Safety barriers are required for explosion-proof engineering – are there any details to keep in mind?
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Safety barriers are required for explosion-proof engineering – are there any details to keep in mind? In terms of engineering design, the devices are of flameproof type; all instruments are also flameproof. The signals used are either 4-20mA or 0-10V, or they can be digital signals. The drawings do not provide detailed information regarding safety barriers, with only the following statement: “The instruments in this design are integrated into the DCS system.” In this design, the current signals from the field instruments pass through the on-site intermediate explosion-proof junction box and then to the terminal cabinet in the control room; from there, they proceed through the safety barrier in the system cabinet before reaching the DCS card system. ” Question 1: Is it necessary to use a safety barrier for digital signals? Question 2: Does it mean buying input-type and output-type safety barriers, installing them in the cabinet, with the signal wires going into the safety barrier first and then into the transmitter? Question 3: Are there any particular considerations regarding the installation of safety barriers in the cabinet? For example, are there any restrictions or regulations regarding the installation location? Are there any standards I can refer to?
If it is an intrinsically safe instrument, a safety barrier is not required; safety barriers are designed for intrinsically safe instruments. Current designs are either intrinsically safe systems or flameproof instruments. Intrinsic safety instruments can be opened on-site for maintenance, while flameproof instruments require power to be turned off before any work can be done on them. If you are working on engineering projects, the manufacturers will design the instrument panels or DCS systems for you; there’s no need to go through such trouble. Question 1: Based on your requirements, it’s generally not necessary for a DCS; without it, the output signals cannot be used. Question 2: The safety barrier requires power supply – make sure to pay attention to the input and output terminals; the intrinsically safe terminals are connected to the field instruments, and intrinsically safe cables must be used. Question 3: Older instrument cabinets had larger safety barriers, with dedicated safety barrier cabinets or mounting brackets; for modern DCS systems, space considerations for installation are sufficient. There is no mandatory requirement; it just needs to conform to the general design of instruments.
This post was last edited by txcc1111 on 2015-6-2 at 12:29. 1 First of all, thank you for helping to clarify this. 2 This is strange; I only have the electrical diagrams available, and they don’t specify whether the equipment is of intrinsically safe type or explosion-proof type. The diagrams only state, “13. The explosion-proof electrical equipment used must be products that comply with current **standards, and its explosion-proof rating and group should not be lower than IIAT2.” ” Dozens of the drawings show instruments marked as ExdIICT4, and all the thermal resistors are indicated as being of the flameproof type; therefore it can be determined that they are all flameproof instruments. Does this result in a contradiction in the design? I work in automatic control programming, so I’m not very familiar with chemical process instruments. . The drawings were also designed by a chemical engineering design institute, a reputable one at that; the pilot project for Wanhua Chemical was designed by them recently
I’m speechless; there’s a problem with this drawing. Flame-proof instruments don’t require safety barriers. There are standards; design institutes generally communicate with clients to determine whether to use intrinsically safe instruments or flameproof instruments. It’s not a problem to use flameproof instruments together with safety barriers, but is it really necessary?
This post was last edited by txcc1111 on 2015-6-2 at 12:53. I called to ask; the situation is that the client asked them to do the design and then have it done by us
I called and was told that a safety barrier is no longer required; thank you
Was it designed by the instrumentation department of the design institute????
Indeed, he might have used other drawings as a template and added an extra line; actually, including it doesn’t harm the project, it’s just a waste of money
1. Based on the device’s hazardous area classification diagram, determine the device’s explosion protection rating and select the appropriate type of instruments for use on-site (intrinsically safe or flameproof). Intrinsically safe instruments are required only in Zone 0; in Zones 1 and 2, both intrinsically safe and flameproof instruments can be used； 2. Decide whether to install a safety barrier based on the explosion-proof type of the instruments on site; intrinsically safe instruments must be equipped with a safety barrier, while flameproof signals do not require one ； 3. When using safety barriers, authentication must be taken into consideration, as well as the compatibility between the safety barrier, cables, and field instruments; special attention should be paid to inductive loads in the intrinsically safe circuit.
. . . . Flameproof instruments no longer require a safety barrier. Intrinsic safety systems require a safety barrier