Even a calm day at sea can be rough on a boat’s electromechanical controls and switches. Boats and other marine vehicles require components that protect against liquid intrusion, corrosion damage, ultraviolet (UV) light exposure, and vibration and shock loads.
Seal Protection from Liquid Intrusion
There are many ways to specify a seal requirement; the most prevalent is the IP (Ingress Protection) rating system in accordance with IEC 60529. To survive in a marine environment, a product should be completely sealed, both above and behind panel, to a minimum of IP68S (watertight). A product meeting IP68S can be submerged to a depth of at least 1 meter of water for more than 30 minutes without liquid intrusion.
Sealing for the above-panel portion is typically accomplished with flexible, moving seals that provide protection from direct exposure to water. Behind-panel sealing is accomplished with a rigid sealant such as epoxy or other formable adhesives.
Corrosion Damage
Chemical and saltwater exposure are two of the most common causes of corrosion damage. To protect against corrosion, a device should be made of plastic materials that are resistant to chemical degradation or stainless-steel alloys that protect its housings from corrosion damage. Further, it is important to choose the correct grade of stainless steel. Although 303/304 grade will work for most applications, 316 grade stainless is the best choice for corrosion resistance.
Secondary protective films add an extra layer of defense against corrosion damage. An example of this are the magnets in Hall effect products. The magnets must be treated with a secondary protective film as iron makes up a large part of the magnets’ composition and will readily rust and deteriorate without additional protection from a conformal-like coating.
Flexible seals are also vulnerable to degradation from both chemical and saltwater exposure. Ensuring a long seal life and the inherent designed seal of the product, material choice is key. Ethylene propylene diene monomers and fluorosilicone are excellent choices for these conditions.
UV Light Damage
Constant exposure to direct or indirect sunlight can severely damage plastic materials and secondary finishes such as painting and anodizing. Plastic material damage falls into two areas: cosmetic, such as fading and discoloration, and the breakdown in the physical properties of the material, which can lead to early device failure.
Material selection is the key to plastic component robustness. Major thermoplastic suppliers have blended UV inhibitors into some of their standard materials. Although these inhibitors do not prevent 100% of UV degradation, they prolong a device’s exposure time without significant physical or cosmetic degradation.
Metallic finishes require anodizing because a standard level of coating does not sufficiently protect against UV. Hard or deep coat anodizing refers to the additional thickness of the anodic coating applied to the product. Oftentimes, an additional coating with a clear, UV-inhibiting film is required to achieve an acceptable device lifetime.
Vibration and Shock
Switch mounting and the internal designed components of the actuating/switching members of an electromechanical switch are very important to survive repeated shock and vibration. Snap-in panel mountings are popular due to the ease of assembly, and flexible snap members must be correctly designed in both form and material selection to produce a lasting and secure mounting. Internal actuating/switching components need to have adequate contact force to prevent vibration and shock-induced contact chatter that could be interpreted as a change of state by modern electronic control systems.
Back Lighting
Wide angle, super-bright LEDs enhance daylight readability as well as nighttime usage. Custom graphics, such as metallized printing, multi-color labels and metal overlays, can add stylish effects in the cockpit or on the control panel.
Switching System
Contact switching of up to 20A is available for direct control of systems while logic-level, long-life systems are invaluable for use in electronic control systems. Non-contact switching, such as Hall effect technology, represents the ultimate choice in long life as well as redundancy for safety-related circuits. Capacitive sensing is a good choice for touchless or light touch switching and sensing.
Visit OTTO’s product page for marine and other specialty applications and consult with our industry experts to select the right control components.