of the response curve is much larger than 2, an indication

that the tube is subjected to fiuidelastic instability associated with TSP-inactive

modes.

16

The response of various tubes is different and the response of each tube

changes with flow rate. The key parameter in this case is the clearance between

the tube and TSP holes. As flow rate changes, the tube configurations also

change, i.e., the contact points of the tubes with TSPs changes with flow rate due

to the change in drag and lift forces.

The motion of Tube 5B is the largest of all instrumented tubes associated with

TSP-active and -inactive modes; however, the TSP-inactive modes are not the

dominant mode of the response. The large amplitudes are believed to be

attributable to the high local flow velocity. The tube is not subjected to fluidelastic

instability.

Based on the frequency band presented in Fig. 19, the dominant mode of each

tube at different flow rates can easily be identified from the spectra.

The response of all tubes is contained in the first passing band; this is in

agreement with the frequency band consideration. The modes include TSP-active

and -inactive modes. In some cases, the frequencies of the active and inactive

modes can be seen clearly in the spectra. As an example, the frequency spectra of

Tubes 1A-H and 2A-H are given in Fig. 9, the lower frequency peaks are TSP-

inactive modes and the higher peaks are TSP-active modes. In some other cases,

only TSP-inactive or TSP-active modes dominate; see Fig. 10 for typical examples.

Among the instrumented tubes, the displacements of the tubes in the first

row in the inlet region are the largest. This can easily be seen by comparing the

displacements of tubes in different locations.

17

The tube displacements in the inlet regions are larger than those in the outlet

region. In addition, the spans close to the inlet nozzle (accelerometer groups B

and C) have larger displacements than spans further av/ay from the inlet nozzle.

The main characteristics of the tube responses are

• TSP-inactive modes are important since some of them are subjected to

fluidelastic instability.

• Fluidelastic instability of TSP-active modes does not occur.

• Tube characteristics (support conditions) change with flow rate.

• The tubes located in the front row in the inlet region have larger

displacements.

• Tube wear may be important owing to the impact/sliding associated with

fluidelastic instability of TSP-inactive modes and turbulence excitation of

TSP-active and -inactive modes.

4.4 Fluidelastic Instability and Wear

From the experimental data, it is noted that fluidelastic instability may

occur, depending on the modes. The critical flow velocities for different cases

were calculated. The flow velocity distribution is not known. Assuming a

uniform flow velocity distribution, the flow velocity is 1.16 ft/sec at 12,700 gpm.

18

The mass-damping parameter is 0.24, assuming a damping ratio of 1%.

Therefore, the reduced flow velocity is 0.84 and 1.84 for TSP-active and TSP-

inactive modes, respectively. On the basis of the existing correlations [9,10], the

critical reduced flow velocity ranges from 1.1 to 2.2, On the basis of the existing

correlations, we expect the tubes are not subjected to fluidelastic instability of TSP-

active modes, but may be subjected to fluidelastic instability of TSP-inactive

modes. This is in agreement with the experimental data.

In the original design, the incoming fluid passes across three passes only;

the reduced flow velocity at 12,700 gpm is 1.96 and 4.29 for TSP-active and TSP-

inactive modes, respectively. Therefore, the tubes are subjected to fluidelastic

instability of TSP-inactive modes and some of the tubes are subjected to fluidelastic

instability of TSP-active modes. The instability of the TSP-active modes had

caused tube damage in the original design.

Once the tubes are subjected to fluidelastic instability of TSP-active modes,

they are not acceptable from the standpoint of flow-induced vibration and it is not

necessary to calculate wear rate because tube leaks will occur within a very short

time of operation. On the contrary, when the tubes are subjected to fluidelastic

instability of TSP-inactive modes, the wear rate is much smaller and its

significance depends on many other parameters. In general, it is difficult to

predict tube wear under such conditions. In CCW heat exchangers, several

important parameters, such as clearance, flow velocity distribution, and wear

rate, are not known. It is impossible to predict tube wear with confidence.

However, as an exercise, tube wear was calculated by means of the approach

taken by Connors [11]. If a wear coefficient of 600 and clearance of 25 mils are

used in the calculations, it is concluded that it will take about 16 years for a tube to

19

wear through. This wear calculation is not accurate and only gives an estimate of

order of magnitude.

