Can one shut-off valve be controlled when the flow rates of the two are low?
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The heating furnace has two feed routes, and the flow rate of each route is controlled by corresponding control valves. There is no flow in the main pipe, but it is necessary to consider the possibility that the transfer pump may fail, resulting in a disruption in the supply of material and causing the furnace tubes to overheat. To prevent the furnace tubes from burning out dry, it is intended to cut off the fuel oil when the flow rate is low. I would like to ask the experts here: 1. Is it possible to use traffic from two channels to achieve control? ； 2. If possible, should it be cut off when one circuit is at a low level, or only when both circuits are at a low level?
A flow meter with two-channel combination can be created in DCS.
Consider using the sum of the flows from the two streams as the interlock signal for shutting down the furnace. However, the original poster could provide more details on the process conditions; are the two streams different types of fuel?
Control can be achieved using two streams of flow, with the fuel oil being cut off via a low-level alarm output. It can be set to cut off only when two channels are at low levels, but to avoid accidents caused by instrument failures, it is more reliable to cut off as soon as one channel reaches a low level. Personal opinion, for reference only....
It can be done within the DCS; it is recommended to set up an alarm for low flow when one channel shows low levels, and a shutdown mechanism for extremely low flow when two channels show low levels.
Dry cooking is absolutely not an option – none of those methods will work; it will lead to serious problems. In mild cases, the tubes might burst, and in severe cases, an explosion could occur. This isn’t a joke. So: 1. It is possible and necessary to use two streams of traffic for control ； 2. The fuel must be reduced or cut off whenever any path is at a low level.
The owner’s setup probably involves a pump that delivers the material, with it going into the furnace through two separate paths; in that case, it’s sufficient to install a flow meter on the main pipe for interlock purposes – if the flow rate falls below a certain value, the interlock will activate and cut off the fuel oil supply.
I think it’s better to install a shut-off valve on the main pipeline and use two flow meters, with a 2-out-of-2 system. If the pump really stops, the flow rate in both pipelines will be low; this 2-out-of-2 system helps to avoid false signals, thereby preventing the shut-off valve from shutting down the pump and causing production to come to a halt!
Add the flows from the two paths together, then trigger an alarm when the lower value is reached; once a low-low alarm is issued, the interlock valve can be shut off
Add the flow values from the two lines; if the flow value is low, shut off the oil inlet valve.
If there are two types of fuel, one being fuel oil and the other being fuel gas, and it is necessary to choose one of them, can a cut-off mechanism be set up for both as well? If so, should two options, A and B, be provided (as a hypothesis): option A is used when fuel oil is utilized, while option B is used when fuel gas is used.