The frontiers - and capabilities - of electronics now extend far beyond what we might have imagined as little as a decade ago, let alone earlier days. It's no longer shocking that the delicate inner workings of microelectronic packages, which uphold the operations of so many of the world's critical communications, defense, medical, energy, aerospace and automotive systems, are capable of performing above and beyond expectations, even in the most extreme environments.
The deepest seas and oceans of the world represent one of the most challenging settings in which electronics have to function at - and ideally above - their expected operating threshold. These circuits, semiconductors, cables and other components could be within the 17,850-ton behemoth hull of an Ohio-class nuclear submarine plumbing the depths for the U.S. Navy, or inside of sensors attached to an offshore oil rig that's part of a major energy conglomerate's latest drilling operation. Whatever the application, it's critical for reliable heavy-duty subsea connectors to be in place so that the proper activities of navigational, sonar, guidance, communication and sensory equipment of these undersea machines are not interrupted.
While properly designed connectors that are mated in dry settings will almost certainly work just fine when submerged later on, underwater mate-able electrical connectors offer a much greater degree of flexibility and allow for maintenance and repairs in critical situations. The latter is a precious commodity in the high-stress applications commonly faced by businesses using subsea vessels or machines. AMETEK designs and manufactures the ELITE series of wet-mate electric connectors at our SCP business. Let's take a closer look at the factors that make these connectors so valuable:
A foundation of material excellence
The true value of wet-mate electrical connectors begins with the strength of the metals used in their manufacture. Necessary attributes include extreme corrosion resistance, tensile strength, minimal electrical conductivity and a high melting point, among others. Several metals and alloys meet all of those requirements, including the following:
Inconel: This variety of stainless steel is referred to as one of the "superalloys" due to its mechanical strength, surface stability and corrosion resistance. Encyclopedia Britannica highlights Inconel - which consists primarily of nickel and chromium, along with small percentages of various filler metals - for its austenitic crystalline structure.
That characteristic provides the alloy with incredible resistance to heat as great as 2,000 degrees Fahrenheit or more, as well as tensile strength and pressure resistance even under such high temperatures, affording it great advantages as a wet-mate connector material. On the other hand, inconel is on the higher end of the cost spectrum and, as a result, may not be the most effective choice for all needs.
316L stainless steel: On the surface, the difference between this stainless steel and its counterpart (316) might appear fairly nominal - 316L contains less carbon in its makeup
Ultimately, though, this variation possesses several qualities that are extremely valuable for wet-mate electrical connectors: 316L stainless steel is well-equipped to resist corrosion after being put through manufacturing processes that involve welding, and even more importantly, it holds up better than 316 in all high-corrosion environments and boasts considerable resistance to heat. (You are more likely choose 316, which has more carbon, for use in a setting where acidic corrosion was the main factor, as it's strongly resistant to the chemical reactions of acidity. On the other hand it's also much more likely to experience weld corrosion than 316L.)
Titanium: Few pure metals have more strength than titanium. According to a presentation by the Phase Transformations and Complex Properties Research Group at Cambridge University entitled "Metallurgy of Titanium and its Alloys," its melting point is an incredible 1,670 degrees Celsius (3,038 Fahrenheit). Titanium also possesses extremely high corrosion resistance, which is why it's frequently used in chemical processing and testing. Even the highly acidic mixture aqua regia, which can melt noble metals like gold and platinum in no time at all, can't manage to break down titanium. All of those attributes, as well as tensile strength at least double that of aluminum, make titanium a great choice for wet-mate connectors.
From a cost perspective, 316L stainless steel is a more than reasonable choice for wet-mate connectors and will stand up to the elements quite well. However, for applications that require truly exceptional corrosion and heat resistance, it's wise to opt for titanium.
Standing up to the pressure
While the ability to perform in a high temperature and corrosion environment matters a great deal for the viability of wet-mate electrical connectors, there is one element that has more significance for these components' success in the long run - withstanding pressure. Virtually all major underwater applications where ships and equipment are thousands of feet below the surface of the water involve the presence of massive pressures reaching up to (and beyond) 10,000 pounds per square inch. If such forces can penetrate the boundaries of a connector - or, for that matter, any other component - any number of service interruptions or system failures can occur, jeopardizing operations and potentially putting human lives at risk.
For purposes of quality control, it's critical to subject wet-mate connectors to pressures of at least 10,000 psi during the design phase and 15,000 psi to complete final testing. Using these thresholds as the minimum helps manufacturers and metallurgists know that connectors and other finished components to be used in similar settings can undergo pressure beyond what they are likely to experience during normal performance circumstances. This provides an extra measure of assurance for energy, naval and naval defense users who need excellence at all times from the interconnects and components upholding their machines' electronic infrastructure. In fact, personnel working for AMETEK's Subsea division use considerably higher-than-average test thresholds when manufacturing ELITE series connectors: minimums of 15,000 psi for design and 20,000 psi for final testing.
Anatomy of the ELITE wet mate connector
As with nearly all similar parts, the ideal wet-mate electrical connector consists of a receptacle and a plug. Both feature the same corrosion, heat- and pressure-resistant metallic composition so that the internal workings aren't vulnerable at any point.
The sealed receptacle, which includes the component's concentric contacts, features an oil-filled primary chamber that fights off the risk of water intrusion. When mated with the plug, the receptacle's contacts are further protected by separate secondary oil chambers with individual seals, so that if one or two of them somehow fail the connector will still operate as it should. Even when the two halves are separate from each other, the female pin of the receptacle maintains its integrity so no water gets in and no oil gets out.
On the other end of this spectrum, the plug's outer sleeve protects its contact bands using yet another oil-filled chamber, and its insulated core displaces the female pin to bring the connection home. Putting the two halves together also wipes the contact bands as another protective measure to keep the wet-mate connector from being compromised by the elements. Pressure balancing of the entire connector assembly, once mated, helps minimize any stresses that might infringe upon the points at which a hermetic seal is formed.
Peak performance over long spans of time
When a naval or research submarine begins its latest mission or assignment, often crew members don't know just how long they will be deployed. The framework of a long-term plan probably exists, but any number of variables can arise that end up changing the scope of the vessel's objectives. In a similar fashion, there's no way to tell how long an offshore oil rig's drilling machinery will remain submerged beneath the waves, along with the various electronics with which it's outfitted that track the extraction of crude oil.
The ELITE series of wet-mate electrical connectors is designed and fabricated with the intent of remaining operational underwater for up to 25 years. This guarantee of longevity, coupled with the water resistance of these components, means that their users don't have to worry about replacing them due to old age, and also allows for underwater maintenance and repair.
Additional essential features of wet mate connectors
For any connector to truly have value, it obviously needs to deliver electricity efficiently with little to no interruption. Perhaps even more critically, the component must be designed for high voltage and current to contain the level of power necessary in all of the most critical undersea applications. Wet-mate connectors should be specified for 500 volts and 5 amps, which are the standards for the ELITE series from AMETEK.
The connector's conductors relative to its size is also important. Smaller is generally better when it comes to any connector, but it also needs enough channels to support proper operations. The ELITE wet mate connector employs three circuit channels to cement the critical bonds necessary for all subsea electronic applications in a robust and compact package.