**3.2 Fuel burners**

A second similar to the previous one model is presented, but in this prototype, gas torches are used instead of infrared heaters. A more in-depth analysis can be read in [18]. The structural design, as well as the analysis of the auxiliary wheel, is the same as in the previous model, but presents some slight differences, which can be seen in **Figure 8**. In this case, the trolley has two auxiliary wheels (5) instead of one at the optimum determined height. Moreover, a thermal insulation cover, preferably made of sheet metal and filled with insulating material (6), has been included, to improve the heat transfer.

The five torches (2) are aligned in parallel in front of the roll. The torches are connected in series with a flexible pipeline (8). Each burner can be controlled separately (7), but they are also controlled by a general regulator (10). An on/off manual valve (9) commands the activation/deactivation of the fuel burners. The gas comes from a pressurized propane bottle through a 10-meter-long flexible pipeline (11). There is very common that a worker just used a single torch, and thus, the heat flux is just applied in localized area. This leads to a nonuniform heating, inducing adherence problems in the overlapping areas. Using a layout with several torches, the heating uniformity can be improved. Gas pressure and fuel burner selection were calculated through a transient CFD simulation iterative process. They also determined the heat transfer to the roll.

In the proposed design, a thermal insulation is included to increase the efficiency of the heat transfer and to reduce the thermal losses by keeping the hot air close to the roll. A CFD analysis has been done to measure the effect of including this thermal insulation cover, and the results are shown in **Figure 9**.

**Figure 8.** *3D model of the fuel burners design [18].*

**Figure 9.** *CFD results: Velocity (left) and temperature maps (right) with or without cover, time = 15 s [18].*

Based on the design and the simulations, a prototype was assembled (**Figure 10**). The hot air flow speed and temperature were determined in laboratory preliminary tests. The propane consumption was also measured, being 2800 g/h of propane per torch.

The flame turns blue at the torch outlet, which means that air is about 1800– 1980°C for propane [19]. In the yellow zone of the flame, the temperatures are lower, between 500 and 750°C. This can be seen in **Figure 10(left)**. In **Figure 10(right)**, the fuel burners operating at a pressure of 2.8 bar also can be seen, and the reached temperature after 10 second of warming on the roll surface. Almost half of the surface of the roll is above 200°C, which is high enough for a properly adherence.

*New Trends in Industrial Equipment for the Improvement of Asphalt Roofing Process DOI: http://dx.doi.org/10.5772/intechopen.101795*

#### **Figure 10.**

*Flow and consumption test of the five torches (left) and temperature of the roll after 10 seconds of heating (right) [18].*

#### **Figure 11.**

*Prototype and results of the asphalt rolls installation.*

**Figure 12.** *Overlaps quality test and bond check.*

Once the preliminary test was done, the outdoor tests of the installation of several adjacent rolls were performed (**Figure 11**). An installation speed of about 1.75 m2 /min was reached, with a 2.8 bar torch pressure and a consumption per torch of 2800 g/h of propane. A good adhesion was obtained on most of the surface of the bituminous sheet. In addition, the overlaps were adhered perfectly one over the other, ensuring isolation (**Figure 12**).
