I have not heard anything about this, but intial application of TMDs was to dissipate vibrations caused by the rocking motion of ships.

Anamul Haque It should work in reducing the vibration levels provided the issue is at a particular frequency and the auxiliary system is tuned as per that frequency. The placement of the TMD is also critical so definitely you will have to check the problematic mode shape of the structure. The concept is widely used in many applications, and I don't see a reason why it would not work here. Structural noise is a completely different topic and it may or may not reduce noise levels.

As far as tuning goes, you most likely don't have a particular fundamental or natural frequency in that application, other than perhaps belt speed divided by idler spacing (i.e. as a basic characteristic, just as a starting point or baseline). The nature of the system's operating dynamics is also dependent on its configuration, or for a conveyor, how is it supported. If noise is due to structural flexure of the conveyor and its support, you may be able to add support structure to increase stiffness and natural structural frequency, perhaps moving the operating characteristic further above from the fundamental or lowest natural frequency of oscillation. Simply adding mass haphazardly, however, in a misguided attempt to improve stiffness for example, may also lower the fundamental frequency, perhaps making sympathetic or resonant vibrations (and associated noise) worse. A long cantilever conveyor is probably nested in a carefully designed engineering truss which is already optimized for that task, and better left as is for that reason. An extended traverse conveyor with multiple suspension or leg points may move parallel or transverse to its long axis with the dynamic deflection generating noise through the support structure. In such cases either dimension may benefit from tensile bracing of simple cable-pairs from hard points of the support truss or beam to fixed anchor points on the ground or on walls at or near the heigh of the belt if possible. Diagonal bracing through both axial and transverse dimensions relative to the conveyor path may prove most effective for the cost of required cable length and fittings, while also being least redundant if that matters. An indoor suspended traverse may apply vibration to sheet metal roof panels that serve effectively as audio radiators, broadcasting the sound of structural vibration. In this case springs placed somewhere along the length of the suspension lines may serve to absorb and reflect some of the structural vibrational energy before that energy reaches the roof or siding panel anchor point. The noise may also be a latent factor of the mass flow rate of the conveyor due to its own bearings and other design features. Identification of the sources of each offending sound component (i.e. squeak or rattle or groan or bang or.... each have specific source types) may offer insight into possible mitigation or lack of any chance thereof if and when that may be the case. lateral deflection of extended slender structure may be greatly stabilized against using only the slightest lateral restoring spring force. But if the conveyed product itself is the noisy culprit, vented enclosure may be the best solution. You must get to know the finer details of your noise and its many possible sources in order to devise and assess any effective mitigation strategy.

A TMD is unlikely to be the optimal solution. Treating the idler rollers seems more effective (see attachment).

Anamul Haque i think yes, we can install a TMD to reduce the vibration in the belt. however i think that the TMd should be installed on the support of the belts.

Anamul, have you yet done a noise and vibration survey of your (very) long transportation belt to find out where noise is generated and an environmental survey to plot the geographical noise map? Tuned mass dampers won’t overcome a lack of general maintenance or an installation built 50yrs ago to absent noise control designs. Where is your belt? Let’s have a look at it on google earth......

Anamul Haque

Firstly it would depend on which type of vibration we are trying to reduce;

1) The general vibration due to the flexibility of the structure:

This is a tough one to tackle as there is no single fundamental frequency in the system. The system's behaviour keeps changing at each time instant based on the weight the belt carries, the position of the weights respect to each other and with respect to the rollers. It is analogous to changing the fundamental frequency of a guitar string by holding and sliding it while it's vibrating. Given this variability in the system is tough to identify a single frequency and suppress it. Even if we place a TMD in such a system I am afraid it will do more harm than add benefit as sometimes these TMD have a tendency to amplify other frequencies.

2) Stick-slip kind of phenomenon causing jerks in the motion of the belt

This one I feel can be resolved by increasing the damping at the rollers or the traction between the roller and the belt.

Hope that helps, feel free to share your thoughts in case you found something interesting while working on this problem.

I do not understand why questions are asked in this Forum and potential solutions ignored. Using TMDs to address a vibration (or poor maintenance) related noise problem with long conveyor systems is sub-optimal as a single TMD will not be sufficient. Earlier in the discussion, I provided a copy of a conference paper that detailed a relatively cheap and effective solution but it does not appear to have even been considered. How long is the conveyor? And how many TMDs do you envisage will be required? Have you undertaken a cost comparison between multiple TMDs and idler roller treatment?

Eric Ancich, sorry for replying to you late and immensely grateful to you for the paper you provided.

We had our basics clear and now we will be working specifically on the Idler/Belt interaction. Do you have any other suggestions other than Idler Surface Improvement to reduce the noise generated due to the interaction?

Lokaditya Ryali, Thomas H. S. Harris, Pranoy Nair, and all the others who answered, thanks a lot!

Annamul, out of curiosity i woukd like to hear the results of a before and after noise survey and the cost breakdown of the measures implemented please. Regards. Jonathan

Jonathan David Binnington , sure, I will.

Eric Ancich, can you please tell me that what did they mean by 'Maximum Indicated Slope (MIS)' in the paper you referred to?

I can't find the details of the term anywhere.

I am unable to answer your question as I had no involvement in writing the paper. I suggest you contact Steve Brown [[email protected]]