5. CONCLUSIONS

On the basis of this evaluation, we have concluded the following:

In the original design, the flow velocity was larger than the critical flow

velocity; therefore, the tubes were subjected to the fiuidelastic instability of TSP-

active modes. The original design was not acceptable and the observed damage

was due to fluidelastic instability.

In the extensively modified version, the tubes are not subjected to the

fluidelastic instability associated with TSP-active modes. Therefore, occurrence of

tube leaks caused by flow-induced vibration is not expected to occur during short-

term operation. Based on the tube response characteristics, it is believed that the

clearance between the tubes and support plate holes is relatively large. Because of

the clearance, wear will result from the sliding and impacting of the surfaces due

to the oscillations associated with turbulence excitation and instability of TSP-

inactive modes. When the unit is put in service, a surveillance program and

follow-up work should be conducted to ensure the safety and predict the useful life

of a unit.

From the experience with CCW heat exchangers, it appears that the state of

the art is such that more work remains to be done. Specifically, the following

items should be emphasized:

20

• Flow Velocity Distribution. An efficient computer code to compute the

flow velocity distribution for general heat exchangers would be very

useful. Currently, few codes can be used for CCW heat exchangers.

Unfortunately, more time and cost will be required to use these codes.

• Wear Prediction. The state of the art is inadequate to predict tube wear.

Very little information is available for wear associated with TSP-inactive

modes and data for TSP-active modes are very limited. The detailed

dynamics of tube/support interaction are still not well understood.

• Tube Response and Prediction of Stability. Methods are available to

predict the critical flow velocity of fluidelastic instability and tube

response to various excitations. However, the methods require further

improvement.

ACKNOWLEDGMENTS

Tests of CCW Heat Exchangers were performed by Bechtel Group, Inc., and

Loutech Taiwan, Inc.

Many engineers in the Nuclear Engineering Department of Taiwan Power

Company have contributed to various aspects of the program; among them are Y.

H. Cheng, S. C. Cheng, T. K. Lee, P. C. Kao, F. Y. Lai, H. H. Lee, and P. F. Wang.

This work was performed for Taiwan Power Company under an agreement

with the U.S. Department of Energy under contract agreement 31-109-ENG-38-

85847.

21

This work was performed for Taiwan Power Company under an agreement

with the U.S. Department of Energy under contract agreement 31-109-ENG-38-

85847.

1. "Test Report: Vibration of Tubes in Component Cooling Water Heat

Exchangers, Phase 1 Tests," Bechtel Group, Inc., San Francisco, CA,

(September 1984).

2. "Test Report: Vibration of Tubes in Component Cooling Water Heat

Exchangers, Phase 2 Tests," Bechtel Group, Inc., San Francisco, CA,

(October 1984).

3. "Final Report on CCW Heat Exchanger Tube Vibration Test, Third Nuclear

Power Station, Taiwan Power Company," by Loutech Taiwan, Inc.,

(December 1988).

4. Sebald, J. F., and Nobles, W. D., "Control of Tube Vibration in Steam

Surface Condensers," Proc. Am. Power Conf., Vol. XXIV, 630-643 (1962).

5. Moretti, P. M., and Lowery, R. L., "Heat Exchanger Tube Vibration

Characteristics in a 'No Flow1 Condition," Final Report: Tubular

Exchanger Manufacturers Association Experimental Program, Oklahoma

State University (1973).

22

6. Shin, Y. S., Jendrzejczyk, J. A., and Wambsganss, M. W., "Effect of

Tube/Support Interaction on the Tube Vibration of a Tube on Multiple

Supports," Argonne National Laboratory, Technical Memorandum ANL-

CT-77-5 (1977).

7. Rogers, R. J., and Pick, R. J., "On the Dynamic Spatial Response of a Heat

Exchanger Tube with Intermittent Baffle Contacts," Nucl. Eng. Des. 36, 81-

90(1976).

8. Chen, S. S., "Vibration of Continuous Pipes Conveying Fluid/' in Flow-

Induced Structural Vibrations, ed. by E. Naudascher, IUTAM-IAHR

Symposium, Karlsruhe, Germany, 1972, pp. 663-675.

9. Pettigrew, M. J., Sylvestre, Y., and Campagna, A. O., "Vibration Analysis

of Heat Exchanger and Steam Generator Designs," Nucl. Eng. Des. 48, 97-

115(1978).

