Aluminum Pipe Union – Threaded, Custom Sizes

GNEE manufactures aluminum pipe unions for detachable connections in industrial piping. A three-piece union allows a pipe section to be disconnected for maintenance without rotating, cutting or dismantling the entire pipe run.

 

We supply aluminum unions in 6061, 6063, 6082, 5083 and 5086, with NPT, BSPT, BSPP and metric thread options. Standard sizes are available from ½″ to 4″, with custom sizes up to 8″ available on request.

 

Before ordering, confirm four key points: nominal pipe size, thread standard and configuration, working pressure and temperature, and sealing method. GNEE can manufacture standard or custom aluminum unions according to drawings, samples and application requirements.

 

 

Specifications of Aluminum unions

Item	Specification
Product	Aluminum pipe union
Alloys	6061, 6063, 6082, 5083, 5086
Tempers	6xxx: T6 / T5 / T4 / O · 5xxx: H112 / H116 / H32 / H321 / O (5xxx is not heat treatable)
Nominal size	¼″ to 8″; common stock sizes ½″ to 4″; custom outside that range
Threads	NPT, BSPT, BSPP, Metric (parallel)
Thread configuration	Female × Female, Male × Female, Male × Male, or custom
Connection	Threaded, socket weld, or custom
Construction	3-piece: two ends + union nut
Surface finish	Mill finish (standard); anodized, polished, sandblasted, powder coated on request
Sealing	Metal-to-metal seat, gasket, O-ring, or per drawing
Inspection	Dimensional, thread gauge, PMI, visual; pressure / leak test on request

 

aluminum pipe unions Sizes

NPS	DN	Threads	Availability
⅛″	DN6	NPT / BSP / Metric	Custom
¼″	DN8	NPT / BSP / Metric	Custom
⅜″	DN10	NPT / BSP / Metric	Custom
½″	DN15	NPT / BSP / Metric	Stock
¾″	DN20	NPT / BSP	Stock
1″	DN25	NPT / BSP	Stock
1¼″	DN32	NPT / BSP	Stock
1½″	DN40	NPT / BSP	Stock
2″	DN50	NPT / BSP	Stock
2½″	DN65	NPT / BSP	Stock
3″	DN80	NPT / BSP	Stock
4″	DN100	NPT / BSP	Stock
6″	DN150	NPT / BSP	Custom
8″	DN200	NPT / BSP	Custom

The inch size is the nominal pipe size (NPS), not the outside diameter of the union body. Body OD, length, nut size and thread length depend on the design. For a replacement union, send a drawing or the old fitting and we match it.

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aluminum unions Alloys

Alloy	What it's good for	Common tempers
6061	All-round choice for machined unions; good strength, easy to machine	T6, T4, O
6063	Extruded designs, smooth surface finish	T5, T6, O
6082	Higher strength for industrial use	T6, T5, O
5083	Corrosion resistance, good for marine	H112, H116, H321, O
5086	Corrosion resistance and weldability	H112, H116, H32, O

5xxx alloys (5083, 5086) are not heat treatable, so T-tempers do not apply. 6063 is mainly an extrusion alloy. Most aluminum unions are machined from 6061 or 6082 bar or forging stock. If you are not sure, tell us the application and we recommend the alloy.

 

aluminum unions Threads

Thread	Standard	Notes
NPT	ASME B1.20.1	Tapered, common in North America
BSPT	ISO 7-1	Tapered BSP, common internationally
BSPP	ISO 228-1	Parallel BSP, seals with a washer or O-ring
Metric	ISO 965	Specify diameter and pitch, e.g. M25 × 1.5

NPT and BSP are different thread systems. They are not interchangeable even when the size numbers look the same. Check the thread on the pipe or equipment you are connecting before ordering.

 

 

Applications of aluminum pipe union

These are the everyday jobs we supply aluminum unions for:

• Compressed air and pneumatic lines – disconnect points around compressors, filters, regulators and dryers
• Water and general utility piping
• Machine and equipment hookups – pumps, valves, filters, pressure gauges and instruments that need regular service
• Maintenance points in industrial lines – anywhere a pipe section has to come off for cleaning or repair
• Marine systems with 5083 / 5086 – hull and deck piping (confirm the alloy suits your water and installation conditions)

If your line carries strong chemicals or hot media, tell us the medium and temperature first. We do not recommend aluminum where the alloy, pressure or medium has not been checked.

