90 Degree Elbow Reducer Tube Adaptor with Swivel Nut 2C9/2D9 — Metric Male 24° Cone with Loose Nut

Why This 90 Degree Elbow Reducer Tube Adaptor with Swivel Nut Passes the Compliance Gate

A swivel nut is only an advantage if it turns freely when it matters. A nut that galls on the body, or a cone seat that is off-centre by a few hundredths, turns a simple assembly into a leak hunt. Every 2C9/2D9 elbow we produce is checked for nut freedom under load (the nut must rotate by hand after the male end has been torqued), the internal 24° cone is measured on a profile projector, and the metric male thread is gauged 6g go / no-go. The nut itself is a separately manufactured component with its own inspection record, so it can be replaced without scrapping the body.

The fitting is a 90° elbow with a metric male 24° cone stud end (DIN 2353 / ISO 8434-1) on one leg and a captive swivel nut with an internal 24° cone seat on the other. “C” (2C9) is the L (light) series, “D” (2D9) is the S (heavy) series.

Core Advantages

• The joint can be aligned after the body is tight. Because the nut is captive and rotates on the body, the port connection and the tube connection are two independent operations — essential where a pre-bent tube run cannot be rotated.
• A reducer by construction. The body bore is machined to step between the port size and the tube size, so one fitting replaces a nipple plus an adapter.
• Replaceable nut. The swivel nut is a separate part with its own material and plating specification; a damaged nut is a cheap replacement, not a new fitting.
• Metal-to-metal 24° cone seat. No elastomer in the sealing path, so the joint tolerates temperature, aggressive fluids and shock.
• Full L and S coverage. Tube 6 mm to 42 mm, L series to 31.5 MPa and S series to 63 MPa.

Especificaciones técnicas

What Is a Reducer Tube Adaptor with Swivel Nut?

It is a 90° forged elbow whose flow path reduces between two connections of different nominal size, with one end threaded as a metric male 24° cone stud and the other closed by a loose (captive) nut that compresses the mating cone against the internal seat. In practice: the male stud goes into a port and is torqued; the swivel nut then picks up the tube end and is tightened separately, with the nut free to rotate to whatever position the tube run requires.

Connection 1 — Metric Male 24° Cone Stud End

The port leg is a metric male stud with an external 24° cone per DIN 2353 / ISO 8434-1 and a 6g metric thread. 2C9 uses the L series thread — M12×1.5 for 6 mm through M52×2 for 42 mm. 2D9 uses the S series thread, one size larger for the same tube (M14×1.5 for 6 mm through M52×2 for 38 mm) with a heavier wall and a higher pressure rating.

Connection 2 — Swivel Nut with Internal 24° Cone Seat

The tube leg is closed by a captive nut with an internal 24° cone seat. When the nut is tightened, the seat is drawn onto the matching external 24° cone of the tube end and the seal is made metal-to-metal. The nut is intended to be turned onto the tube end while the body is held, which keeps the port joint undisturbed.

This cone system is not interchangeable with the other two in common use: the 60° cone (BSP, DIN 3861 / ISO 1179) and the 37° flare (JIC, ISO 8434-2) have different included angles, contact diameters and thread forms. A joint assembled across systems may hold at low pressure and then weep at temperature.

Dimensional Data

In the drawing, E, F are the thread designations of the two connections, D1, D2 the tube outside diameters, l1 the stud length to the leg centreline, L1 the length of the stud leg, L2 the height of the nut leg, and S1, S2, S3 the across-flats hexes of the body, the stud end and the swivel nut respectively.

L1 and L2 lie on perpendicular axes. For a swivel-nut elbow the two directions are dimensionally different and cannot be swapped by rotating the fitting: the nut leg length determines how far the tube end projects, and the stud leg length determines the manifold stack height. Confirm the L and H directions of your installation drawing against the catalogue dimensions before ordering.

Full Dimension Table (Part Number Matrix)

Values as published in the HENGHUA catalogue drawing. Dimensions in millimetres.

Thread Size and Dash Chart

As with the whole DIN 2353 system, the heavy (S) series uses one thread size larger than the light (L) series for the same tube OD. The swivel nut thread follows the same size rule.

Material and Heat Treatment

Bodies and swivel nuts are carbon steel, forged or machined from bar, hardened according to pressure class and finished in trivalent chromium or zinc-nickel, with the nut plated in the same batch as its body so that the two do not gall or show a colour mismatch. Stainless 304 / 316L is available to order. The swivel nut can be specified separately if a different material or a locking feature is required.

Working Pressure and Operating Envelope

The pressure column is the working pressure for the L or S series connection, not a burst pressure; a 4:1 burst ratio is typical of the body. The lower-rated of the two connections governs the assembly, and the tube wall thickness sets a further limit — the swivel nut joint is rated together with the tube end it compresses.

