Understanding safety functions: Fluctuations, loss and restoration of power sources

Voltage vs time plot showing a voltage sag condition.

Control systems must be protected against fluctuations and power loss, whether electrical or fluidic. Fluctuations and losses are well defined in IEC, IEEE and ISO standards. Careful design of electrical systems, including the use of UPSs for electrical control systems and the careful design of pneumatic supply systems, including the proper sizing of pneumatic accumulators for compressed air-powered logic, is essential.

Understanding safety functions: Response time

A stopwatche with a movong hand and athe words "response time" next to it.

This post deepens the discussion of safety-related parameters. Safety functions are control functions whose failure causes an immediate increase in risk. ISO 13849-1 [1] defines several common safety functions to develop safety-related control systems. In this post, I will discuss the response time safety-related parameter.

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Understanding safety functions: Safety-related parameters

An old, white, control panel with the paint peeling off it in many places, and many dials and gauges showing various readings.

Safety-related parameters are control system variables whose incorrect setting immediately increases the risk to the user. Some of the most common include safe-reduced speed and safe standstill, but temperature, pressure and other process parameters can also be safety-related. Defining what machine parameters are safety-related and then designing control hardware and software to meet the functional…

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CSA Z432 Public Review Open!

CSA Z432 Public Review is open. If you are a user, a builder of machinery, or an evaluator of machinery, this is your opportunity to see the draft of this important standard and to make comments to help the Technical Committee improve the standard on your behalf. Note: The start of the public review period…

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Emergency Off (EMO) vs Emergency Stop

EMO Button, red with yellow surround. Credit: D. Nix

The concept of Emergency Off (EMO) used by the semiconductor manufacturing sector is similar in many ways to the emergency stop used in all other types of machinery, with some differences. This article covers the differences between these concepts. NOTE: This is a long post! TL;DR: EMO and emergency stop are very similar; however, some…

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