Smith Flow Control and Netherlocks have merged. We are now Sofis.

Netherlocks valve interlocks

Premium quality interlocks, solid and simple Dutch valve interlock design.

Established premium design

Netherlocks valve interlocks were introduced to the market in 1993. The Dutch design of the valve interlock is based on extensive experience with the major oil and chemical companies in The Netherlands. Nowadays, these companies are key users of Netherlocks interlocks all over the world.

Safe and efficient valve operation

Valve interlocks guarantee safety and a right-first-time approach to manual valve operation through a key transfer principle. Valve interlocks are mechanical devices which are permanently mounted to your equipment. They avoid operator error by forcing operators to follow recommended procedures. By eliminating human error, they save money and remove safety risks.

Netherlocks Valve interlock on multi rotation valve
Valve interlocks on pressure relief valves

Optimize your operating performance

  • Guaranteed right-first-time operation
  • Higher equipment efficiency and asset availability
  • Reliable process-status feedback through colour-coded key positions
  • Improved HS&E performance

Premium design

  • Integral lock assembly
  • AISI 316 stainless steel

Quotes from our clients

Netherlocks has supplied manual valve interlocks for many of our FPSO’s. They provided excellent support, from specification to delivery and final installation of our projects. Due to their extensive experience, Netherlocks is considered by SBM to be a key player in the interlocking market.- Engineering Team Topside SBM Offshore (USA)
Netherlocks has installed many interlocks to our PSV installations. Valve interlocks avoid dangerous situations, by blocking off the operating PSV until similar relief capacity has been connected to the system.- Michel Immerzeel, Team Leader Mechanical, Shin-Etsu B.V.
Sabic’s relationship with Sofis is very good. The people at Sofis are cooperative and always look for a suitable solution for the various valve safety issues we experience at Sabic. Netherlocks interlocks and the Power Wrench are typical examples of products that perfectly suit our requirements.- J. Habets, Senior Dayshift Operator, HDPE Polymers – Production, SABIC Europe B.V.

Optimal reliability

  • Anti-tamper assembly
  • Linear key improves reliability and operability
  • Uniquely-coded keys for each lock
valve interlocks securing pressure relief valves

Universal applicability

  • Fits any quarter- or multi-turn valve
  • Fits high rotation (2000+) handwheel-operated valves
  • Integrates adjacent equipment into operational sequencing

Easy installation

  • Bespoke mounting kit for perfect fit
  • Sequence-free commissioning with one-time Q-card commissioning keys

A Netherlocks valve interlock for every piece of equipment

How do Netherlocks interlocks work?

Netherlocks valve interlocks are used as an industry standard by renowned companies to create a safer working environment.


Sofis offers you support through local service centres and a network of certified local service partners. This enables efficient installation and maintenance of your Sofis products. We strive to create partnerships with our clients, providing a turnkey approach to service. This will lead to a reduction in your total cost of ownership.

Go to support