MEMBRAN ARRANGEMENT WITH SELF-HEALING PROPERTIES

Description

[0001] The invention relates to a diaphragm valve with a diaphragm that seals between spaces and the diaphragm is clamped between a lower housing part and an upper housing part of the diaphragm valve by means of screws.

[0002] Such diaphragms are used, for example, in diaphragm valves, diaphragm actuators, or diaphragm pumps. In diaphragm valves, the diaphragm preferably seals the valve on a sealing surface. Such a diaphragm valve is described, for example, in DE 195 05 747 A1. In a diaphragm pump, the fluid to be pumped is separated from the actuator by the diaphragm. Diaphragm actuators are used, for example, in the form of pneumatic actuators, such as in control valves. In this case, a diaphragm, preferably coupled to a spindle, is moved by compressed air.

[0003] Diaphragm valves can be used to meter various fluids, such as gases, vapors, or liquids. For example, diaphragm valves can be used to meter or distribute highly viscous or very adhesive fluids. Diaphragm valves effectively prevent deposits and thus contamination. Valves based on the diaphragm principle are the metering devices with the lowest dead volume. In addition to their very small dead volume, diaphragm valves are also designed for optimized drainage, ensuring residue-free removal of the fluid.

[0004] This is particularly important for pharmaceutical plants and manufacturing processes, as these are subject to stringent validation requirements to ensure consistent and reproducible quality. These requirements necessitate the ability to run various processes within a single plant. Besides the actual production process, these typically include cleaning, disinfection, and sterilization. Due to their advantageous design features, diaphragm valves have become the preferred fitting in sterile process technology.

[0005] The membranes used form movable, sealing walls that separate two spaces with usually different fluids (gases, liquids) and often also different pressure conditions.

[0006] An important quality characteristic of a membrane is its flexibility, that is, its ability to move perpendicular to the mounting surface (membrane surface), which may be mechanically driven. Furthermore, the membrane's durability is important, especially when conveying aggressive media.

[0007] The flexibility and durability of a membrane depend primarily on the material from which it is made. Elastomers are mainly used as base materials for membranes, and these can be reinforced with fabric inserts to achieve greater strength. Membranes made of ethylene propylene diene monomer (EPDM) rubber have proven effective as elastomers. EPDM is a terpolymer elastomer (rubber) and therefore a synthetic rubber. The material is characterized by high elasticity and good chemical resistance.

[0008] Dynamically stressed membranes can develop cracks on the surface of a membrane layer, as this is where the dynamic alternating stress is highest. Such a crack in the membrane surface can have various negative consequences. In sterile applications, fluid that has penetrated such a crack cannot be cleaned, or can only be cleaned with great difficulty. A cleaning or sterilizing fluid may not be able to reach these areas, which can lead to persistent microbial contamination in a sterile process.

[0009] The dynamic stresses during membrane operation can cause an initial crack in the membrane surface to propagate further and potentially lead to complete membrane rupture. This can result in the release of conveyed fluid, which, depending on the type of fluid, can pose a risk to human health and pollute the environment.

[0010] US patent 000006138550 describes an unreinforced diaphragm for diaphragm pumps with a surface PTFE coating. The coating is intended to cause self-healing in the event of a diaphragm rupture.

[0011] WO 2018 / 204826 A1 discloses a solid-state valve comprising a valve body with an opening for the passage of high-pressure fluid, a diaphragm arranged over the opening to retain the high-pressure fluid in the valve body, and a wire on the diaphragm, wherein the application of electricity to the wire causes selective failure of the diaphragm, resulting in a rapid release of a large quantity of pressurized fluid through the valve body and the diaphragm.

[0012] US patent 2009 / 0115142 A1 provides a boot arrangement for a joint comprising an inner layer and an outer layer. The inner layer consists of a first material, and the outer layer consists of a second material that differs from the first. The outer layer at least partially covers the inner layer, and the second material comprises a self-healing polymer.

[0013] DE 10 2011 000 410 A1 describes an article made of a wear-prone material, which, according to a first material variant, consists exclusively of a polymeric material with elastic properties, or, according to a second material variant, is a composite material formed from a polymeric material with elastic properties in combination with a textile material and / or a thermoplastic material and / or an inorganic material, wherein the article according to the invention is characterized in that a system of capsules is incorporated into the material, comprising a first group of capsules containing a substance or a mixture of substances with conditioning properties; a second group of capsules containing a substance or a mixture of substances with self-healing properties; and a third group of capsules containing a substance or a mixture of substances that signals an impending article failure.The respective substance effect occurs after the capsules of the first, second, and third groups are ruptured. This capsule system is used particularly in air spring bellows with an inner layer, an outer layer, and an embedded reinforcing layer.

