When it comes to sealing, not all connectors are created equal. Sealed connectors destined for use in transportation equipment must be rugged and protected in order to provide reliable performance. A variety of sealing strategies ensure smoother travels.
The world of transportation represents a combination of some of the harshest conditions anywhere on planet Earth. These vehicles are required to withstand extreme weather conditions, from the frozen wastes of the arctic to the heat of the jungle. So, the electronic systems and devices within them, as well as the components they’re comprised of, must be made of temperature-resistant materials that can take the swings from extremes, along with potentially high temperatures in engine bays. Transportation equipment is also exposed to everything from dirt and dust to aggressive chemicals in the course of normal operations and cleaning processes. At the same time, these systems are subjected to the shock and vibration that is part of normal operating conditions for mobile outdoor equipment. There are almost countless ways that interconnects can be damaged in transportation environments. sealed connectors
Sometimes, the abuse that connectors suffer comes from the people that operate the machinery. I once visited a customer that ran a superbike racing team. They were using a new connector in the ignition system of these precision machines and were having problems with corrosion. This new interconnect was exquisitely made — slim, lightweight, and designed specifically for the motorsport market. However, I discovered that the team washed down their bikes after every race with diluted, high-octane racing fuel. Little wonder that the lightweight aluminum shells of the sealed connectors were suffering.
Selecting sealed connectors for transportation applications therefore require an expansive knowledge of the specific environments in which they will be used, maintained, and stored. Of particular concern will be the choice of materials, both for the connector body and for materials used in the system to seal the connector against the elements. While it might be tempting to specify connectors with robust stainless-steel shells, which are resistant to corrosion and contamination, few vehicles enjoy the luxury of unlimited weight. In the transportation market, more weight generally means more fuel or energy is needed, which translates to higher operating costs. Lightweight materials, whether metal or plastic, are a must for this market.
As such, the materials used to seal the connectors that will be deployed in transportation applications must be lightweight as well as rugged and effective at preventing ingress. The two most common types of sealed connectors specified for transportation applications are hermetically sealed and environmentally sealed connectors. Hermetically sealed connectors are most commonly used in military and aerospace applications. These connectors are sealed against air and gases using design strategies and materials that provide an extremely tight and protected fit. Environmental seals are an added interface that seals connections against a specified level of ingress, generally expressed as an IP or ingress protection rating.
In environmentally sealed connectors, O-rings are typically used to provide a watertight, interface-to-interface seal and gaskets are used to provide protection around the wires as they enter the connector body. The combination of qualities that is required for these components can be complex. Polymers that are flexible at room temperatures can become brittle in freezing conditions, and other materials that can handle temperature extremes may be vulnerable to the chemicals frequently found around engines. So, care must be taken to choose the right solution. Is there a material that works for both? Are there specific design features in the connector housing or latching mechanism, such as internal locking, that help enhance IP ratings? These are the questions you must ask before you select a connector for these types of applications. Working with a connector supplier that has experience with the unique needs of the transportation market can help identify suitable solutions for specific challenges.
What Happens When Sealed Connectors are Unmated?
Another important consideration when thinking about sealed connectors it what happens when the connector is unmated. Something that is not always obvious when reading specifications is that most waterproof connectors are only sealed when they are mated. Connectors work in pairs, and the mated pairs serve to seal each other against the ingress of contaminants. If the pair becomes unmated through a loss of connection, either by disruption or during maintenance procedures, the connector interfaces generally become vulnerable. Without the protection of the seal created by the mated pair, most sealed connectors will not provide a waterproof seal of their own. Even in the rare products that remain sealed when the connector is unmated, the exposed mating face will still have a higher risk of contact damage.
At first glance, this may not appear to be of concern to most designers. Connectors are designed to be plugged in, after all. However, there are pitfalls to consider. A connector that is not designed to resist the shock and vibration of the transportation environment might become loose and disconnect at a critical moment. Any connector that is left intentionally unmated — such as to ease testing or to prepare for future capabilities — must be sealed correctly using a cap, hood, cover, or boot, depending on the connector type and products available from the supplier.
There is one more piece of advice that I can impart, though, for the best connector in the world is only as good as the person who installs it. Allow me to use an example to illustrate my point, taken not from the world of connectors, but from the world of switches.
Several years ago, I was making a video to demonstrate how components are tested and, to show the techniques, we were using vandal-resistant switches. The accepted test method was to fasten the switch to a wall panel and, using a pendulum, allow heavy weights to impact the face of the switch to determine how much damage it could withstand. We were full of confidence, having already completed one set of tests using a small switch. When it was time to test a more substantial example, I installed the second switch, primed the experiment, and allowed the weight to fall.
The switch broke.
At first, I panicked. I was in the manufacturer’s own laboratory, using their equipment on their switch. I was afraid I had identified a manufacturing flaw or a design failure. Instead, I had installed the switch incorrectly. My mistake was as simple as installing a stainless-steel washer and a silicon rubber O-ring in the wrong order. With such a simple (and seemingly insignificant) error, I had rendered an awfully expensive switch useless.
Selecting sealed connectors for transportation applications is therefore a process to be approached with care. There are many connectors available that promise IP-rated sealing against the elements, but the transportation market demands greater reliability and performance. Many major manufacturers and distributors offer dedicated automotive and transportation solutions.
Know your environment, choose your materials wisely, and make sure you read the instructions.