Valve interlocking enforces and guarantees a pre-defined sequence of operation, and therefore eliminate human error. They are used as an industry standard by renowned companies to create a safer working environment.

They are used in many applications where safe and ‘first time right’ valve operation is required, such as pressure relief valves (PSV), pig launching and receiving, inert gas systems, pump start up, flare lines, boiler blow-down, ‘2 out of 3‘ and decoking.

Our manufacturing partner, SOFIS, manufactures valve operation systems such as mechanical valve interlocks, portable actuators and valve position indicators. It is the world’s largest interlock manufacturer, providing bespoke design solutions that protect people and property throughout the world.

Teksal Safety is the Australian and New Zealand distributor for SOFIS Smith Interlocks (formerly Smith Flow Control) and SOFIS Netherlocks valve interlocking and process safety systems, and supports Sofis’ complete range, including supply, installation, commissioning and training services.


Plant operations, when performed incorrectly, can have catastrophic consequences in safety-critical industries. To mitigate the effects of human error, valve interlocking systems are widely employed in risk management strategies, forming an important component of process safety. A valve interlocking system ensures a predetermined sequence of valve operations can be achieved by using a “trapped key” principle.

Available in quarter-turn and multi-turn versions, valve interlocks are designed to suit all types of valves and can be fitted to the valve without needing hot work or modification to the host valve. When used with other Sofis interlocks, operators are compelled to follow the correct sequence of operation of all valves and equipment within the interlock sequence.

Given the diverse applications interlocks can be used for, as part of HAZOP or design reviews, we can help define and review the sequence and create the interlock specifications.

For more information about any of these products, call 1300 TEKSAL or email