 

Sealing

How the union seals depends on the design:

Metal-to-metal seat – machined faces pressed together by the nut

Gasket

O-ring – usually with parallel threads such as BSPP

Custom arrangement per drawing

Confirm the sealing method, seal material and working pressure before production. For pressure service we can arrange a pressure or leak test.

 

Pressure and Temperature of aluminum pipe union

There is no single pressure rating for "an aluminum union". The safe rating depends on size, wall thickness, alloy and temper, thread type, sealing design and temperature. Aluminum also loses strength at high temperature, so a rating is only valid for the design and service conditions we agree on.

To quote accurately, send us:

Nominal size and thread – e.g. 1″ NPT Female × Female

Alloy and temper – e.g. 6061-T6

Working pressure and test pressure

Operating temperature and service medium

Quantity

Drawing, CAD file or sample, if you have one

We confirm the working pressure and testing requirements for your specific design before production. We do not apply one blanket rating to every union.

 

Quality Inspection

Material – mill certificate and PMI check on request

Dimensions – checked against the approved drawing

Threads – checked with the correct gauge for NPT, BSPT, BSPP or metric

Sealing faces – machined and inspected

Visual – no burrs, scratches or damage

Assembly – components and nut fit properly

Pressure / leak test – on request, per your specification

 

Standards

Aluminum unions are not covered by one "union standard" the way steel or iron fittings are. For aluminum, the relevant standard is ASME B16.52 – forged nonferrous fittings with threaded and socket-weld ends. ASTM B247 (forgings), ASTM B221 (extruded bar) and ASTM B209 (plate) cover the material forms.

What this means for you: we build your union to your drawing and to the material and inspection requirements of your project. We review the standard you want and tell you honestly whether it applies before production. We do not claim standard compliance just because the material is aluminum.

 

Custom Unions (OEM)

Send us a drawing, sample or CAD file and we make:

Non-standard sizes

Any of the four thread systems

Male / female combinations

Custom body dimensions and port layouts

Bulkhead designs (through a panel or tank wall)

Special sealing and surface finishes

Special inspection and documentation

Custom work is normal for us. If a standard union does not fit your system, we build one that does.

 

Send us a drawing

Other Aluminum Fittings

We also make aluminum elbows, tees, crosses, couplings, caps, reducers, bushings and flanges. Order the whole fitting list for one project from one supplier.

Trade Terms

Lead time	Stock sizes 7–15 days; custom sizes 20–35 days (per drawing)
Payment	T/T or L/C at sight
Incoterms	FOB, CIF, DDP – tell us your port and we quote delivered price

 

Packaging

Small unions: individually protected, packed in cartons

Bulk orders: wooden pallets; wooden cases or reinforced pallets for export

Threads, sealing faces and machined surfaces are protected against impact and dirt in transit

 

 

FAQ

 

What is an aluminum pipe union?

A union is a pipe fitting that connects two pipe ends and can be opened later. Loosen the nut and the two sides separate, so you can pull out a pump, filter or valve without cutting or rotating the whole pipe line.

Union vs coupling – what's the difference?

A coupling is a simple connector; to take it apart you usually have to unthread the pipe. A union is a 3-piece fitting with a nut, so it opens and closes in seconds. Pick a union anywhere a section may need regular removal.

What threads can you make?

NPT, BSPT, BSPP and metric. NPT and BSP are different systems – tell us the thread on your pipe or equipment.

What alloys do you use?

6061, 6063, 6082, 5083 and 5086. 6061 is the common choice for machined unions; 5083 / 5086 for marine service.

How much pressure can an aluminum union take?

It depends on the design – size, wall thickness, alloy, thread and sealing. Send us your working pressure and we confirm a design for it.

Can you make custom aluminum unions?

Yes. Custom sizes, threads, body dimensions, bulkhead designs, sealing and finishes, from your drawing, CAD file or sample.

Can I order other aluminum fittings with my unions?

Yes – elbows, tees, couplings, caps, reducers, flanges and more, all in one order.

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