Questions regarding cable selection
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This post was last edited by The project’s progress on 2022-1-18 at 12:09. It concerns the cable for the limit switch of the valve; the limit switch is of PNP type. When bidding for the overall project, KVVP4*1.5 was chosen as the cable type. Since a large quantity of such cables was required, multi-core control cables were used for the valves. Now that the construction drawings are being prepared, I’ve reviewed previous posts and am hesitating about whether it’s necessary to add additional screens to the main computer display Also, the electrical interface for the valve limit switch is generally a 1/2’’ NPT interface, right? Can anyone find out what the outer diameter of ZR-DJYJPVRP2*3*1.5 is?
Actually, a 4-core cable can be used, and there is generally no interference. For this electrical connector, imported products usually use 1/2’’ NPT connectors, while domestic products tend to use M20×1.5 connectors; it’s not certain, so ask the manufacturer
Okay, this connector is fine for multi-core control cables; but for computer cables, the cable needs to be thicker
Is this the NMAUR signal? Then there’s no need to hesitate – not only does it need to be replaced with DJYPVRP, but it also has to be intrinsically safe. To understand the meaning of dividing the screen into sections, it’s because analog signals are prone to interference. The electrical interface is actually a standard issue; you should first ask the owner if there are any unified requirements. If not, efforts should be made to standardize it within this project as well.
Q1: Is it necessary to change the computer’s main screen to a split screen? A1: It’s not necessary. Although the standards specify that multi-core cables should be used for instrument signals, with a split screen and a summary screen being preferred, this is because the feedback i signal from the instrument positions is of digital type, and there are generally no high-voltage currents or solenoid valve inductions in the field. Q2: The electrical interface for the valve limit switch is generally a 1/2’’ NPT interface, right? A2: Generally, one signal corresponds to one electrical interface, but there are also cases where they share the same interface, depending on the company’s requirements or the manufacturer’s product design. For interface types, there are M, NPT, G, and many others; here we standardize on NPT (you can search on Baidu to learn about its advantages and disadvantages). As for the size to choose, it depends on the thickness of the cable, and whether it is armored depends on whether the cable is armored. You can also refer to HG21581: What is the outer diameter of HK105 Q3:ZR-DJYJPVRP2*3*1.5? A3: It is recommended to consult the supplier of the cable, as there can be slight variations from one supplier to another. Due to a change in position, I lost a lot of documents for confidentiality reasons; the data I have available is as follows: 12*2*1.5, with a diameter of ~35.4 mm ； 8*3*1.5, diameter~29.4mm ； 1*2*1.5: diameter ~9.3 mm; 1*3*1.5: diameter ~9.8 mm; 24*1.5: diameter ~21.7 mm. If the branch is armored, an additional 2 mm should be added roughly. Theoretically, 2*2*1.5 can also use 1/2 NPT, but 3/4 NPT is recommended (after checking the outer diameter of the cable, confirm with the fitting manufacturer whether it fits). Other questions: 1. Why does the general contractor choose 2*3*1.5? Generally, for DI signals, 2 cores are sufficient, that is, 2*2*1.5 is enough. Other question: Generally, using 4*1.5 or two 2*1.5 connections depends mainly on cost – the former costs 8.49 yuan per meter (depending on copper prices), while the latter costs 2*5.06 yuan per meter; in terms of installation costs, it’s 5.52 yuan per meter for the former and 2*5.52 yuan per meter for the latter (estimated costs).
The PNP output should be a high-low level signal, right?
Question 1: It’s not the general contractor who needs to make the changes. This switch output uses a three-core cable, and I want to replace it with a computer-based split-screen and master screen setup using multi-core control cables