Safety barrier issue
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I have a question for everyone: do intrinsically safe instruments necessarily need to be connected to a safety barrier? I saw this claim on the Internet, but after checking GB3836.4, although there is a chapter on safety barriers, it doesn’t seem to state explicitly that a safety barrier must be used. Is there any place where such a clear requirement can be found?
A safety barrier is also known as a safety holder. It is a safe interface for intrinsically safe circuits; it enables two-way transmission of electrical signals between the safe area (intrinsically safe) and the hazardous area (non-intrinsically safe), and it can prevent the transfer of energy from the hazardous area to the safe area in the event of a failure. General safety barriers come in Zener type and isolation type. DCS systems and PLCs generally do not have the function of safety barriers.
Intrinsic safety instruments are instruments that possess intrinsic safety； To establish a true safety loop, it is necessary to isolate it using a safety barrier ； Explosion protection in hazardous areas requires the establishment of an intrinsically safe circuit.
It’s needed; everything was already explained in detail upstairs.
Okay, thank you all. There is a problem on site related to the ASCO intrinsically safe solenoid valves: the tests conducted in the factory showed normal performance. However, after being installed on site – two years have passed since then – attempts were made to adjust them. As a result, the solenoid valves did not receive any power; when 24V voltage was applied to them, the relay module got damaged. The voltage couldn’t reach the solenoid valves. This kind of issue occurs frequently, and no safety barriers have been installed on site either.
This post was last edited by qugd on 11/6/2019 at 11:45. Intrinsic safety instruments are not just individual devices; they are considered in terms of a circuit or system as a whole. All electrical and auxiliary equipment in the intrinsically safe circuit must comply with intrinsically safe specifications, including intrinsically safe instruments, intrinsically safe cables, as well as safety barriers; only then can a complete intrinsically safe circuit be formed. Without a safety barrier, that circuit is not explosion-proof at all. In the standard specifications for explosion protection, intrinsically safe design is covered as a separate category; how could it then be said that safety barriers are optional? Since safety barriers are mentioned (especially since this component used for signal isolation is specifically defined as a safety barrier), it is clear that its function is essential.
It is also possible to power intrinsically safe instruments using this intrinsically safe power supply. Safety barriers are inexpensive and widely used, but they also have significant performance drawbacks; sometimes using them can lead to various problems, such as loss of precision or signal distortion......
There are two ways to connect intrinsically safe instruments to DCS systems and PLC IOs: one is using regular IOs together with safety barriers, and the other is using intrinsically safe IOs that are connected directly to the instruments, without the need for safety barriers.
Meters used in hazardous environments must be connected to a safety barrier.
If there’s enough budget, safety guards will be installed; if not, it’s not necessary. The DCS manufacturers can also meet the requirements