Because you need a cover in the outdoor spa

The first is obvious.

A good design and insulated roof greatly improves the energy efficiency of a spa esterior. The cover slows down the rate of water evaporation, which removes heat from the water left in the spa. Also, evaporation control will result in maintaining proper water chemistry, which will reduce the use of necessary chemicals. These facts help control spa operating costs.

It is probably understood by everyone that ultraviolet radiation from the sun is harmful to all plastic materials. Acrylics have very good resistance to sunlight, which is why they are commonly used for windows, skylights, airplane awnings, etc. However, it is not perfect. Although, we can’t understand all polymer shapes that damage sunlight, we know we need to minimize exposure. Therefore, it is recommended to use a cover when the spa is not in use.

Another issue in relation to acrylic spas is the formation of cracks or fissures. Both of these phenomena, failure due to excessive stress. First, let’s review the construction process. Acrylic spas are produced by heating and forming a flat sheet in a mold with the shape of the spa. The sheet is stretched from the upper edge to the bottom of the mold cavity (spa foot well). Obviously, several things happen. As the sheet is stretched, it becomes thinner and weaker. The thickness of acrylic in the foot well is normally in the range of 0.030″. This stretch imparts underlines, and some of the tension remains after it cools down. Next, most spa “shells” are reinforced with polyester resins containing fibers cut from glass. Thus, it becomes a composite material structure with each material having unique properties. There are tensions along the hull of the spa, and arise from the thermoforming and reinforcing the measurements, and by the weight of the water and the people who use the spa. The resistance of the material is effected by temperature and exposure to chemicals.

The crack(s) in the acrylic layer occur when the stress exceeds the strength of the material. Stress can be thermally based or mechanically induced. If the caps are not used correctly, the surface (acrylic) is subject to large temperature swings from sunlight during the day, at very cool temperatures at night. This heating and cooling can lead to cracking failure due to expansion and contraction fatigue. The mechanical stress created by the combined weight of water and people can also lead to cracks. Therefore, these should be minimized by suitable support devices under the shell – especially under the seats. The increase in temperature reduces the strength of the material, so if stress and temperatures are high, a crack can occur. Since stress is usually highest at the spa edge, cracks usually start there, and spread to the center. The use of a cover will minimize the effects of temperature, and reduce the likelihood of crack formation. See the image for an example. of cracks at the edge.

Another type of phenomenon cracks cracking. A mania is different from a crack in that it cannot be felt on the surface, and may be able to withstand a load. Many studies have shown that both conditions must be present for tiny cracks to occur on an acrylic hydromassage surface. They are: 1) the high stresses within the acrylic and the) presence of a liquid or solvent tension-2 crack. The presence of just one of these conditions does not cause cracking. Both must be present. Manias form in highly stressed regions. Stress can occur due to thermal or mechanical forces. Cracking occurs mainly in amorphous, brittle polymers such as polystyrene (PS), acrylic (PMMA) and polycarbonate (PC). The acrylic used for spas is one specially designed to withstand the environment of the normal spa, but will fail in very harsh conditions. The cracking appears as very small microcracks on the surface. The stress opens up the tightly wound polymer chains in the material. This condition makes it easier for liquid molecules to penetrate the molecular structure of acrylic and diffuse along polymer chains.

The cracking mechanism is stress cracking molecules act as a lubricant, which allows polymer chains to separate from each other when stressed, creating very small cracks. Depending on the amount of stress and aggressiveness of the chemical agent, the small cracks continue to grow in size. Since the strength of acrylic decreases with temperature, the use of a cover will minimize thermal stress, and reduce the risk of cracking. Since the most ridden cause of cracking is the presence of a chemical, it shows the importance of avoiding the use of cracking chemicals with stress on the acrylic surface. Only use approved chemicals for cleaning and maintaining water chemistry.

Finally, many manufacturer’s warranties are void when no cover is used.

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By Catharine Bwana