10. Chen, S. S., Flow Induced Vibration of Circular Cylindrical Structures.

Hemisphere Publishing Corp., 1987.

11. Connors, H. J., "Flow-Induced Vibration and Wear of Steam Generator

Tubes," Nucl. Technol., 33, 311-331 (1981).

DISCLAIMER

This report was prepared as an account of work sponsored by an agency of the United StatesGovernment. Neither the United States Government nor any agency thereof, nor any of theiremployees makes any warranty, express or implied, or assumes any legal liability or responsi-bility for the accuracy, completeness, or usefulness of . . , . information, apparatus, product, orprocess disclosed, or represents that its use would not infringe privately owned rights. Refer-ence herein to any specific commercial product, process, or service by trade name, trademarkmanufacturer, or otherwise does not necessarily constitute or imply its endorsement recom-mendation, or favoring by the United States Government or any agency thereof. The viewsand opinions of authors expressed herein do not necessarily state or reflect those of theUnited States Government or any agency thereof.

Table 1. History of CCW Heat Exchangers

1. Trains A and B of Unit 1 were placed in service in December 1982, andJanuary 1983, respectively.

2. Tube leakage was discovered in March 1983. Damage was found at supportsand midspans.

3. The manufacturer's action taken after tube leakage:

* Damage was considered to be attributable to inappropriate design of theinlet flow distributor.

• Modifications, as follows, were recommended to alleviate the problem:

a. Replacing the original flow impingement plate by a flow deflector.b. Replacing 306 tubes from each heat exchanger with heavier tubes (8WG

12vs.BWG18).c. Eliminating 114 tubes from each heat exchanger and plugging the holes

in the tubesheets and baffles.

4. The CCW Heat Exchangers of Units 1 and 2 were placed in service in Januaryand February of 1984, respectively, after modifications were made in responseto manufacturer's recommendations.

5. Bechtel Group, Inc. performed Phase-1 test.

Test of Train A after modifications in February 1984. Six tubes at the inletregion and three tubes at the outlet region were instrumented.

Train A was tested again with the flow deflector rotated 90 degrees.

6. Additional modifications were recommended on the basis on the results of thePhase-1 test.

Staking the bottom 14 tube rows in bays 1, 2 and 3.

Installing perforated plates in bays 2 and 3.

7. Modifications of Unit 2 were completed in June 1984, and those in Unit 1 werecompleted later.

8. Bechtel Group, Inc. performed Phase-2 test in July 1984.

Train B of Unit 2 and Train A of Unit 1 were tested.

Train B of Unit 2 was retested.

9. Taipower decided to order two new CCW heat exchangers and to modify two ofthe original CCW heat exchangers

10. The modification of the original CCW heat exchanger was completed byTaiwan Machinery Manufacturing Corp. in 1988.

11. Loutech Taiwan, Inc., performed tests on the modified Train B of Unit 1 inSeptember 1988.

12. Taipower and Argonne National Laboratory performed an evaluation of CCWheat exchangers.

Table 2. Natural Frequencies in Hz of CCW Tubes

All TSPsActive

2.38B48E+012.47746E+012.61928E+012.80613E+013.02973E+013.28225E+013.55647E+013.84557E+014.14246E+014.43886E+014.72400E+014.98308E+015.19570E+015.33561E+015.416e8E+019.55004E+019.74398E+011.0O413E+02i,04170E+021.08504E+021.13254E+021.18294E+021.23513E+021.28796E+021.34005E+021.38959E+021.43402E+021.46972E+021.49222E+021.52036E+022.24451E+022.27477E+022.32095E+022.37882E+022.44457E+022.51509E+022.58773E+022.66008E+022.72974E+022.79427E+02

TSP 2Inactive

1.13053E+012.39328E+012.49449E+012.65018E+012.84452E+013.062Q9E+013.29786E+013.55885E+013.84635E+014.15166E+014.46243E+014.76359E+015.03460E+015.24556E+015.41605E+016.81634E+019.55977E+019.77727E+011.00993E+021.04873E+021.09095E+021.13550E+021.18346E+021.23522E+021.28941E+021.34393E+021.39611E+021.44234E+021.47717E+021.52035E+021.76043E+022.24604E+022.27996E+022.32972E+022.38855E+022.45133E+022.51733E+022.58778E+022.66092E+022.73303E+02

