NO20190759A1

NO20190759A1 - Abrasive blasting silencer

Info

Publication number: NO20190759A1
Application number: NO20190759A
Authority: NO
Inventors: Erik Nagel
Original assignee: Beerenberg Services As
Priority date: 2019-06-19
Filing date: 2019-06-19
Publication date: 2020-12-21
Also published as: NO346212B1

Description

Abrasive blasting silencer

The present invention relates to a silencer or muffler for a nozzle used for industrial abrasive blasting, commonly referred to as sandblasting. During industrial sandblasting, an operator holding the sand blasting nozzle is exposed to severe noise, limiting the allowed time for a shift to typically two hours a day due to HSE (Health, Safety and Environment) regulations. On a typical offshore installation, it is therefore common to have a group of eight people to enable continuous operation of one sandblaster. Costs for sandblasting operations are therefore high, and the amount of people involved is resource intensive.

It is thus a purpose of the present invention to reduce the noise generated in sandblasting operations below a threshold level to allow sandblasting personell to work a full shift without being limited by HSE regulations due to exposure to noise. The aim is typically to reduce the noise with 6dB.

It is also an object of the present invention to provide a silencer that is cost effective and easy to maintain by an operator and that is manufactured of basic materials to reduce costs. This and other advantages are achieved with the present solution.

This is achieved with the present invention.

The present invention concerns an abrasive blasting silencer comprising a longitudinal housing with an abrasive blasting nozzle attachment portion adapted to locate an abrasive blasting nozzle outlet forming a blasting nozzle outlet area close to an inlet of a main chamber extending from the nozzle attachment portion. A silencer insert with an inner bore in line with and extending from the blasting nozzle outlet area and to an abrasive blasting silencer outlet for abrasive blasting material and pressurised air, is located inside the main chamber. An annulus is formed between the main chamber and a silencer insert outer diameter.

A resilient layer inside the main chamber may surround the annulus.

The abrasive blasting nozzle attachment portion may be formed of a first tubular element and the a main chamber may be formed of a second tubular element fixed to the first tubular element with a transition piece, whereby the first tubular element, the second tubular element and the transition piece form a silencer housing.

The silencer insert may extend internally from an inlet end of the silencer housing to an outlet end of the silencer housing.

The silencer insert may include a bore at an inlet end of the silencer insert with an inner diameter corresponding to an outer diameter of a cylindrical portion of a standard abrasive blasting nozzle.

The silencer insert may include perforations extending between the inner bore of the silencer insert and an annulus formed between the main chamber and a silencer insert outer diameter.

The silencer insert may include a continuous inner surface in the inner bore of the silencer insert. The term continuous bore is intended to cover “unperforated” or without holes or bores in the inner wall of the main bore. The inner diameter of the main bore may however vary.

Furthermore the invention relates to an abrasive blasting silencer insert adapted for an abrasive blasting nozzle with an outlet opening for the blasting material and air and a cylindrical outer portion with an outer nozzle diameter, the abrasive lasting silencer insert having:

a first cylindrical section with a first outer diameter and an abrasive blasting nozzle attachment portion with a first inner diameter corresponding to the outer diameter of the abrasive blasting nozzle the insert is adapted for, and

a second cylindrical section with an outer diameter greater than the first outer diameter and a damping portion with an inner bore with an inner diameter larger than the diameter of the abrasive blasting nozzle outlet the abrasive blasting silencer insert is adapted for.

The abrasive blasting silencer insert may be made in one single piece of plastic material.

The abrasive blasting silencer insert may include perforations extending between the inner bore of the damping portion and the outer diameter of the second cylindrical section.

Furthermore, the application concerns a longitudinal abrasive blasting silencer housing. The housing includes a cylindrical abrasive blasting nozzle attachment portion with an attachment portion inner diameter corresponding to the outer diameter of a first cylindrical section of an abrasive blasting silencer insert, a cylindrical main chamber section with an inner diameter greater than the attachment portion inner diameter, and a transition section connecting the cylindrical abrasive blasting nozzle attachment portion and the cylindrical main chamber section.

The longitudinal abrasive blasting silencer housing may be made of aluminium.

Furthermore, the invention concerns an abrasive blasting assembly comprising an abrasive blasting nozzle in an abrasive blasting nozzle attachment portion of an abrasive blasting nozzle silencer, locating an abrasive blasting nozzle outlet forming a blasting nozzle outlet area close to an inlet of a main chamber of the silencer extending from the nozzle attachment portion. A silencer insert with an inner bore in line with and extending from the blasting nozzle outlet area and to an abrasive blasting silencer outlet for abrasive blasting material and pressurised air, is located inside the main chamber. Perforations extend between the inner bore of the silencer insert and an annulus formed between the main chamber and a silencer insert outer diameter.

