Airtac SAILB Rear Lock Cylinder SAILB125X250
The AirTAC Airtac SAILB Rear Lock Cylinder SAILB125X250 is a genuine double-acting ISO 15552 profile cylinder with a Ø125mm bore, 250mm stroke and a built-in spring-applied, air-released mechanical lock in the back cover — it holds the load at the retracted (rod-in) stroke end even when air is lost.
- BoreØ125 mm
- Stroke250 mm
- Port sizeG1/2
- Lock positionBack cover
- Rod threadM27×2
- UnlockAir + manual
About the Airtac SAILB Rear Lock Cylinder SAILB125X250
The AirTAC SAILB125X250 is a double-acting ISO 15552 profile cylinder featuring a spring-applied, air-released mechanical lock housed in the back cover. Because the lock engages when the piston reaches the retracted stroke end, it secures your load safely in the rod-in position without requiring continuous live air pressure. Delivering 6136N of push force and 5734N of pull force at 0.5 MPa, this 125mm bore unit is built for heavy-duty holding.
Unlike a standard SAI cylinder, this SAIL model uses a static locking pin that engages after the rod stops, rather than clamping at an arbitrary mid-stroke point. The variable air cushion at the locker end is 24mm, intentionally shorter than the 40mm cushion at the free end to accommodate the locking mechanism. The lock releases automatically via air supply or manually via a lever, and the barrel features dual sensor grooves compatible with CMSE reed and DMSE electronic switches if a magnet is added.
Airtac SAILB Rear Lock Cylinder SAILB125X250 Technical Specifications
| Model | Airtac SAILB Rear Lock Cylinder SAILB125X250 |
|---|---|
| Series | SAIL ISO 15552 cylinder with lock |
| Bore size | Ø125 mm |
| Stroke | 250 mm |
| Acting type | Double acting, with lock |
| Port size | G1/2 |
| Rod thread | M27×2 |
| Lock type | Spring-applied, air-released (back cover) |
|---|---|
| Unlock | Automatic (air) & manual |
| Operating pressure | 0.15 – 1.0 MPa |
| Temperature | -20 to +70 °C |
| Speed range | 30 – 500 mm/s |
| Cushion | Adjustable (40 mm free end / 24 mm lock end) |
| Max stroke | Up to 1500 mm |
Specifications follow the official AirTAC SAIL datasheet (ISO 15552). Confirm against the product label before installation. Port options: PT / G.
How the Lock Holds
The lock is spring-applied and air-released: a spring drives a lock pin into the rod when the release air is removed, so the load is held at the retracted (rod-in) stroke end without live pressure. Supply air to the release port to unlock automatically, or use the manual release lever.
The lock engages only when the piston reaches the stroke terminal on the back-cover side — it is a static end-of-stroke hold, not a mid-stroke clamp and not a moving-rod brake. For locking at any position along the stroke, choose a BSAI clamp-lock instead.
Theoretical Output Force (Ø125mm)
| Pressure | Push force | Pull force |
|---|---|---|
| 0.5 MPa | 6136 N | 5734 N |
| 0.7 MPa | 8590 N | — |
| Max (@1.0 MPa) | 1251 kgf | |
Cylinder thrust is separate from the lock's holding capability. Actual usable force is lower than theoretical due to friction and back-pressure — size with a margin.
Where the Airtac SAILB Rear Lock Cylinder SAILB125X250 Is Used
Vertical Load Holding
Secures heavy lifting platforms in the retracted position on power loss, preventing gravity-driven drops without needing continuous air pressure.
Machine Safety Guard
Holds a safety guard firmly in the closed, rod-in position during operation, ensuring the barrier remains locked until air is actively supplied to release.
Clamp and Hold
Maintains a heavy workpiece clamp at its retracted stroke end after the machine stops, providing a stable static hold during loading or unloading.
Is the Airtac SAILB Rear Lock Cylinder SAILB125X250 the Right Lock Cylinder?
Choose this 125mm bore cylinder when an application requires 6136N of push force at 0.5 MPa, stepping up from the 80mm bore which provides 2513N. If your load demands less force, the 100mm bore offers 3927N. Select the SAILB configuration specifically because the load must be held at the retracted stroke end; choose SAILF instead if the extended position needs holding, or select a BSAI clamp-lock cylinder if you must lock the rod at a mid-stroke position.
For safe operation, never use a fast-exhaust valve with this lock cylinder, as back-pressure on the locker side can accidentally release the pin; always use an independent-exhaust solenoid valve. If human safety depends on the load staying retracted, add an independent safety measure. The 250mm stroke operates within the 30-500mm/s speed range, and replacement matches require a 125mm bore, 250mm stroke, back locker position, PT port threads, and standard carbon steel rod.
Quick checklist
- ✓ Hold needed at the retracted (rod-in) end?
- ✓ Or lock anywhere → use BSAI
- ✓ Independent-exhaust valve fitted
- ✓ Port/thread type (PT/G)
- ✓ Extra safety measure for people
Airtac SAILB Rear Lock Cylinder SAILB125X250 FAQ
At 0.5 MPa operating pressure, the 125mm bore provides 6136N of push force and 5734N of pull force. At the maximum 1.0 MPa pressure, it delivers 1251 kgf.
The lock is spring-applied and air-released, engaging only at the retracted stroke end to hold the load statically without live pressure. It unlocks automatically via air supply or manually via a lever, but it is not a dynamic brake for a moving rod.
Related AirTAC Lock & Standard Cylinders
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