Two flow meters are installed on one pipeline

Are you not clear as to why two separate flow settings are needed, or why the flow going to the DCS should have a certain quality while the flow going to the SIS uses orifice plates? Safety interlock system: (Sensors) For a level 1 safety interlock system, its sensors can be shared with the process control system ； For a level 2 safety interlock system, its sensors should be separated from the process control system ； For a level 3 safety interlock system, its sensors should be separated from the process control system, and different types of sensors should be used.

It’s strange: why is the mass flow rate fed into the DCS while the data from the orifice plate is fed into the SIS? After all, mass flow meters have high precision; if the data from the orifice plate is used in the SIS, wouldn’t it be easier to trigger a cascade shutdown compared to using a mass flow meter?

Instruments fed into the SIS interlock system, in accordance with the design specifications of the SIS system, need to be installed separately from those fed into the DCS system. Instruments involved in interlocking usually have SIL rating requirements; to date, there is no known SIL certification for mass flow meters. Mass flow meters are generally considered to be measuring instruments, and such instruments are typically required to have high accuracy. Typically, the flow rate that enters a SIS is measured using an orifice plate in combination with a differential pressure transmitter. The reason for this is that the orifice plate itself generally does not cause any problems; it is simply a steel plate with a hole in it. Differential pressure transmitters come with SIL certification, and as long as they are installed properly and properly insulated, they usually do not present any issues, offering high reliability.

Oh, come and learn*; the explanation makes sense – thumbs up! ! !

This post was last edited by seiluobin on 2015-6-20 at 17:22. If a sensor fails, both the DCS and SIS systems will stop working. That’s why two sensors are used: one connected to the DCS and another to the SIS. However, using two flow meters is rather extravagant; usually, separate sensors are used for parameters like temperature and pressure. Orifice plates are reliable but have slightly lower precision. In many cases, we use orifice plates for regulation while relying on flow meters for indication – in other words, the flow meter serves as an auxiliary device to the orifice plate. I asked those with more experience, and they said that flow meters tend to break easily in the field, and they often need to be recalibrated

Not bad, learning * has been very helpful