Extraction system with non-return valve

Abstract

extraction system (10) comprising - a housing (12) with an inlet nozzle (13) and an outlet nozzle (14) and a chamber opening (36) closed by a burst disc (29), - a chamber (15) arranged in the housing (12), which connects the inlet nozzle (13) and the outlet nozzle (14) in a flow-conducting manner, - a non-return valve (16) pivotable about a pivot axis (18), by means of which the inlet nozzle (13) can be automatically closed when a gas pressure (Pk1) present in the chamber (15) is greater than or equal to a gas pressure (Pk2) in the inlet nozzle (13), characterized in that the extraction system (10) further comprises a pressure relief device (38) with an interior (37) and an opening (41), wherein - the interior (37) of the pressure relief device (38) is decoupled from the chamber (15) when the rupture disc (29) is intact and is flow-conductingly connected to the chamber (15) when the rupture disc (29) is destroyed and - the interior (37) of the pressure relief device (38) is separated from the outside environment (33) by a surface structure (40).

Description

[0001] The invention relates to an extraction system with a non-return valve according to the preamble of claim 1.

[0002] An extraction system is understood to be a system that transports disruptive particles or gases via an airflow. Preferably, the extraction system is used to extract chips and / or dust from woodworking, plastics processing, or metalworking machines. Air is preferably used as the carrier medium for the disruptive substances. The extraction system comprises piping, check valves, fans, and / or blowers that generate an airflow by means of which the unwanted substances are extracted from one or more emission points, depending on the application, and fed to a central collection point, for example, a separator or filter system.

[0003] The extraction system comprises a housing with an inlet and an outlet. Inside the housing is a chamber that connects the inlet and outlet. A pivotable check valve is located in this chamber. The check valve automatically closes the inlet if the gas pressure in the chamber is greater than or equal to the gas pressure in the inlet.

[0004] A non-return valve is a protective system designed for explosion isolation, preventing a dust explosion from spreading to other parts of the extraction system via connecting pipes or ducts. The non-return valve is positioned opposite the process flow and thus prevents the propagation of an explosion in the opposite direction.

[0005] The process flow direction refers to the direction in which the dust and other particles to be conveyed in the extraction system are conveyed when the extraction system is used as intended.

[0006] Such an extraction system is known from DE 20 2010 000 446 U1. The chamber of the extraction system known from DE 20 2010 0004 446 U1 has an opening at its top, which is closed by a rupture disc. The rupture disc acts as a pressure relief device and is designed so that it bursts when subjected to a predefined pressure on one side, allowing the pressure to escape through the opening in the housing thus released.

[0007] If an explosion occurs in a section of the extraction system downstream of the check valve in the process flow direction, the overpressure generated by the explosion propagates towards the housing and thus towards the rupture disc and check valve. This forces the check valve against the inlet nozzle. The inlet nozzle is closed, and the area upstream of the check valve is explosion-proofed from the area downstream of the check valve.

[0008] Simultaneously with the sealing of the inlet nozzle, the rupture disc is destroyed, as it is designed so that a pressure increase caused by an explosion exceeds a predefined burst pressure. The destroyed rupture disc releases the housing opening, allowing pressure equalization between the outer and inner areas of the housing or the extraction system.

[0009] Regarding the explosion-proof decoupling of extraction systems using check valves, DIN EN 16447 must be observed in Germany. This standard states that the primary objective of testing a check valve for flame propagation caused by an explosion is to prevent the spread of explosion flames. The check valve should therefore provide explosion-proof decoupling between two adjacent areas of an extraction system. The test according to DIN EN 16447 is considered passed if neither flames nor sparks appear on the side of the check valve facing away from the dust explosion and the valve remains closed for a sufficient duration to prevent flame propagation.

[0010] In the event of an explosion in an extraction system with an integrated rupture disc housing, a negative pressure can develop in the housing chamber under unfavorable circumstances. To prevent the check valve from being pulled away from the inlet nozzle and the initially closed check valve from being released in such a case, check valves known in the prior art incorporate holding devices. These holding devices are often not simple springs positioned to pull the check valve towards the inlet nozzle, but rather more complex mechanisms.

[0011] The holding device can, for example, include a locking mechanism that automatically locks the check valve in its position closing the inlet nozzle.

[0012] A disadvantage of the known extraction system is, firstly, that any flames generated by an explosion can escape through the opening to the outside and cause consequential damage or even a fire in the system or building. Secondly, the non-return valves known as state-of-the-art often require, for safety reasons, a complex retaining device to ensure that the valve remains closed for a sufficient period of time after an explosion.

