**1. Introduction**

Nowadays, roofing methods play an essential role in the energy efficiency and weather resistance of buildings and houses [1]. One common roof protection method is to install asphalt coatings. Specialized workers generally do asphalt roofing manually. They typically carry a single Liquefied Petroleum Gas (LPG) burner to apply the heat to the rolls. Workers perform several steps when roofing: locating the rolls, aligning them with respect to the previous rolls, unrolling them, applying heat, and finishing them <sup>o</sup>ff. A worker can install around 20–25 rolls per day (200–250 m2) using this manual procedure. Such a reduced capacity for manual installation has motivated patents and developments of new systems and equipment to facilitate and enhance roll installation speed.

Patent EP0466249 [2]—a method and apparatus for applying a bituminous sheet to a substrate—presents a roller system with a previously heated additional drum wherein the asphalt roll is heated. Another patent US4725328 [3] was claimed for a mechanism that includes two heating torches perpendicular to the roll. Heating torches were located at both ends to increase adherence where the rolls overlap. Patent US 2013228287 [4] has been commercialized using the name Unify-ER by the company RES Automatisation Contrôle [5]. This device applies heat to the roll through a longitudinally distributed set of LPG burners. This equipment shows a roll installation speed of 1 m/min, claiming a rate of 18 rolls per hour, but requires two workers; thus, this device provides an installation of 480 m<sup>2</sup> per day per person. Although it is faster and much more efficient than the manual technique, the large number of frames, structure and auxiliary mechanisms leads to a total weight of 180 kg. Such a high weight considerably hinders its use on weak roofs. In addition, the excessive size of the equipment makes it difficult to be transported in small vans. Other commercial equipment are the Seal-Master 1030 from Schäfer Technic GmbH and the Bitumenbrenner from Bamert Spenglerei GmbH. From a practical point of view, the main disadvantages of all the previous systems are that they are heavy, too large for operation on small roofs and difficult to transport. On the other hand, manual installation only requires a single torch and propane bottle. The lightweight equipment that we present in this article provides a fast, high quality application capacity, while being light and small enough to be transported and used in most cases.

All previous patents and products enhance asphalt roofing speed but they all require gas burners to heat the asphalt up for its installation. Gas burners generate CO2 and SO2 emissions, which must be reduced as much as possible. Roofing has attracted the attention of environmental administrations in order to reduce their emissions. For example, the Asphalt Roofing Manufacturing Association (ARMA) developed emissions factors for asphalt-related air emissions for all the relevant processes in the manufacture of roofing asphalt [6]. Moreover, a measurement of 75.2 kg CO2eq per roll was estimated in [7] and the installation stage in buildings was found to be responsible for the majority of those emissions. Infrared heating could be an alternative option to gas burners [8], but its applicability is limited to places where a high electrical power source is available. Therefore, it is necessary to reduce the gas consumption as much as possible by optimizing the heat transfer from torch burners to asphalt rolls.

Besides speed and gas consumption, roofing workers' health must also be guaranteed and protected. When doing manual installation, workers often do not use safety prevention equipment in order to improve their speed, at the expense of increasing the risk of accidents. A proper way to prevent occupational illnesses, injuries and fatalities is to design systems and equipment that allow workers to operate efficiently [9]. Moreover, inadequate posture during manual roofing may cause a rise in the number of illnesses and injuries. The equipment presented in this article allows workers to operate in safer conditions and to prevent work injuries. We hope that the equipment presented in this article will help workers during manual installation, reduce installation risks, increase installation speed, optimize gas consumption and will be light and practical for use on any type of roof. Furthermore, the shorter the installation time of the asphalt rolls, the lower the CO2 emissions; thus, the presented equipment even provides an improvement in the human factor because, during the installation of asphalt rolls, humans are also a source of emissions (eating, creating waste, using electricity, etc.), and the impact of their emissions decreases if the working time is reduced.

The presented equipment consists of a lightweight trolley mechanism that allows the installation of asphalt rolls in a quicker, cleaner, and safer way. This trolley includes a set of five parallel torches located in front of the roll to heat the asphalt up. Asphalt rolls are directly placed on the floor, so the worker does not have to lift them. As the worker pushes the trolley, auxiliary wheels unroll the roll, while the worker can control the heat application. The equipment also includes an insulation cover to maintain and increase the heat transfer from the torches to the roll. This allows for the uniform and continuous heating of the roll for its installation on the ground, which is synchronized with the unrolling. Moreover, the trolley has two small compaction drum rollers in both lateral sides, in order to assure the adherence of the asphalt where the rolls overlap.