[0014] US Patent 2,387,433 A discloses a valve for inflatable objects, comprising a stem made of rubber or similar material, having a cavity and an opening at one end extending from the object, a self-sealing plug received in the cavity of the stem, a closure cap (5) that fits into the opening to retain the plug in the stem, and a connecting tongue and groove device on the stem and the cap to releasably secure the cap in the opening.

[0015] US 2011 / 0023611 A1 describes a self-healing composite material comprising a fiber-reinforced polymer matrix, wherein the polymer matrix comprises a thermosetting polymer and a thermoplastic polymer.

[0016] EP 2 505 719 A2 discloses geocomposite articles capable of forming a barrier against highly conductive water, such as seawater, and their manufacturing process for waterproofing surfaces that come into contact with highly conductive water. The geocomposite article's mat consists of a woven or non-woven geotextile web or mat containing a powdered or granular, partially cross-linked acrylamide / acrylate / acrylic acid copolymer over its entire main surface(s). The powdered or granular copolymer exhibits an unexpectedly high free swelling value when hydrated with highly conductive water, such as seawater.A liquid-impermeable cover film is glued to the upper main surfaces of the filled, copolymer-bearing geotextile to form a primary water barrier layer with high conductivity, which, if it tears, is sealed by the swelling of an underlying layer of water-insoluble, partially cross-linked acrylamide / acrylic acid copolymer.

[0017] EP 3 323 583 A1 discloses a diaphragm valve according to the preamble of claim 1. The object of the invention is to provide a diaphragm assembly with a diaphragm that self-seals suddenly occurring cracks. Furthermore, the diaphragm should meet the operational requirements while maintaining extremely durable properties. Additionally, the sealing of a crack should be detectable without taking the diaphragm assembly out of service. The diaphragm should be manufactured in the most cost-effective and particularly simple manner possible, with minimal material waste.

[0018] This problem is solved according to the invention by a diaphragm valve according to the features of claim 1. Preferred embodiments can be found in the dependent claims, the description, and the figures. According to the invention, a medium for sealing cracks within the

[0019] The membrane of the diaphragm valve is arranged, wherein, in the event of membrane damage in the form of a membrane tear, the medium, upon contact with a conveying fluid, exhibits a reactivity to close the membrane tear.

[0020] Advantageously, the medium is arranged in a viscous and / or pasty form within the membrane. Preferably, the medium is enclosed between two layers of the membrane. In an alternative embodiment, the medium can also be gaseous and / or solid.

[0021] According to the invention, the medium is chemically reactive, preferably selectively chemically reactive. This means that the medium remains trapped within the membrane during periods of dynamic stress, which can be prolonged, and only upon membrane damage in the form of a crack, when it comes into contact with the conveyed fluid, does it exhibit this chemical reactivity to seal the crack. This ideal property of the medium is its ability to self-heal and, in the event of membrane damage, prevents unplanned plant downtime and / or hazards to people and the environment from escaping conveyed fluid.

[0022] Ideally, the medium is chemically reactive through hydration and / or complex formation. This is particularly advantageous for liquid conveying fluids, especially aqueous solutions, emulsions, and suspensions. This type of reaction effectively seals membrane cracks and allows dynamic membrane operation to continue.

[0023] In one advantageous variant, the medium reacts via a cross-linking reaction to heal an EPDM-based membrane in the event of a crack. This leads to the rapid sealing of the crack and effectively prevents any interruption of operation.

[0024] The volume increase according to the invention of at least a part of the enclosed medium leads to a sealing of a membrane tear and heals a suddenly occurring damage to the membrane.

[0025] According to the invention, the medium exhibits an adhesive and / or bonding effect with at least one membrane material, in particular with the ethylene propylene diene monomer rubber of the membrane layers. This enables an ideal sealing of a suddenly occurring membrane rupture.

[0026] Advantageously, the medium comprises a thermoplastic. Thermoplastics, also called plastomers, are plastics that can be deformed within a specific temperature range. This process is reversible, meaning it can be repeated many times by cooling and reheating back to a molten state.

