river measurements report - masson marine s.a.s · 8 masson marine { river measurements report {...

RIVER

Noise and vibrations report

Date of Issue : September 3, 2009

Paul-Edouard GOLLEMASSON MARINE5 rue Henri Cavallier89100 Saint Denis les [email protected]

Company Restrictedc© MASSON MARINE 2009

The information contained in this document is MASSON MARINEproperty. Disclosure to third parties or reproduction in any from whatsoever

without written consent is forbidden.

mailto:[email protected]

Contents

1 General specifications 3

2 Sound measurements 42.1 Microphone positions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42.2 Overall noise for different speed . . . . . . . . . . . . . . . . . . . . . . . . 42.3 Waterfalls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42.4 Full forward . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62.5 Noise when manoeuvring . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72.6 Propeller noise? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

3 Vibrations measurements 103.1 Full forward . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103.2 Waterfall sensor input shaft axial . . . . . . . . . . . . . . . . . . . . . . . 113.3 Ceiling isolation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

4 Conclusion 13

2

MASSON MARINE – RIVER Measurements report – September 3, 2009 3

1 General specifications

SHIP IDENTIFICATION

Name RIVER

Reg N◦ 02331458

Test date 20 aout 2009

Type Tanker

Length 125 m

Country NL

PROPELLER

Type FPP / NOZZLED

Brand AMV

Blade N 5

Line shaft L

Diameter 1800 mm

ENGINE

Brand/Type CATERPILLAR / V16

Model 3516

SN TTD00261

Power 1451 kW @ 1600 rpm

Rotation CCW

Mounting Flexible

Flexible

GEARBOX

Type MMW16500

SN 27121

Ratio 4.95

Rotation CW

Mounting Rigid

Oil SAE 30

PTO Type 0

PTI No

Trailing P No

Observations

• Engine room door opened during measurements, tanks fully loaded, ventilation isswitched on (except if the contrary is mentioned).

• Ship is finished, the crew is complaining about a noise appearing at low speed andthe two aft cabins do have a noise level above regulations.

• No measurements have been done in living quarters.

• The table below give the gear excitation of each gear mesh according to the enginespeed N express in revolutions per minute and the order n (n = 1 ⇒ main gearmesh frequency, n = 2⇒ harmonic 2 of gear mesh,. . . ).

Ki K2 Kpto Kpump

hn(N) = 50nN60

hn(N) = 20nN60

hn(N) = 79.45nN60

hn(N) = 19.86nN60

Tab. 1: Gear mesh excitations according to engine speed and harmonic number

c© MASSON MARINE 2009

4 MASSON MARINE – RIVER Measurements report – September 3, 2009

2 Sound measurements

2.1 Microphone positions

Two microphones were used during the sea trail, one was placed close to the gearboxk2 inspection cover (1), about 20 cm in order to really mesure what is coming from thegearbox. The second one was placed about 50 cm above the engine (2).

Note For shipping inspection the distance should be 100 cm

Fig. 1: Microphone on the gearbox, 20 cm frominspection cover

Fig. 2: Microphone beyond the engine, 50 cmfrom engine

2.2 Overall noise for different speed

Fig. 3: Overall SPL (dBA), sailing forward

As you can notice the noise in the engine room is not high. The Sound Pressure Level(SPL) when sailing forward is 110.3 dBA @ 1600 rpm on microphone at 20 cm fromgearbox.

2.3 Waterfalls

The waterfall view is a 3 dimensional diagram representation. In our case frequencycorrespond to the X-axis, engine speed correspond to Y-axis and the Z-axis (here thecolors, defined by the scale on the left) represent the value corresponding to this speedand frequency.



Fig. 4: SPL profile during an engine run up (650 up to 1550 rpm), gearbox microphone

On this waterfall we can identify one gear order which seems to be harmonic 5 of K2

and is discussed later in this report. Also the engine turbo clearly appear as a strongnoise generator. The same graph is displayed below, viewed from the engine microphone.

Fig. 5: SPL profile during an engine run up (650 up to 1550 rpm), engine microphone

The gear order can still be perceive but start to disappear in the surrounding noise.The gear noise is the same but as the distance between gearbox and microphone is higherthe level corresponding to the gear order and catch by the microphone is lower. On theother hand as we get closer to the turbo with the second microphone, its ”excitation”



seems stronger. . . Also always watch out carefully the color scale for each display, becausethe maximum value recorded is always showed with a dark red whether it is 50 dBA or100 dBA. In our case maximum value is 108 dBA for the gearbox microphone whereas itis 102.3 dBA for the engine microphone.

