PLC/Control

Question 1

what are central PLC logics?

Answer 1

1- FBD
2- LD
3- Sequential
4- Structural text

Question 2

main logics?

Answer 2

1- AND
2- OR
3- NOT

Question 3

Performance Level (PL)

Answer 3

In machine building, this refers to manageable units on which life safety systems are frequently used. ISO 13849-1 was developed with this context in mind. The standard takes into account the machinery directive and considers safety functions from both a qualitative and quantitative perspective. To classify various technical safety performance capabilities, it defines five Performance Levels (PL a, b, c, d, e), representing the average probability of dangerous failure per hour (PFH). ISO 13849-1 specifies an iterative process for designing and validating the safety-related parts of a control system (SRP/CS).

Question 4

Safety Integrity Level (SIL)

Answer 4

The chemical industry was the driving force behind basic safety standard IEC 61508. As a result, the focus was on basing safety statements on how likely the reliable response to the function requirements is to occur, should a safe response be required. In terms of architecture, chemical and process-technical facilities tend to be large and complex. The life safety systems here are designed to rarely have to take action. The term SIL (SIL 1, 2, 3, 4) is derived from IEC 61508. IEC 62061 also defines the SIL claim limit, and describes the iterative process for determining and validating the SIL of safety-related electrical, electronic and programmable control systems (SRECS).

Question 5

PL and SIL table

Answer 5

PL Mean probability of a critical outage [1/h] SIL
a ≥ 10-5 to < 10-4 –
b ≥ 3 x 10-6 to < 10-5 1
c ≥ 10-6 to < 3 x 10-6 1
d ≥ 10-7 to < 10-6 2
e ≥ 10-8 to < 10-7 3