Are isolation barriers useful for flameproof instruments?

A barrier is generally used to protect the system and to prevent interference from the shielding and the circuits that make up the system; it functions as a sound conduit, and sometimes it is also used for transmission purposes. Both flameproof instruments and other types of instruments can be used; they certainly have their uses.

The function of isolation is to prevent interference; the purpose of using explosion-proof instruments with isolation barriers is to ensure explosion protection, and safety barriers are required

The people upstairs may not be aware of the function of safety barriers. A safety barrier is actually a type of safety device that uses an isolation transformer in its structure, which is why it’s called a safety barrier. In intrinsically safe circuits, even though the field environment poses an explosion risk, the circuit itself is intrinsically safe, so no explosion will occur. In the control room, although the circuits aren’t intrinsically safe, the environment there is safe, so again, no explosion will happen. The problem is that signal lines connect the field area to the control room, and this can allow unsafe electrical sparks from the control room to reach the field area. Therefore, it’s necessary to have a barrier between the field area and the control room to prevent the transfer of energy – this is the function of a safety barrier. Explosion-proof instruments enclose their circuitry within a thick metal casing; the circuit itself isn’t safe, but when sparks are generated, the explosion is contained within the casing, preventing it from causing an explosion in the surrounding area. This provides explosion protection. However, once the casing is opened, such as during maintenance, the explosion-proof capability is lost. Thus, their level of safety is lower than that of intrinsically safe instruments. It can be seen then that intrinsically safe instruments cannot provide explosion protection without a safety barrier, while explosion-proof instruments, since their circuits aren’t intrinsically safe, won’t see any benefit from having a safety barrier either, making it redundant.

It’s useless. Only intrinsically safe instruments use isolation barriers to separate the circuits in hazardous areas from those in non-hazardous areas ； For intrinsically safe instruments, on-site installation and operation are subject to strict requirements and must comply with relevant standards. It has nothing to do with the isolation barrier.

Explosion-proof and intrinsically safe types are used differently; explosion-proof instruments do not require intrinsically safe equipment.

There is no point in using a safety barrier. If the site allows the use of intrinsically safe instruments instead of flameproof ones, then what is the need for a safety barrier?

j’s opinion on upstairs in-s-n is completely correct! ! An isolation barrier is actually a type of safety barrier; it utilizes an isolation transformer in its structure, which is why it is called an isolation barrier. In intrinsically safe circuits, even though the field environment may be explosive, the circuit itself is intrinsically safe, so no explosion will occur. In the control room, although the circuits are not intrinsically safe, the environment there is safe, so again no explosion will happen. The problem is that signal wires connect the field area to the control room, and this can allow unsafe electrical sparks from the control room to reach the field area. Therefore, it is necessary to have a barrier between the field area and the control room in order to restrict the transfer of energy – and this is the function of a safety barrier. Flameproof instruments enclose their circuitry within a thick metal casing; the circuit itself is not safe, but when sparks are generated, the explosion is contained within the instrument casing, preventing an explosion in the surrounding area. This provides flameproof protection. However, once the casing is opened, such as during maintenance, the flameproof capability is lost. Thus, their level of safety is lower than that of intrinsically safe instruments. It can be seen that intrinsically safe instruments cannot provide flameproof protection without a safety barrier, while flameproof instruments, since their circuits are not intrinsically safe, do not benefit from having a safety barrier either, making it redundant.

Agree with what was said on floor 4; it makes no sense to use flameproof instruments together with safety barriers. Surge protectors are generally installed on flameproof instruments

Regarding the statement that \"However, since the circuits of flameproof instruments are not intrinsically safe, adding a safety barrier does not serve to limit energy, making it redundant,\" I would like to ask you the following: 1. Is the choice of flameproof instruments always due to the fact that their circuits are not intrinsically safe? It could also be because such instruments cannot be designed as intrinsically safe versions (for example, electromagnetic flowmeters, etc.)； 2. The function of a safety barrier is, as you said, to isolate the intrinsically safe environment at the site from the non-intrinsically safe environment in the control room through this barrier, thereby limiting and reducing energy levels and preventing sparks from spreading to the site. When flameproof instruments are used, adding a safety barrier can also serve to limit energy, although it is somewhat redundant, as flameproof instruments are capable of containing the energy generated by explosions within their metal enclosures, preventing explosions from occurring in the external environment. I’m not sure if my understanding is correct; please give me some guidance! :)

The one on the 10th floor is fine. But the statement on the 4th floor that \"it is possible for unsafe electrical sparks from the control room to reach the field\" is problematic: it should be something like this – the safety barrier prevents energy from reaching the field, so that the amount of energy that reaches there is not sufficient to ignite explosive gases. When there is a malfunction or spark in the equipment at the field, the energy of those sparks is not enough to ignite explosive gases; that’s why it is called intrinsically safe. However, the energy required to ignite explosive gases varies, which is why gas groups B and C are distinguished! Instead of transmitting unsafe sparks to the site, how do sparks get transmitted? Intrinsic safety instruments must be equipped with a safety barrier; otherwise, they do not constitute an intrinsic safety circuit. Flameproof instruments cannot be equipped with safety barriers; doing so only has disadvantages and no benefits at all. To use an analogy for flameproof instruments, they are like having a strong structure – internal explosions won’t cause them to break, nor will they allow sparks to escape and trigger external explosions! Safety barriers come in two types: Zener and isolated. There are some issues that cannot be resolved in Zener diodes, and they are caused by the structure of their circuitry itself: their ability to resist interference is poor. Because from the field transmitter to the I/O cards in the DCS, for example, the circuits are continuously connected! There is no “disconnection,” so any interference at the site is transmitted into the system. This is also why, during the 1990s when DCS systems were widely used, unexpected malfunction problems often occurred; it wasn’t that the quality of those DCS systems was poor, but rather there was too much interference. One drawback is that there are serious issues with grounding; it is not possible to completely isolate the ground at the site, resulting in a problem with two grounds. In 2000, I was involved in diagnosing DCS issues at many refineries, analyzing complex and difficult problems; it was challenging to arrive at convincing solutions. It’s also difficult to find a solution. Isolated safety barrier: It is usually isolated by a transformer; the circuit is \"disconnected\" from the field to the control room, so that excessive interference from the field cannot reach the DCS. Since the widespread use of isolated safety barriers, many unexplained malfunction problems in the control room have significantly decreased. This is also experience gained by thinking about things in reverse after later using isolated safety barriers. One example will suffice to illustrate this: everyone has used thermocouples, right? The structure of the measuring end (temperature-sensing end) of a thermocouple comes in insulated and grounded types; in fact, the grounded type is connected to the ground at the installation site. The shell-connected type has a faster response speed than the insulated type. If a shell-connected type is used, an isolated safety barrier must be employed; using a Zener barrier will inevitably lead to the problem of two-point grounding, which cannot be avoided. Therefore, it is recommended that everyone use isolated safety barriers as much as possible, and avoid using Zener barriers. I hope the above will help everyone understand the issues related to safety barriers.