Industrial plants are still wasting energy too often, because fittings and other plant components with complex surface molding remain uninsulated. For these kinds of components, ContiTech has now developed a highly adaptable insulation system, which cures all by itself when exposed to the plant’s heat – thanks to a silicone rubber from WACKER.
In every individual microsphere, the gas is trapped like in a balloon.
Industrial plants require heat to manufacture, process and finish products. This so-called process heat represents a significant cost factor, especially for energy-intensive sectors such as the chemical, metal-producing and metal-processing industries. According to a study by the Federal Ministry for Economic Affairs and Energy, German industry spent a total of 1,700 petajoules (or 473 billion kilowatt-hours) of energy in 2013 solely to provide process heat – almost two-thirds of its entire energy consumption.
Nevertheless, many companies still neglect the thermal insulation of their plants. Substantial amounts of heat are lost to the surroundings, unused, via the surfaces of hot plant components. A study by the European Industrial Insulation Foundation (EIIF) shows that, in industrial plants, an average of ten percent of surfaces either completely lack insulation or are fitted with defective thermal insulation.
Mats Made of Mineral Wool
To insulate plant components that are hotter than 130 degrees Celsius, the only real option available to operators had previously been mineral wool. The long pipework that transports superheated steam to individual facilities at many large companies, for example, is insulated with mats made of mineral wool and clad with aluminum-coated zinc sheets – a proven and economical method. However, the parts of the piping systems that are difficult to insulate due to their complex surface structures are usually left out. This includes branches, flanges and transitions between different pipe diameters, for example, as well as built-in parts such as gate, rotary slide and other valves.
Nevertheless, many companies continue to underestimate the heat lost by such fittings. According to the German Energy Agency (dena), a single uninsulated fitting with a connecting dimension of 100 millimeters, through which steam flows at 100 degrees Celsius, loses as much heat as an insulated twenty-meter pipe of the same diameter. A single uninsulated valve can account for annual heat losses worth up to several hundred euros. Just imagine how many such energy-related weak points might be found in an entire factory.
Plant components with complex surfaces such as these flanges are easy to insulate with flexibly adaptable silicone-elastomer mats from ContiTech.
Energy consultancy firm Ecofys extrapolated these heat losses to obtain a value that is representative of German industry as a whole. Ecofys estimates that domestic production sites could save 106 petajoules (or 22 billion kilowatt-hours) of heating energy every year if their operators were to thermally insulate all uninsulated plant components and repair damaged insulation. While these measures would cost around €180 million, they could save the companies €750 million in energy costs every year.
Dr. Jens Storre, who works as a chemist at ContiTech Elastomer-Beschichtungen GmbH in Northeim (Lower Saxony, Germany), explains why fittings and similar built-in parts are often still uninsulated despite such considerable savings potential. “It must be possible to operate these plant components after they’ve been insulated and they must remain accessible for maintenance and repair work. In addition, they usually have such complex designs that thermal insulation with conventional materials is only possible with great effort, if at all.” Dr. Storre is responsible for the research and development of elastomer sheets at ContiTech. He was involved in developing the flexible Conti® Thermo-Protect insulation system.
Silicone elastomers are rubber-elastic solids derived from polyorganosiloxanes. They are obtained from silicone rubber in a process known as curing (vulcanizing). Here, the polymer chains of the organosilicon macromolecules form a three-dimensional network and the rubber hardens. Silicone elastomers are characterized by a property profile that makes them indispensable in many industrial applications: extraordinary heat resistance, low-temperature flexibility, chemical inertness and biocompatibility. They have a strongly hydrophobic, i.e. water-repellent, surface and do not absorb water; they are very good electrical insulators and poor thermal conductors. A typical characteristic is their high resistance to a large number of physical and chemical influences, which is why, unlike organic rubber compounds, they do not age. Thus, their chemical, physical and technical properties remain virtually constant over the temperature range of roughly -50 to +200 degrees Celsius. Silicone elastomers are also able to withstand continuous exposure to oxygen, ozone and UV radiation.
Effective at Temperatures up to 250 Degrees Celsius
Designed for plant components with difficult geometric shapes, such as flanges, rotary slide valves, branches or gate valves, the system opens up new possibilities for thermal insulation at temperatures of 130 to 250 degrees Celsius. This temperature range is important in the chemical, machine-construction and pulp sectors, as well as in several processes used by the food industry, for example.
