Bronze hex coupling/union, female-female NPT thread — class 125 (B103)
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Hex coupling in brass bronze with female NPT thread on both ends, to splice two pipe runs of the same diameter in a straight line. The manufacturer catalog calls it "B103 - Union", but the cross-section view and the photograph show a fixed single-piece hex body, without the center nut and removable seat that characterize a three-piece (ground-joint) union able to disconnect without rotating the pipe. This sheet documents the actual product: it is a coupling, useful for splicing two pipes that CAN rotate freely, not for service points requiring frequent disassembly.
IMPORTANT: reference data — may differ from the physical product; verify with an advisor before buying.
SKU VT-RAC-B103 (B103 bronze union/coupling) · 4 diameters 1/8″–1/2″ · sold by the unit
1. Technical specifications
Dimensions by diameter
| NPT size | Hex width [in] | L (overall length) [mm] | Weight [g] |
|---|---|---|---|
| 1/8″ | 1/2″ | 17.5 | 9 |
| 1/4″ | 5/8″ | 21.3 | 16 |
| 3/8″ | 13/16″ | 25.0 | 36 |
| 1/2″ | 15/16″ | 30.0 | 39 |
IMPORTANT
This technical data sheet is a reference guide to the properties of this product type; it is not a quality certificate for the product you are buying. The measurements, dimensions and physical or geometric characteristics of the product supplied may vary by manufacturer, heat and lot, and may even fall outside the cited standards. If any of these figures is critical to your design or build, verify it with one of our advisors against the physical product or the lot's mill certificate, so you can be fully certain of what you are buying. · Original data sheet: tectul.com/en/conduccion-de-fluidos/racores-y-acoples/ficha-tecnica-b103-union-bronce.html
Complete, verified table from the manufacturer sheet (March 2022 revision).
General specifications
| Product | Bronze hex coupling, female NPT thread on both ends, fixed single-piece body |
| Material | Cast brass bronze |
| Thread | NPT per ANSI/ASME B1.20.1 |
| Pressure rating | Class 125 (ASME B16.15): 200 psi (13.8 bar) ≤66 °C with water/oil/non-flammable gas · 125 psi saturated steam |
| Commercial range | 1/8″, 1/4″, 3/8″, 1/2″ NPT |
| Applicable standards | ASME B16.15 · ANSI/ASME B1.20.1 |
2. Correction: fixed coupling, not a three-piece union
In industrial plumbing, "union" usually designates a three-component fitting (two threaded halves plus a center nut that joins them with a tapered or flat seat) allowing the line to disconnect without rotating either pipe run — essential when both ends are already fixed (for example, between a valve and a pump). The cross-section view and photograph of this product instead show a solid single-piece hex body with two internal female threads: it is a repair/extension coupling. To install it, one of the two pipe runs must be able to rotate freely on its axis until fully threaded in; if neither end can rotate, this product will not work and a true three-piece union is required.
3. Frequently asked questions
Does this product have a removable center nut like a three-piece union?
No. It is a fixed single-piece hex body with female thread on both ends. If you need to disconnect the line without rotating either pipe run, you need a three-piece (ground-joint) union, which is a different product.
Can I use it to splice two pipes that are already fixed at both ends?
Not with this coupling: one of the two runs must be able to rotate freely until fully threaded into the body. If both ends are fixed, you need a three-piece union.
What pressure rating does it have?
200 psi (13.8 bar) cold up to 66 °C, and 125 psi with saturated steam — the same class 125 rating (ASME B16.15) as the rest of the threaded bronze line.
4. Application notes
Feasibility
Suitable for splicing or extending threaded pipe runs of the same diameter when at least one of the two ends can rotate freely. It is not a substitute for a three-piece union at points requiring disconnection without rotating the pipe.
Installation
Seal both threads with PTFE tape or a fluid-compatible sealant. Thread the fixed end in fully first, then rotate the free run into the other end until tight; always hold by the body's hex, never by the pipe.
Design
Verify in the installation drawing that at least one of the two pipe runs can rotate freely before specifying this coupling; otherwise specify a real three-piece union. Rating valid cold (≤66 °C); for steam, 125 psi.
5. Technical notice and limitation of liability
The pressures, dimensions, weights and other characteristics in this sheet are theoretical calculation values obtained from nominal properties published in the standards cited (ASME B36.10-2022, ASME B31.3-2024, ASTM A106/A106M-19a, ASTM A53/A53M-24, API Spec 5L 46th ed.). They guide selection; they are not a certificate of conformity for any given lot.
The actual behavior of each lot varies with manufacturing — wall tolerance (up to −12.5%), out-of-roundness, residual stresses — and with the raw material — chemical composition within the ranges the standard allows, heat-to-heat differences. To certify a lot, the tests defined by its product standard are required: tensile test, flattening test and hydrostatic test, documented in the manufacturer's mill test certificate (MTC), which TECTUL supplies upon request; testing of the lot in an independent laboratory can also be arranged.
These values must not be used as the sole criterion in critical or safety applications, or wherever failure of the line may compromise people, property or the environment: in such cases the design belongs to the project's responsible engineer under the applicable code (ASME B31.3, B31.1 or the one governing the installation), with the design temperature, corrosion allowance and load cases of the actual service. Before deciding with these data, consult our technical team.
Sources
- ASME B16.15-2020 — Cast Bronze Threaded Fittings: Classes 125 and 250
- ANSI/ASME B1.20.1-2013 (R2018) — Pipe Threads, General Purpose, Inch (rosca NPT)
- Ficha de fabricante "B103 - Union" (catálogo de accesorios roscados de bronce, IMR/TECTUL, revisión marzo 2022): tabla completa de ancho hexagonal, L y peso para 1/8″–1/2″; vista de sección transversal del cuerpo
This data sheet is the property of TECTUL, part of the Industrias IMR group. Reproduction without attribution is prohibited. Original document and updates: tectul.com/en/conduccion-de-fluidos/racores-y-acoples/ficha-tecnica-b103-union-bronce.