Is it necessary to install a safety barrier for flameproof instruments when they are integrated into a DCS?

In the chemical industry, especially in environments with flammable and explosive gases, flameproof instruments can indeed enhance on-site safety. However, when the signals from these instruments need to be transmitted to the DCS system, installing safety barriers serves as an additional safety measure. This is primarily done to limit the amount of electrical energy and signal strength that can be transmitted from the DCS system to the field, thereby preventing any hazards caused by exceeding preset thresholds. Although flameproof instruments have built-in explosion-proof capabilities, the function of a safety barrier is primarily to isolate and protect, ensuring that even in the event of a failure within the system, it will not cause an explosion in the external environment. Therefore, from the perspective of maximizing safety, it is reasonable for the client to require the installation of safety barriers inside the DCS cabinet. As for the specific regulatory requirements, although you mentioned that no relevant standards could be found, in practice, it is always recommended to follow those that comply with the International Electrotechnical Commission (IEC) or other relevant safety standards. Specifically, reference can be made to the design and installation requirements for explosion-proof electrical systems outlined in the IEC 60079 series of standards. It is recommended to communicate further with the owners to find out whether their requirements are based on specific safety standards or previous safety assessment results. .

I want to know what the basis is, whether there are any standards, and if I made a mistake in the design.

Generally, only intrinsically safe instruments require a safety barrier, while ordinary flameproof instruments do not need one. But adding a partition fence doesn’t affect usage, and it can also protect the card holders. This is something that homeowners can do at will if they have the money; there are no regulations prohibiting its addition, and it’s not necessary in terms of design, but it can be added if the homeowner requests it.

This post was last edited by qugd on 2024-4-29 at 15:33. This matter should be discussed in detail with the user. The hazardous area classification should be Zone 1, as flame-proof instruments are used; to ensure the safety of the signals and instruments, an isolation barrier is sufficient. However, the reasons why the user requests the addition of safety barriers should be clearly discussed with the user. If flameproof instruments are used on-site, but the output signal may be an intrinsically safe signal, it is understandable and appropriate to install a safety barrier in the signal circuit in such cases. If it’s merely to ensure a certain level of safety, then using safety barriers without inertial instruments seems a bit excessive. Given the environmental conditions in the area mentioned by the poster, it’s really not necessary to use intrinsically safe instruments. Of course, if users are treated as gods, replacing the isolation barrier with a safety barrier doesn’t cost much. As long as the users cover the expense, the safety barrier can be installed, and they should be informed that the cables also need to be replaced with intrinsically safe cables to ensure proper operation. All two-wire instruments should be upgraded to intrinsically safe versions, and four-wire instruments should use intrinsically safe output types. Additionally, safety barrier cabinets and terminal boxes must be added to ensure reliability.

It’s all money involved; the owner didn’t mention this when signing the contract, and now they want to add it – that will only increase the costs.

Everything that does not violate the principles shall be done as Party A’s boss dictates； In cases where principles are violated, actions must still be taken in accordance with the principles; however, prior agreement with Party A is required.

As for the design aspect, your proposals must be in line with the design; if the design documents require certain elements to be included, then you need to add them when preparing your proposals. Generally, they are safety barriers or isolation barriers. If it wasn’t added during the design phase, then the customer has to add it now, at an extra cost.

Intrinsic safety is achieved by limiting the electrical energy that reaches hazardous areas. Intrinsically safe instruments installed on-site are powered with energy-limited supply to ensure their proper operation. Unlike intrinsically safe instruments, such as flameproof instruments, whose power supply requirements do not meet intrinsically safe standards, these instruments may not function properly if they are connected to the DCS via safety barriers. However, composite explosion-proof instruments with an explosion-proof enclosure and a intrinsically safe core are acceptable.