Short description of the enclosed figures:

Fig. 1 is a perspective view of a typical sand blasting tank of the prior art;

Fig. 2 is a side view a typical standard blasting nozzle of the prior art;

Fig. 3 is a perspective front view of the standard blasting nozzle of fig.2;

Fig. 4 is a side view of a typical standard connecting piece of the prior art;

Fig. 5 is a perspective front view of the standard connecting piece of fig.4;

Fig.6 is a perspective view from the front of a silencer of the invention in a with an insert installed;

Fig. 7 shows the silencer of fig.6 from the side with a nozzle installed;

Fig. 8 shows the silencer of fig.6 and 7 schematically in cross section from the side with the insert and nozzle installed;

Fig. 9 is a perspective view of a synthetic or plastic insert;

Fig. 10 is a perspective view of the synthetic or plastic insert in an alternative embodiment;

Figs. 11 is a perspective view of an embodiment of the invention with a shorter main chamber and an elastic inner liner;

Fig. 12 is a side view of the embodiment of fig 11; and

Fig. 13 is a side view of an elastic inner liner.

Detailed description of an embodiment of the invention with reference to the enclosed figures:

Fig. 1 shows a typical sand blasting tank 1 according to the prior art and that is used in connection with the present invention. Abrasive blasting material (typically sand) is filled into container 2. The sand blasting tank 1 is connected to a compressor through a compressor inlet 3 and sand and compressed air is expelled through an outlet 4. A hose (not shown) connects the outlet 4 to a blasting nozzle held by an operator. A dead-mans handle with a separate hose shuts down the air supply upon release.

Figures 2 and 3 are a side view and a perspective front view respectively of a typical standard blasting nozzle 5 of the prior art. The blasting nozzle 5 includes a threaded inlet portion 6 with an inlet opening 7 and an outlet opening 8 for the blasting material and air. The diameter of the outlet opening varies depending on the application. An inside of the blasting nozzle 5 is normally covered with a hard wearing material to prevent premature abrading and wear of the nozzle interior. The blasting nozzle 5 has a cylindrical outer portion 9. The nozzle 5 typically has an outer diameter of 37mm and a length of 155mm. The length of the cylindrical outer portion 9 is typically 126mm.

Figures 4 and 5 are a side view and a perspective front view respectively of a typical standard connecting piece 10 of the prior art, connecting the blasting nozzle and the hose (not shown) from the sand blasting tank outlet (fig.1, ref 4). The connecting piece 10 includes inner threads 11 mating with the threads of the threaded inlet portion of the nozzle (fig.2, ref.6). The threads also screws onto the outside of the hose without any further elements. An operator holds onto the connecting piece 10 upon operation.

The silencer of the invention is used in connection with abrasive blasting equipment of the above described type.

Figures 6, 7 and 8 shows the silencer 20 of the invention in a perspective view from the front with an insert 21 installed, from the side with a nozzle 5 installed and in schematically in cross section from the side with the insert 21 installed respectively. The silencer is retrofitted to an existing nozzle and can be used for nozzles with varying inner nozzle diameter.

The diameter of the silencer outlet 28 is larger than the diameter of an outlet of the nozzle.

The silencer 20 includes a housing 12 with a main chamber 22 in aluminium and the insert 21 in a synthetic material. The insert 21 is held to the main chamber 22 with set screws or grub screws (not shown) in threaded bores 23 at an forward (downstream) end portion 24 of the main chamber 22. The main chamber is typically made of a 260mm long aluminium main chamber tube with a 100mm outer diameter and a 94mm inner diameter. A flat end portion or transition piece 26 is fixed to the inner end of the main chamber tube and a nozzle fixture portion 25 formed as a 105mm long aluminium tube with an outer diameter of 66mm and an inner diameter of 60mm is secured to the centre of the flat end portion 26. The flat end. The nozzle fixture portion 25 surrounds an opening in the flat end portion with a diameter corresponding to the inner diameter of the nozzle fixture portion 25. The ratio between the inner length and the inner diameter is thus 2,48:1 and is typically within the range 1,5:1 to 3,5:1. per

A second set of set screws 27 shown as wing nuts extending through the nozzle fixture portion 25 and a portion of the insert 21 is pressed against the cylindrical outer portion of the nozzle to hold the silencer 20 to the nozzle (nozzle 5 of fig.2 and 3).

The insert 21 includes a circular silencer outlet 28 for the abrasive blasting material entrained in air.

