Tag Archives: safety relays

Differences between ESD and F&G Safety Relays

From John Tan | August 6, 2020

There are 2 main applications of safety relays in the process industry. Phoenix Contact describes them as the Emergency Shutdown (ESD), and Fire & Gas (F&G) applications. Across the industry, there are many terms used to describe these 2 applications. In this article, we will have a look at the different terms and understand the uniqueness of each application.

Application A	Application B
Emergency Shutdown (ESD)	Fire & Gas (F&G)
De-energized To Safe (DTS)	Energized To Safe (ETS)
De-energize To Trip (DTT)	Energize To Trip (ETT)
Normally Energized (NE)	Normally De-energized (ND)

Terms to describe the 2 applications

Emergency Shutdown Application

Under normal operating conditions, a load like an electrical motor, must be continuously powered. The ESD safety relay which is used to power up a load must also be continuously powered and is described as Normally Energized (NE).

During a safety incident (e.g. the electrical motor is overheated), the load needs to be switched off to achieve a safe state. As the power status of the safety relay and load has a direct relationship, switching off (de-energizing) an ESD safety relay, will result in the load being switched off as well. Thus, the terms, De-energized To Safe (DTS) and De-energize To Trip (DTT) are used to describe this phenomenon.

Example of ESD relay application drawing

Fire & Gas Application

Under normal operating conditions, a load like a sounder and a beacon is not powered. The F&G safety relay is only required to be powered up during a safety incident and to allow the sounders and beacons to sound off the alarm and provide light signals. Under normal operating conditions, the F&G safety relay is Normally De-energized (ND).

During a safety incident (e.g. a gas leak or fire incident), the load needs to be switched on to achieve a safe state. As the power status of the safety relay and load has a direct relationship, switching on (Energizing) an F&G safety relay will result in the load being switched on as well. Thus, the terms, Energized To Safe (ETS) and Energize To Trip (ETT) are used to describe this phenomenon.

Some people might be confused by the term, Energize To Trip (ETT). This is because the word “Trip” is commonly used on circuit breakers, where “Trip” here refers to power down. However, the word “Trip” has a deeper meaning and can be used to describe the powering up and down of a load. A similar word for “Trip” is “Trigger”, and you can think of it as “Energize To Trigger”.

Example of F&G relay application drawing

Summary

The key differences between the ESD and F&G safety relays are the type of load they are connected to, the definition of a safe state and the energy state under normal operating conditions. For ESD, the loads are usually machines used in production; the definition of the safe state is to switch off the relay / load and is normally energized under normal operating conditions. For F&G, the load are usually sounders and beacons, the definition of the safe state is to switch on the relay / load and is normally de-energized under normal operating conditions.

In Phoenix Contact, we provide smart solutions for functional safety, from non-contact safety switches to complex controllers. Our applications range from machine building, the automotive industry, and the process industry. Our products are also SIL certified, which allows you to meet your project requirements easily.

Example of PxC Functional Safety Products

Why Use Safety Relays?

From William Tan | January 29, 2018

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Let’s say you are asked to be a Design Engineer for a day and are tasked to come up with a Process Control Safety System. What are the questions you should ask?

What happens to the Safety Instrumented Systems (SIS) when the relay contact is welded?
When did it happen?
Where can you find this faulty relay?
Why did this happen?
Who will be responsible for monitoring this fault?

Safety Relays are devices that implement safety functions. In the event of a hazard, a safety relay must work to reduce risk to an acceptable level. The safety relay must initiate a safe and reliable response as well as monitor the integrity of its function.

The Process Automation Fire & Gas System is always on standby mode and it becomes more important to have multiple diagnostics to make sure the relays used in the Fire and Gas System Safety remain functional with all wiring connected.

7 Functions the ideal safety relay should have for Fire & Gas Systems:

Power loss diagnostics to field devices such as the Beacons, Solenoid Valves and Fire Sounders.
Field devices disconnection diagnostics.
Alerts when Field Devices short circuit.
Welded relay contacts diagnostics.
Able to Proof Test relay points without the use of external power.
Diagnostics via the same cable to the relay coil by the use of test pulse filtering. This also saves money as there is no need for additional DI cards and cables for monitoring function.
Option for redundant connection to the relay coil.

Safety Relay Connections

PSR-PC50 Series SIL Coupling Relay

The Phoenix Contact PSR-PC50 series SIL Coupling Relay has the 7 functions you are looking for and it can also be used for power adaptation and electrical isolation in Safe-State-ON applications up to SIL 3 according to IEC 61508 as well as IEC 61511.

This category 3 device is designed for installation in zone 2 potentially explosive areas. By filtering the controller test pulses, premature failure of the safety relays is prevented. The contact side is fully monitored for open circuits and short circuits as well as load and diagnostics supply voltage. If an error occurs, the internal device input impedance is affected. As such, the test pulses sent from the controller are disrupted and the error is reported to the corresponding digital output without additional wiring effort.

