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HEATING AND VENTILATION


Table 1. Readings on the exterior surface of 3-inch steel pipes. Insulation type


Thick mm


Pre insulated polyurethane Elastomeric rubber Glass wool


Polyethylene foam Polystyrene foam


35 20 25 25 25


l In the indoor areas, drips of condensation on ceilings were generated causing spots of mould and damage, as well creating favourable environments for the development of fungi and bacteria dangerous to health. In the case of outdoor areas, the pipes were protected with galvanized sheet linings or with canvas wraps with anti-fungal paints, and, in both cases, they suffered significant degradation, exposing the insulation to the weather causing deterioration. Heating pipes, which used this type of insulation lost their elasticity and ended up cracking, mainly at points where water circulates at temperatures close to 100˚C.


Following these observations, it was decided that the insulation of pipes on site was not the optimum solution for this project, particularly in the case of pipes that are water cooled at low temperatures, where condensation led to damage of the pipes and their surroundings. This was in addition to the problems of low efficiency due to insulation failures. Therefore, the project team decided to


focus on working with pre-insulated seamless steel pipes with a polyurethane foam insulation and a continuous jacket of high-density polyethylene. The team were already aware of the use of this approach within food industry projects. This type of pipe is widely used in


large-scale systems for transporting cold or hot media, such as district heating or district cooling, industrial applications and transportation of fuels and gases, mainly due to the high performance and reliability needed within these areas. Until the beginning of this project, these types of solutions had only been used in food industries in Uruguay, mainly for the conduction of steam and process water at low temperatures, and there was no other documented experience for HVAC systems on buildings of the size of this project. Faced with this lack of experience, the


following questions arose: l Was this solution economically viable for these types of projects? After comparing the cost of materials for this solution, against solutions previously installed on site, as well as


IFHE DIGEST 2020 T1 ˚C


70 50 58 43 55


T2 ˚C


68 48 45 32 50


dif T ˚C


2 2


13 11 5


T env. Length Term. cond ˚C


m


20 20 20 20 20


the installation time for both solutions, the team calculated that there was a significant advantage in using pre- insulated pipes. This was aside from the savings in operating costs due to improved efficiency of insulation and less maintenance.


l Was this solution technically viable for these types of projects? In the case of industrial facilities or district heating/cooling applications, large outdoor spaces are available for the passage of pipes, or the pipes can be buried in wide ditches. However, in the case of hospital facilities, systems are usually confined within small spaces, located in shafts and ceilings. Therefore, it was necessary to analyse the viability of the assembly of the system, particularly in terms of evaluating the spaces where various fittings would be mounted and insulated. The analysis showed that there would be no major difficulties and thus, the solution was considered viable.


The Danish company Logstor Industry, producer of pre-insulated pipes, was asked to deliver technical support, and the company analysed the project to identify the most convenient system within their range of solutions, studying the different technical specifications. The project team chose the Logstor


pre-insulated bonded pipe system, with seamless steel pipes between three- quarters of an inch and 10 inches, with Series 1 polyurethane foam insulation, and high-density polyethylene jacket; 6m long pipes were chosen for their ability to be used within the confined spaces of the building and reduce transportation costs via shipment in standard containers. When the joints, elbows and branches


are tightly welded to the pipe, they will be covered with half polyurethane shells, wrapped with a thermo-shrinkable polyethylene sleeve that is adjusted to the final size with a propane torch, on the site. The edges are welded to the pipe polyethylene jacket with a hot melt material already integrated to the edges of the thermo-shrinkable sleeve. This solution results in a pipe that is completely hermetically sealed against the ingress of


245 26 41


100 34


w/m.k


Loss ˚C/m lineal


0.03 0.008163265 0.037 0.076923077 0.041 0.317073171 0.032


0.11 0.038 0.,147058824


water and steam, as well as a continuous insulation that ensures a very low loss of energy. Further, the pipe remains unchanged by the effect of environmental corrosion and oxidation, as there is no accumulation of condensation. The finish of the continuous jacket, without open joints, prevents points of accumulation of fungi that can affect the insulation and the surrounding environment. The high-density polyethylene jacket


provides robust protection against mechanical impacts ensuring that the insulation remains intact during the assembly of the pipes and during operation. Also, the density of the insulation and the jackets, allows the supporting fittings to be mounted directly over the jacket, eluding the thermal bridges to the supporting structure. Logstor Industry gave on-site technical support and training to the contracted staff responsible for the assembly of the pipes. It was possible to quickly streamline the assembly processes and the completion of the insulation.


Conclusion Until now, a large part of this project has been executed with more than 3500 m of pre-insulated pipes installed. After 12 months of operation with the system, no insulation failures resulting in condensation drips have been found. The total cost of the investment was lower than estimated for a system carried out on site. Although the time of assembly and welding of steel pipes was the same as it would have been if another insulation had been used, the time of termination of the insulation was reduced to less than 20% because it was limited only to the termination of unions, elbows and valves. As it can be seen from Table 1, the loss


of energy is significantly lower in this system than in pipes with other existing types of insulation installed on the building. Ultimately, it is necessary for all


professionals linked to the sector to challenge the belief that it is only possible to have hospitals with sustainable technologies in developed economies. Fundamentally, it is possible to create increasingly efficient healthcare buildings, regardless of economic and technological development.


IFHE 49


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