Overview

Trapped key interlocking is versatile, robust and can be used to solve complex safety sequences, particularly where multiple energy sources exist. Electrical, pneumatic, hydraulic, and kinetic energy sources can all be interlocked using mGard products, and typically at a fraction of the cost of alternative solutions.

Fortress mGard products are designed, tested and TUV approved for use in Category 4/PLe safe control systems. A single Fortress interlock does not require additional safety components added to meet PLe.

All mGard systems can be designed to incorporate safety, or personnel keys, an ideal solution for whole body access requirements, and one that is recommended in multiple international machinery safety standards.

mGard is particularly effective in reducing installation cost, by reducing wiring, whilst not reducing safety performance.

ISO/TS 19837:2018 is the technical specification relating to trapped key interlocking, our mGard range is designed to meet or exceed all requirements. Fortress keeps a database of all keys and locks and their locations to prevent the unintentional duplication of key codes at a location, regardless of the original purchaser.

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Key benefits

Mechanical only, no wiring

Forced sequential process

Harsh, robust design

  • Controls operations in sequence to reduce the need for programmable logic
  • Eliminates electrical wiring to access points reducing cost of cabling & installation
  • Multiple energy sources can be controlled in sequence to remove integration requirements between different technologies
  • Robust construction to survive the most demanding environments
  • 3rd party approved to PLe for applications requiring high reliability
  • Special purpose units can be designed to provide solutions for specific needs
  • Suitable for applications up to SIL3 Cat. 4 PLe
  • Over 300,000 unique key codes possible
  • 9 Key/lock colour options
  • Non-masterable & masterable lock options
  • Non-stainless or stainless steel construction of all system components
  • Large range of switch variants for electrical isolation
  • Non-solenoid, solenoid, voltage sensing and electrical time delay options
  • Bolt modules & valve interlocks for pneumatic & hydraulic isolation
  • Panel & enclosure mount options

Contact us and we can help define your trapped key interlock system.

At Fortress we will always look to assist with project delivery and efficiency by supporting on the design of trapped key interlock systems. Our team can be on hand to survey equipment on site, interpret system drawings or discuss concepts early on in project design.

The advantage of trapped key systems is that any number of power sources can be interlocked into any number of access points. Determining part numbers and a bill of materials may initially appear complex but a Fortress representative can assist with this and provide engineering drawings of each component.

Using key engravings and colour coding will also make sequences easy to understand and simple to follow. With 30 characters of text and 9 colours available we can define a coding system for you and record all keys supplied so every key supplied is unique.

Using end user information and project documentation we can coordinate across multiple integrators and equipment suppliers.

Contact us and we can help define your trapped key interlock system.

At Fortress we will always look to assist with project delivery and efficiency by supporting on the design of trapped key interlock systems. Our team can be on hand to survey equipment on site, interpret system drawings or discuss concepts early on in project design.

The advantage of trapped key systems is that any number of power sources can be interlocked into any number of access points. Determining part numbers and a bill of materials may initially appear complex but a Fortress representative can assist with this and provide engineering drawings of each component.

Using key engravings and colour coding will also make sequences easy to understand and simple to follow. With 30 characters of text and 9 colours available we can define a coding system for you and record all keys supplied so every key supplied is unique.

Using end user information and project documentation we can coordinate across multiple integrators and equipment suppliers.

What is Trapped Key Interlocking?
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How Trapped Key Interlocks work
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All downloadable assets

To have access to the mGard technical information, please login to

  • Select from our range of high-coded compact yet robust interlocks here.
  • Use our Datasheets / drawing generators to create technical files, datasheets, and CAD for your selected product.
  • Convert your unique ITM number into a Fortress part number using our Reference tool
  • Calculate the performance level of your unique safety system using our SISTEMA library
  • Click here for more Fortress Product tools

Access control in manufacturing

Fortress offers the ability to control who can access industrial equipment safely alongside when they can access safely. Data of who, when and where from access events is collated for efficiency analysis.

We are experts in providing safety solutions for automation

Contact us for tailored guidance and solutions for your machinery safety applications.