When designing connectors for use in applications in harsh environments, such as oil refineries, chemical plants, and industrial settings, special consideration must be given to protect not only the component but the end application as well. Depending on the market and application, protection requirements can include, but arent limited to, NEMA ratings, surge protection, EMI shielding, environmental sealing and reliability. Each of these requirements can be addressed by design considerations which include the connector materials and plating.

NEMA-Rated Products

Many equipment manufacturers require an industrial connector that, when designed into the box, can maintain a NEMA-rated explosion-proof environment. While this isn necessarily a technical challenge, the connector must structurally withstand the NEMA class 7 standard. In applications such as chemical plants, oil exploration and drilling rigs—generally anywhere there is energy production outside of solar, resulting in a potential for explosion—explosion-proof components are paramount. Ultimately, the main concern addresses the materials used to construct the insulator. While a plastic insulator is not suitable because the plastic will blow out during an explosion, a metal connector with a hermetic, glass-sealed insulator will conform to NEMA standards.

Surge Protection
Connectors must also be able to withstand surges common in equipment for harsh environments. Lighting strike, also referred to as transient voltage spike, is a common design consideration for surge. By utilizing capacitor-based filter connectors, including planar array or Chip-on-Flex connectors,surge spikes can be suppressed down to 18 volts or less, depending on the device.

Despite this capability, it is still rather difficult to meet both the surge rating requirements and size constraints as required by equipment manufacturers. Connectors were previously designed with isolated components such as diodes and capacitors to create a filtering network to withstand surge spikes, but the  resulting devices required large-size packages to accommodate multiple components. Today, some connector solutions incorporate filter chips placed in an array on the back of the connector and attached to the signal pins, providing surge protection in a much smaller package.

Chip-on-Flex filter connector designs, for example, replace current planar array capacitors with advanced design flex circuits where individual chip capacitors are surface-mounted adjacent to the contact. Because the contact is not soldered directly to the capacitor, thermal stress points associated with the current planar array designs are eliminated. Such designs are EMP- and surge-protected with a zener chip diode and filtered, grounded, and isolated feed-through contact options further ensure a robust design resistant to surge, thermal shock, and vibration.

In advanced commercial markets – such as alternative energy – standards are being defined and product designs revolutionized, starting at the component level. Recent enhancements in connector technology, including insert and contact materials, housing designs, and manufacturing processes, have enabled connectors to be specified for applications in solar, wind and nuclear power, as well as in electric vehicles. In each application, these developments play an integral role in the development of advanced connector designs.

Wind and Solar Power

From generator to motor, motor to fuel cell, and in between, wind power devices require a myriad of advanced connector designs to link each device and control the system amperage. To minimize losses throughout the system, highly efficient interconnects must be employed. Highly efficient, no-loss connectors are achieved through the use of advanced conductive materials.

Highly conductive materials start with specific copper alloys, such as tellurium; design and construction of the contacts; and the dielectric insert technology to isolate currents. Creating the insulation between the actual grounds or conductors in multiple lines of power is critical in terms of developing highconductivity devices. For high power and efficiency, a full 360-degrees of metalto-metal is most desirable in connector construction. While typical socket-andcontact designs are suitable for low frequency signal applications, these standard designs exhibit loss in high frequency applications. Full metal designs, with shielding for each pin and within the connector housing, maintain signal integrity and therefore allow maximum power transmission. Used in the field and subjected to environmental elements, such connectors also must be sealed to IP67/IP68 requirements.

Photovoltaic solar panels are used to convert sunlight directly into energy. Similar to wind turbines, solar panels are being increasingly used to generate power for businesses and homes, and require a series of interconnects to connect the solar panel modules, inverters, and control system without loss. While eliminating all loss is unrealistic, tellurium is often used in place of brass or stainless steel in connector contacts, because it is a more efficient conductor and exhibits less loss than other materials. To accommodate the series of interconnects, innovations such as ITT Interconnect Solutions’ Stackable Interconnect (shown below) are often implemented.