Fig. 7 clearly shows the threaded inlet portion 6 of the nozzle 5. The inlet opening 7 is located at the upstream end of the nozzle 5. The three set screws 27 extend through threaded bores in the tubular nozzle fixture portion 25 and through the insert to hold both the insert and the nozzle 5. The insert is thus sandwiched between the nozzle 5 and the tubular nozzle fixture portion 25. The tubular nozzle fixture portion 25 is typically 105mm long, has an outer diameter of 66mm and an inner diameter of 60mm. The set screws are typically m8.

Fig. 8 is a schematic cross-section of a silencer of the invention. The silencer includes an aluminium silencer housing 12 and a plastic insert 21 inside the housing 12. The housing has a cylindrical main chamber 22, a cylindrical nozzle fixture portion 25 and diameter transition piece 26 formed as a plate and connecting the cylindrical main chamber 22 to the cylindrical nozzle fixture portion 25.

The cylindrical nozzle fixture portion 25 is secured to a standard nozzle 5 with a nozzle inlet 7, a nozzle outlet 8, a cylindrical outer portion 9 and a threaded section 6. The nozzle is located in an inlet bore or rear attachment portion 30 in the insert 21 to locate the nozzle outlet 8 in a blasting nozzle outlet area 14 at, or close to, an inlet of an inner main bore 36 providing a noise damping section of the insert 21. The blasting nozzle outlet 8 can be flush mounted with the inlet of the bore 36. Set screws 27 in threaded bores in the housing and extending through set screw bores 31 in the insert 21 holds the nozzle in the silencer. The inner main bore 36 ends in the silencer outlet 28 for the abrasive blasting material entrained in air. The annulus 29 is formed inside the main chamber 22 between the main chamber 22 cylindrical inner wall and the cylindrical outer wall of the insert. The bores 33 between the inner main bore 36 and the annulus form the perforations in the insert 21. A seal 37 is located between front distance piece 34 and the inner diameter of the main chamber.

The silencer is concentric and the centre of the bore forms an extension in a direct line through a longitudinal centre line of the nozzle.

The ratio between the diameter of the inner main bore 36 of the insert 21 and the diameter of the nozzle outlet 8 is typically 3,5:1 and can be in the range 1,5:1 to 6,5:1

The insert 21 extends the entire length of the housing 12.

Figures 9 and 10 show the synthetic or plastic insert 21 with the rear attachment portion 30 with an outer diameter corresponding to the inner diameter of the tubular nozzle fixture portion 25 and an inner diameter corresponding to the outer diameter of the cylindrical portion of the nozzle. The rear attachment portion 30 includes set screw bores 31 to allow the set screws for the nozzle to extend through the rear attachment portion 30 and to hold the silencer to the nozzle.

In the embodiment of fig.9, the insert is without perforations, and the area of the insert 21 adapted to be located inside the main chamber is without perforations. This area may however have a material thickness / mechanical properties that dampen the most prominent noise frequencies.

In the embodiment of fig.10, the insert 21 includes a 233mm long perforated area 32 covered with individual 12mm bores 33 in an area of the insert 21 that will be located inside the main chamber of the silencer when the insert is installed. The bores 33 extend from a central inner bore with a diameter of 42mm and to an outer cylindrical portion of the perforated area 32. The holes are organized in 12 rows of 14 holes each. A front distance piece 34 with an outer diameter corresponding to the inner diameter of the main chamber, and the rear attachment portion 30 centralises the plastic insert inside the silencer. The housing annulus is formed between the outer diameter of the perforated area 32 and the main chamber of the silencer. The front distance piece 34 and the forward end portion 35 can be integrated in the insert as shown in fig.9 or be separate parts as shown in fig.10. The part of the insert 21 adapted to be located inside the main chamber, could also be perforated openings without a circular cross-sections and the openings do not have to have walls perpendicular to a longitudinal axis through the insert.

The seal can be provided between the front portion of the insert and the main chamber 22 to prevent air and abrasive material from entering the gap between the main chamber and the insert at the forward end and to prevent wear of these components.

The insert 21 is inexpensive to manufacture and quick and easy to exchange without tools by an operator. It can thus be allowed to wear and does not have to endure extended use without being changed.

Figs. 11, 12 and 13 show an embodiment of the invention with a shorter main chamber an elastic inner liner 40 forming a resilient layer inside the annulus formed in main chamber 22. The elastic inner liner 40 will be located in the annulus between the synthetic insert and the inner diameter of the main chamber 22 when the insert is installed. The inner liner 40 is formed of a rubber tube and may be used to further attenuate the sound waves inside the main chamber 22.

