Emergency Stop

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itref55

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How often or should an emergency stop push button or pull cord be tested after being tested during the initial instillation of the device?
 
I am not aware of any mandated testing period. Certainly the machine should have a maintenance schedule to which the Estops can be added. On most of our equipment I would be happy with a frequency of once/year or more. The period of a year or less is mainly to make sure it keeps getting scheduled.

They should also be tested after any decent modification to the machine tool hazardous motion. I wouldn't worry after adding a pilot light but I would worry after adding a soft start.

By the way, at installation where the machine has a PLC, try the following:
Since most PLCs are not safety rated - in the PLC, force the Estop inputs INACTIVE. The machine should continue to run. Then hit an Estop. If the Estop does not stop the machine then you have a wiring problem.
 
pfalcon said:
I am not aware of any mandated testing period. Certainly the machine should have a maintenance schedule to which the Estops can be added. On most of our equipment I would be happy with a frequency of once/year or more. The period of a year or less is mainly to make sure it keeps getting scheduled.

They should also be tested after any decent modification to the machine tool hazardous motion. I wouldn't worry after adding a pilot light but I would worry after adding a soft start.

By the way, at installation where the machine has a PLC, try the following:
Since most PLCs are not safety rated - in the PLC, force the Estop inputs INACTIVE. The machine should continue to run. Then hit an Estop. If the Estop does not stop the machine then you have a wiring problem.
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There are SIL systems that are required to be tested at certain intervals and the results be documented. If your device is part of such system, it may fall under those guidelines.
 
pfalcon said:
SIL? What is it?
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Safety Instrumented Systems are designed to provide protection of life and property. Their design is based on risk evaluation procedure, use of voting and redundancy as well as using components that have a record of performance.

WiKi:
"Safety Integrity Level (SIL) is defined as a relative level of risk-reduction provided by a safety function, or to specify a target level of risk reduction. In simple terms, SIL is a measurement of performance required for a Safety Instrumented Function (SIF).
Four SILs are defined, with SIL4 being the most dependable and SIL1 being the least. A SIL is determined based on a number of quantitative factors in combination with qualitative factors such as development process and safety life cycle management. The requirements for a given SIL are not consistent among all of the functional safety standards."

Two main Standards identify the core: IEC 61508 and ISA S84.

It is mainly used in the Process Industry, but its principles of a methodical approach have universal use.
 
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