PLC

Input/Output Architectures

Input/Output Architecture in the control system We will give an overview of most common input/output architectures in a control system, depending on whether the priority is “Safety” or “Availability“. 1-Architectures of Inputs The following image shows the most common configurations. The letter “D” in yellow stands for “Diagnosis” and usually is associated with the Safety […]

Input/Output Architectures Read More »

Relay Redundant System

Relay Redundant System Let’s see a simple example of how we can increase the safety of our design using conventional electromechanical relays. Suppose we have a high pressure steam line with three safety pressure switches wired to an intermediate relay. We also make a wired 2 out of 3 logic, so that the circuit is

Relay Redundant System Read More »

Availability versus Safety

Availability versus Safety This is an important point to be considered when designing a control system with a programmable logic controller. The analysis must be performed with all the elements involved: the PLC, field instruments, valves, motors, dampers, etc. In addition, it is essential to analyze the process or machine. The design will be very

Availability versus Safety Read More »

What’s a safety PLC?

What is a safety PLC? Let’s try to explain it in a simple way for non-experts. The fundamental difference with a general purpose PLC is summed up in one word “Diagnosis”. In addition, there are differences in terms of internal architecture, software and firmware, and certification for applications where compliance with a certain SIL level

What’s a safety PLC? Read More »