Security interlocks

Together with Netherlocks, SMITH FLOW CONTROL belongs to the SOFIS group manufacturing process safety equipment and is specialised in the manufacture of Interlock security locking.

In the case of security interlocks, a locking device operated by a special key is mounted onto the valve. The key can be kept, for example, on a special key stand in the control room of the production plant. A valve fitted with a security interlock cannot be operated before the security mechanism has been released using the individualised key. While the key to the security lock is in the control cabinet, a tag attached to it specifies the valid position of the valve associated with the key. In such a case, process deviations can be coded by providing the keys with tags of different basic colours, for example – in this way, a glance into the key cabinet will tell if all valves are in their so-called default position.

Possibilities for system locking – sequences

In addition to the operation of individual valves, the Interlock system is also suitable for the security locking of valve groups in cases where it is important to operate certain valves in the exact predetermined order. For example, TUKES now demands that in the case of tanks with several safety valves it must be ensured that all safety devices are not accidentally closed at the same time.
The Interlock locking system greatly facilitates such compliance. See the sequence example.

Installation to existing valves

The Interlock security locking suits all valve models (including actuator-controlled valves) and nominal sizes. It is also easy to install afterwards. In such cases, our installers will measure the principal dimensions of the existing valve’s stem, based on which the plant will produce an adapter piece between the locking device and the valve. Our installation team has completed the manufacturer’s official training course, which means that security lock installation and tuning will be handled with ease.