TSP 3InactJve

9.68389E+002.39275E+012.48674E+012.62322EI012.80663E+013.043B6E+013.32520E+013.63698E+013.96541E+014.28958E+014.54128E+014.72946E+014.99427E+015.22849E+015.41581E+016.49951E+019.55868E+019.76213E+011.00489E+021.04179E+021.08759E+021.14026E+021.19731E+021.25641E+021.31414E+021.35919E+021.39086E+021.43571E+021.47461E+021.52035E+021.70462E+022.24585E+022.27741E+022.32180E+022.37920E+022.44969E+022.52867E+022.61100E+022.69198E+022.76585E+02

TSP 4Inactive

9.53309E+002.39177E+012.47919E+012.62222E+012.B3474E+013.09982E+013.36640E+013.57155E+013.85633E+014.20758E+014.56757E+014.89305E+015.02601E+015.20820E+015.41540E+016.43080E+019.55670E+019.74738E+011.00469E+021.04707E+021.09784E+021.14751E+021.18557E+021.23706E+021.29952E+021.36271E+021.41933E+021.44225E+021.47154E+021.52034E+021.69312E+022.24553E+022.27520E+02 .?.32211E+022.38809E+022.4652BE+022.53571E+022.58937E+022.66472E+022.74758E-I-02

9222233334445,5,5,6,9.9.1.1.1.1.1.1.1.1.1.1.1.1.1,2.2.2.2.2.2.2.2.2.

TSP 5Inactive

.51959E+00

.39064E+01

.47765E+0I

. 63923E-I01

.86230E101

.05253E+01

.29078E+01

.6315SE+01

.97486E+01

.16079E+01

. 4727IE+01

.84508E+01

.34234E+O1

.19770E+01

.41472E+01

.41603E+01

.55442E+0174437E+0100799E+02,05206E+0208902E+0213414E+0219654E+0225808E+0229097E+0234623E+0241092E+0246170E+0247017E+0252031E+0269085E+0224517E+0227486E+0232747E+0239495E+0244902E+0251894E+02 '61017E+0269207E40273149E+02

TSP BInactive

9.51825E+002.38852E+012.49456E+012.62225E+C12.85222E+013.04704E+013.34421E+013.60336E+013.90738E+014.23021E+014.48968E+014.84973E+015.01855E+015.30070E+015.40789E+016.41220E+019.55012E+019.77780E+011.OO463E+O21.05040E+021.08789E+021.14413E+021.19067E+021.24690E+021.30252E+021.35013E+021.41028E+021.44153E+021.4B675E+021.51990E+021.69032E+022.24452E+022.28015E+022.32154E+022.39318E+022.44784E+022.53491E+022.59662E+022.68039E+022.74624E+02

TSPs 2 & l\Inactive

B.29776E+001.25001E+012.39854E+012.50390E+012.65102E+012.85479E+01.3.11S83E+O13.38327E+013.57531E+013.85679E+014.21025E+014.57386E+014.91663E+015.19907E+015.41526E+016.05711E+017.06316E+019.57002E+019.79375E+011.01002E+021.05086E+021.10094E+021.15084E+021.1B641E+021.23711E+021.29995EH021.36372E+021.42288E+021.47022E+021.52033E+02I.63128E+021.80180E+022.24763E+022.28230E+022.32974E+022.39309E+022.468B9E+022.53823E+022.58943E+022.66510E+02

TSPs 3 & AInactive

4.66164E+001.32502E+012.39716E+012.49075E+012.62533E+012.83516E+013.11056E+013.42886E+013.76846E+014.C8698E+014.31113E+014.58220E+014.89624E+015.16138E+015.31758E+015.41642E+017.29944E+019.56835E+019.77076E+011.00526E+021.04718E+021.10005E+021.15936E+021.22136E+021.27918E+021.31901E+021.36535E+021.41980E+0?1.46557E+021.49476E+021.52036E+021.84664E+022.24733E+022.27853E+022.32271E+022.38848E+022.46978E+022.55829E+022.64736E+022.72761E+02

