This model is discontinued
AirTAC has phased out the SI series. You can still order this code here: we ship the direct replacement SAI40X255, 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 SI40X255
The AirTAC Airtac SI40 Standard Cylinder SI40X255 is a double-acting ISO 15552 (orig. ISO 6431) profile-barrel cylinder with a Ø40mm bore and 255mm stroke, G1/4 air ports and adjustable end cushioning. This model is discontinued — the direct replacement is the SAI40X255, which matches its ISO interface, bore, stroke, force and mounting.
- BoreØ40 mm
- Stroke255 mm
- Port sizeG1/4
- Acting typeDouble acting
- Rod threadM12×1.25
- StatusDiscontinued → SAI40X255
- 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 SI40X255
The AirTAC SI40X255 is a discontinued double-acting ISO 15552 profile cylinder with a 40 mm bore and 255 mm stroke. It delivers 628 N push force at 0.5 MPa through a G1/4 port. The direct replacement is the SAI40X255, matching the interface, bore, stroke, force, and mounting. The SAI features an upgraded piston seal with two Y-shaped one-way elements for low start-up pressure and long life. For sensing, note this specific SI40X255 SKU lacks a magnet and cannot accept a switch.
Because this stroke exceeds 300 mm? No, at 255 mm it is compact, but users should still avoid side loads. The SAI family also introduces variants the legacy SI lacked, such as the SAIL air-released lock, the SAIF built-in valve, and the BSAI clamp-lock. Standard seals are NBR, but a Viton H option extends the operating temperature from -20 to +150 C. The original CS1-B/DS1-B sensors only apply to magnet-equipped models.
Airtac SI40 Standard Cylinder SI40X255 Technical Specifications
| Model | Airtac SI40 Standard Cylinder SI40X255 |
|---|---|
| Series | SI ISO 15552 profile cylinder (discontinued) |
| Replacement | SAI40X255 |
| Bore size | Ø40 mm |
| Stroke | 255 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 SAI40X255 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 SAI40X255 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 SI40X255
| SI | ISO 15552 profile-barrel cylinder (discontinued). |
|---|---|
| 40 | Bore size in mm. |
| ×255 | 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 SI40X255 Is Used
Component Clamping
Ideal for securing medium workpieces during machining, utilizing the 628 N push force at 0.5 MPa to hold parts firmly within automated fixtures.
Package Diverting
Drives diverter arms on packaging lines, where the 255 mm stroke provides sufficient travel to redirect boxes between parallel conveyor belts.
Replacing the Airtac SI40 Standard Cylinder SI40X255 with the SAI40X255
To replace the discontinued SI40X255, order the SAI40X255. Verify your ISO 15552 mounting interface (LB foot, FA flange, or TC trunnion), the 40 mm bore, 255 mm stroke, and G1/4 port. This non-magnet SKU cannot support sensing; if position detection is needed, order an SAI40X255S. The 16 mm carbon steel rod handles standard loads, but for corrosive environments consider the SUS304 (B) rod option. Sizing both ways: the 40 mm bore gives 628 N push at 0.5 MPa, while the neighboring 50 mm bore offers 982 N if you need more force. Remember, a plain cylinder does not hold load on air loss—the cushion only decelerates. For secure holding, use an external pilot check valve or switch to the SAIL lock variant.
Replacement checklist
- ✓ Same ISO 15552 interface → SAI40X255
- ✓ 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 SI40X255 FAQ
Yes, the SI40X255 is discontinued. The direct replacement is the SAI40X255. It is dimensionally interchangeable per ISO 15552, retaining the same 40 mm bore, 255 mm stroke, 628 N force, G1/4 port, and mounting accessories.
The 40 mm bore utilizes a G1/4 air port and a 16 mm rod. Theoretical forces are: 628 N push and 528 N pull at 0.5 MPa; 879 N push at 0.7 MPa; 1130 N push at 0.9 MPa; and a maximum force of 128 kgf at 1.0 MPa.
Request a Quote for the SAI40X255
Send us the quantity and destination. We confirm price, stock and lead time on the SAI40X255 replacement — usually within 7-8 hours.