Airtac SAILB Rear Lock Cylinder SAILB125X250S
The AirTAC Airtac SAILB Rear Lock Cylinder SAILB125X250S 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 SAILB125X250S
The AirTAC SAILB125X250-S is a double-acting ISO 15552 profile cylinder featuring a built-in mechanical lock in the back cover. Because the lock is spring-applied and air-released, cutting the release air automatically drives a lock pin into the rod, securely holding the load at the retracted stroke end without requiring live pressure. In the 125mm bore class, this actuator delivers a robust 6136N of push force and 5734N of pull force at 0.5 MPa, making it well-suited for heavy vertical lifting tasks.
Equipped with a magnet for position sensing, this model works seamlessly with AirTAC CMSE reed and DMSE solid-state switches fitted into the dual-side sensor grooves. To accommodate the locking hardware, the variable air cushion at the locker end is notably shorter at 24mm compared to the 40mm cushion on the free end. Furthermore, unlocking is achieved either automatically by supplying air to the release port or manually via a lever, ensuring operational flexibility during maintenance.
Airtac SAILB Rear Lock Cylinder SAILB125X250S Technical Specifications
| Model | Airtac SAILB Rear Lock Cylinder SAILB125X250S |
|---|---|
| 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 SAILB125X250S Is Used
Vertical Lift Safety
Secures heavy elevated loads in the retracted position on power loss, preventing sudden drops in lifting machinery.
Power-Outage Hold
Maintains a static clamp on the rod end during air pressure failure, keeping gates and heavy doors safely locked.
Machine Guarding
Holds safety barriers firmly closed at the stroke end until the release air is deliberately supplied to unlock.
Is the Airtac SAILB Rear Lock Cylinder SAILB125X250S the Right Lock Cylinder?
When evaluating force requirements, stepping down to an 80mm bore yields 2268N of pull at 0.5 MPa, while moving up to a 160mm bore provides a substantial 9425N. Choose this SAILB configuration when the load must be safely held in the retracted rod-in position; for holding at the extended rod-out position, the SAILF variant is required. If your application demands clamping at an arbitrary mid-stroke point rather than the stroke end, the BSAI clamp-lock cylinder is the correct alternative.
Remember that this is a static holding lock that engages only after the cylinder stops, not a dynamic brake for a moving rod. Valve selection is critical: avoid fast-exhaust valves and use an independent-exhaust solenoid valve, as back-pressure on the locker side can unintentionally release the lock. For any safety-critical lifting where human safety depends on the load staying up, always add an independent safety measure. To replace this unit, match the 125mm bore, 250mm stroke, back locker position, PT tapered port threads, and the -S magnet option.
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 SAILB125X250S FAQ
At 0.5 MPa, this 125mm bore cylinder provides 6136N of push force and 5734N of pull force. The maximum allowable operating pressure is 1.0 MPa.
The lock is spring-applied and air-released, located in the back cover to hold the rod at the retracted stroke end. It engages statically after the piston stops and can be unlocked automatically via air supply or manually via a lever.
Related AirTAC Lock & Standard Cylinders
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