Storage and Handling of Sandwich Panels
Sandwich panels can be expected to provide many years of rust-free service provided precautions are taken during storage. This chapter outlines the procedures necessary to properly transport, store and handle the required sandwich panel packages at the construction site.
- Sandwich panels must be transported to the construction site in a safe manner, in accordance with generally accepted safety standards. These panels:
- The panels should be loaded on trucks in such a way that they do not fall off the trailer, do not hinder the driving of the vehicle and do not hinder the unloading of the panels;
- must be secured to the trailer with a system that ensures that the load is evenly distributed and supports the movement of the panels during transport;
- must be loaded and secured in such a way that they do not become unstable when the fastening system is released at the construction site.
Panel package lifting operations
At the time of unloading the truck, or during normal handling operations, the bundles of panels can be lifted using a forklift or a crane, depending on the length of the bundles:
- packages up to six meters in length can normally be lifted with a forklift truck; in this case, the forks must be separated up to the maximum length, and the load must be centered on the forks;
- Packages up to ten meters long can be lifted with a crane using nylon straps at least 200 mm wide (Fig 7.1). Wooden strips, at least 200 mm wide and 2 cm wider than the width of the package, should be inserted between the strips and the package (Fig. 7.2). Under no circumstances should metal cables be used instead of nylon straps, as these could damage the panels. Packages longer than ten meters should be lifted using a crane, following the same indications given for panels up to ten meters in length. In this case, however, a spreader bar must be used to keep the nylon straps at a certain distance. The panel should be fastened from two points, separated by a distance equivalent to three-fifths of the total length (Fig. 7.3).
Storage of panel packs
Where sandwich panels are not lifted directly into position, they should be stored at the construction site, taking care to protect them from adverse weather conditions and from possible accidental impact by operators and moving vehicles, moving to perform normal construction operations.
The panel packages cannot be stored directly on the ground, as their elements can be damaged and it can be very difficult to lift the individual panels. The bundles of panels should be stored on a rigid, flat surface and placed on polystyrene or wooden spacers, spaced no more than one meter apart (Fig. 7.4). This storage configuration also allows air circulation under the package and prevents water that might accumulate on the ground from seeping into the package itself.
The packages should be placed in a slightly inclined position (min. 5%) to facilitate condensation drainage and prevent water accumulation (Fig. 7.4).
A maximum of three bundles can be stacked one on top of the other if wooden or polyester spacers are inserted between them (Fig. 7.5). Obviously, the stacking height must be limited to ensure that the ground supports and lower elements are capable of supporting the load.
The polyethylene used to wrap the package is not suitable for prolonged exposure to open air, as sunlight can modify its properties. For this reason, packages stored in an outdoor area should be protected with an impermeable and air-circulating cover to prevent moisture formation (Fig. 7.6). It is best not to cover the stack of panels with dark or heat-absorbing fabrics to avoid heat build-up.
Another consideration is related to the protective film with which the panels are normally delivered. This film should not be exposed to sunlight, as it is not resistant to UV rays and may deteriorate to the point of being difficult to remove. This explains why, according to the panel use instructions, the film must be removed within four months after delivery of the panels. This film is normally removed at the time of panel installation but, when storing a package in an outdoor area, it is recommended to remove it from the topmost panel that is exposed to direct sunlight (Fig. 7.7).
The following additional factors should be considered when storing sandwich panels:
- the storage area should be chosen in such a way as to minimize package handling during the construction process
- sandwich panels should be stored in a cool, dry, shaded place away from direct sunlight;
- panel packages should be stored in a stable manner, even in windy conditions;
- under no circumstances should panels be stored near or in contact with salt water, corrosive chemicals, ashes or fumes generated or released within the construction site or in enclosed facilities;
- Every day it is necessary to carry out an inspection of the stored packages. If the waterproof cover has been damaged, it should be repaired with a compatible waterproof tape;
- open packages should be covered again at the end of each day to prevent moisture ingress;
- if the panels get wet, they should be removed from the packages and dried separately;
- the packages must remain wrapped during handling operations and until it is time to install the individual panels.
