By Jay Bartsias, senior product manager, Turck Connectivity, Laura Schweitz, product manager, Turck Connectivity
Working on the northern Canadian plains in winter often means wrestling with negative double-digit temperatures every day. These harsh conditions created big cabling problems for an oil and gas company. Where they operate, cable jackets were cracking as they unspooled, and frozen cable wouldn’t lay flat.
Their initial cables were the best available. As they reexamined the market, they found a new solution that could stand up to the brutal winter temperatures and prolonged exposure to the elements.
New materials and robust overmolded designs are improving dependability across harsh applications, where temperatures, shock, vibration, moisture, oils and dust are everyday concerns.
When connectors were assembled by hand in the field, a gland was used on the back end to seal the connector and protect it from the environment. This was a time-consuming process, with risks of moisture ingress and mis-wiring during installation.
Overmolded designs changed this situation. All critical connector and cable connection elements were protected against ingress by a mold body, and no assembly was required.
Overmolded designs are increasingly popular for harsh applications, as they deliver better durability, simpler installation and fewer errors. These benefits ensure shorter downtime during replacement and maintenance because connectors can be shipped directly to the field and plugged in, out of the box.
In one example, a manufacturer of refined petroleum dispensing systems had an ongoing problem with its connectivity solution. The dispensing systems rest on trailers, and are constantly traveling to resupply gas stations. This movement led to recurring ingress issues because the cables were not properly sized to the connector, and the overmold wasn’t well constructed. Rather than continuing to replace connectors with the same design, the manufacturer switched to an overmolded connector and cable with stronger approvals and better fit.
Modern material options expand capabilities
The material of a connector-cable unit has a huge impact on its performance because it must withstand the chemicals, temperature fluctuations and hazards of the environment.
Plastics are the most common housing material for connectors and cables, and new variations are coming out to advance where and how they can be used. Common plastics used in connectivity solutions include:
—Thermoplastic polyurethane (TPU): This is the most prevalent plastic found on overmolded connectors. It typically holds up well to common oils and cutting fluids, but isn’t suitable for use with alcohols or solvents.
—Polyvinyl chloride (PVC): This plastic is suitable for a range of temperatures (typically -40 degrees Celsius to 105 degrees Celsius) and washdown environments. It is not suitable for weld slag resistance, alcohols or solvents.
—Polybutylene terephthalate (PBT): These materials best tolerate heat and won’t reflow at high temperatures.
—Polypropylene (PPRO): This suits washdown applications or when caustic materials are present.
—Thermoplastic elastomer (TPE): This plastic suits welding applications, alkalines and alcohols. It’s not suitable for use with solvents or greases.
Some manufacturers use potted stainless steel housings to offer the next layer of protection. Different grades of stainless steel are suitable for different environments, but 316 is recommended for harsh applications. Lower grades, such as 303 and 304, may corrode with highly caustic chemicals and are less durable.
Design tips to choose the best connectivity solution
Beyond overmolding and materials, there are four main criteria when choosing a cable or connector for harsh environments – ingress protection, chemical compatibility, vibration and temperature.
–Ingress protection: Ingress ratings have evolved with new ratings for harsh environments. Most harsh applications require at least IP65 protection. IP69K carries the toughest and most aggressive water and ingress benchmarks for a product. Food and beverage applications along with any washdown environments are best fits for IP69K, but this rating is also increasingly requested for other applications. NEMA test standards are also helpful to determine ingress protection.
–Chemical compatibility: Chemical compatibility ensures that a product will handle specific chemicals and compounds in an application. For example, PVC does not hold up to weld slag, whereas a TPE material is excellent at resisting weld slag. Manufacturers and distributors can advise the appropriate material.
–Vibration: Vibration can be particularly hard on connectors and cables. The connector must have features that maintain the proper torque of the connector and prevent it from loosening. Contact design is critical so that vibration does not damage the contact-mating interface. Additionally, the materials and plating of the contacts are important to provide strength and durability as well as electrical performance. For example, machined or turned contacts are typically more robust than stamped and formed pieces, and gold plating will offer better electrical properties over tin plating. High-stranded wires are recommended to improve cable flex, especially for robotics or C-track applications.
–Temperature: Low and high temperatures can affect cable and connector operation. Product specifications typically include optimal operating temperature ranges to ensure reliable performance. In applications where the temperature can fluctuate, there is risk of ingress from condensation and pressure changes. It is important to have a connector with IP ratings suitable for that type of environment.
Key considerations for Industrial Ethernet systems
As mentioned earlier, Industrial Ethernet is increasingly being adopted for harsh environments because of its speed in data transmission. Some additional considerations should be taken for connectivity in these systems.
The first is the connector design. Standard office or commercial Ethernet connectors are RJ45 designs, which aren’t suited for demanding applications. Circular M12 connectors are a better and more robust option. The design is often overmolded, and higher IP ratings mean that these connectors can be used outside the panel. Commercial RJ45 connectors are typically rated IP20 for use inside a panel or other protected environment.
For cables, choose a solution approved for industrial use rather than a commercial Ethernet cable. Because of the environment, Industrial Ethernet cables may be moved, stepped on or flexed. For these applications, choose a cabling option with an extruded jacket, which will hold pairs together and keep them properly aligned, minimizing opportunities for cross-talk.
Per NEC Article 800, a CM-rated cable approval works well for Industrial Ethernet installations, and in some instances can be installed in cable trays. For hazardous locations, it is recommended to use Industrial Ethernet cables with ITC/PLTC approval, which are suitable for use in Class 1 Division 2 areas. UL inspectors commonly look for 600 V cable rating on Industrial Ethernet jackets, which indicates a cable is suitable for use near other 600 V cables when best installation practice is followed.
Guide to ingress protection (IP) ratings for harsh environments
IP ratings of IP65 and higher are often required in harsh environments. Here’s a quick look at what these ratings mean.
–IP65: No penetration of dust; jet water – water which is hosed against the enclosure from every direction may not cause damage.
–IP67: No penetration of dust; temporary immersion in water – water may not enter the enclosure in such quantity as to cause damage when the enclosure is held under water for a set period of time using predetermined pressure (1 meter deep for 30 minutes).
–IP68: No penetration of dust; continuous immersion in water – water may not enter the enclosure in such quantity as to cause damage when the enclosure is held under water for a set period of time using predetermined pressure (depth and time greater than IP67, as determined by the manufacturer).
–IP69K: No penetration of dust; water at high-pressure/steam jet cleaning – water which is directed against the enclosure from every direction with extremely high pressure may not cause any damage (14 to 16 liters/minute at 8,000 to 10,000 kilopascals (kPa)).
Filed Under: Factory automation, Design World articles, Connectors (electrical) • crimp technologies, IoT • IIoT • internet of things • Industry 4.0