[0013] The object of the invention is to eliminate the described disadvantages, to improve the fire protection of an extraction system, and to make the extraction system cost-effective overall.

[0014] This problem is solved by an extraction system with the features of claim 1. The extraction system comprises: - a housing with an inlet nozzle and an outlet nozzle and a chamber opening closed by a rupture disc, - a chamber arranged in the housing, which connects the inlet nozzle and the outlet nozzle in a flow-conducting manner, - a non-return valve that can be pivoted around a rotary axis, by means of which the inlet nozzle can be automatically closed if a gas pressure present in the chamber is greater than or equal to a gas pressure in the inlet nozzle.

[0015] The extraction system further includes a pressure relief device with an interior and an opening, wherein - the interior (37) of the pressure relief device (38) is decoupled from the chamber (15) when the rupture disc (29) is intact and is flow-conductingly connected to the chamber (15) when the rupture disc (29) is destroyed and - the interior of the pressure relief device is separated from the outside environment by a flat structure.

[0016] In simplified terms, the extraction system according to the invention incorporates a special pressure relief device mounted on the rupture disc. This offers the advantage that flames triggered by an explosion cannot spread outwards through a shattered rupture disc, but are instead smothered within the pressure relief device without escaping. Furthermore, pressure fluctuations caused by the sudden rupture of the rupture disc are prevented or at least significantly reduced. Consequently, no negative pressure develops within the pressure relief device or within the housing connected to it, which would pull the check valve away from the inlet nozzle. The opening of the filling nozzle thus remains securely closed even without a retaining device.This is particularly advantageous because the presence of a retaining device to block the non-return valve can have negative effects and increase the risk of explosion with dusts that have a low KSt value. The KSt value is a key classification parameter that describes the explosiveness of a dust-air mixture.

[0017] In a preferred embodiment, the surface structure of the pressure relief device is woven from threads or fibers into a fabric or nonwoven. Unlike a surface structure made from, for example, a film, a fabric or nonwoven can be configured such that small gaps remain between the threads or fibers. These gaps allow the passage of gas while simultaneously preventing dust or other particles contained in the extraction system's process stream from escaping the system. Thus, the surface structure of the pressure relief device can be designed so that the overpressure generated during an explosion does not rupture the structure, but rather is relieved by the escape of gas through the structure.

[0018] The threads or fibers used to form the sheet structure preferably consist of a heat-resistant metal or a plastic. These heat-resistant threads or fibers cool any flames striking the sheet structure from the inside to such an extent that, as the explosion wave progresses, only gases, but no flames, pass through the sheet structure.

[0019] Furthermore, the surface structure can be designed not as a single layer, but rather as a multi-layered structure. By selecting a suitable number of layers, the overall resistance and permeability of the surface structure can be designed to meet the required specifications.

[0020] The pressure relief device can, in principle, have any type of outer contour, for example, spherical or cylindrical. Preferably, the contour is formed by a support frame integrated into the pressure relief device, which is coupled to the surface structure on its inner or outer surface. In simplified terms, the surface structure can form an inner or outer skin around the support frame. Furthermore, the support frame can be integrated into the surface structure, for example, inserted between an inner and an outer surface structure.

[0021] Preferably, the support frame and the surface structure are flexible so that they can adapt to a free space specified with regard to the extraction system. Furthermore, in the event of an explosion, the flexibility allows for a preferably reversible deformation of the pressure relief device.

[0022] Further measures improving the invention are described in more detail below with reference to the figures and preferred embodiments of the invention.

[0023] The figures show: Fig. 1 shows an extraction system in operating mode; Fig. Figure 2 shows the extraction system in the event of an explosion.

[0024] Identical or similar elements in the following figures may be designated with the same or similar reference numerals. Furthermore, the figures of the drawing, their description, and the claims contain numerous features in combination. It is clear to a person skilled in the art that these features can also be considered individually or combined into further combinations not described in detail here. The invention expressly extends to embodiments that are not defined by combinations of features from explicit cross-references in the claims, meaning that the disclosed features of the invention can be combined with one another in any way that is technically feasible. The exemplary embodiments shown in the figures are therefore merely descriptive and are not intended to limit the invention in any way.

[0025] The terms “upper”, “top”, “lower”, “left” or “right” used below refer to the arrangement of the components of the extraction system shown in the drawing, which corresponds to the use of the system for conveying a dust-air mixture in one operating mode.