Rango de temperatura

NBR-based seals in associated components: −40 °C to +120 °C. FKM: −20 °C to +200 °C. The 24° cone joint has no elastomer in the sealing path; the limit is normally set by the tube end and by the plating.

How to Read the Part Number Matrix

2C9-12 is family 2C9 (elbow, swivel nut, L series), size 12 = 6 mm tube / M12×1.5 at the stud end. 2D9-14 is the S series equivalent: 6 mm tube, M14×1.5. The suffix follows the series, not the tube in millimetres, so the same tube appears under two different numbers. Quote the tube OD, the thread and the series when cross-referencing an OEM number.

Selection and Ordering

Selection Checklist / Decision Table

Cross Reference Service

Send the OEM number, the two thread sizes, the tube ODs or a photograph of the assembly. We return a mapped part number with both leg dimensions filled in, and confirm which leg carries the swivel nut.

Packaging and Logistics

The swivel nut is supplied fitted to the body and staked so it cannot be lost in transit but still rotates freely on arrival. Standard export packing with thread protectors, cartons and pallets; certificates referenced to the heat number.

Installation and Fitment Guide

Step-by-Step Assembly

1. Verify the port cone is metric 24° (DIN 2353 / ISO 8434-1) and the thread matches the series ordered.
2. Clean the stud cone and the port seat. Remove swarf, paint and old sealant.
3. Lubricate the stud thread lightly. Never apply sealant to the 24° cone.
4. Screw the stud into the port by hand, then tighten to the stud torque while holding the body hex (S1).
5. Present the tube end to the swivel nut. The nut is free to rotate; hold the body and turn the nut by hand until it is snug.
6. Tighten the swivel nut to its own torque with a second wrench, holding the body so the port joint is not disturbed.
7. Pressurise, check the port joint and the nut joint separately, and re-check after the first thermal cycle.

Torque and Sealing Notes

The stud end and the swivel nut are two separate joints with two separate torque values. Both are metal-to-metal 24° cone joints and neither uses sealant or tape. Under-torque leaves the cone short of full contact; over-torque deforms the cone and the port, and a deformed cone can never be recovered by tightening further. Always use two wrenches — one on the body, one on the nut or the tube end.

Installation Warnings

• Do not use the swivel nut to pull the stud into the port; they are independent joints.
• Do not mix 24°, 60° and 37° cone components.
• Do not use thread sealant anywhere on this fitting.
• Do not reuse a cone that has been over-torqued, galled or dented.
• Do not rotate the body after the stud joint has been torqued; use the swivel nut to align the tube instead.

Applications and Industries

Swivel-nut elbows are used on mobile equipment, machine tools, hydraulic power units, presses, injection-moulding machines, shipboard hydraulics and test rigs — anywhere a tube run is pre-bent and cannot be rotated, or where the port and the tube differ in size. The 90 degree elbow reducer tube adaptor with swivel nut is the fitting that lets the tube side be positioned independently of the port side.

OEM Customization and Quality Traceability

Reducer combinations (mixed port and tube sizes), special leg lengths, special nuts, locking nuts, alternative hex, stainless bodies and customer plating are produced to drawing. Incoming material verification, first-article inspection, nut-freedom checks after stud torque, thread and cone gauging, proof pressure testing on sample lots and final inspection are recorded against the order, with EN 10204 3.1 certificates on request.

FAQ

What does the swivel nut actually do? It lets the tube connection be made and aligned while the port joint stays tight — the two joints are independent.

Is the swivel nut captive? Yes. It is supplied on the body and cannot be lost, but it rotates freely so the tube end can be presented at any angle.

Does the swivel-nut joint need sealant? No. Sealing is by the internal 24° cone seat against the tube end cone.

Can I use it as a reducer? Yes — the reducer version steps between a larger port thread and a smaller tube end, or the reverse. Specify both ends when ordering.

2C9 or 2D9? Same geometry, different series: L (light) for 2C9, S (heavy) for 2D9.

Can I replace just the nut? Yes. The swivel nut is a separate component and can be supplied on its own.

Solicitar un presupuesto

Send the part number, both thread sizes, the tube ODs, the material, the quantity and the working pressure. We will confirm the series, the swivel-nut configuration and the leg dimensions, and quote with the inspection documentation included.

Related products in this range: reducer tube adaptor with swivel nut 2C/2D (straight) · 90° elbow fittings adapter 1C9/1D9 · 90° elbow bulkhead fittings adapter 6C9/6D9 · branch tee fittings with swivel nut BC/BD · equal tees AC/AD.

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