FLOATING DEVICE PROVIDING NOISE REDUCTION PROPERTIES
The present invention relates to a floating noise reduction system for moving and/or falling fluids, the process for manufacturing of such system and the use of such system.
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This application claims priority from European patent application No. 10 163 520.9-2213 filed on May 21, 2010, all of which is incorporated herein by reference in its entirety for all purposes.
FIELD OF THE INVENTIONThe present invention relates to a floating noise reduction system for moving and/or falling fluids, the process for manufacturing of such system and the use of such system.
BACKGROUND OF THE INVENTIONFalling or dropping and flowing fluid, especially water, is known to create significant noise that becomes a health and safety concern for work personnel and a nuisance for nearby residents. A prominent case is in cooling towers of power plants where costly measures have to be taken to reduce the noise. The conditions in cooling towers are among the worst for any sound dampening installation, as there is a permanent high water impact like from a waterfall moving round in circles. The resulting force can cause severe damage or at least accelerated fatigue to installations of any kind. Additionally, there has to be appropriate, i.e. highly efficient, drainage as any sound damping installation of course has to work above the water surface situation at the base of the tower. Thus, if a system can work under cooling tower conditions it is likely to work everywhere, e.g. also when applied on flowing fluids.
Some scope in sound attenuating systems has been put on cooling tower noise reduction for a.m. reasons. As the most widespread method, a noise protection wall around the base of the cooling tower is 1. costly and 2. only will reduce the noise emitted at ground level but not the noise escaping through the top opening, other measures had been examined. One approach consists in applying grid-like or mesh-like systems that should disperse the water flow and the noise, subsequently, such as in CN 200972335, CN 100533033, CN 2341088 and CN 2453381. The claimed noise reduction of 15-30 dB of the latter could not be reproduced during our examinations. Honeycombs as damping elements are mentioned in CN 2823955 and CN 1862206, but honeycombs or hollow systems in general are notorious for creating resonance sound, or “drumming”, of course. All the a.m. systems are mainly based on metalwork and/or rigid plastics and thus do not possess material immanent dampening properties. To improve that situation, JP 8200986 claims the use of a combination of water permeable and non-permeable synthetic resin mats, however, also those materials are rather rigid and the drainage properties—despite the claimed drainage ridges—are poor, leading to water agglomeration on top of the mat which will increase the noise level again. CN 2169107 mentions damping mats and particles; however, the claimed system is not able to provide sufficient structural integrity for the application. Another approach is focussing on plate systems where the plates themselves are supported by a damping device and also disperse water, such as in CN 201003910, CN 201302391, CN 201302392, CN 201302393, CN 201184670, CN 1945190 (all describing combinations of rotating and fixed plates, partially combined with pipe systems), CN 201311202 (microporous plates), CN 2821500 (plates, rings and surface structures as known from acoustic indoor systems), JP 56049898 (complex metalwork with damping inlays). Other systems described in the literature are: CN 2447710 and CN 2438075 (use of floating balls) and CH 451216, DE 3009193, DE 1501391, DE 2508122, EP 1500891, SU 989292. The latter documents, as well as a publication (M. Krus et al: Latest developments on noise reduction of industrial induced draft cooling towers, Veenendaal, 2001, pp 33-38) all mainly refer to systems consisting of floating devices which are supporting or carrying the damping system, consisting of mat-like structures, means, some elasticity or flexibility has been acknowledged to be beneficial for sound dampening; JP 58033621 at last mentions that “soft cover” may reduce falling water noise (for sluice doors). However, those systems are not consequently using the potential of elastic dampening and exhibit deficiencies in floating properties as well as in drainage performance; and some systems again are sensitive to mechanical impact.
SUMMARY OF THE INVENTIONA major object of the present invention thus is to provide a floating noise reduction system or material combination not showing the above mentioned deficiencies but exhibiting a significant and sustainable level of noise reduction over all concerned frequencies and showing an additional drainage effect and high mechanical wear resistance.
Surprisingly, it is found that such system or material not showing the above mentioned disadvantages can be made from a combination of expanded elastic material with a floating mechanical support made from expanded polymer.
