When designing industrial equipment, the operating temperature of the product is often at the top of the list for design engineers. This makes sense, after all, you don’t want to keep replacing failed equipment. However, while engineers give a lot of thought to heat in the equipment itself, the performance of the connectors and cables that join different devices is often overlooked.
Jonathan Parry, Senior Vice President of Global Operations and European Managing Director at cables and connectors company PEI-Genesis, explains how to choose an extreme temperature connector.
For the average member of the public, choosing a connector is often as simple as deciding between a one or two metre USB cable, and we still get very annoyed when the connection starts to become unreliable.
For the engineer the choice is far more complex, and the consequences far more serious than having to wiggle the connector until it works. A dropped connection could mean losing control of heavy autonomous equipment, a stopped machine and jammed-up production line, or many other detrimental effects that are best avoided.
While the working equipment in industrial settings is often well monitored by governing software and vigilant engineers, it’s often the case that the connectors are overlooked. This is despite them being just as crucial as any other piece of line equipment.
Hot stuff
Heat, particularly in the extreme, is a factor that engineers constantly tackle.
Heat is a natural consequence of many industrial processes, and many more still involve heat directly in the process, such as smelting and other metalworks.
Most equipment uses active cooling to control this heat, such as ventilating fans, cooling lubricant sprays and water-cooling. For the connectors however active cooling is often not possible, which makes the choice of connector in the first instance very important.
When dealing with hot environments it’s tempting to pick a connector with a metallic housing, such as steel or aluminium, simply because these metals typically don’t melt before a few-hundred degrees Celsius. Doing this overlooks major problems, however. For instance, the connector enclosure might easily withstand the high temperatures in question, but the components inside may not. The tightly packed and enclosed nature of connectors also means they act as a heatsink because heat isn’t actively wicked away, meaning the temperature inside the connector may be far higher than expected.
Many connectors, such as common USB and serial ports, rely on plastic inserts to house the contacts, while other connectors may also enclose electronic components such as resistors, ballasts and rectifying circuits, which may be susceptible to temperatures lower than the enclosure material.
Even if temperatures don’t actually melt or scorch these plastic components, procedural stress caused by the high temperatures, as well as the effects of thermal expansion and contraction can cause connectors to fail well before their expected lifecycle.
Particular attention must be paid to connectors in hot and enclosed environments, such as on trains and boat engine rooms. Here low-smoke-zero-halogen (LSZH) plastics are often used to avoid the build-up of dangerous fumes or explosive atmospheres created by burning or outgassing plastics.
There are many examples of connectors that are been specifically designed for extreme temperatures. These connector will use specialised LSZH plastic or ceramic inserts and a variety of enclosure materials, giving them the capability to meet the stringent ISO 834-1 fire standards where the connectors are exposed to temperatures as high as 800 degrees Celsius for 15 minutes.
Leaving connectors out in the cold
Sliding back down the scale, we reach the arena of cold-temperature connectors. This initially seems far easier to solve than heat, primarily because most industrial processes are exothermic, but there are still some serious considerations to be made.
The cold temperatures that connectors are exposed to are often natural, with connectors being continually exposed to the elements. These cold environments often preclude the use of many plastic and rubber enclosed connectors because they can freeze and crack, creating openings for moisture to wreak havoc on delicate electronic components.
This makes metal a seemingly attractive choice, but in practice it’s often prohibitively complex to design a metal enclosure with tolerances tight enough to protect from the weather. As temperatures fluctuate, the tight metal seals will inevitably fail simply due to thermal expansion and contraction.
With the correct choice of connector configuration and materials, however, this style is perfectly possible. There are many ostensibly low-temperature capable connectors, but the best boast IP67 and DIN 400 50 ratings. Connectors like these are enclosed in PVC nitrile plastic, or similar materials that remain flexible, supple and resistant to cracking down to temperatures as low as -40 degrees Celsius.
Many industries treat connectors as a quick, one-time decision taken during integration, despite the consequences of failure perpetually bringing the problem back onto the agenda. With some more consideration, though, it’s possible for that decision to be truly long-lasting, and ensures that you make the most out of the connecting equipment.
