This model is discontinued
AirTAC has phased out the SI series. You can still order this code here: we ship the direct replacement SAI50X18S, 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 SI50 Standard Cylinder SI50X18S
The AirTAC Airtac SI50 Standard Cylinder SI50X18S is a double-acting ISO 15552 (orig. ISO 6431) profile-barrel cylinder with a Ø50mm bore and 18mm stroke, G1/4 air ports and adjustable end cushioning. This model is discontinued — the direct replacement is the SAI50X18S, which matches its ISO interface, bore, stroke, force and mounting.
- BoreØ50 mm
- Stroke18 mm
- Port sizeG1/4
- Acting typeDouble acting
- Rod threadM16×1.5
- StatusDiscontinued → SAI50X18S
- 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 SI50 Standard Cylinder SI50X18S
The AirTAC SI50X18S is a discontinued double-acting ISO 15552 profile cylinder with an 18 mm stroke and a 50 mm bore, delivering 982 N push force at 0.5 MPa. It features a G1/4 port, an M16x1.5 rod thread, and 30 mm adjustable air cushions at both ends. AirTAC replaced this legacy unit with the SAI50X18S, a direct upgrade retaining the exact ISO 15552 mounting interface, bore, stroke, and port size.
The SAI replacement introduces an upgraded piston seal with two Y-shaped one-way elements for lower start-up pressure and extended life. If you need load holding on air loss, note that a plain cylinder drifts and the cushion only decelerates; use an external rod lock, pilot check valve, or the SAIL/BSAI lock variants. This -S model includes a piston magnet for CS1-B/DS1-B switches.
Airtac SI50 Standard Cylinder SI50X18S Technical Specifications
| Model | Airtac SI50 Standard Cylinder SI50X18S |
|---|---|
| Series | SI ISO 15552 profile cylinder (discontinued) |
| Replacement | SAI50X18S |
| Bore size | Ø50 mm |
| Stroke | 18 mm |
| Acting type | Double acting |
| Port size | G1/4 |
| Rod thread | M16×1.5 |
| 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, 30 mm |
| Max standard stroke | Up to 1200 mm |
Specifications follow the official AirTAC SI datasheet (now discontinued). The SAI50X18S carries the same ISO 15552 ratings. Confirm against the product label before installation. Thread options: PT / G / NPT.
Theoretical Output Force (Ø50mm)
| Pressure | Push force | Pull force |
|---|---|---|
| 0.5 MPa | 982 N | 825 N |
| 0.7 MPa | 1374 N | — |
| Max (@1.0 MPa) | 200 kgf | |
The SAI50X18S produces the same force from the same bore. Actual usable force is lower than theoretical; size with a margin.
Model Code: Airtac SI50 Standard Cylinder SI50X18S
| SI | ISO 15552 profile-barrel cylinder (discontinued). |
|---|---|
| 50 | Bore size in mm. |
| ×18 | 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 SI50 Standard Cylinder SI50X18S Is Used
Short-Stroke Clamping
Ideal for holding parts during machining, utilizing the 982 N push force at 0.5 MPa to secure workpieces firmly within a compact 18 mm travel distance.
Package Diverting
Provides rapid actuation for sorting or diverting light packages on a conveyor line, operating efficiently at speeds between 30 and 800 mm/s.
Ejector Mechanisms
Delivers a fast, compact ejection stroke for small parts in automated assembly, taking advantage of the precise 18 mm stroke and G1/4 air port.
Replacing the Airtac SI50 Standard Cylinder SI50X18S with the SAI50X18S
To replace the SI50X18S, order the SAI50X18S and verify your ISO 15552 mounting fixture, 50 mm bore, 18 mm stroke, G1/4 port (PT/G/NPT), and magnet requirement. The SAI family also adds SAIF (built-in 4M valve) and SAIL/BSAI lock variants the SI lacked. When sizing, a 50 mm bore yields 982 N push at 0.5 MPa; if you need less force, a 40 mm bore provides 628 N, while an 80 mm bore offers 2513 N. For any application needing secure load holding without live air, remember the cushion only decelerates and cannot prevent drift—select a SAIL or BSAI lock cylinder, or add an external pilot check valve. The 18 mm stroke is very short, so side-load and rod-bending risks are minimal, but always verify guide alignment.
Replacement checklist
- ✓ Same ISO 15552 interface → SAI50X18S
- ✓ Same bore / stroke / force
- ✓ Port/thread type (PT/G/NPT)
- ✓ Magnet (-S) for sensors?
- ✓ Mounting reused (FA/FB/CA/CB/CR/LB/TC)
Airtac SI50 Standard Cylinder SI50X18S FAQ
Yes, the AirTAC SI50X18S is discontinued. The direct replacement is the SAI50X18S. It features the same ISO 15552 mounting interface, 50 mm bore, 18 mm stroke, output force, and G1/4 port, fitting directly into existing fixtures.
The 50 mm bore features a G1/4 air port. The force ratings are: 982 N push and 825 N pull at 0.5 MPa, 1374 N push at 0.7 MPa, 1767 N push at 0.9 MPa, and a theoretical maximum of 200 kgf at 1.0 MPa.
Request a Quote for the SAI50X18S
Send us the quantity and destination. We confirm price, stock and lead time on the SAI50X18S replacement — usually within 7-8 hours.