In the accompanying drawings,
The claimed material comprises at least one layer (A) of expanded polymer based material with open cell (open porosity) structure (
The claimed system comprises at least one layer (B) of expanded polymer based material different or same as for (A) with either open or closed cell structure (
The claimed material furthermore may comprise one or more additional layers (C) within and/or between layers (A) and/or (B) that may provide additional drainage and/or damping and/or other properties, such as preferably reinforcement, impact resistance etc. The layers (C) can e.g. comprise fibres, e.g. as mesh, or nonwoven, wire mesh, resin sheet etc. of any kind; see
The claimed material furthermore may comprise a link system (D) that connects individual pieces, e.g. tiles, comprising layers (A), (B), and optionally (C) together, but still leaving room to move and float. (D) can comprise metalwork, woven bands, elastic links etc., or a combination thereof. (D) is fixed either into layer (B)/(C)—as the structurally toughest ones—or into the system, i.e. (B), from underneath or above or by a combination of both methods. Care has to be taken that (D) will not negatively influence the floating properties (weight) and the flexibility of the whole system. Cardan joints or axle bearing based links or other flexible linking methods are therefore preferred. An accordingly strong layer (C) between (A) and (B) can also take the part of (D) if the pieces of (A) and (B) are connected onto (C) keeping some distance between the respective tiles. However, a connection system (D) is preferred where individual tiles can be easily exchanged, e.g. for maintenance purposes.
It is a prominent advantage of the claimed material that it is providing excellent damping together with draining effect due to its composition and structure and that it additionally shows built-in anti-fatigue properties due to its composition, allowing long-term use even under harsh conditions.
A further advantage of the claimed material is the possibility to adapt its properties to the desired property profile (concerning mechanics, damping/absorption, fluid intake, hydrophilic or hydrophobic character, porosity etc.) This can be achieved by modifying the expansion agent(s), the expansion process and the polymer base material composition, as well as the density, and, if required, the crosslinking system(s). The material thus can be altered to damp/absorb from high to low frequencies or frequency bands (see
Another basic advantage of the claimed material is the fact that its noise reduction properties are very constant over a wide temperature range leading to the fact that its performance remains unchanged no matter if it is used in summer or wintertime.
It is a further important advantage of the claimed material that it will reduce both the ground level noise as well as the top level noise at cooling towers (see table 1 and
It is another important advantage of the claimed material that it can be applied for noise reduction both of falling/dropping and flowing fluids.
It is another advantage of the claimed material that it is environmental friendly as it does not comprise or release harmful substances, does not affect water or soil or nature in general and as it is recyclable by separating the layers and then grinding or melting them individually.
A resulting advantage of the material is the fact that it can be blended or filled with or can contain scrapped or recycled material of the same kind to a very high extent not losing relevant properties significantly, which is especially the case for (B) and (C).
It is another advantage of the claimed material that its expanded structure provides insulation properties, thus, it can be beneficial for keeping fluids warm or cold in addition to the damping properties.
It is a prominent advantage of the claimed material that it can be produced in an economic way in automatic or semi-automatic shaping process, e.g. by moulding, extrusion and other shaping methods. It shows versatility in possibilities of manufacturing and application. It can be extruded, co-extruded, laminated, moulded, co-moulded etc. as single item or multilayer already and thus it can be applied in almost unrestricted form.
It is a further advantage of the claimed material that it can be transformed and given shape by standard methods being widespread in the industry and that it does not require specialized equipment.
It is another advantage of the claimed material for the application that it is long-lasting and durable, however, easy to change in case of maintenance and thus will reduce running costs for the user.
EXAMPLESPreparation of Test Samples
1. Floating layer (B): an extruded, expanded and cut PET board of 25 mm thickness and 1000×1000 mm width (ArmaStruct®, Armacell, Münster, Germany) was coated with a silicone adhesive layer (ELASTOSIL® R plus 4700, Wacker Chemie, München, Germany) to give the floating part of the system. A sinus shape ridge structure (distance peak to peak of 35 mm) was applied to one surface by thermoforming embossing and pin holes of 20 mm diameter were drilled into the board in a distance of 80 mm.
