Weld Bungs

Q: What material weld on fitting should I use for an aluminum or steel tank?

Match the fitting to the tank’s base metal. Use a 6061 T6 aluminum weld on fitting for compatible aluminum fabrication. Choose a listed mild steel NPT weld bung for mild steel work. Use a listed stainless steel AN weld bung only with a stainless compatible fabrication plan. Aluminum is not a direct substitute for steel. Before welding, have a qualified fabricator confirm the tank alloy, bung material, filler and welding process.

Q: Is this weld on fitting an AN flare fitting or an NPT threaded fitting?

Evil Energy offers both types, plus hose barb options. A male AN weld on bung mates with an AN hose end and seals at the 37° flare , not at the straight threads. A female NPT weld bung accepts a matching tapered pipe thread. A weld on hose barb fitting provides a direct hose connection. Select the type already used by the mating hose end or component because AN, NPT and hose barb connections are not interchangeable.

Shop Evil Energy weld on fittings for adding permanent ports to custom fuel tanks, fuel cells, reservoirs, intercooler piping and other fabricated automotive systems. This collection brings together male AN weld bungs, female NPT weld bungs and aluminum hose barb adapters, so you can choose the connection that matches the rest of your plumbing. Building the tank as well? Explore our fuel cell fittings and tank accessories.

How to Choose Weld On Fittings: AN, NPT or Hose Barb

Male AN weld on fitting: Choose this when your hose end mates to a 37° AN flare. The sealing surface is the flare, not the straight thread. Complete the connection with compatible AN fittings.
Female NPT weld bung: Choose the exact tapered NPT size used by your mating component. Pair it with compatible NPT fittings. AN and NPT sizes are not interchangeable.
Weld on hose barb: Choose the barb outside diameter that matches the hose inside diameter when the build calls for a direct hose connection.

Match the Weld Bung Material and Plan the Installation Before Cutting

Use an aluminum bung for compatible aluminum fabrication, and select a listed mild steel or stainless steel option only for a compatible metal and welding plan. Evil Energy offers 6061 T6 aluminum models, selected steel options and locating steps on selected weld fittings to help hold the part during fit up. Before drilling, confirm the fitting’s weld end diameter, tank wall, port location, inside clearance, line size and connection type. A qualified fabricator should choose the welding process and filler, protect the threads or 37° seat from heat and spatter, and inspect the finished port before service.

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FAQs about Weld Bungs

What material weld on fitting should I use for an aluminum or steel tank?

Match the fitting to the tank’s base metal. Use a 6061 T6 aluminum weld on fitting for compatible aluminum fabrication. Choose a listed mild steel NPT weld bung for mild steel work. Use a listed stainless steel AN weld bung only with a stainless compatible fabrication plan. Aluminum is not a direct substitute for steel. Before welding, have a qualified fabricator confirm the tank alloy, bung material, filler and welding process.

Is this weld on fitting an AN flare fitting or an NPT threaded fitting?

Evil Energy offers both types, plus hose barb options. A male AN weld on bung mates with an AN hose end and seals at the 37° flare, not at the straight threads. A female NPT weld bung accepts a matching tapered pipe thread. A weld on hose barb fitting provides a direct hose connection. Select the type already used by the mating hose end or component because AN, NPT and hose barb connections are not interchangeable.

What size weld on fitting do I need for a fuel feed, return or vent line?

Size the port from the complete fuel system, not from tank capacity alone. For the fuel feed fitting, begin with the pump outlet, hose, filter and regulator requirements; the fitting should not create a smaller restriction than the planned line. Size the fuel return fitting for the pump and regulator’s bypass flow. Size the fuel tank vent fitting according to the tank and fill cap vent design. If the connected hose end is 6AN, select a 6AN male bung. If the component uses NPT, match its exact NPT size.

Can this fitting be TIG or MIG welded without damaging the threads?

These are weldable fittings, but neither TIG nor MIG makes thread damage impossible. The appropriate process and filler depend on the tank metal and the selected bung material. A qualified fabricator should control heat, keep weld spatter away from the threads and 37° sealing seat, and inspect the connection after cooling. For any previously used tank, follow the OSHA hot work requirements: the container must be thoroughly cleaned of flammable residue, isolated and vented before welding; inert gas purging is recommended.

What size hole should I drill before installing the weld on fitting?

There is no universal drill size based only on the AN or NPT label. Measure the weld end locating step on the exact fitting being installed, then size the opening so that the locating section seats with a close, even fit. Confirm the measurement on the physical part before cutting the tank. Do not use the nominal thread size or hose size as the drill diameter, and verify internal clearance and port orientation before welding.

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Weld Bungs

How to Choose Weld On Fittings: AN, NPT or Hose Barb

Match the Weld Bung Material and Plan the Installation Before Cutting

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How to Choose Weld On Fittings: AN, NPT or Hose Barb

Match the Weld Bung Material and Plan the Installation Before Cutting

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