Precautions during panel handling
Each panel must be unloaded and handled with care to avoid damage or bending, and to prevent abrasions to the surface finish. The following suggestions should be followed to avoid possible damage to individual panels during normal handling operations:
a panel should never be held by its shortest part, nor should it be moved in a horizontal position; it should be raised along its longitudinal axis, to a point one meter from both edges, and moved in a vertical position (Fig. 7.8). For panels longer than three meters, it is recommended that they be lifted by more than two people;
when removing a panel from a package, it should never be allowed to slide over another panel. Instead, the loose panels should be rotated at the top of the package on their longitudinal axis and then lifted to avoid scratching the bottom panel;
Soft gloves should be worn when handling the panels.
To facilitate the handling of the sandwich panels, the bundles of panels can be lifted and placed on the roof, after having carefully checked the load-bearing capacity of the structure. Prior to placing any package on the roof, a package placement plan should be made by determining how much of the roof area a package would cover. The bundles should be placed on the roof parallel to the truss and roof slope structures, according to the direction in which the panels will be installed. Depending on the slope of the roof, prepare appropriate barriers to prevent them from sliding and falling, and ensure that they cannot be blown away by the wind.
Lifting of panels for installation
When installing sandwich panels, installation crews often encounter the problem posed by the following conditions:
ever-increasing thermal insulation requirements, which means that panels are being made thicker and thicker;
special fire protection requirements, which lead to the use of non-combustible insulation materials, such as mineral wool, which is heavier than polyurethane foam;
the current trend towards larger spans and ever shorter time requirements result in the use of ever longer panel lengths.
Sandwich panel lifting operations for installation purposes can be performed following several methods. The main parameters to be taken into account when choosing the lifting method are basically the overall cost, accident prevention aspects and protection against possible damage to the panels.
Vertical lifting methods
These methods are essentially based on the use of a cable with brackets to attach the panel. These methods are mainly used for vertical wall packing operations, or for lifting panels of reduced length to the roof.
The first method uses a cable with two equipped supports and whose profile has a thickness of at least 3 mm. The lower bracket holds the lower part of the panel in place, while the upper bracket has a sliding device that holds the upper part in place. The lifting device is completed by a safety ring with a spring clamp and a guide rope (Fig. 7.9).
The second method uses a single bracket with a lifting ring and four holes. The holes are used to screw the bracket to the top of the panel, while the ring allows the entry of a lifting hook (Fig. 7.10).
Horizontal lifting method
This method is mainly used for horizontal wall paneling operations, or for lifting panels of significant length to the roof.
This method of panel lifting is based on the use of two jaws, equipped at their ends with plates, necessary to distribute the locking pressure over a larger part of the surface of the metal skin (Fig. 7.11). The plates can be equipped with hemispherical adapters to better adapt to the profiled surface of the panels (Fig. 7.12). Clamps are placed at both ends of the panel to keep it stable during the entire lifting process (Fig. 7.13).
Vacuum lifting devices
Sandwich panel installation using vacuum lifting equipment (Fig. 7.14) uniquely combines speed of installation with operational safety, ergonomics and surface protection.
The weight and length of the elements to be installed are not the only factors that can benefit from these lifting devices. They also have significant advantages compared to other installation systems:
reduction of sandwich panel installation costs, thanks to shorter installation times and a better rationalization of the construction process;
- The installation equipment avoids heavy physical lifting efforts;
- the safety of operations will be increased during installation;
- not so many additional aids are necessary;
- this type of installation protects the materials.
The vacuum devices, which can be lifted by crane or winch, are equipped with a sophisticated safety system that constantly monitors the status of the batteries and vacuum circuits. Optical and acoustic signaling devices provide advance warning of possible malfunctions. A suitably sized vacuum backup system maintains the load capacity even in the event of power supply or vacuum unit failure, until the load can be safely deposited, following optical and acoustic signals.