Airtac SAILB Rear Lock Cylinder SAILB125X300
The AirTAC Airtac SAILB Rear Lock Cylinder SAILB125X300 is a genuine double-acting ISO 15552 profile cylinder with a Ø125mm bore, 300mm 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
- Stroke300 mm
- Port sizeG1/2
- Lock positionBack cover
- Rod threadM27×2
- UnlockAir + manual
About the Airtac SAILB Rear Lock Cylinder SAILB125X300
The AirTAC SAILB125X300 is a double-acting ISO 15552 profile cylinder featuring a spring-applied, air-released mechanical lock housed in the back cover. It securely holds the rod at the retracted stroke end, making it ideal for safely suspending heavy vertical loads during a power loss. In the 125mm bore class, it generates 6136N of pull force at 0.5MPa, supported by a robust 32mm carbon steel rod.
Because the lock occupies the rear endcap, the variable air cushion on that locker end is engineered shorter at 24mm compared to the 40mm cushion on the free end. The lock engages statically only after the piston stops at the stroke terminal; it is not a dynamic brake for a moving rod. To release the load, supply air to the release port for automatic operation or use the manual release lever.
Airtac SAILB Rear Lock Cylinder SAILB125X300 Technical Specifications
| Model | Airtac SAILB Rear Lock Cylinder SAILB125X300 |
|---|---|
| Series | SAIL ISO 15552 cylinder with lock |
| Bore size | Ø125 mm |
| Stroke | 300 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 SAILB125X300 Is Used
Vertical Lift Safety
Secures elevated heavy platens in the retracted position automatically when air pressure drops, preventing uncontrolled drops.
Heavy Conveyor Hold
Locks a retracted diverter or gate in place during a pneumatic power failure to maintain material flow control.
Clamp and Secure
Holds a heavy workpiece at the stroke end without consuming continuous live air, ensuring stable positioning during machine pauses.
Is the Airtac SAILB Rear Lock Cylinder SAILB125X300 the Right Lock Cylinder?
Select this 125mm bore when a 100mm cylinder (providing 3681N pull at 0.5MPa) lacks the lifting capacity, but before stepping up to a 160mm bore (9425N pull). Choose the SAILB configuration specifically when the load must be secured in the retracted position; if you need the rod held extended, select the SAILF variant instead. For applications requiring the load to be clamped at an arbitrary mid-stroke point rather than the stroke end, the BSAI clamp-lock cylinder is the correct choice.
The lock is a static holding device and does not stop a moving rod. Avoid using fast-exhaust valves with this cylinder; back-pressure on the locker side can inadvertently release the lock, so an independent-exhaust solenoid valve is required. If human safety depends on the load remaining suspended, always add an independent mechanical safety measure. At a 300mm stroke, the extended leverage increases side-load risks; ensure external guide rails are used to prevent rod binding. Replacement specifications: 125mm bore, 300mm stroke, back locker, PT 1/2 port, no magnet, and standard mounting options including FA, FB, CA, CB, LB, and TC.
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 SAILB125X300 FAQ
At 0.5MPa, the 125mm bore provides 6136N of pull force and 8590N of push force. At 0.7MPa, the push force is 8590N and pull is 5734N. The maximum operating pressure is 1.0MPa.
The lock is spring-applied and air-released, engaging statically only when the piston reaches the retracted stroke end in the back cover. It does not clamp at mid-stroke. It unlocks automatically via air supply to the release port or manually via a lever, and requires an independent-exhaust solenoid valve to prevent back-pressure from releasing the lock.
Related AirTAC Lock & Standard Cylinders
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