KUVAG opens up possibilities
Perfected technologies for every type of application
From the automatic pressure gelation process to prepreg winding, we provide optimized materials, suitable molds, and concepts individually adapted to customer needs for durable, high-quality insulation solutions.
Automatic pressure gelation process
The cost-effective automatic pressure gelation process is ideal for manufacturing medium to large amounts of insulators in series production. KUVAG has been continuously developing this process for over 40 years. The use of superior molding concepts, optimized epoxy resin systems, and advanced process control enables products to be manufactured for critical mechanical and electrical requirements.
This process involves components like epoxy resin, hardener, fillers and special additives being homogeneously mixed and degassed under vacuum and at defined temperatures. KUVAG uses more than 80 customized epoxy resin formulations, which have been optimized in terms of their hydrophobicity, high-temperature resistance, flame retardancy and special mechanical or other properties. These reactive compounds are injected under pressure into heated molds with up to eight cavities, usually equipped with pretreated and pre-tempered casting inserts in a semi-automated process. Demolding and transfer to special curing ovens for full polymerization occur after the respectively optimized gelling time expires.
Vacuum casting technology
Our vacuum casting technology is the method of choice, especially for insulators in the high-voltage range or insulators requiring high volumes of casting resin. KUVAG has been perfecting and further developing this technology for many years. We focus particularly on superior mold concepts that enable the highest process control and excellent product quality even for very complex and large-volume products.
The technology involves components like epoxy resin, hardener, fillers, and special additives being homogenized and degassed in a vacuum under strictly controlled conditions. In addition to aluminum oxide, which is widely used because of its SF6 resistance and its decomposition products, other fillers can also be used. Casting into pre-tempered molds, which are usually preloaded with specially pretreated and pre-tempered casting inserts takes place in atmospherically evacuated chambers. KUVAG uses an innovative proprietary mold concept based on the definition of different heating zones and targeted control of the polymerization reaction. The gelling reaction of the reactive epoxy mixture is controlled using special heating stations before the product is demolded and transferred to curing ovens for complete polymerization.
Filament winding technology
Filament winding is a wet winding method for producing high-quality composite tubes. The winding of composite fiber materials is mainly used to manufacture cylindrical components that have to withstand high mechanical stresses with low component mass. The excellent electrical insulation properties of fiber-reinforced composites enable them to be used, among other things, for components subject to high mechanical stresses in high-voltage and extra-high-voltage engineering. KUVAG experts assist our customers in selecting their material and tube dimensioning and design, thus covering a wide range of application areas.
This technology involves glass fibers and fibers made of other materials being wetted with a preformulated matrix coating and then wound in layers onto a rotationally symmetrical mandrel. KUVAG has a large selection of winding mandrels ranging from an internal diameter of 20 mm to 2500 mm. The epoxy resin system used and the layer structure at different winding angles define the properties of the tube (for instance, pressure tubes, flexible tubes). These tubes are then cured under defined temperature conditions and subsequently removed from the winding mandrel. That is often followed by further mechanical processing of the product or further operations such as encapsulation with silicone or the application of coatings.
Silicone encapsulation technology
The wide range of applications where silicone insulators and components are used extends from the technology for transmission networks to distribution networks and transport infrastructure. LSR (liquid silicone rubber) or solid HTV (high-temperature vulcanization) silicones are applied depending on the desired product properties. KUVAG produces a wide range of products for insulation applications, where silicone is applied to structures made of fiberglass-reinforced rods, epoxy resin or even ceramic surfaces.
Liquid silicones are additive-curing silicone rubbers consisting of two components mixed in a dispensing unit and crosslinked at high temperatures with a very short cycle time. Solid silicones are supplied as a one-component system in blocks or bales, which are crosslinked in the respective mold at temperatures of up to 220°C. Encapsulated injection molded parts or structures are usually specially pretreated to ensure perfect bonding between substrate and surface. KUVAG uses largely self-developed tools to ensure the highest precision, efficiency and processing quality.
Vacuum impregnation
High-performance composite components are indispensable in switchgear for high-voltage and extra-high-voltage engineering. Their very high mechanical load capacity yet low weight and outstanding electrical properties are crucial in this sector. KUVAG produces a wide range of products such as switch rods or housings for gas-insulated or air-insulated switchgear. We have over many years been successful in developing the process technology for producing such components and enjoy a leading position in this field.
The vacuum impregnation process involves fibers or fiber fabrics made of glass, high-strength aramid or polyester embedded in a special epoxy resin matrix in a two-stage process. In the first step, fibers or fabrics are wound onto rotationally symmetrical mandrels in a product-specific layer structure. Additional functional layers are often applied, such as GIS films for products with SF6 resistance. In a second process step, the wound fibers are soaked in an epoxy resin bath under vacuum, and the composite tubes are subsequently cured. Further processing usually includes cutting to length, mechanical processing and the attachment of metal fittings. KUVAG uses special bonding/jointing techniques to achieve the highest strengths.
Compression molding
Compression molding to produce fiber-reinforced composite products is an established processing method for use with sheet molding compounds (SMC) and bulk molding compounds (BMC). SMC refers to panel-shaped, dough-like molding compounds made from thermosetting reactive resins and glass fibers. Their high load-bearing capacity, long service life, resistance to even harsh weather conditions or contact with alkalis or acids, and good electrical properties mean that SMC components have an extremely wide range of applications. KUVAG has, in this context, predominantly specialized in applications relating to the electrical industry and traffic engineering.
KUVAG uses presses with a closing force of between 100 and 1000 tons. This technology entails pressing a stack of malleable SMC, fiber-reinforced, semi-finished blanks into a heated mold. Appropriately pretreated metallic components like fasteners or electrical conductors are frequently inserted into the mold, and the SMC is allowed to flow around them during the pressing process. The components are then mechanically reworked as soon as they have been cured. This process can guarantee good repeatability of dimensions and material properties and high cost-efficiency in large-scale production.
Prepreg winding
Prepreg winding produces high-quality, cylindrical composite tubes that need to exhibit high mechanical strength at low component mass. Pre-impregnated, semi-finished products made of fibers or fabrics like glass, natural fibers, or paper and various matrix materials are used. The wide range of composite plastic materials enables a very diverse application area for these products. KUVAG supports its customers with customized solutions for varied, mostly industrial application areas.
This process involves semi-finished products pre-impregnated in layers, being wound sheet by sheet onto a rotationally symmetrical, pre-tempered mandrel. KUVAG has a large selection of winding mandrels ranging from an internal diameter of 10 mm to 1000 mm. The matrix material and the fabric are used to define the tube’s properties. Depending on the matrix, tubes are cured under defined temperature conditions and then pulled off the mandrel. A subsequent mechanical reprocessing of the product at high precision frequently occurs to ensure the functionality of the finished product.