[0027] According to the invention, the medium comprises a superabsorbent polymer. Superabsorbent polymers are plastics capable of absorbing many times their own weight in liquids. These are primarily water or aqueous solutions. Upon absorbing the liquid, the superabsorbent polymer swells and forms a hydrogel. This property is particularly advantageous for sealing membrane tears.

[0028] Preferably, the medium consists of a thermoplastic-elastomer composite material. According to the invention, a swellable material composition is provided, consisting of a thermoplastic matrix containing at least one elastomeric material as a first dispersible phase and at least one superabsorbent as a further dispersible phase. This composite material is ideally suited to seal a membrane tear due to both its ideal composition and its membrane-layer-like structure.

[0029] In an alternative embodiment of the invention, the medium can be designed similarly to the material composition described in EP 1 616 906 A1.

[0030] The viscosity of the medium is chosen so that the material can flow quickly enough into a suddenly occurring crack and seal it without being flushed out of the membrane by the conveying fluid.

[0031] Ideally, the medium is arranged between two EPDM layers of the membrane. With this arrangement according to the invention, it is conceivable that cracks on both the fluid-facing and the fluid-free side of the membrane can be sealed. Compression molding is a particularly suitable manufacturing method for this application. Compression molding is a manufacturing process for slightly curved or flat components. Thermoplastic materials or elastomers can also be processed. At the beginning of the process, a molding compound, which in this case comprises at least two elastomer layers, a layer of the medium, and a one-piece structure of reinforcing elements including a membrane screw arranged between them, is placed into a cavity, which is then heated. The cavity is then closed using a pressure piston. The pressure forces the molding compound into the shape defined by the tool.In the case of elastomers, this leads to the melting of the plastic. After cooling, the finished part can be removed from the mold and further processed.

[0032] Ideally, the medium is at least partially surrounded and / or completely enclosed by a shell. The shell acts as a protective element, ensuring that the medium is protected during the membrane manufacturing process, such as compression molding, as well as during dynamically stressed operation. Only when a crack occurs does the medium exert its chemical reactivity to seal the crack.

[0033] In another embodiment of the invention, the medium is arranged within an EPDM layer of the membrane. In an alternative embodiment, the medium is arranged in the form of inclusions within an EPDM layer of the membrane. For both embodiments, the membrane can be manufactured using the injection molding process. Injection molding is a process in which the respective elastomer material, mixed with portions of the medium, is liquefied (plasticized) using an injection molding machine and injected under pressure into a mold, the injection mold, in which a structure of reinforcing elements is already arranged. Alternatively, individual arrangements of the medium and / or a layer of the medium can already be arranged in the mold around the reinforcing element. Furthermore, a membrane with medium but without reinforcing elements according to the invention is also conceivable. In the mold, the elastomer material expands through cooling or...A crosslinking reaction then transitions the material back into the solid state. After opening the tool, the finished part—the membrane with the arranged and / or enclosed medium—can be removed. The cavity of the tool determines the shape and surface structure of the finished part.

[0034] Preferably, the medium is designed as a layer positioned between two EPDM layers. This ensures, to a particularly advantageous extent, that the crack can be sealed regardless of its location. According to the invention, the medium layer extends over more than 70% of the membrane area, preferably more than 80%, and particularly more than 90%.

[0035] Membrane failure can lead to significant costs in application. Besides material development to increase performance and determining wear behavior to enable predictive maintenance, self-compensation of damage represents an optimization of membrane utilization. A self-sealing membrane that restores its structural integrity after a tear is ideal for plant operation free from unplanned downtime.

[0036] To enable predictive maintenance, a conductive structure for detecting membrane conditions is arranged on at least one of the layers. This allows for easy determination of whether a membrane tear has self-sealed and whether replacement should be considered during the next scheduled plant shutdown.

[0037] Such a conductive structure for detecting membrane states can, for example, be an ink containing carbon particles, as disclosed in EP 3 415 759 A1 and / or a data acquisition device including a sensor, as described in DE 10 2018 213 002 A1.

[0038] The medium according to the invention, as well as the arrangement of the medium within the membrane, serve to seal cracks in dynamically operated membranes.

[0039] Further features and advantages of the invention will become apparent from the description of exemplary embodiments with reference to drawings and from the drawings themselves.

[0040] This shows: Figure 1 shows a sectional view of a diaphragm valve, Figure 2 shows a partially cut-away diaphragm with medium for sealing cracks.

