NPT Feedthroughs & Conduit Seals

NPT, or National Pipe Thread, is a tapered mechanical interface common in the electrical feedthrough industry.  NPT threads are simple and cost-effective to machine as well as install.  Each thread size has its own pressure ratings when paired with certain materials (softer metals like brass tend to hold less pressure than a high-strength nickel alloy).  NPT plugs engage with receptacles with a tape or sealant applied to the plug threads.  As the threads engage, the fitting is tightened, creating the seal.  This differs from an SAE thread, which would have parallel threads and an O-ring seal at the base of the plug or a metal cone seal at the end of the threads.

Douglas Electrical Components manufactures a variety of hermetic NPT feedthroughs. These designs are specified in vacuum and positive pressure applications as well as hazardous and non-hazardous environments.  Douglas can integrate wires, cables, or connectors to feed power, signal, or optical fiber through the bulkhead fitting while maintaining a hermetic seal.  Epoxy allows the conductors to pass through the fitting while hermetically sealing it within the feedthrough. This design can be set to prevent the penetration of liquids or gases from one side of the bulkhead to the other. In explosion-proof atmospheres, the hermetic feedthrough prevents the penetration of hazardous liquids and gases from reaching an ignition source with enough energy to cause an explosion.

Types of NPT Feedthroughs

NPT Wire Feedthroughs / Wire Bushings

Hermetic NPT feedthroughs, referred to in the oil and gas industry as wire bushings or conduit seals, allow for an electrical interface through a bulkhead or conduit. Epoxy seals the wires or conductors to create a high density, robust seal.  In-house pressure or vacuum testing ensures the seal meets the application requirements.

The feedthrough can be machined using various materials including aluminum, brass, stainless steel, and nickel alloys such as Alloy 625 or 718.  The feedthrough material will help dictate both the pressure rating as well as corrosion resistance.  The thread chosen for the NPT feedthrough will also influence the pressure rating.  In oil and gas instrumentation, ½” NPT is a popular threaded connection due to its compact size and availability of ½” conduit pipes.

Custom NPT wire feedthroughs are available to customer specifications.  While the thread itself will meet the industry standard, the interface that a customer needs can be customized.  This can allow for simpler, faster installation with an OEM design. Connect wires, cables, connectors, and fiber within an NPT fitting to meet your requirements.

Explosion-Proof Conduit Seals Available

Douglas manufactures both standard and custom NPT feedthroughs.  Our standard designs are available with both non-hazardous and hazardous configurations.  Conduit seals are available as certified to UL1203 with options for Groups A, B, C, D, our JacketSeal is a non-hermetic, water-proof conduit seal. Douglas Electrical will also partner with customers to certify a design within their hazardous location certification.  This can create more customization and streamline the process for certification to the exact requirements.

NPT Connectors

Connectors continue to gain popularity in various industries for their convenience. Hermetic NPT feedthroughs are commonly designed with integral circular connectors such as the M12 connector. This enables quick installation in a cost effective package. Other industrial connectors, push-pull connectors, and MIL-Spec connectors are available for integration into an NPT, yet can be limited based on the diameter of the connector compared to the diameter of the connector and mating cable assembly.

NPT Terminal Seals

NPT Feedthroughs are designed for integration into HVAC/R equipment for power transmission.  These feedthroughs are commonly referred to as hermetic terminal seals. The Douglas Electrical Components portfolio offers standard hermetic terminal seals in both NPT and face seal designs. This allows for customers to cost effectively transmit power through the copper threaded stud through the hermetic seal.

Thermocouple NPT Feedthroughs

Thermocouple NPT feedthroughs are simple designs to transmit temperature signals in and out of a bulkhead. Thermocouple NPT feedthroughs are common with a single-ended NPT nipple of brass or stainless steel. The number of conductors can vary based on the application, thermocouple type, wire thickness and conductors.