Airtac BU Double Female Thread Straight Connector BU0404-S
SUS304 stainless variant (-S)The AirTAC Airtac BU Double Female Thread Straight Connector BU0404-S is a genuine double female connector rated to 3.0 MPa proof pressure and 0 to +150 °C, for joining threaded pipe runs.
- TypeDouble female connector
- SeriesBU
- Working pressure0 - 1.0 MPa (0 - 10 kgf/cm2)
- Proof pressure3.0 MPa
- Temperature0 to +150 °C
- No minimum order. A single piece can be ordered.
- Ready in 3–5 business days. That is the time we take to process the order and hand it to the carrier. Transit time after that depends on the destination.
About the Airtac BU Double Female Thread Straight Connector BU0404-S
The BU0404-S is a straight double female connector in SUS304 stainless steel: a hex-bodied coupling with a PT 1/2in female thread on each end, used to join two male-threaded ports or pipes in line. It belongs to AirTAC's nickel-plated-and-stainless metal joint family, which is rated well beyond the usual one-touch resin fittings: 3.0 MPa proof pressure and a working temperature span of 0 to +150 C.
Unlike a reducing connector, the BU ladder only exists in equal sizes - 0101, 0202, 0303 and 0404 - so a BU0404-S always marries 1/2in to 1/2in with no change in bore. The -S suffix gives you the part solidly in SUS304, dimensionally identical to the standard version, which is why it is chosen for wash-down lines and anywhere copper-free construction matters. No gasket, seal cartridge or tube is involved: the seal is made by the PT male threads you screw into each female end, so use appropriate thread sealant on both joints.
Airtac BU Double Female Thread Straight Connector BU0404-S Technical Specifications
| Model | Airtac BU Double Female Thread Straight Connector BU0404-S |
|---|---|
| Type | Double female connector |
| Series | BU |
| Connection | Threaded both ends |
| Body material | Stainless steel 304 (-S variant) |
| Working pressure | 0 - 1.0 MPa (0 - 10 kgf/cm2) |
|---|---|
| Negative pressure | -750 mmHg (10 Torr) |
| Proof pressure | 3.0 MPa |
| Temperature | 0 to +150 °C |
| Thread standard | PT (Rc tapered) unless the code says otherwise |
Nickel-plated metal body. AirTAC does not publish a per-part material breakdown for this family. This family is rated to 150 °C, but the TUBE is usually the limit - confirm your tubing's temperature rating before running it hot. Stainless (-S): SUS304 body throughout, for copper-free and corrosive environments. Pressure and temperature ratings are unchanged from the nickel-plated version. AirTAC publishes flow as a characteristic curve rather than a single figure, so no L/min value is listed.
Model Code: Airtac BU Double Female Thread Straight Connector BU0404-S
| BU | Double female connector. |
|---|---|
| 4 / 6 / 8 / 10 / 12 | Tube outside diameter in mm (3.2 mm exists on the mini series). |
| M5 / 01 / 02 / 03 / 04 | Thread: M5x0.8, 1/8", 1/4", 3/8", 1/2" (M3 on the mini series). |
| D | Black. Blank = grey. |
| -S | Stainless-steel body. |
Fitting & Sealing Notes
- check Cut the tube square and clean before pushing it home, or the seal will leak.
- check Push until it stops, then pull back to check the chuck has gripped.
- check To release, press the collet ring fully in and pull the tube out.
- check Threaded parts arrive with sealant on the thread; M5 sizes use a sealing gasket.
- check Match the tube OD exactly - a 6 mm fitting will not hold 1/4" tube.
Where the Airtac BU Double Female Thread Straight Connector BU0404-S Is Used
Food plant wash-down mains
Suspending or extending 1/2in air and water runs beside wash-bay equipment, where the SUS304 body shrugs off daily caustic hose-down that would pit a plated brass adapter.
Copper-free plating line air
Joining 1/2in feeds to rinse and dryer stations in electroplating shops, where the copper-free stainless construction avoids traces of copper reaching the process baths.
Marine and dockside services
Tying 1/2in instrument-air or wash-water spurs on vessels and quay-side machinery, in salt-laden air where a nickel-plated fitting alone would corrode at the threads.
Is the Airtac BU Double Female Thread Straight Connector BU0404-S the Right Part?
BU0404-S is the top of the equal-size female ladder, so there is no larger BU to step up to - if one side needs to be 1/2in and the other smaller, that is a job for the BD male-female range (BD0304 or BD0204) or a BB connector plus a reducing bush. The only neighbour down is BU0303, which drops both ends to 3/8in and suits lighter lines where 1/2in ports are simply over-specified. Step down only when flow demand allows; stepping up from here means moving to a different family.
Choose this over two separate adapters when you want one solid stainless piece joining a 1/2in line permanently - fewer joints, fewer leak paths, and no plating to worry about. If you actually need to blank an unused 1/2in port rather than continue the line, the honest answer is the BZ04 hex plug, not a connector.
Quick checklist
- ✓ Tube outside diameter matches exactly
- ✓ Thread size and standard match the port
- ✓ Working pressure within 0 - 1.0 MPa (0 - 10 kgf/cm2)
- ✓ Temperature within 0 to +150 °C
Airtac BU Double Female Thread Straight Connector BU0404-S FAQ
This is a double female connector with a PT 1/2in female thread on both ends, body in SUS304 stainless steel. Family ratings: working pressure 0-1.0 MPa (0-10 kgf/cm2), negative pressure down to -750 mmHg (10 Torr), proof pressure 3.0 MPa, and a service temperature of 0 to +150 C. The stainless variant carries exactly these same figures as the standard BU0404 - it is not re-rated.
No. The BU range is built equal-size only - the codes run BU0101, BU0202, BU0303 and BU0404, so both female ends are always the same thread. For a 1/2in to 3/8in transition you need a BD or BB connector (for example BD0304 or BB0304) instead. Also remember these are PT-thread fittings; if your pipework is specified in NPT or G, confirm thread compatibility before ordering.
Authorized Export Seller
Genuine AirTAC parts produced by AirTAC factory.
1-Year Warranty
Covers non-human-caused product damage.
Fast Dispatch
Standard parts are processed and dispatched in 3-5 business days.
Fast Reply
Most inquiries answered within 7-8 hours.
Related AirTAC Fittings & Tubing
Request a Quote for Airtac BU Double Female Thread Straight Connector BU0404-S
Send us the quantity and destination. We confirm price, stock and lead time — usually within 7-8 hours.