Explosion Proof Trapped Key Control Isolation Switch (SS-ISB-CB-EX)
The SS-ISB-CB-EX Isolator Switch forms the first stage of a Trapped Key Interlocking System and installs externally in hazardous locations where explosive gas or dust may be present. Turning the key rotates the internal cam mechanism, opens the safety contact block, and isolates the control circuit. Once the circuit fully de-energises, the operator can withdraw the key and transfer it to the next device in the Trapped Key sequence.
During normal operation, the isolator key stays trapped inside the SS-ISB-CB-EX to keep the equipment energised. When the key remains trapped, the safety contacts close and supply power. When the operator turns and removes the key, the safety contacts open and remove power. The operator can then insert the key into the next interlock device, such as a Key Exchange Unit or a single-point interlock like a Handle Interlock. The mechanism blocks any attempt to re-energise the equipment until the operator returns and reinserts the isolator key.
The internal contact block (LS-EX) carries full approval for Zones 1, 2, 21, and 22 and complies with IECEx/ATEX requirements. We manufacture the device in the UK using a 316 stainless steel housing and barrel assembly to maximise corrosion resistance, impact strength, and durability in demanding environments. The design also achieves IP69K ingress protection for high-pressure, high-temperature washdown applications.
- Body Material: 316 Grade Stainless Steel
- Ingress Protection: IP69K
- Contacts: 2-Pole or 4-Pole Ex Rated Contact Blocks
- Zones: 1, 21, 2, 22
- Ex Marking: Exd IIC T6 (-20 ≤ Ta ≤ +60C) Gb / Ex tb IIIC T85C (-20 ≤ Ta ≤ +60C) Db
