Many questions regarding the selection and application of isolation barriers
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Do people use more safety barriers or isolation barriers? What are the brands? How is it being used? Should the barrier be domestic or imported? Which one? How is it being used? MTL and P+F come in floor-mounted versions, which facilitate wiring; however, some people say that once the floor plate is damaged, all the isolators on that same plate cease to function. Should everyone use a baseplate type or a rail type? How is it being used? Regarding temperature isolation gates, there are those with temperature compensation functionality and those without it; each has its advantages. The advantage of those with temperature compensation is uniformity among DCS cards, but some people find it troublesome to program the isolation gates using a laptop. Isolated grid DCS with temperature variation requires a temperature card. Which of the two methods will everyone use? How do you feel? Also, regarding intrinsically safe systems, what do the standards say about thermal resistance and thermocouple signals? In theory, intrinsically safe systems are designed to limit energy levels, but thermocouples and thermal resistors have very low amounts of energy at the field level. Is it to prevent large-energy signals from being mistakenly introduced to the field area indoors? This possibility is very small. It seems that for thermocouples and thermal resistors, explosion-proof designs used on-site are sufficient, but people generally use isolation barriers – is there really any need for that? This post was last edited by Changfeng Jiwanli on 2009-3-30 at 11:39.]
The certification system for safety barriers in imports is relatively well-established. In China, such systems exist as well, but it’s unclear whether they actually work or not
For design purposes, track-type safety barriers are selected, with imported brands such as MTL, P+F, and Ubil. Domestic ones are very cheap, so I don’t dare to use them. There are thermal resistors, thermocouples, and digital signal safety gates, but they are generally not used. As the original poster said, the signal is relatively weak; it is sufficient to choose an explosion-proof rating that meets the required standards. If a temperature transmitter is used in an explosion-proof area and operates in an intrinsically safe circuit, a safety barrier must be installed. If an explosion-proof type of instrument is selected, a safety barrier is not required.
1. For our factory, important or hazardous production equipment generally uses imported isolation gates, MTL, or P+F； There are more options with Zener gates (domestically produced), and their performance is fairly good. 2. There were problems with the Zener gates; due to grounding issues, an entire batch of Zener gates failed, which had a significant impact.
1. Our company uses safety barriers of various brands, including both domestic and imported ones. Among the domestic brands are the Xiyi 5362 series and those from Yueqing, while among the imported brands is P+F. The safety barrier is performing well. 2. Zener-type safety barriers from P+F should be used with caution; poor grounding can lead to the failure of the entire system. 3. For temperature isolation barriers, it is best to use those with temperature sensing capabilities, as this facilitates unified signal handling. 4. As required by the specifications, thermal resistors and thermocouples also need to use isolation barriers; however, in practical applications, they are often connected directly to the DCS terminal blocks, without the use of safety barriers or isolation barriers.
1# Over thousands of miles of distance… Does the thermistor signal enter the control cabinet directly through the thermistor safety gate, or does it first pass through a temperature converter before reaching the safety gate and then entering the control cabinet? Please help answer this question.
The thermistor signal enters the control cabinet directly through the thermistor safety barrier; there are too many such connections here
7# olala-1: Could you explain the specific wiring method? The correspondence between the signal inputs and outputs and the safety gate interfaces.
Our company uses both safety barriers and isolation barriers, with some being imported and others domestic. The imported ones are mostly of the MTL type, and they perform well; we have only had to replace a few of them over 4 or 5 years. Among the domestic products, those made by Beijing Weisheng are of good quality as well. Last week, during maintenance, one of these barriers was taken apart and turned out to be defective – it had been manufactured in 1997! 12 years of use is definitely worth it. . . . For 5 cabinets, in total, less than 20 replacements were made! We generally don’t use Zener types; they are disposable and troublesome to keep as spare parts. . . All use isolated type
It is recommended to choose models that are mounted on DIN rails; P+F offers power supply boards that can be installed directly on DIN rails. By placing power modules at both ends of such a board, power redundancy is achieved, and the hassle of wiring for the safety gate’s power supply is avoided. It is recommended to choose a type with temperature sensing for the temperature control; although the safety barrier also needs to be configured during setup, the I/O cards can all be set to 4–20mA, which facilitates flexible configuration of these cards. Generally, the project design phase in China is not thorough; additional modifications are necessary during debugging, and these modifications are often quite extensive. Therefore, flexible adjustment of components becomes very important.
I’ve seen both of these connection methods; it depends on the specific requirements
The costs of these two methods are roughly the same. I think it’s best to use a thermal resistance clip directly, without needing a thermal resistance safety barrier. Because using a thermal resistance safety barrier is equivalent to adding another wiring point, which creates an additional potential point of failure.
Whether using a baseplate mounting method or a wiring method, it is not advisable for multiple safety barriers or isolators to share the same protective device (fuse or circuit breaker).
Additionally, many safety barrier configurations now come with functions for open-circuit and over-limit output settings, and similar options are available in DCS card configurations as well. In practice, it is important to avoid duplicate settings to prevent confusion. It is recommended that such settings be made in the DCS, as this makes it easier to locate faults when problems arise. After all, it’s quite troublesome to have to use a notebook, a communication cable, and then connect to the safety barrier to check its settings.
I think safety barriers with a base plate are good; our factory uses them a lot, and there have been hardly any problems with them.
In my opinion, safety barriers and isolation barriers are pretty much the same; those imported are slightly better than domestic ones, but paying such a high price for that slight improvement isn’t worth it. Domestic products that have passed the Nanyang explosion-proof certification are generally sufficient for use, and our factory uses only domestic products. A few of them generate a lot of heat, but since they are located in control rooms where air conditioning is always on, it’s not a big problem. Our company mainly uses central control systems, but most of these systems are OEM products; we haven’t found out which specific company manufactures them! It is recommended to use guide rails, as it is more convenient. As for whether temperature sensing should be included, it depends on whether it is a new system being installed and whether such functionality is needed based on the operating conditions. If it is a new system and the site does not have strict explosion-proof requirements, it is advisable not to add temperature sensing, as it would introduce an additional point of failure. Intrinsic safety barriers are designed primarily to prevent other electrical signals from being transmitted to control cards or to the field via resistive signal cables, due to factors such as interference or lightning strikes
I would like to ask whether the MTL5541 analog input safety barrier can be used for four-wire analog input signals as well, in addition to being used with two-wire transmitters