The insulation material is a silicone-rubber blend that cures to form a microporous silicone elastomer. The base chosen by ContiTech, which belongs to the Hannover-based Continental group, was a solid silicone rubber from WACKER that cures via a platinum-catalyzed addition reaction. “Their property profile makes silicones ideal for this application,” explains WACKER sales manager Christoph Schlegel. “They are aging-resistant, withstand high temperatures and are poor thermal conductors. The selected silicone rubber yields a silicone elastomer that also has a very high tear and tensile strength.”
Cured hose insulation is particularly flexible and robust. Pre-slit hoses are available in various thicknesses. Closed insulation is also available.
Although the thermal conductivity of an average silicone elastomer is quite low at around 0.2 watts per meter, the elastomer can only be used as an efficient thermal insulation material in porous form. The gas in the many pores significantly increases the thermal insulation effect. However, it is essential that the material’s pores are neither interlinked nor connected to the ambient air – every individual pore is isolated. Experts refer to this kind of pore structure as closed-cell.
If the pores were open, convection would enable the gas to transport heat from the hot to the cold side. Dr. Storre generates the closed-cell pore structure in his insulation material with the aid of tiny, extensible, hollow spheres that are filled with a gas. “Mixed into the silicone rubber, these hollow microspheres represent gas-filled pores. In every individual microsphere, the gas is trapped like in a balloon,” explains ContiTech’s elastomers expert.
Furthermore, ContiTech treats the material with a heat stabilizer and a flame-retardant additive. As a result, the microporous elastomer achieves a thermal conductivity of only 0.08 watts per meter and Kelvin, measured at 200 degrees Celsius. “This brings our silicone insulation material to the same level as mineral wool. A ten-millimeter-thick insulation layer is sufficient to reduce heat losses by around 65 percent,” emphasizes Dr. Storre.
Conti® Thermo-Protect is available as molded parts, sheets, hoses and as a paste. In cartridge form (Conti® Thermo-Protect Paste), the uncured insulation material is easy to dispense and ideal for sealing slits and holes.
Protection against Injuries
The insulation material is elastic and compliant. As a result, it is not only able to withstand vibrations and shocks, but also protects people from getting injured or burned whenever they bump against the hot fittings.
The ContiTech insulation system therefore also offers benefits for occupational safety. Only a few millimeters thick, the silicone sheets can be used to insulate exposed, hot plant components that are located in an employee’s work space and which could not be insulated until now. Thanks to the insulation, the employee won’t be hurt by touching these components.
ContiTech provides the uncured, malleable material in the form of sheets, but also manufactures prefabricated and cured molded parts and hose insulation.
A ten-millimeter-thick insulation layer around this pipe is enough to reduce heat losses by around 65 percent.
The sheets of uncured material have the consistency of modeling clay, can be cut with a knife and shaped by hand. As such, the material can be perfectly tailored to plant components with complex shapes and can also be pressed into narrow openings or undercuts. Since the material adheres well to both metal surfaces and itself, pre-cut pieces can be mounted manually and joined together to form a closed cover without the need for adhesive.
Installation of the thermal insulation is correspondingly simple. The fitter takes the measurements, cuts suitable pieces out of the kneadable sheet, places them around the component to be insulated and forms a closed cover out of them. Any joints that are created in the process are sealed by pressing the material together. If the pipe which contains the component that is enveloped in the uncured insulation material is then put into operation, the material cures all by itself – a high operating temperature ensures rapid curing. This creates a thermally insulating molded part that envelops the hot fitting like a custom-made jacket, even in the case of difficult geometrical shapes. The thermal insulation is also quick and easy to dismantle and install again at a later stage – the plant component remains accessible at all times.
Payback in Months
Thanks to the new insulation system, ContiTech customers can now efficiently reduce heat lost by plant components that could previously not be insulated. The costs are modest, while the cost savings can be substantial. “In most cases, the investment pays off within only a few months,” says Dr. Storre with conviction.
ContiTech plans to enhance its insulation system and add new products to it. One target, for example, is to render the material even more heat-resistant. Dr. Storre is also working on developing a material that has a slightly lower viscosity than the modeling-clay-like product. This kind of material could be applied with a trowel. WACKER will support these developments with suitable silicone components, too.