2.4 Full forward

The overall SPL was 110.3 dBA average on 30 s under 1600 rpm at the gearboxmicrophone. On the graph 6 I listed some gears orders that can be identify. Orders 1, 2,4, 5 of K2 gear mesh are present (designed by marker 1-x, where x stands for the order),as well as order 1 of pump gears and orders 2, 3, 4 and 5 from the KPTO gears. Pleaserefer to the graph for the value of each.

Fig. 6: SPL profile in dBA average on 30s at 1600 rpm, sailing forward

I also use the max peak marker in order to determine the 5 first maximum level, theresults are listed in the table below.

Peak n f [Hz] Level [dBA]

1 342.97 98.0

2 854.7 93.1

3 942.6 92.6

4 532.8 91.9

5 682.8 91.4

Tab. 2: Main peaks and their matches when sailing forward at 1600 rpm

Only order 1 of K2 gear mesh appear in the 5 maximum level given by the peak markerfunction. You also notice the turbo noise which creates quite a wide band frequencyexcitation. The power band marker (see graph 7)allowed me to quantify the total power



contained in its excitation band from 10.4 kHZ up to 11.4 kHz roughly. The turbo noiseis equivalent to a 88.7 dBA noise generator, although its maximum peak is 82 dBA.

Fig. 7: SPL profile in dBA average on 30s at 1600 rpm, sailing forward

2.5 Noise when manoeuvring

The owner also hear a noise when he is manoeuvring with steering, unfortunately Icould not notice a strong noise variation implying the consequence of steering. The graph8 shows the noise measured during 30 s while the captain was steering. The reason cansimply be that the microphone is not at the best place to record this noise variation.

Fig. 8: Waterfall view of noise on 30 s period, steering and sailing forward 1500 rpm



2.6 Propeller noise?

During the sea trail we also notice that there is a noise when running at idling speeduntil 1000 rpm roughly. The level measured by the sensors on the gearbox does not showvariations denoting something wrong inside the gearbox. I must say that the sensors wereplaced to diagnose an eventual problem on the gearbox not on the propeller. . .

However when we really zoom into the engine or gearbox microphone we can see a lotof sidebands spaced of 8 Hz (for 965 rpm engine speed).

Fig. 9: Zoomed average spectrum of engine mic, 15 average, 0.5 Hz resolution, forward 965 rpm

To have a better view of this sidebands the cepstrum is displayed below. The cepstrumis the Fast Fourrier Transformation of the spectrum. The x-axis represent the Quefrencyin s.

Fig. 10: Cepstrum view of spectrum 9



You may think that the peaks appearing on the cepstrum are harmonics but the spacebetween them is not constant (1.5, 2). Also they are not in entire order of the outputshaft speed (0.825, 1.23, 2.47). I even compared with the output shaft bearings defectfrequencies, nothing match.

3 Vibrations measurements

Vibrations at several points have been collected, not all of them are displayed herecause they do not present a particular interest.

Fig. 11: Some sensor placements on the gearbox

3.1 Full forward

Fig. 12: Vibration profile at input shaft axial sensor



If you look to the graph 12, you will noticed that the vibration level is very low, theoverall valus is 0.553 g and order 1 of K2 is only 0.2 g. According to the standard AFNORE 90 300 the level on the gearbox is very low. The standard classified machines thanksto their overall speed value on the 10 Hz - 1000 Hz bandwidth. A ”good” machine interm of vibration has its value under 2.8 mm/s, the value here is 2.68 mm/S (graph 13).

Fig. 13: Velocity obtained from graph 12, 2.68 mm/s overall

3.2 Waterfall sensor input shaft axial

Fig. 14: Waterfall representation of acceleration at input shaft axial sensor

On fig.14, you can see some diagonal lines that correspond to the K2 gear meshharmonics. In order to better compare their level, I extract the 6 first orders (graph 15).



Fig. 15: 6 first orders of K2 which are orders 20, 40,. . . of input shaft speed (see table 1

The extraction graph shows that order 1, 2 and 5 have the highest contribution on thevibration measured at this point. Also we can notice that each order level is influencedby speed and the vibration produce does not necessary increase with rotation speed.

3.3 Ceiling isolation

In the second half of measurement I placed one sensor on the ceiling in order to checkits isolation against vibration. The two following graphs shows the difference between onesensor on the gearbox and one sensor on the ceiling.

Fig. 16: Engine room ceiling isolation, sailing forward 1600 rpm



Fig. 17: Engine room ceiling isolation, sailing backward 1600 rpm

4 Conclusion

According to the measurements the gearbox does not create high noise level, and it isalways below the regulations.

The vibrations created by the gear meshes are very low, which means that the vibrationstransmit by the gearbox to the ship structure is also low. According to AFNOR standarddue to its low overall velocity level, this gearbox is classified in the ”good” range.

Moreover the vibration isolation of the ceiling seems all right, and the noise that theowner is complaining about is not linked to the gearbox so I advice looking more on thepropeller side.


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