Airtac SAILB Rear Lock Cylinder SAILB125X300S
The AirTAC Airtac SAILB Rear Lock Cylinder SAILB125X300S 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 SAILB125X300S
The AirTAC SAILB125X300-S is a double-acting ISO 15552 profile cylinder featuring a spring-applied, air-released mechanical lock housed in the back cover. This lock engages automatically to hold the rod securely at the retracted stroke end whenever release air is cut, dropping the load safely without relying on live pressure. In the 125mm bore class, it delivers 6136N of push and 5734N of pull at 0.5MPa, making it suited for heavy vertical lifting tasks.
This model includes a magnet for position sensing with AirTAC CMSE reed and DMSE electronic switches. The variable air cushion at the locker end measures 24mm, intentionally shorter than the 40mm cushion at the free end to accommodate the locking mechanism. Standard carbon steel rod material provides durable service for industrial actuation.
Airtac SAILB Rear Lock Cylinder SAILB125X300S Technical Specifications
| Model | Airtac SAILB Rear Lock Cylinder SAILB125X300S |
|---|---|
| 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 SAILB125X300S Is Used
Vertical Lift Safety
Holds heavy lifted loads securely in the retracted position during a sudden air pressure loss or emergency stop.
Heavy Material Stop
Acts as a robust end-of-stroke stop for large conveyor diverter arms, locking the mechanism rigidly during transit.
Gate and Door Hold
Secures heavy industrial loading bay gates in the closed position without continuously consuming compressed air.
Is the Airtac SAILB Rear Lock Cylinder SAILB125X300S the Right Lock Cylinder?
Select this 125mm bore cylinder when a 100mm bore (providing 3681N pull at 0.5MPa) lacks the force to hold your load, but a 160mm bore is physically too large. Choose the SAILB configuration specifically when the load must be secured in the retracted position; if your application requires holding the rod while extended, select the SAILF variant instead. Because this unit features a 300mm stroke, external guide rails should be used to prevent excessive side-loading on the rod.
The SAIL lock is a static holding device that engages only after the piston stops at the stroke terminal, not a dynamic brake for a moving rod. It cannot clamp at an arbitrary mid-stroke point; for intermediate positioning, the BSAI clamp-lock cylinder is required. Avoid using fast-exhaust valves with this cylinder, as back-pressure on the locker side can inadvertently release the lock; use an independent-exhaust solenoid valve instead. If human safety depends on the load remaining suspended, always add an independent mechanical safety measure.
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 SAILB125X300S FAQ
At 0.5MPa operating pressure, this 125mm bore cylinder provides 6136N of push force and 5734N of pull force. At 0.7MPa, the push force increases to 8590N.
The lock is spring-applied and air-released, located in the back cover to hold the rod only at the fully retracted stroke end. It engages statically after the cylinder stops and is released by supplying air to the release port or by using the manual release lever.
Related AirTAC Lock & Standard Cylinders
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