If you have any questions or want to know more about this product, please feel free to send us an enquiry at marketing@phoenixcontact.com.sg and a product representation can be arranged to discuss in more detail.

Safety is by Choice, Not by Chance.

From William Tan | May 29, 2017

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Phoenix Contact's Safety Relays Are you selecting a safety relay just to meet the SIL3 requirements?

Who will be responsible for conducting the Proof Test to ensure it is still safety relays are still safe to use?

Which is critical? Safety relays without diagnostics or the Safety relays with diagnostics?

Safety is a Choice, Not by Chance

The graphics below explains the functional principle of the force guided /positive driven contacts in the event of a welded contacts and that’s where the normally closed contacts come into action to provide feedback to inform the system of the failure in relay contacts.

In this case when the relay is de-energized, the normally closed contact cannot close properly having a gap of 0.5mm.

Click the image to see the animation of how Force-guided relays work

Safety relays for ESD-Emergency Shut-Down Systems should have:

1) Force guided relay enables a feedback path just in case of welded contacts and ~~eliminates the need for~~ simplifies Proof Testing. (ESD-Emergency Shut Down and F&G-Fire & Gas systems)

Emergency Shut Down System Circuit

Safety relays for F&G-Fire & Gas Systems should have:

The diagram below shows connection details for a safety relay used by Fire & Gas Systems. The Fire & Gas System is always on standby mode and it becomes more important to have multiple diagnostics to make sure the Fire and Gas System Safety Relay is still functional and all wirings are connected.

Fire & Gas System

Diagnostics for lost power input to field devices: Beacons, Solenoid Valves, Fire Alarm Bell.
Field devices disconnection diagnostics.
Short circuit field device diagnostics.
Diagnostics for any welded contacts.
Proof Test points (TP1, TP2, TP3) without the use of external power.
All diagnostics via the same cable (A1,A2) by the use of test pulse filtering.
Option for redundant connection (A1’, A2’).

If you have sales enquires to know more about this product, please feel free to send us an enquiry at marketing@phoenixcontact.com.sg and a sales visit can be arranged to discuss in more detail.

Coupling relays for safety-related activation

From Gary Lim | July 14, 2015

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In recent years, safety-related activation has become increasingly important in the field of process technology.

As a result, with PSR-PC50, Phoenix Contact offers a coupling relay that has been specially developed for this area and that can be used according to SIL 3.

The coupling relay was specially designed for failsafe controllers in the field of process technology. As such, all requirements for use in applications up to SIL 3 are fulfilled, according to IEC 61508. Internally, the device has six contacts that are switched in parallel as well as in series. In this way, the safety required is taken into account, as well as the necessary availability.

Continuous diagnosis poses a challenge for planners and planning engineers. Generally speaking, the controller diagnosis ends at the coupling module used. Often this is not sufficient for many users. To this end, the line/load monitoring function of the PSR-PC50 relay enables seamless diagnostics from the controller to the actuator. Open circuits as well as short circuits in the on-load voltage supply and diagnostic supply voltage are monitored. If an error occurs during normal operation, in all established safety systems it can be reported via the existing control line back to the corresponding digital output. In this way, the need for additional installation time and other digital inputs required for actuator readback is eliminated.

Introducing 2 New Products of Phoenix Contact

From | March 31, 2015

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Powerful New Safety Relays are Just 6mm Wide

The new PSR Mini relays from Phoenix Contact are the world’s slimmest safety relays with the power of a large safety relay. With their compact 6-mm width, they ensure high safety thanks to positively driven contacts.

Phoenix Contact’s new relay technology makes this compact design possible. The design is based on a slim but powerful basic relay characterized by minimal space requirements, low energy consumption, and high system availability.

The safety relays switch loads up to 6 amperes, are compatible with many signal transducers, and can be used in many different applications thanks to extensive approvals. This makes the new products especially suitable for mechanical engineering and process industry applications.

For users, these slim modules require up to 70 percent less space. Since only a single enabling contact is needed, applications can be built with new and improved cost-effectiveness. Safety relays can even be used to build distributed systems in potentially explosive areas. The terminal carriers also enable the use of system cabling solutions for a fast and correct start-up and field connection.

The complete PSR Mini range of safety relays consists of 6-mm and 12-mm models.

New EH Housing from Phoenix Contact

Introducing the latest addition to housing family, EH housing – the universal housing system with modular concept which is tailored for your electronic application needs.

EH housing offers you simple design-in, thanks to its variable housing form factor – high and flat design!

Let us look into details of this marvelous housing family. For a functional device concept, PCBs can be installed in all three space direction. Free choices of PCB connection technologies are available from Phoenix Contact. We have them all incorporated seamlessly into our latest EH housing. From conventional terminal blocks, plug and headers, to RJ 45, or even USB ports, to cover your wide range of today’s electronic application!

Do you want to house your PCB?

Do you want to save more to maximize your profit for your product?

Do you want your PCB to be covered within Phoenix Contact superb quality and reliable housing?

Talk to us now! We are always available for you!