[0026] Fig. Figure 1 shows a schematic sectional view through an extraction system 10 according to an embodiment of the invention. The extraction system 10 comprises a housing 12, which includes an inlet nozzle 13, an outlet nozzle 14, a chamber 15 extending between the two nozzles 13 and 14, and a check valve 16. The inlet nozzle 13 is flow-conductingly connected to the chamber 15, which is flow-conductingly connected to the outlet nozzle 14. The two nozzles 13 and 14 thus form openings in the chamber 15, which is otherwise gas-tightly sealed by the housing 12. Arrows 28 and 35 indicate the process flow direction of an airflow that is generated by a blower (not shown) during normal use. In the illustrated embodiment, the chamber 15 also has a chamber opening 36 on its upper side, which is closed by a rupture disc 29.

[0027] The check valve 16, located in chamber 15, is pivotally mounted on the housing 12 about an axis of rotation 18 in the direction and opposite direction of arrow 19 by means of a pivot bearing 17. The axis of rotation 18 runs in Fig. 1 perpendicular to the drawing plane.

[0028] Due to gravity, the check valve 16 is forced in the direction of arrow 19 against a stop 20, which is provided at the chamber-side end of the inlet nozzle 13. When the check valve 16 is in contact with the stop 20, the inlet nozzle 13 is closed by the check valve 16. In the illustrated embodiment, a spring 21 is provided to assist the closing movement of the check valve 16. The spring 21 is fixed at one end to the check valve 16 and at the other end to the inlet nozzle 13, so that it pulls the check valve 16 against the stop 20.

[0029] The inlet nozzle 13 has a flange 22 to which a pipe 23 is attached, which is connected to a first system component 24 of a pneumatic conveying system. Furthermore, the outlet nozzle 14 has a flange 25 to which a pipe 26 is attached, which leads to a second system component 27 of the conveying system, which includes, for example, a dust filter.

[0030] From plant section 24, an explosive dust-air mixture flows in the direction of arrow 28 – and thus in the process flow direction – through the pipeline 23 into the inlet nozzle 13. If the check valve 16 is closed, a pressure Pk2 builds up in the inlet nozzle 13, which after a certain time is sufficiently high to open the check valve 16 against gravity and against the force of the spring 21. Fig. The position shown in Figure 1 is to be pivoted in the opposite direction of arrow 19 about the axis of rotation 18. In operating mode, i.e., with a dust-air mixture flowing from the inlet nozzle 13 through the chamber 15 into the outlet nozzle 14, the gas pressure Pk2 in the inlet nozzle corresponds to the gas pressure Pk1 in the chamber 15, neglecting a slight pressure drop caused by the flow characteristics.

[0031] Thus, in operating mode, the dust-air mixture flows into chamber 15 and out through the outlet nozzle 14 in the direction of arrow 35. From the outlet nozzle 14, the dust-air mixture flows through the pipe 26 to the system component 27. The check valve 16 floats on the flow of the dust-air mixture, indicated by arrows 28 and 35, so that the check valve 16 does not swing back into its closing position. A stop (not shown) can be provided to limit the pivoting movement of the check valve 16 in the opposite direction of arrow 19.

[0032] The chamber wall 30 on the upper side of the housing 12 has a chamber opening 36. A pressure relief device 38 is inserted into the chamber opening 36 by means of a flange 39, sealing the chamber opening 36.

[0033] The pressure relief device 38 according to the illustrated embodiment has a substantially spherical outer contour which is formed by a support frame 43 and a surface structure 40 made of metal threads attached to the support frame 43. In principle, the pressure relief device 38 can have any desired outer contour and can be adapted to specific requirements and / or a predefined installation space by means of a suitable support frame.

[0034] In simplified terms, the surface structure 40 made of metal threads forms an outer skin around the support frame 43 and encloses a cavity located within the pressure relief device 38.

[0035] The pressure relief device 38 has an opening 41 on its underside. When the rupture disc 29 is intact, the opening 41—and thus the interior 37 of the pressure relief device—is decoupled from the chamber 15. If the rupture disc 29 bursts due to a pressure increase in the event of damage, the opening 41 creates a transition between the chamber 15 of the housing 12 and the interior of the pressure relief device 38. The sheet structure 40, which in the illustrated embodiment is made of metal threads, is designed to withstand a sudden pressure increase, for example, caused by an explosion, and to allow the gases flowing into the pressure relief device 38 through the opening 41 to escape through the sheet structure 40 into the surrounding environment 33. The sheet structure 40 therefore has meshes and / or capillary passages.

