DuctorSeal® Series Hermetic Wire / Cable Feedthroughs

Hermetic is defined as any enclosure that prevents gasses and liquids (fluids) from migrating across the bulkhead. A common industry leakage rate is <1×10-8 cc-Helium/second. A hermetic electrical feedthrough will need to limit leakage from one side (vacuum pressure) to the other (atmospheric). Douglas customizes feedthroughs using a hermetic epoxy to seal within the bulkhead between pressure/vacuum and atmosphere. DuctorSeal is a product focused on the hermetic sealing of wires and/or cables within the bulkhead down to the conductor.

A hermetic wire feedthrough is a type of electrical connection that is used to transmit electrical signals or power through a hermetic seal. A hermetic seal is a barrier that prevents the exchange of gases or liquids between the inside and outside of an enclosure, and is often used to protect components or devices from external factors such as moisture, dust, or contamination. Douglas will hermetically seal virtually any wire or cable conductor type using its low-outgassing, hermetic epoxy.

Yes. DuctorSeal is designed as a hermetically sealed bulkhead wire feedthrough. It can be integrated with virtually any mechanical interface. Bulkhead wire feedthroughs are commonly installed control panels and cabinets to prevent moisture and gases from penetrating the system while feeding power or signal in or out of the system. DuctorSeal provides the hermetic seal at the conductor within the bulkhead to completely protect the system. This is a step beyond where a traditional cement-based seal will protect.

A vacuum feedthrough is a more specific type of hermetic feedthrough.  The bulkhead fitting is sealed and tested to ensure a hermetic seal between the vacuum pressure side of the feedthrough and the atmospheric side.  Vacuum feedthroughs are common in vacuum systems, semiconductor equipment, gloveboxes, and space simulation systems. As more systems integrate instrumentation and sensors directly into the testing environment, electrical feedthroughs need to maintain the vacuum pressure environment. Vacuum feedthroughs typically integrate vacuum flanges such as CF flanges or KF flanges.  These mechanical interfaces are offered in standard sizes that integrate into industry systems that often come with pre-populated ports.  Other fittings are also possible including radial O-ring seals, which offer a smaller footprint.

Epoxy based seals allow more flexibility in design. Conductors can pass directly through the epoxy, allowing a simpler assembly process. Epoxy also permits closer spacing between conductors than a traditional glass-to-metal seal, thus having more possible within a single space. Cost and lead time can also be a factor, as the time and effort to create the glass-to-metal seal can exceed those of a hermetic epoxy seal.  To learn more about the differences between the technologies, read our whitepaper: Hermetic Seal Types

Yes, Douglas Electrical Components can integrate connector plugs (male) and receptacles (female) into your assembly. This simplifies the process for our customers and ensures that we electrically test the entire assembly. Vendor-specific connectors, terminals, and sockets can be designed into the assembly directly at the bulkhead or at the end of a length of wire or cable. If the connector itself needs to be hermetic, Douglas Electrical utilizes our PotCon series to apply an epoxy potting treatment that fills the gaps in third-party hermetic connectors that cannot meet the leak test requirements of the applications.  The connector can be integrated directly into the bulkhead fitting or we can create a cable harness with integral connectors.

What are the standard tests available for electrical feedthroughs? Douglas Electrical Components offers mechanical and electrical testing. Pressure leak tests through a bubble test can be performed on assemblies. Vacuum leak testing can certify that products meet the agreed upon specification. High Potential, known as Hipot, testing verifies the electrical performance of the feedthrough on each assembly.

Yes. Most of our operation’s production is based upon made-to-order semi-custom and custom electrical feedthroughs. Our technical sales and application engineers partner with customers to find solutions for the end product. We combine many COTS (commercial-off-the-shelf) connectors and wires with our in-house machined components to manufacture cost-competitive solutions with a quick turnaround.

Cable feedthroughs include the jacketed cable within the feedthrough housing and assembly whereas wire feedthroughs are traditionally individual conductors. Douglas Electrical can hermetically seal cables for power, signal, and fiber applications. We ensure the jacket of the cable is hermetically sealed within the epoxy feedthrough. Our epoxy can bond to or be prepared to bond to various cable jacket materials to create the hermetic seal required.

This question is commonly asked in conjunction with wire density. There are various factors that determine how many conductors can fit within a single hermetic wire feedthrough. We need to understand parameters such as the wire gauge/thickness, number of conductors, and inside diameter of the feedthrough to ensure the proper flow of epoxy. Douglas Electrical will partners with customers to review these design factors to create a high-density hermetic feedthrough. Overall, a hermetic wire feedthrough can offer greater density than competing technologies such as glass-to-metal seals.

A wire bushing or line bushing is a type of wire feedthrough where the wire is sealed within a fitting such as a threaded conduit fitting. These terms are most common in the oil and gas industry.  Douglas wire bushings are sealed wires and/or cables within a fitting to prevent the penetration of liquids or gases. Wire bushings are available with UL1203 Class I Division 1 Explosion proof ratings. Avoid the process of cementing wire fittings by using a pre-sealed line bushing in your application to transmit power or signal in hazardous locations.