Issues with sequentially installing flow meters
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I have seen very few cases where flow meters are installed sequentially on a single pipeline. I met someone really strange recently. Two mass flow meters are installed on one pipeline, and both need to be connected to the SIS; through a two-way safety barrier, the signals are sent to the DCS as well. This is a foreign project that does not use domestic standards, and currently no one in China is involved in the basic design of the instruments and controls; therefore, no inquiries have been made regarding the reasons and purposes behind such settings. The medium is gas; it is estimated that one of them is nitrogen and the other is ozone (not in Chinese or English, translated using Baidu Translate). The pressure is not high, only a few bars. Everyone is welcome to discuss this; it would be great if some experts could provide direct solutions{:3_64:}
Two-out-of-two interlock for flow rate; after division into two streams, it is displayed on the DCS
As a supplementary note, the two function codes are: FIA-(Z) and FICA-(Z)
Just to add here, these two flow meters are connected in series.
I personally think interlocking is the most likely possibility; other options are less likely
However, the function code does not indicate a Z interlock; it can only be seen that it goes into SIS mode
I have encountered a situation where two mass flow meters were installed on one pipeline; both flow meters were connected to the SIS, and one of them formed a flow control loop with the control valve on that pipeline. Two mass flow meters are installed: firstly, to achieve very high measurement accuracy; secondly, so that the two meters can be used for mutual comparison, and to prevent the shutdown of the system in the event of a failure in one of the meters. I wonder what the original poster finds strange?
It seems this is related to the safety level of the instrument loops required by SIS. For example, a instrument may not be able to meet its SIL level.
The original poster has seen little of the world, which is why they find it amazing. Two mass flow meters connected in series within a single pipeline – this is probably very rare in domestic projects, after all, they are quite expensive.
In state-owned enterprise projects, this really isn’t a big deal. A chandelier in such a hall can cost over 10 million – it’s something that people like us can’t even afford to dream of owning. Haha
Perhaps this parameter is very important, so a double safeguard is needed...