In this article, we present the mechanical and thermal design and an analysis of the equipment, CFD simulations for the calculation of heat transfer, a description of the manufacturing and assembly, a preliminary thermal test, and an operational test of this new equipment, demonstrating the claimed advantages. To conclude, we include a list of lessons learned after the tests that may help to improve the equipment in further developments.

#### **2. Design and Analysis**

The described lightweight equipment is basically a lightweight trolley design that facilitates the installation of asphalt rolls. This equipment is composed of the following elements: a light trolley structure, four wheels for the motion of the trolley, an auxiliary wheel for unrolling the asphalt roll, a set of five torches aligned parallel to the roll, a top thermal insulation cover to avoid heat loss, small drum rollers for the compaction of the asphalt in the overlaps and general gas flow regulators and switches.

#### *2.1. Mechanical Design and Analysis*

Figure 1 compiles three views of the trolley. The isometric view shows the trolley (1), which can be pushed using a handle placed at a comfortable height for the worker. A total of four wheels (3) allow for the smooth motion of the equipment. The rear wheels are blocked and the front wheels are free to allow steering, so that the worker can precisely drive and guide the trolley. The asphalt roll (4) is located inside the main frame. The trolley has two locating stops on both laterals to keep the roll in the right position and allow for the re-direction of the roll while it is being unrolled. In addition, the trolley has two auxiliary wheels (5) located behind the roll, and at a height lower than the radius of the roll. These auxiliary wheels transmit the pushing force tangentially to the roll. A thermal insulation cover made by rock wool (6), which maximizes the heat transfer, covers the whole roll. Additionally, the trolley includes two small drum rollers (12) for the compaction of the asphalt where rolls overlap.

**Figure 1.** Isometric and orthogonal views of the design: 1—trolley, 2—torches, 3—wheels, 4—asphalt roll, 5—auxiliary wheels, 6—thermal insulation cover, 7—individual flow regulator, 8—gas pipeline, 9—on/off valve, 10—main flow regulator, 11—main pipeline from propane bottle, 12—drum rollers.

Figure 1 also shows the set of five torches (2), which are parallel and aligned in front of the asphalt roll. A flexible pipeline (8) connects all the torches with the main gas pipeline. Each torch flow can be individually regulated (7), but is also regulated by a general flow regulator (10) placed close to the handle. The activation of the torches is set and controlled by an on/off manual control valve (9). The gas is provided from a propane pressurized bottle through a flexible ten-meter-long pipeline (11).

The equipment is specially adjusted for ten-meter-long, one-meter-wide 3 kg/m<sup>2</sup> asphalt rolls. The main dimensions are depicted in Figure 2. Smaller roll sizes could be compatible with the equipment, but the positions of the locating stops may be modified, placing larger or shorter limits on the rolls. For wider rolls, modifications to the whole structure would be necessary, as well as the repositioning of the torches. The total trolley mass is 16 kg, excluding the compaction drum rollers.

**Figure 2.** General dimensions of the equipment in millimeters.

During installation, it is not necessary to lift the roll from the ground, since the trolley directly moves and unrolls it. Hence, there is no need to add heavy auxiliary rolls for unrolling, which makes the entire system much lighter and saves workers' energy. The unrolling mechanism and structure of the trolley follows the design shown in [10] and the patent in [11]. The mechanism is based on a pair of auxiliary wheels.

Standard 3 kg/m<sup>2</sup> asphalt rolls weigh 30 kg and are 0.25 m in diameter. The friction coefficient between concrete and asphalt is estimated as μ = 0.4. Thus, with a maximum friction force of F = μ·m·g = 117.6 N, almost 12 kg of horizontal pushing force is needed. Such a value is easily achievable for a construction worker. This implies that there could be an issue—if the trolley directly pushes the roll, the worker might be able to slide the roll without unrolling it. This could be severely problematic at the start of the installation of the roll because, at this point, there is no adherence between the asphalt and ground. One solution to prevent sliding is to include auxiliary wheels in order to facilitate unrolling. These auxiliary wheels permit the conversion of the horizontal thrust into a tangent force, making the unrolling much easier.