2. Sponge like open cell absorbing layer (A): A rubber compound (Armaprene® N H, Armacell, Münster, Germany) was extruded, expanded and cut to an open cell foam mat of 25 mm thickness and 1000×1000 mm width and then laminated onto the plain surface of (B) as single or double layer by heating the composite up to 120° C. in a hot air oven, using the a.m. adhesive.
3. Skeleton structure open cell absorbing layer (A): A reticulated polyurethane foam mat of the type 80 poles per inch (SIF®, United Foam, Grand Rapids, U.S.A.) of 25 mm thickness and 1000×1000 mm width was laminated onto the plain surface of (B) as single or double layer by heating the composite up to 120° C. in a hot air oven, using the a.m. adhesive.
Experimental Setup
The experiments were carried out on test equipment proposed and developed by the University of Bradford, UK (Prof K. Horoshenkov). The setup (see
The absorber foam samples (A) were tested in single and double layer configurations placed on top of the floating layer (B) by adhesion as described above. The distance between the top surface of the top foam layer and the bottom of the perforated water tank was kept 2 m in all the experiments to ensure the same terminal velocity of the water droplets. The following items of equipment were used for sound recording and analysis:
(i) one PC with WinMLS 2004 build 1.07E data acquisition and spectrum analysis software and 8-channel Marc-8 professional sound card.
(ii) four calibrated Bruel and Kjaer microphones, ½″ type 4188.
(iii) one 4-channel B & K Nexus conditioning amplifier type-2693 set at 1V/Pa.
The audio channels were calibrated to 94 dB using a standard B&K microphone calibrator (Type 4230, no: 1670589). The ⅓-octave sound pressure level spectra were measured on the four channels and used to calculate the mean ⅓-otave level spectrum and the broadband sound pressure level (see
Results
Table 1 shows the good damping properties of already a standard sponge structure open cell material. The noise reduction effect even gets much better when very open cell (“skeleton structure”) material is applied. Another incremental improvement can be found in a combination of both.
The frequencies being damped or absorbed also give an indication about the performance of the materials and material combinations.
Claims
1-9. (canceled)
10. A system for noise reduction of moving fluids, including waves, comprising at least one open cell absorption layer and at least one mixed cell absorption and drainage layer wherein both layers, the open cell and the mixed cell layer are obtained from expanded polymer based material showing a total average density of less than 1000 kg/m3.
11. The system according to claim 10 wherein the mixed cell layer contains at least 70% closed cells and shows a density of less than 700 kg/m3.
12. The system according to claim 10 wherein the open cell layer shows a density of less than 500 kg/m3.
13. The system according to claim 10 wherein the open cell layer comprises reticulated foam.
14. The system according to claim 13 wherein the reticulated foam shows a cell structure of 10 to 300 pores per inch, wherein the polymer based material cell wall columns show a diameter thinner than the average cell diameter.
15. The system according to claim 10 wherein the mixed cell layer comprises at least one of polyolefin or polyalkylidene terephthalate.
16. The system according to claim 10 where at least one of drainage holes or ridge structures are applied in at least one of the mixed cell layer or the open cell layer.
17. A process for manufacturing the material according to claim 10 comprising forming said layers in at least one of a moulding and adhesion process, continuous extrusion process or co-lamination, followed by applying said system to a desired structure.
18. A system according to claim 10, for noise reduction of moving fluids, flowing fluids, falling fluids or fluids creating waves.
19. The system of claim 11 wherein the mixed cell layer density is less than 300 kg/m3.
20. The system of claim 12 wherein the open cell layer density is less than 200 kg/m3.
21. The system of claim 14 wherein said cell structure is 20 to 120 pores per inch.
22. The system of claim 18, for noise reduction of water channels, water ponds, in cooling towers or at shores.
Type: Application
Filed: May 11, 2011
Publication Date: Dec 15, 2011
Applicant: ARMACELL ENTERPRISE GMBH (Munster)
Inventors: Heribert QUANTE (Marienmuenster), Mark SWIFT (Queensbury), Jürgen WEIDINGER (Munster)
Application Number: 13/105,599