P4: Functional Safety - PFD calculation First Part
A continuous probability distribution is indicated with f(x) and is usually called Probability Density Function (PDF). It is expressed by an equation and it can be represented as in the Figure 1.5 {1.4.2.1}. The bell curve is just an example of a pos...
Process Safety
The three legs of North America product Safety
THE DOUBT: is the knowledge of the NEC, or NFPA 70, important when assessing the electrical conformity of my machinery for export to USA?
CONSIDERATION 1: When...
UL and CSA Conformity
P5: Functional Safety - PFD Calculation Second part
In the first part of the article we introduced the concepts of Unreliability function F(t) and of Reliability Function R(t). The former is the base for the parameter PFD(t) and the one used to indicate the reliability of a Safety Instrumented Functio...
Process Safety
P6: The average probability of dangerous failure per hour (PFH)
In the previous articles we explored the Parameter PFDavg: Average Probability of Failure on Demand. It is used to indicate the reliability of a Safety Instrumented System operating in Low demand. We will now explore the domain of Safety-related Cont...
Process Safety
P7: Functional Safety in High demand - ISO 13849-1 categories
ISO 13849-1 is intended to be used in the design and evaluation of safety-related parts of the control system (SRP/CS) and only the part of the control system that is safety-related falls under the scope of the standard. It applies to SRP/CS for high...
Process Safety
Proof Test and Diagnostic Coverage
THE DOUBT: What is the difference between a Proof Test and a Diagnostic Test?
CONSIDERATIONS: The Proof Test concept is coming from IEC 61508 and it is im...
Process Safety
High versus Low Demand
THE DOUBT : What does it mean that a Safety Control Systems is operating in High or in Low Demand and why is it important to know it?
CONSIDERATIONS:...
Process Safety
Safety Contactors and their usage
THE DOUBT: What is a safety contactor and is their usage compulsory in a Safety related control circuit?
CONSIDERATION 1: There are 2 main types of contac...
Functional Safety
Well-tried components
THE DOUBT
Why are well-tried components important in Machinery Safety?
CONSIDERATIONS
The concept is defined in both ISO 13849-1 and IEC 62061. Those...
Functional Safety
Short-circuit aspects: NEC vs IEC
There are several differences between the North American and International electrical standards (published by IEC).
One of those differences is the way...
UL and CSA Conformity
