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Demands on cooling pipes
When using traditionally insulated cooling pipe systems, there is a great risk of developing condensed water in the insulation. The water typically gathers on the undersurface of the pipe, where the condensed water over time forms visible icing or condensation on the jacket. Condensed water reduces the insulation properties, which results in increased energy consumption, increasing medium temperature and a constant deterioration of the insulation and the carrier pipe.
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Installation, Cooling
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At the same time condensed water will accumulate in the insulation until it reaches complete water/moisture saturation. Corrosion problems such as rust formation on the outside surface and galvanic corrosion due to differences of the material and temperature between the components and the pipe sections may occur.
In order to avoid moisture penetration into the insulation it is important to ensure that the jacket material is impervious and that the insulation is pressure resistant so that the jacket can resist mechanical impacts. Pipe supports can be a potential risk factor in a traditionally insulated pipe system as they can form thermal bridges and thereby occasion energy loss. Therefore icing often forms on and around the pipe supports.
In order to eliminate such problems the following demands must be made on cooling pipe systems:
Watertight jacket material
High tensile strength of insulation and jacket
Dimension stability
Long thermal life
Pipe supports positioned directly on the jacket pipe
When these demands are fulfilled, the users will have a stronger and energy-efficient system compared to traditional solutions. The new energy-efficient systems entail a long-term improved overall economy and reduction of operational problems.
Construction of pre-insulated pipes
Pipe systems for use in the cooling industry are basically constructed in the same way as pipes for the district heating industry: A factory-insulated carrier pipe with polyurethane foam and a black or white polyethylene (HDPE) plastic jacket. Carrier pipes are suitable for transport of ammonia or similar products within the cooling industry.
Insulation
The insulation material is composed of hard polyurethane foam (PUR) made of polyol, isocyanate and a foaming agent (cyclopentane). As earlier described, energy loss is a general problem. Normally, energy loss is only an issue in connection with heat installations, but it is also a problem and an important factor in the installation of cooling pipe systems, as energy losses cause damage to the insulation. The CO2 carbon dioxide tax has been introduced in most of the industrial countries resulting in increasing costs for a majority of the industrial companies.
Jacket
The jacket material consists of black or white polyethylene with high density (HDPE). It is watertight to liquids of molecular shape. The watertight HDPE jacket eliminates the traditional risk of condensed water in the insulation. Specific demands are imposed on cleaning of the production facilities in the food and drink industries. This also applies to pipe systems, when the cooling pipes are installed in a visible place. The pipe systems must be high-pressure or low-pressure cleaned to avoid bacteria. Pre-insulated HDPE jacket pipes are suitable for these purposes, as they can stand up to everyday high-pressure or low-pressure cleaning with chemicals. Furthermore, the jackets are resistant to salty water and the black jacket is UV-resistant. Cooling pipes in cold stores and food firms are often placed on the roof of the buildings, which implies that the pipe systems are often used as gangways. This results in damages on the jacket material and sunken insulation material and gives cause for great energy losses and reduction of the pipe system's cooling efficiency. Moreover, there is a risk that corrosion on the pipe surface will spread quickly.
Pipe supports
Contrary to traditionally insulated pipe systems, the pipe supports are positioned directly on the jacket surface of the pre-insulated pipe systems and thereby eliminate the risk of penetration of condensation, leaking connections between the supports and the jacket and damaged mastic. In addition to this there will be no formation of traditional thermal bridges and icing around the supports at the pre-insulated pipe systems.
An alternative option
It is often a challenging process to change over from traditional insulation solutions to alternative pre-insulated solutions, but the cooling industry has recognized the advantages of this solution a long time ago, especially in the case of big ammonia-based systems. But the systems also apply to copper pipe systems. Many advisors believe that the jackets always require surface-treatment when it comes to traditional insulation so as to avoid corrosion arising from water penetration, but it is quite unnecessary to surface-treat pre-insulated pipe systems.
References:
YORK
AXIMA
GRASSO
