Did you know? 60° / 55°

NPT and BSPT have different flank angles, 60 against 55 degrees. They will screw together for a few turns and still not seal reliably.

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Straight weld-on bulkhead unions

Tube fittings

Straight weld-on bulkhead unions take a pipe run through a tank wall or a partition. The spigot is welded into the plate, the pipe clamped on the opposite side by union nut plus cutting ring. This group lists 69 items.

Selection starts at the pipe outside diameter: the light series covers 6 to 42 mm, the heavy series 6 to 38 mm, nut threads running from M12x1.5 to M52x2. Spigot dimensions of 20 to 60 mm plus the material, stainless steel 1.4571 or phosphated steel, complete the choice.

⚡20 pipe sizes - light series from 6 to 42 mm outside diameter, heavy series from 6 to 38 mm.

⚡Nut threads M12x1.5 to M52x2 - the metric thread follows the pipe size, for instance M16x1.5 at 10 mm light series or M42x2 at 30 mm heavy series.

⚡Weld spigot 20 to 60 mm - from a 20 mm spigot on 6 mm heavy series pipe up to a 60 mm spigot on 38 mm pipe.

⚡Stainless steel 1.4571 - corrosion resistant version, for example 6 mm heavy series pipe on a 20 mm spigot or 8 mm pipe on a 22 mm spigot.

⚡Phosphated steel - standard material across the whole size span, such as 12 mm heavy series pipe on a 28 mm spigot.

⚡Version without nut - body supplied free of the union nut where nut plus cutting ring are already on site.

These unions are fitted to tanks, oil reservoirs and machine panels wherever a line has to pass through a wall while staying tight at that point. The welded spigot carries the load of the pipe run. Small bores from 6 mm serve control lines, sizes from 25 mm upward feed main runs; the 1.4571 version is chosen where wall plus pipework must stay corrosion resistant.

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Straight weld-on bulkhead unions

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