SY is a PVC control cable with a galvanised steel wire braid between the inner and outer sheaths, finished in a transparent PVC jacket so the braid is visible. The braid gives useful mechanical protection and a degree of electrical screening without the stiffness and weight of steel wire armour. It is widely used on machine tools and production plant where the cable needs more robustness than plain YY but must still be routed by hand.
Key applications
- Control and instrumentation wiring on machine tools
- Production line and conveyor control circuits
- Flexible connections to machinery in damp or wash-down areas
- Runs where the cable is exposed to knocks but not to vehicle traffic
- Interconnection between control panels and field devices
- Replacement for YY where mechanical protection is needed
Features and benefits
- Galvanised steel wire braid resists crushing and impact
- Braid also provides partial electromagnetic screening
- Far more flexible and easier to route than steel wire armoured cable
- Transparent sheath allows visual inspection of the braid
- Wide core-count and size range for mixed control and power duties
Specification notes and limitations
The most common misuse of SY is treating it as armoured cable. The steel braid is not armour to BS 5467 or BS 6724 and must not be relied upon as a circuit protective conductor or earth path — a separate CPC is required, and SY is not a substitute for SWA. It is also not suitable for direct burial or for unprotected outdoor use: the transparent sheath is not UV stable and will degrade in sunlight, and water that reaches the braid will corrode it. Respect the bending radius — typically four times the overall diameter fixed and about twelve and a half times when flexed — and terminate the braid in a gland designed for braided cable so the wires are not left loose and bridging live parts.
