Issues regarding the new interlocking logic
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A shut-off valve needs to be added at the outlet of the hydrogenation feed pump to prevent the feed material from flowing into the low-pressure system when the pump stops operating. However, the flow meter at the pump outlet only provides automatic control and display functions; based on the existing flow meter, it is possible to separate flows A, B, and C in order to enable the shut-off valve to stop operating in case of low flow rates； Additionally, if flow interlock cannot be implemented, could it be modified so that the cut-off valve stops operating after both feed pumps shut down simultaneously? Is this reasonable?
The pump shutdown interlock valve is properly designed
Replace the flow meter on the main outlet pipe of the two pumps with an orifice plate, using 4 orifices. One pair goes to DCS, three pairs go to SIS2003. Implement low-traffic interlock.
Thank you for the responses from the two people above. I also think that replacing the flow meter is a complicated process that requires shutting down operations; however, stopping the pumps is simpler – it can be done by feeding the signals from the two pumps into the SIS system. Thank you. Are there any relevant standards or specifications?
1. First, the process interlock function (cause and effect) is proposed by the process engineering team. It should be carried out by the instrumentation team; don’t put the cart before the horse. Don’t take responsibility either. 2. The pump shutdown trigger signal or pump operation can serve as interlock factors. However, pump responses often include glitches or false responses, requiring a delay function block. 3. The interlock circuits for hydrogen feed pumps usually have SIL rating requirements, which may not be met in the above cases. To implement a function, especially the interlock function for critical equipment, instruments, and electrical systems, many factors need to be taken into consideration. It’s not just about connecting one or two wires; it has to make logical sense. 4. And there are many other aspects as well.
Thank you, master. There aren’t that many people in our small courtyard; each task is handled by a single specialist. Hehe, what’s your contact information? I’d like to ask you some questions
Take a look at the previous picture. . . Two pumps, how many flow meters are needed? How many cut-off valves? Are there any control valves such as FVs downstream? Is there an automatic return valve on the pump’s bypass?
Personally, I recommend installing a shut-off valve at the pump’s outlet; as mentioned above, an automatic backflow valve (with check function) would also work.
The interlock for stopping the pump is acceptable and reasonable； This form of interlocking is everywhere.
Shutting down the pump and closing the valves is standard procedure. However, if the status is obtained via communication rather than direct wiring, it is unreliable; false signals can easily occur, requiring a delay element to filter them out. Moreover, if the main pump fails and the backup pump has not yet started, the interlock will activate to close the valve. To reset it, a status signal from one of the pumps is necessary, which can lead to pressure buildup. It is personally recommended to install 3 pressure transducers on the outlet branch pipes and main pipes, with a 2-out-of-3 voting system, and to use the pressure signals for interlock purposes. For reference.
What was said on the 5th floor is correct – the instruments are designed in accordance with the requirements of the manufacturing process and equipment, and one cannot act on their own initiative. In addition, the SIL classification and assessment as well as **some documentation requirements need to be considered. Be careful to ensure that there are no common failure modes in the control circuits and interlock circuits; a single flow interlock is not reliable.