[0041] The in Figure 1The illustrated diaphragm valve has a lower housing part 1, which includes ports 2, 3 and a weir 4. The weir 4 serves as a seat for the diaphragm 5. The diaphragm 5 is clamped between the lower housing part 1 and an upper housing part 7 by means of screws 6. The upper housing part 7 integrates the elements necessary for actuating the diaphragm 5, such as an actuator 8, which in this embodiment is designed as a handwheel, and a spindle 9. A pressure piece 10 is attached to the spindle 9. The pressure piece 10 is slidably arranged in the upper housing part 7 and is guided by an inner wall of the upper housing part 7. Actuating the actuator 8 causes a vertical displacement of the pressure piece 10 via the spindle 9, so that the diaphragm 5 deforms and the free cross-section between the weir and the diaphragm assembly can be increased or decreased.

[0042] Figure 2Figure 5 shows a partially cut membrane 5 containing medium 13 for sealing cracks. The membrane 5 comprises a first layer 11, which is arranged on the fluid side. The membrane 5 also comprises a second layer 12, which forms the back side of the membrane assembly. Both layers 11 and 12 are made of an elastomer, in particular EPDM. The medium 13, which is surrounded by a sheath 15, is arranged between the two EPDM layers 11 and 12. The membrane 5 also includes a pin-like element 14, which in this embodiment is designed as a membrane screw.

[0043] The in Figure 2 The pin-like element 14 shown can have a thread. According to the illustration in Figure 1 The pin-like element 14 is designed as a diaphragm screw and has an external thread which is screwed into an internal thread which is formed in a pressure piece 10.

[0044] Membrane 5 according to the illustration in Figure 2The compound consists of two EPDM layers 11, 12 and an intermediate medium 13 for sealing cracks, which are bonded together by vulcanization. If the membrane 5 suddenly cracks during operation, the medium 13 escapes and / or swells in such a way that, by means of a crosslinking reaction according to the invention, the crack is sealed and the membrane 5 can continue to be dynamically loaded during system operation.

Claims

1. Diaphragm valve with a lower housing part (1), an upper housing part (7), connections (2, 3), a weir (4), and a diaphragm (5) that separates chambers from each other in a sealed manner and the diaphragm (5) is held in place by means of screws (6) between the lower housing part (1) and the upper housing part (7) of the diaphragm valve, characterized in that a chemically reactive medium (13) is enclosed in the diaphragm (5) to seal tears, wherein the medium (13) is only becoming chemically reactive upon the occurrence of diaphragm damage in the form of a diaphragm tear upon contact with a pumped fluid thereby closing the diaphragm tear.

2. Diaphragm valve according to claim 1, characterized in that the medium (13) is chemically reactive in hydration and / or complex formation.

3. Diaphragm valve according to one of claims 1 to 2, characterized in that the medium (13) has an adhesive and / or bonding effect with at least one diaphragm material.

4. Diaphragm valve according to one of claims 1 to 3, characterized in that the medium (13) comprises a thermoplastic.

5. Diaphragm valve according to one of claims 1 to 4, characterized in that the medium (13) comprises a superabsorbent.

6. Diaphragm valve according to any one of claims 1 to 5, characterized in that the medium (13) is a thermoplastic elastomer composite material.

7. Diaphragm valve according to one of claims 1 to 6, characterized in that the medium (13) is arranged between two layers (11, 12) of the diaphragm (5).

8. Diaphragm valve according to one of claims 1 to 6, characterized in that the medium (13) is arranged within a layer (11, 12) of the diaphragm (5).

9. Diaphragm valve according to one of claims 1 to 6,8 characterized in that the medium (13) is arranged in the form of inclusions within a layer (11, 12) of the diaphragm (5).

10. Diaphragm arrangement according to one of claims 1 to 9, characterized in that the medium (13) is designed as a layer.

11. Diaphragm valve according to claim 10, characterized in that the layer covers more than 70% of the diaphragm area, preferably more than 80% of the diaphragm area, in particular more than 90% of the diaphragm area.

12. Diaphragm valve according to any one of claims 1 to 11, characterized in that the medium (13) is at least partially surrounded by a sheath (15), in particular completely enclosed.

13. Diaphragm valve according to claim 7, characterized in that at least one of the layers (11, 12) has a conductive structure for detecting diaphragm states.