Understanding safety functions: Indicators and alarms

A man in a white hardhat and high-visibility vest stands in a large process plant control room holding a walkie-talkie and looking towards a screen with alarm annunciations displayed. The control room is mostly white, so the man's vest, the instruments and displays pop out of the image.

This is the final installment in the series on understanding safety functions. When indicators and alarms come up in conversations between machinery controls engineers, large process plant control rooms like those shown at left often come to mind. While this is certainly true, there are many instances on smaller machines and assembly lines where alarms…

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โŒ ISO 13849-1:2023 โ€“ Do Not Use โŒ

This is a first On Thursday, 2023-04-27, ISO published ISO 13849-1:2023, the 4th edition of the dominant functional safety standard for machinery. Usually, I would be the first to tell you that you should buy the standard as quickly as possible and start using it immediately. Today is not a normal day. As Command Module…

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Understanding safety functions: Safe speed and safe standstill

A red sign with white block letters reading "reduce speed."

In this post, I’ll discuss two safety-related parameters: safe speed and safe standstill. Speed control is a very common machine function. Conveyors, mixers, pumps, and many other applications rely on variable-speed drives. Some speed parameters are also safety-related because variations in speed can increase the risk to workers. See this post for more information on…

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Understanding Safety Functions: the start/restart function

Car engine start/stop button

After the safety-related stopping and the reset functions, the start/restart function is the next most common. Without a start/restart function, there is no way to make the machine do what it’s supposed to do. If you’re designing a machine control system, you need to understand this function.

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What is risk assessment?

Risk assessment began as a discipline in the late 1960s, with some of the earliest formal papers published in the early 1970s [1] and [2]. The early researchers were part of the US military and were interested in reducing the risks for military personnel carrying out their duties.

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