This model is discontinued
AirTAC has phased out the SI series. You can still order this code here: we ship the direct replacement SAI40BX250S, with the same bore, stroke, output force, port and mounting, so it fits the same application. The SAI replacement keeps the same ISO 15552 mounting interface, bore, stroke, output force and accessories, so it drops straight into existing fixtures. It is the current-production version of this cylinder with an upgraded piston seal.
Airtac SI40 Standard Cylinder SI40BX250S
The AirTAC Airtac SI40 Standard Cylinder SI40BX250S is a double-acting ISO 15552 (orig. ISO 6431) profile-barrel cylinder with a Ø40mm bore and 250mm stroke, G1/4 air ports and adjustable end cushioning. This model is discontinued — the direct replacement is the SAI40BX250S, which matches its ISO interface, bore, stroke, force and mounting.
- BoreØ40 mm
- Stroke250 mm
- Port sizeG1/4
- Acting typeDouble acting
- Rod threadM12×1.25
- StatusDiscontinued → SAI40BX250S
- 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 SI40 Standard Cylinder SI40BX250S
The AirTAC SI40BX250S is a discontinued double-acting ISO 15552 profile cylinder featuring a SUS304 stainless piston rod, a 40mm bore, and a 250mm stroke. Delivering 628 N push force at 0.5 MPa, it is directly replaced by the SAI40BX250S. This direct upgrade shares the same ISO 15552 mounting interface, G1/4 port, and M12x1.25 rod thread, fitting existing fixtures perfectly.
The SAI successor introduces an upgraded piston seal with two Y-shaped one-way elements for lower start-up pressure and longer life. The -S magnet supports legacy CS1-B/DS1-B sensors, while the SAI family adds SAIL, SAIF, and BSAI lock variants the SI lacked.
Airtac SI40 Standard Cylinder SI40BX250S Technical Specifications
| Model | Airtac SI40 Standard Cylinder SI40BX250S |
|---|---|
| Series | SI ISO 15552 profile cylinder (discontinued) |
| Replacement | SAI40BX250S |
| Bore size | Ø40 mm |
| Stroke | 250 mm |
| Acting type | Double acting |
| Port size | G1/4 |
| Rod thread | M12×1.25 |
| Fluid | Air (filtered by 40µm element) |
|---|---|
| Operating pressure | 0.15 – 1.0 MPa |
| Proof pressure | 1.5 MPa |
| Temperature | -20 to +70 °C |
| Speed range | 30 – 800 mm/s |
| Cushion | Adjustable, 27 mm |
| Max standard stroke | Up to 1200 mm |
Specifications follow the official AirTAC SI datasheet (now discontinued). The SAI40BX250S carries the same ISO 15552 ratings. Confirm against the product label before installation. Thread options: PT / G / NPT.
Theoretical Output Force (Ø40mm)
| Pressure | Push force | Pull force |
|---|---|---|
| 0.5 MPa | 628 N | 528 N |
| 0.7 MPa | 880 N | — |
| Max (@1.0 MPa) | 128 kgf | |
The SAI40BX250S produces the same force from the same bore. Actual usable force is lower than theoretical; size with a margin.
Model Code: Airtac SI40 Standard Cylinder SI40BX250S
| SI | ISO 15552 profile-barrel cylinder (discontinued). |
|---|---|
| 40 | Bore size in mm. |
| ×250 | Stroke length in mm. |
| -S | Optional built-in magnet for sensor position sensing. |
Legacy SI-family variants: SID (double rod), SIJ (adjustable stroke) — each maps to its SAI equivalent (SID→SAID, SIJ→SAIJ). Rod material: carbon steel (blank) / SUS420J2 (A) / SUS304 (B).
Where the Airtac SI40 Standard Cylinder SI40BX250S Is Used
Stainless Rod Diverters
Ideal for packaging lines where the SUS304 rod resists washdown moisture while diverting light loads with 628 N push force.
Compact Assembly Presses
Provides precise 528 N pull force for seating small components in automated cells using standard ISO 15552 foot mounts.
Replacing the Airtac SI40 Standard Cylinder SI40BX250S with the SAI40BX250S
To replace the SI40BX250S, order the SAI40BX250S keeping the exact 40mm bore, 250mm stroke, G1/4 port, and ISO 15552 mounting. Retain the -B SUS304 rod and -S magnet, noting the SAI uses current AirTAC switches instead of legacy CS1-B/DS1-B. For sizing alternatives, a 32mm bore offers 402 N push, while a 50mm bore provides 982 N at 0.5 MPa. Because stroke is 250mm, ensure guide alignment to prevent rod bending under side loads. For load holding on air loss, note the cushion only decelerates; use an external pilot check valve or SAIL lock variant.
Replacement checklist
- ✓ Same ISO 15552 interface → SAI40BX250S
- ✓ Same bore / stroke / force
- ✓ Port/thread type (PT/G/NPT)
- ✓ Magnet (-S) for sensors?
- ✓ Mounting reused (FA/FB/CA/CB/CR/LB/TC)
Airtac SI40 Standard Cylinder SI40BX250S FAQ
Yes, the SI40BX250S is discontinued. The direct replacement is the SAI40BX250S. It shares the same ISO 15552 mounting interface, 40mm bore, 250mm stroke, output force, and G1/4 port, fitting existing fixtures seamlessly.
The G1/4 port bore delivers 628 N push and 528 N pull at 0.5 MPa, 879 N push at 0.7 MPa, 1130 N at 0.9 MPa, and a theoretical max of 128 kgf at 1.0 MPa. It operates at 30-800 mm/s with a 27mm adjustable air cushion.
Related AirTAC SAI Cylinders
Request a Quote for the SAI40BX250S
Send us the quantity and destination. We confirm price, stock and lead time on the SAI40BX250S replacement — usually within 7-8 hours.