Table 3. Natural Frequencies ot the TSP-active Modes of Tubes BWG 12 and 18

Modes

123456789

1011121314151617180920

Tube BWG 12Hz

23.924.826.228.130.332.835.638.541.444.447.249.851.953.454.295.597.4

100.4104.2108.5

Tube BWG 18Hz

21.522.323.625.327.329.632.134.737.440.042.644.946.848.048.886.187.990.593.997.8

oFig. 1. Arrangement of Baffles and Support Plates

I ' ' I ' ' I ' 'I M i l

I I I f f' ' I '

! • • 1+-»

• ' m 11 ' i • • i ' •

i i i i

15 13 11 9 7

TRAIN A

TUBE FRETTING DAMAGEATSUPPORT

FLATTENED TUBE SURFACE

2/3/4 FLATTENED SURFACESFOUND ON ONE SPAN

flff i

Fig. 2. Damage Inspection of Removed Tubes

CCW HXs, Unit 1(Both Train A and B)

Daaage Appeared at Supports as Follows:

EX A EL-3-1£1-26-2E5-1-2/3/4/5/8£5-4-1/2/3/4/6/9E5-51-3/4/6/9£5-54-1/2/3/4/6/8E29-26-6£53-1-1

HX B EL-3-2/4El-26-2/3E5-1-2/4/5/6/7E3-4-2/3/4/5/6/7/9/10/12/13/14E5-51-1/2/3/4/5/6/7E53-4-8/9E53-51-5E53-38-6

El-3-2/4Row 1 (from bottom), tube 3 (fron left) at support plates 2 and 4

Fig. 3. Location of 28 Tubes Selected from Each Heat Exchanger

Fiq. 4. Peak-to-Peak Displacements as Function of Flow Rate

5000 1.000e+04 1.500e+04FLOW RATE, gpm

1 0 0 200 300 400

Frequency500 100 200 300 400 500

Fig. 5. Frequency Spectra of Tube 1H, a Typical Tube

Fig. 6. CCW Heat Exchanger Modified by TMMC

13

/ > A / W V A / \ / V A A A A A A y A . V ^ . A y y A^ A A/NyV̂ y V \A/W*V/**/ VVVW yVW VW\A Ay^ A ^ V A A / V W V V V W

\ y V . y v y y ^ y \ A y V / \ y y y v

VVVV^AyY^y^;Ay^Av^r,/^/^AAAA^AA7^y^y^y^yvX/V^/AAAXXA/A/. A/v^Ay^A/Vv^yV^yV^y•vVV^y^AAy^y^Ay^vVAAy^Ay^yvv^y^XAy\X\A,VVVV>AAyVV^AA/kyvV\Ay\AAAyNA/\/V\AAy\A/^yV^AA/VA/Vyv^A-AAy^Ay^A/\y^vv^y^y^/^V•\AyV^Ay\.AA^^y^yVV^AyV^y^ A X X A / /\.-••%Ayv\Ay^/VV

NAyV^yV^y^y^Ay^AAy^AyVV^y^y^Ay^AAA/v^/V^AAX

VV^AAXXAy^Ay•VVVV^AyXAyVN''

A.AyNy^cVAAy^yVVAyVAAy^AXy^AAAAAAAAj^ «- A ~ - - ' - AAAy%* 9

^y\Ay\yV

\A A * /s A X A A A \ X \ ' V V V ' - VV VV VVV V VVVN W V V W V VV ' vf v v V V V-' VV V W v V W \AyOC^XYAYAi/VY^^^ 1 ,̂ AAv^Ay^Av^A.̂ A.VVVV^AAAv^A'

NAAA^y^AAy^y^AAAAXy^AOOOOvAA A ^ y ^ ^ ' ^ ' ^ \AAyVV^y\AA^%A/vV\AAAA^VAyV\A/Ay^WNyA^"A,A.AAA/WA-VWW\.XyVV\AAAA'WW/OO^^YXVVYV , ' w ̂ '"^Wvv^A-V\/VVVV\Ay^AyvVAA-• AAAAyV^A,rtv^y\AyVV\A.XAA/Jr ŷv̂ Aŷ A.-• •AyV^-^AAAAAAAAAAAy\AA.-.-AAA.\/V\A'5 AAAy\A_Ay\AA/\AA "AAA/

