Contactors used in Safety Applications
There are three types of contactors used in Safety-related control Systems:
Electrical Safety and Arc Flash Mitigation
ISO 13849-1
It is one of the two standards used in machinery and, at least in Europe, it is the most used of the two, the other being IEC 62061. It is divided in two parts:
Functional Safety
Direct Opening Action
The electrical output of an interlocking device has two types of technologies
Machinery Safety
IEC 62061
This is the second standard applicable to machinery and, so far, the least used for the reasons explained in the book. However, there is confidence that, with the publication of the 2021 edition, there will be more and more machinery manufacturers wh...
Functional Safety
"Proven in use" and "Prior use"
THE DOUBT: What is the difference between a Proven in Use and a Prior Use Device?
Actually the two terms are quite similar and it is very easy to mix t...
Process Safety
Fault Considerations and Fault exclusion.
A Safety system has to be reliable; but how many faults should be taken into consideration? A redundant system can be designed with two sensors and two redundant final elements but, in case of two faults, we are in trouble! In general, the following ...
Functional Safety
The difference between Route 1H and Route 2H
THE DOUBT: What is the difference between Route 1H and Route 2H?
Let’s try to place the subject into the main picture. When you hear about Route 1H and 2...
Process Safety
A brief history of Functional Safety standards
In machinery, one of the first safety standards was BS 5304 “Code of Practice for Safety of Machinery”, first published in 1975
Functional Safety
P1: Reliability data for components used in Safety Systems
THE DOUBT: What are the main reliability data for components used in Safety Applications?
When you deal with components used in Safety Critical Systems yo...
Process Safety
Functional Safety in USA and Canada: the Concept of “Control Reliable”
In Europe, in the 90’s, the reference standard for Functional Safety of Machinery was EN 954-1. At that time, Safety-related Control Systems were classified in 5 Categories: from Category B to Category 4.
UL and CSA Conformity
P2: The Safe Failure Fraction and the Architectural Constraints
A Safe failure is the failure of an element, inside a component that plays a part in implementing a safety function, that results in a spurious operation of the safety function. That means, it places the machine into a safe state (it generates and em...
Process Safety
P3: Considerations on the Safe Failure Fraction in High and Low Demand
In a previous article we presented an important parameter, used in both high and Low Demand Mode Safety Systems: the Safe Failure Fraction.
Process Safety