In addition to materials selection, the connector contact designs for wind and photovoltaic solar power applications must also be touch-proof. For example, if separating the junction is necessary for repair purposes while the wind generator is still spinning, one must be very careful to not touch the connector contacts as the generator produces enough energy [amperage] to be fatal. If the interface on the active side of the contact system is made touch-proof, the person performing the repair will not be shocked if their finger touches the connector. To do this, a plastic plunger is often placed over the male pins. This design prevents the potential for human shock by allowing the female contacts to come in contact with only the metal male pin, thus providing an effective finger-proof solution.

These connectors must have an extremely low contact resistance and be properly sealed so that after months or even years in the field, they don’t build up oxidation. If oxidation occurs, the contact resistance will increase over time, negatively impacting the effectiveness of the connector and thus the amperage generated through the system.

In commercial and military aircraft applications, EMC (electromagnetic compatibility) conformity, EMI (electromagnetic interference) and EMP (electromagnetic pulse) protection are paramount to maintaining the integrity of electronic signals, the information that is being transmitted, and consequently the overall performance of the device. Traditional methods of EMI and EMP protection include mounting additional devices to the circuit board. Yet, such solutions are costly, less effective, and do not conform to increasing real estate constraints. Alternatively, inroads are being made in EMI and EMP protection through mounting chip capacitors and TVS devices to flex circuits within a connector — as opposed to the circuit board — to protect against lightning induced transients, voltage surges, and electromagnetic interference and ESD pulses, all while conforming to the cost and size limitations of aircraft applications.

Electromagnetic interference and electromagnetic pulse are factors in the distortion of electronic signals in nearly all commercial and military aerospace applications, as EMI and EMP can distort the signals and cause noise, thereby impacting the information that being transmitted. Because of the nature of the application, navigation equipment, displays, and other electronically transmitted information must be both highly accurate and reliable.

As such, manufacturers are forced to protect against both radiated and induced signal threats. The interconnect system can serve as the gatekeeper into these costly systems that are highly sensitive to voltage induced transients. Protectionis most effective at the interface to the system, placed within the connector. In most of today applications, protection includes capacitive filtering following the protection device to maximize the surge protection to the system. Historically, interconnect manufacturers have been providing solutions within the connectorsthat have been effective but costly.

Traditional EMI and EMP Protection Methodologies

Protecting aircraft electronic systems from lightning transients, voltage surges, EMP, and EMI is traditionally accomplished using one of two methodologies, both of which involve attaching a transorb to every contact in the interface connector.

The first method involves physically attaching a device to the side of each contact within the connector and grounding it to the connector shell. This solution incorporates processes that solder the device and then overmold it to isolate and insulate the poles of the device from each other. Surge and leakage current testing of the contact assembly is always mandatory since the processing greatly affects the performance of the product. The small physical size of the device required to accomplish this method minimizes its power dissipation capabilities and results in a longer connector due to TVSS (transient voltage surge suppression) and filtering.

The second method involves attaching a pre-tested JANTX-certified device with leads to the contact via circuit boards or other similar techniques, the other end being connected to the shell. This method offers the ability to use off-the-shelf devices with a wide range of power handling capabilities. However, the larger physical size of the leaded devices necessitates increased connector size, usually both in length and diameter.

Whether designing casualty power connectors for shipboard use, high power connectors for electric submersible pumps in oil wells, or high temperature connectors for use under railway cars, manufacturers must ensure that the parts function in these environments at all times. Materials selection is critical, and whether the connector is designed for submersible, high shock and vibration, high pressure or extreme temperature environments, customers need to know the connector they’ve selected is proven for such use.

It’s imperative to engage with a connector company that is experienced in designing for these harsh environment applications and that is also familiar with testing parameters from a regulatory and standard bodies standpoint.

Connectors for Ship, Oil and Rail

Ship, oil, rail and even energy applications require highly robust connectors that operate properly at all times while conforming to stringent qualifications. For example, casualty power connectors employed on navy ships and aircraft electrical servicing cables used on navy carriers not only must meet all MIL qualifications, such as MIL-DTL-24552, MIL-DTL-32180 and VG95234, but they are also ITAR (International Traffic in Arms Regulations)-controlled and subject to further qualification testing.