The elastic inner liner 40 forming the resilient layer is typically a rubber material, an elastomeric material or a soft plastic material.

The length of the main chamber may be tuned to the wavelength of the noise generated by the pressurized air and the abrasive material exiting the nozzle.

The dimensions indicated in the description are included to bring forward an order of magnitude of the size of the silencer.

Claims

1. An abrasive blasting silencer comprising a longitudinal housing (12) with an abrasive blasting nozzle attachment portion (13) at a first end, the abrasive blasting nozzle attachment portion being adapted to locate an abrasive blasting nozzle outlet (8) of an abrasive blasting nozzle (5) in an abrasive blasting nozzle outlet area (14) close to an inlet of a main chamber (22) of the housing (12), extending from the nozzle attachment portion (13);

a silencer insert (21) with a main inner bore (36) in line with, and extending from the blasting nozzle outlet area (14) and to an abrasive blasting silencer outlet (28) for abrasive blasting material and pressurised air, inside the main chamber (22); and

an annulus (29) formed between the main chamber (22) and a silencer insert outer diameter.

2. The abrasive blasting silencer of claim 1, further including a resilient layer in the annulus (29).

3. The abrasive blasting silencer of claim 1 or 2, wherein the abrasive blasting nozzle attachment portion (13) is formed of a first tubular element and the a main chamber (22) is formed of a second tubular element fixed to the first tubular element with a transition piece (26), whereby the first tubular element, the second tubular element and the transition piece form the silencer housing (12).

4. The abrasive blasting silencer of claim 3, wherein the silencer insert (21) extend internally from an inlet end of the silencer housing (12) to an outlet end of the silencer housing (12).

5. The abrasive blasting silencer of claim 3, wherein the silencer insert (21) includes a bore at an inlet end of the silencer insert (21) with an inner diameter corresponding to an outer diameter of a cylindrical portion of a standard abrasive blasting nozzle.

6. The abrasive blasting silencer of any of the previous claims, wherein the silencer insert (21) include perforations extending between the inner bore (36) of the silencer insert (31) and an annulus (29) formed between the main chamber (22) and a silencer insert (21) outer diameter.

7. The abrasive blasting silencer of one of the claims 1-5, wherein the silencer insert (21) include a continuous inner surface in the inner bore (36) of the silencer insert (31).

8. An abrasive blasting silencer insert (21) adapted for an abrasive blasting nozzle (5) with an outlet opening (8) for the blasting material and air and a cylindrical outer portion (9) with an outer nozzle diameter, the abrasive blasting silencer insert (21) having:

a first cylindrical section with a first outer diameter and an abrasive blasting nozzle attachment portion with a first inner diameter corresponding to the outer diameter of an abrasive blasting nozzle; and

a second cylindrical section with an outer diameter greater than the first outer diameter and a damping portion with an inner bore (36) with a second inner diameter larger than the diameter of the abrasive blasting nozzle outlet (8) the abrasive blasting silencer insert (21) is adapted for.

9. The abrasive blasting silencer insert (21) of claim 8, made in one single piece of plastic material.

10. The abrasive blasting silencer insert of claims 8 or 9, including perforations extending between the inner bore (36) of the damping portion and the outer diameter of the second cylindrical section.

11. The abrasive blasting silencer insert of claims 8 or 9, wherein the silencer insert (21) include a continuous inner surface in the inner bore (36) of the silencer insert (31).

12. A longitudinal abrasive blasting silencer housing (12) comprising:

a cylindrical abrasive blasting nozzle attachment portion (13) with an attachment portion inner diameter corresponding to the outer diameter of a first cylindrical section of an abrasive blasting silencer insert (21);

a cylindrical main chamber section with an inner diameter greater than the attachment portion inner diameter; and

a transition section connecting the cylindrical abrasive blasting nozzle attachment portion (13) and the cylindrical main chamber section.

13. The longitudinal abrasive blasting silencer housing (12) of claim 12, made of aluminium.

14. An abrasive blasting assembly comprising an abrasive blasting nozzle (5) in an abrasive blasting nozzle attachment portion (13) of an abrasive blasting nozzle silencer, locating an abrasive blasting nozzle outlet (8) forming a blasting nozzle outlet area (14) close to an inlet of a main chamber (22) of the silencer extending from the nozzle attachment portion (13);

a silencer insert (21) with an inner bore in line with and extending from the blasting nozzle outlet area and to an abrasive blasting silencer outlet (28) for abrasive blasting material and pressurised air, inside the main chamber (22); and perforations (32) between the inner bore (36) of the silencer insert (21) and an annulus (29) formed between the main chamber (22) and a silencer insert outer diameter.