Can cables be mixed?
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To add eight cut-off valves, can the solenoid valves and the cables for the feedback signals be placed at the site using a single 48-core cable? Will this have any impact?
For valve position feedback, you need to check whether it is intrinsically safe; if not, it’s just a difference between DI/DO, and I don’t think there’s much of a problem. By the way, isn’t a 48-core cable too thick? It’s better to use a cable with a diameter of 1.5 mm or more for solenoid valve signals. If it is intrinsically safe, it is best to route it separately according to the specifications.
The power supply and other signal lines need to be isolated, as this 48-core cable is unshielded, and the power cable for the solenoid valve can generate electromagnetic interference.
The solenoid valve of the cut-off valve, as well as the switch feedback signals, are all digital signals and power voltage signals; therefore, using a multi-core cable poses no problem. However, such cables can make maintenance more difficult in the future. Over time, the markings on the individual wires of the cable become hard to see, and this is even worse if the wires of the multi-core cable are all the same color. If there is a need to identify the wires or if a fault occurs, it will be very difficult to locate the source of the problem. Therefore, it is recommended to use separate cables for wiring; if that is not possible, it is essential to label each connection with its corresponding wire number.
It was initially designed to use 24 cores to control 4 switch valves; a 48-core box would be too large. All cables are twisted pairs, and it comes with a main screen as well as sub-screens.
There should be no issues with digital feedback, as the cable trays are separate. A similar solution was used before to reduce costs; now a terminal conversion box has been installed. There is dual shielding from the cabinet to the box, with dimensions of 24*2*1.5, while there is single shielding from the box to the instruments, with dimensions of 2*1.5. It’s quite convenient to repair.
According to Code for Electrical Design of Civil Buildings JGJ16-2008, 24.9.6: For ordinary control cables with a conductor cross-sectional area of 1.0–1.5 mm2, the number of conductors should not exceed 30; for armored control cables, this limit is 24 conductors.
The wire diameters of the solenoid valve and the feedback wire are different; it is best to lay them separately. Generally, it is not designed to have a single cable run.
It is best not to use the same cable for control lines and signal lines; however, this has little impact on the feedback signals of on-off valves, but it has a significant effect on control valves. The feedback from the cut-off valve is fine.
First, it is necessary to calculate the voltage drop in the solenoid valve circuit; if the voltage loss is too large, it can cause the solenoid valve to operate improperly.