Programmable Safety Relay—Guardian of the System

Small safety control systems, such as emergency shutdowns, flammable, explosive or toxic gas detection, usually involve less than 100 IO points. These systems are widely used in industries with safety hazards, such as oil and gas fields, oil and gas pipelines, petrochemicals, chemicals, and offshore platforms, to ensure accident control and the safety of personnel and facilities. Programmable Safety Relays play a critical role in these systems, ensuring they can quickly respond to various emergencies, thereby ensuring safety.

Application of Programmable Safety Relays in Tank Area Renovation

CHENZHU provided a unique safety system solution for a company's tank area renovation. The raw materials stored in the tank area are combustible and toxic gases, posing safety hazards to daily production and nearby personnel. To mitigate risks, numerous temperature sensors and gas detectors were installed on-site, such as RTD, hydrogen detectors, and hydrogen sulfide gas detectors. The client's safety requirements were: when the detected temperature or gas concentration exceeds preset values, or when the emergency stop button is pressed, on-site alarm devices must issue audible and visual alarms and send alarm signals to the local monitor and central control room, while shutting off key valves and initiating emergency ventilation measures. To achieve this, CHENZHU provided an integrated solution based on Programmable Safety Relays.

System Architecture of Programmable Safety Relays

In our solution, field signals such as RTD, TC, or 4-20mA analog signals are connected through safety barriers certified to SIL2. The safety barriers output one digital signal and one analog signal. The analog signal enters the remote intrinsic safety standard I/O module, processed by the PLC controlling system, and transmitted to the central control room and local HMI display through MODBUS-TCP protocol. The digital signal from the safety barrier is connected to the SIL3 certified Programmable Safety Relays, achieving overall system safety control and alarm requirements at SIL2 level.

For digital field signals, such as emergency stop buttons, they are directly connected to the Programmable Safety Relays, meeting SIL3 safety control and alarm requirements.Programmable Safety Relays have a communication gateway module mounted on the left side, transmitting signals to the central control room and local HMI display through a switch and MODBUS-TCP protocol.

Technical Features of Programmable Safety Relays

Programmable Safety Relays output signals come in two types: transistor and contact, to meet different load requirements. DC 24V loads with currents less than 0.5A are directly controlled by the Programmable Safety Relays; for loads with supply voltages higher than 24V but less than 250V, programmable relay output expansion modules can be used, with a load capacity of up to 4A, or external safety coupling relays can be used.

Programmable Safety Relays master module provides 20 safety inputs, 4 transistor safety outputs, and 4 transistor standard outputs. If the total IO points exceed 28 points, expansion modules can be added to the right side. There are two types of expansion modules: the first provides 12 safety IO points, and the second provides 4 independently controllable safety relay contacts. The expansion modules connect to the master module via a bottom TBUS connector, with a maximum of 10 expansion modules per master module.

Programming and Configuration of Programmable Safety Relays

Programmable Safety Relays use graphical programming and come with numerous safety and standard function blocks, such as logical "AND", "OR", "NOT", edge triggering, delays, counting, emergency stop, reset, etc. The programming can be easily completed in three steps: add function blocks, connect function blocks, and check the program. Additionally, the parameters of the safety barriers, such as preset upper and lower limits, can be configured through software tools, making the entire system configuration more flexible.

In this project, in addition to CHENZHU's Programmable Safety Relays and safety barriers, we also used PLC, IO modules, switches, power supplies, terminals, rails, etc. The entire solution is low cost, easy to implement, and simple to maintain, making it particularly suitable for new small safety systems or the renovation of small safety systems.

Programmable Safety Relays, as an important component in modern industrial safety control systems, provide excellent performance and reliability, offering solid safety guarantees for various industrial applications. CHENZHU is committed to providing high-quality products and solutions to help industries achieve higher levels of safety control and automation.