\A/VVVV\AvT^/\Ay\yv\AA AAyAA/\AAAA/\Ay\AAAAAA/\AAAy

\ A - - H p V ^ y

INLET INSTRUMENTATION DEPTH

A 25.5 !N. (TUBE 1-4 & 20, GROUP A)

• 65 IN. (TUBE 5-9 &19, GROUP B)

• 107 IN. (TUBE 10-15, GROUP C)

• 149 IN. (TUBE 16-18, GROUP D)

OUTLET INSTRUMENTATION DEPTH

• 25 IN. (TUBE 11 & 2', GROUP E)

X 64.25 IN. (TUBE 3'-5\ GROUP F)

• 106 IN. (TUBES 61 & T, GROUP G)

Fiq. 7. Instrumented Tubes

11C-H

4\; • • • ? * ! •

TV. 1 . . : . ,

Ullllu

J •:

fBjnriT

; i H 5 4 i

Liiiiiillllyi'iiiiiiiiiii,

' . • • • • ! •

gpm

145,000

11C-V

140,000

130,000

120,000

110,000

qj...j..4...j....j 100,000

90,000

76,000

•*3i:

J : : :

=..; (I

iuiOl

i! H

yil

T e l•••••!• •{••ii-

!G jn?

U : :"

..J....

.!*...:

iiiiliiibui....

60,000

140 0 140

Frequency, Hz Frequency, Hz

Fiq. 8. Frequency SDectra of Tube 11C

TSP-InactiveModes

mtnu

TSP-ActiveModes

Tube 1A-H10,000 gpm

140.

TSP-InactiveModes

ml nut

TSP-ActiveModes

Tube 2A-H145,000 gpm

P-Q.

140.

Fig. 9. TSP-Inactive and TSP-Active Modes

TSP-Inactive Modes

mlnuTube 5F-H1200 GPM

TSP-Active Modes

Tube 5B-V7000 GPM

Hz. 140.

Fig. io. Either TSP-Inactive or TSP-Active Modes Are Dominant

TUBE 1A-V

0.1

EBUJQ

0.011000 10000

FLOW RflTE, gpm

100000

0.1

£

LUQ=3H

0.011000

TUBE 1A-H

10000

FLO ID RflTE, gpm

100000

Fig. 11. Displacement of Tube 1A

TUBE 5B-V

£UiQ

t o.i-Ja.z

0.011000 10000

FLOW RflTE, gpm100000

TUBE 5B-H

ESuuQ

to.i

z

0.011000 10000

FLOW RflTE, gpm100000

Fig. 12. Displacement of Tube 5B

0.1TUBE11C-Y

E£

o3

0.011000 10000

FLOW RflTE, gpm100000

0.1 TUBE 11C-H

10000FLOW RflTE, gpm

100000

Fig. 13. Displacement of Tube 11C

CM

CM

CO

1ST MODE, 23.9 HZ

3RD MODE, 26.2 HZ

4TH MODE, 28.1 HZ

5TH MODE, 30.3 HZ

TSP-flCTlUE MODES

Fiq. 15. The First Five Modes of TSP-Active Modes

1ST MODE, 11.3 HZ

2ND MODE, 23.9 HZ

3RD MODE, 24.9 HZ

4TH MODE, 26.5 HZ

5TH MODE, 28.4 HZ

TSP 2 SNflCTlUE

Fig. 16. The First Five Modes of TSP-Inactive Modeswhen TSP 2 is Inactive

8.30 HZ

12.5 HZ

TSP2 RNDTSP 4 INRCTIUE

4.66 HZ

13.25 HZ

TSP 3 HND TSP 4 INflCTlUE

Fiq. 17. The Fi rs t Two Modes for TSPs 2 and 4 Inactive andTSPs 3 and 4 Inactive

TSP 2 INflCTlUE 11.31 HZ

TSP 3 INflCTlUE 9.68 HZ

TSP 4 INflCTlUE 9.53 HZ

TSP 5 INflCTlUE 9.52 HZ

TSP 8 INflCTlUE 9.52 HZ

Fig. 18. The First TSP-Inactive Mode for One TSP Inactive

FIRST

STOPPING

BANDFIRST

PASSINGBAND

SECONDSTOPPING

BAND

SECONDPASSING

BAND

'7/777.

OHZ 50 HZ 100 HZ 150 HZ

Fig. 19. Frequency Bands for Tube BWG12