[0036] Fig. Figure 2 shows the extraction system 10 according to Fig. 1. In the event of an explosion. Such an explosion can be triggered, for example, by exceeding a critical pressure of a dust-air mixture inside the extraction system 10. Originating from an explosion source 42, the pressure increases abruptly, and explosive gases flow through the outlet nozzle 14 in the direction of arrow 44 – and thus against the process flow direction – into chamber 15, leading to a rapid increase in the gas pressure Pk1 prevailing in chamber 15. This pressure Pk1, which can reach several bar, is significantly greater than the pressure of the dust-air mixture flowing into the inlet nozzle 13, so that the check valve 16 is pivoted in the direction of arrow 19 against the stop 20 and closes the inlet nozzle 13.

[0037] Simultaneously, explosive gases, flowing in a direction 32 indicated by an arrow, strike the rupture disc 29 and destroy it. The destroyed rupture disc is in Fig. 2 not shown. Instead of the bursting disc 29, it shows Fig. 2 rather, that the chamber 15 is flow-conductingly connected to the interior 37 of the pressure relief device 38. The explosion gases – and any flames present – ​​flow through the released opening 41 into the interior of the pressure relief device 38. The interior of the pressure relief device 38 is available for pressure relief.

[0038] If flames enter the interior of the pressure relief device 38, they are extinguished there. The sheet-like structure 40, formed from metal threads, cools the gases heated by the explosion or the flames produced by it to such an extent that the escape of flames from the pressure relief device 38 is prevented. However, the significantly increased internal pressure Pk1 caused by the explosion leads to gases being vented through the sheet-like structure 40 to the outside into the environment 33, that is, to the open air.

[0039] Even during rapid changes in pressure between overpressure and underpressure in chamber 15, the check valve 10 remains in its position closing the inlet 13, a position supported by the spring 21 if necessary. If the pressure in chamber 15 then rises again, the check valve 16 is already in its position closing the inlet 13, preventing any explosive gases from entering the inlet 13. Because the check valve 16 is relatively sluggish with respect to an opening movement in the opposite direction of arrow 19 due to its weight and the force of the spring 21, a brief period of underpressure in chamber 15 is insufficient to open the check valve 16 due to the dust-air mixture flowing into the inlet 13 in the direction of arrow 28.

[0040] It should be noted that according to a modification of the embodiment, the spring 21 can also be omitted, so that the check valve 16 pushes against the stop 20 in the direction of the arrow 19 solely due to its gravity. Reference symbol list 10 Extraction system 11 - 12 cases 13 inlet nozzles 14 outlet nozzles 15th Chamber 16 Check valve 17 swivel bearings 18 Rotation axis 19 Closing direction 20 attacks 21 spring 22 flange 23 Pipeline 24 first plant section 25 flange 26 Pipeline 27 second plant section 28 Flow direction 29 Burst disc 30 wall 31 - 32 Flow direction 33 Environment / Atmosphere 34 - 35 Flow direction 36 Chamber opening 37 Interior 38 Pressure relief device 39 flange 40 planar structures 41 Opening 42 Source of explosion 43 Support frame (of 38) 44 direction Pk1 Gas pressure (in 15) Pk2 Gas pressure (in 13) QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 20 2010 000 446 U1

[0006] DE 20 2010 0004 446 U1

[0006]

Claims

[1] Extraction system (10) comprising - a housing (12) with an inlet nozzle (13) and an outlet nozzle (14) and a chamber opening (36) closed by a bursting disc (29), - a chamber (15) arranged in the housing (12) which connects the inlet nozzle (13) and the outlet nozzle (14) in a flow-conducting manner, - a non-return valve (16) pivotable about a rotational axis (18), by means of which the inlet nozzle (13) can be automatically closed when a gas pressure (Pk1) present in the chamber (15) is greater than or equal to a gas pressure (Pk2) in the inlet nozzle (13), characterized by that the extraction system (10) further comprises a pressure relief device (38) with an interior space (37) and an opening (41), wherein - the interior (37) of the pressure relief device (38) is decoupled from the chamber (15) when the bursting disc (29) is intact and is connected to the chamber (15) in a flow-conducting manner when the bursting disc (29) is destroyed, and - the interior (37) of the pressure relief device (38) is separated from the external environment (33) by a surface structure (40). [2] Extraction system (10) according to claim 1, characterized by that the sheet material (40) of the pressure relief device (38) is knitted from threads or fibers to form a woven fabric or a nonwoven fabric. [3] Extraction system (10) according to claim 2, characterized by that the threads or fibers are made of a metal or a plastic and are preferably heat-resistant. [4] Extraction system (10) according to one of claims 1 to 3, characterized by that the sheet material (40) is constructed in multiple layers.

Images