Connectors are also often employed in energy applications such as electric submersible pumps in oil wells. Used at the surface and deep within the well, these connectors, as well as connectors and splices for metal-clad cables used in permanent down-hole gauges in oil and gas wells, must provide safe penetration for electrical power at all times.

Regardless if the application is for navy carriers, oil wells, passing electrical energy through pressure barriers or even railway applications such as electronically controlled pneumatic (ECP) brakes, connectors in these applications will be exposed to high shock, vibration, pressure and temperature conditions, as well as fluctuating environmental factors. As such, there are critical component parameters that must be met when designing connectors for ship, oil, rail and energy use.

Critical Component Parameters

When sourcing connectors for these harsh conditions, voltage specifications, size and resistance to environmental elements are just a few of the critical design parameters that must be considered.

Temperature is a concern, particularly in rail applications where components must be flame-retardant. While materials like neoprene are suitable for temperatures ranging from -55°C to +25°C, connectors utilizing silicon are capable of operation from -55°C to +200°C. Further still, some connectors are designed to meet European CEN/TS 45545 standards governing railway fire safety, and thus must be capable of withstanding a high temperature exposure period of at least 15 minutes at the ISO 834-1 heating curve, where maximum temperature is 800°C.

High-temperature connectors are often constructed with machined copper alloyplated contacts, a machined stainless steel shell and ceramic inserts. Conventional connector inserts are constructed with plastic or rubber, but these materials melt under the extreme temperatures of a fire. Ceramic, however, is resistant to fire and brittleness caused by moisture evaporation, and the rigidity of the material makes it less susceptible to vibration and breaking. A ceramic insert is kept in place in the shell by the use of a metal retention ring. As a result, the connector is easy to disassemble, allowing for quick, simple field maintenance and service.

Sealing for ship, oil and rail applications requires more than meeting IP69 or IP69K standards. Because of the applications, oftentimes connectors must be waterproof to 10 meters for up to 12 hours. Including wire sealing silicon rubber grommets on the plug and receptacle interface further enhances the robustness of the connector by sealing the wires against humidity, water and fluid penetration. Additionally, shock and vibration resistance is often specified to 50G and 20G, respectively. Once again, the use of a metallic retention clip provides a high integrity contact that will not release under extreme shock and vibration conditions. Designing a connector with bayonet coupling further ensures robustness, high vibration resistance as well as the ability to withstand moisture ingress.

Finally, as in many markets, size is a critical factor in component designs. While many connectors are small in size, especially given the amount of power they are often capable of delivering, customers continually seek smaller designs. Energy applications, such as passing electrical energy through pressure barriers, often requires connectors capable of 5000VAC at up to 200A (that’s about 800KW – enough energy to power 200 homes!).

Because of advancements in materials – such as the use of thermosetting elastomeric materials and PEEK (polyaryletheretherketone) engineered plastics, smaller, circular connector solutions are available down to 3" in diameter for many harsh environment applications, even for those requiring higher power and where resistance to high temperatures, high pressures, corrosive liquids and gases are imperative.

Sourcing Connectors, Testing and 3rd Party Approvals

Worldwide standards for ship, oil, rail and energy applications differ from country to country. This is particularly true for DIN rail specifications. NACE (National Association of Corrosion Engineers) International and API (American Petroleum Institute) set standards for materials and corrosion resistance, as well as suitability of products for service in hazardous locations, while military and ITAR specifications further define connector designs.

Engaging with a connector manufacturer that is experienced in each of these areas takes the guesswork out of designing for high temperatures, high-pressure interfaces, and a myriad of other design challenges. Because these parts are being used in oftentimes critical applications and situations, customers’ do not want to be part of the suppliers’ learning curve; to maintain high levels of quality and performance, and avoid dangerous results, they want parts from a manufacturer with a proven track record. Working with a manufacturer who is familiar with meeting the testing parameters of regulatory and standard bodies further streamlines design and development processes, while ensuring the connectors meet all necessary regulations. Inhouse testing capabilities such as hydrostatic testing to 19,000 psi, down-hole environment testing to 450°F at 7,000 psi, as well as continuous quality improvement programs, further reinforce a connector manufacturers’ position as an expert ship, oil and rail connector source.