Technical data
Jabitherm pre-insulated pipe systems
The design criterion for the insulation thickness is to prevent condensation on the outer jacket. The calculation of heat losses from insulated pipes is carried out using the equation for several concentric pipe layers.
The thermal resistance of the insulating layer is essentially determined by the λ value of the insulating material. The λ value of polyurethane depends on the temperature and the age of the polyurethane. The λ value is determined in several layers; the temperatures at the boundary layers are determined and the λ values of the PUR layers are iteratively calculated.
The internal heat transfer value αi is determined by the flow velocity and the physical conditions of the fluid; as a rule, a fixed value must be used here.
The external heat transfer value αa is determined by the conditions on the outer jacket of the pipe. It depends heavily on the installation conditions (wind, self-convection, radiation, etc.). It contributes significantly to whether moisture can form on the outer surface of the jacket. The αa value is also strongly dependent on temperature and is therefore determined iteratively.
The design criterion for the insulation thickness is to prevent condensation on the outer jacket. Depending on the relative humidity and the above-mentioned criteria for the heat transfer value αa, the surrounding air can condense on the outer jacket and lead to undesirable dripping on the pipe. This condition is achieved when the surface temperature on the outer jacket is below the dew point of the environment. The Jabitherm calculations determine the dew point of air under the given conditions and determine the minimum insulation thickness to prevent condensation/p>
Calculation of heat losses for pre-insulated pipes
The internal heat transfer value αi is determined by the flow velocity and the physical conditions of the fluid; as a rule, a fixed value must be used here.
The external heat transfer value αa is determined by the conditions on the outer jacket of the pipe. It depends heavily on the installation conditions (wind, self-convection, radiation, etc.). It contributes significantly to whether moisture can form on the outer surface of the jacket. The αa value is also strongly dependent on temperature and is therefore determined iteratively.
The design criterion for the insulation thickness is to prevent condensation on the outer jacket. Depending on the relative humidity and the above-mentioned criteria for the heat transfer value αa, the surrounding air can condense on the outer jacket and lead to undesirable dripping on the pipe. This condition is achieved when the surface temperature on the outer jacket is below the dew point of the environment.
The Jabitherm calculations determine the dew point of air under the given conditions and determine the minimum insulation thickness to prevent condensation and determine the minimum insulation thickness to prevent condensation
THERMAL EXPANSION OF PRE-INSULATED PIPES
Das Ausdehnungsverhalten von vorisolierten Rohren bei thermischer Belastung entspricht dem des unisolierten Rohres. Obwohl es sich hier um ein isoliertes Verbundrohr handelt, überwiegt der Anteil des Mediumrohres am Aufbau des Verbundsystems.
Die Bewegung des produktführenden Rohres wird über die hohe Haftkraft des Polyurethanschaumes dem Außenmantel aufgezwungen. Die Stabilität des Außenmantels in Verbindung mit der druckfesten Polyurethan-isolierung führt dazu, dass klassische Gleitlager auf dem Schutzmantel befestigt werden können.
Vorteil dieses Systems ist Übertragung der Bewegung des Mediumrohres ohne Unterbrechung der Isolierung auf die Gleitlager. Festpunkte bedürfen einer besonderen Betrachtung, die Erfahrung hat jedoch gezeigt, dass häufig die Scherfestigkeit des vorisolierten Rohres ausreichend ist, um auch Festpunkte am Außenmantel befestigen zu können.
Corrosion resistance of pre-insulated pipes.
The corrosion resistance of pre-insulated pipes is significantly improved compared to conventional systems.
A diffusion-resistant metal jacket, frictionally connected to closed-cell polyurethane foam insulation and produced under controlled conditions, forms an extremely stable, long-lasting and wear-resistant pipe system.
Points such as moisture in the insulation, condensation or ice formation on the outer jacket can be eliminated with pre-insulated pipes. The corrosion resistance is supported by the possibility of attaching pipe holders to the outer jacket.
Deflection of pre-insulated pipes
The friction-locking composite system of pre-insulated pipes leads to a stiffening of the pipe. The additional weight of the insulation and the outer jacket is carried by the composite, so the general rules for calculating the support width can also be applied as usual to pre-insulated pipe systems. Particularly heavy pipes require closer inspection.
Thermal insulation
The thermal insulation of pre-insulated pipes consists of a foam structure with self-contained cells. The pre-insulated pipes are made from this material with single, double or multi-layer insulation.
Operating temperature: -200°C to +120°C
Thermal conductivity (λ): 0.027 W/mK (at 20°C (68 F), 70 Kg/m³)
Compressive strength: 0.15 MPa at 10% relative deformation
Proportion of closed foam cells in the foam: min. 88%
Design
The design is directly related to the application of the pipe system and is developed in close collaboration with the customer. The operating temperature (-200°C to +120°C), fire resistance, use in potentially explosive areas and mechanical influences on the pipe are crucial for the design.
Foam density
The effectiveness of the thermal insulation depends on the foam density. A high foam density of the insulation creates a force-fitting connection between the medium pipe and the outer jacket, but reduces the insulating effect. In return, a lower foam density increases the thermal insulation effect of the thermal insulation; the mechanical strength is only slightly changed.
Coordination
The optimal coordination of these influencing factors is the challenge when creating a specific product solution. The product concept is supported by the modular principle; the design is determined closely based on the requirements of the customer and the company. The outer jacket (exception: plastic) is manufactured as a folded fold jacket with an internal fold, is diffusion-tight against moisture or dust and has a smooth outer surface.