Selection of instrument cables
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I’d like to ask if there are any problems with using ZR-KVVRP cables for the signal lines of flameproof instruments. Our company has been using this type of cable for several years now, and no issues have arisen. However, the design institute now refuses to allow its replacement; they insist on using DJYVPR cables instead. What models of instrument cables do others use?
The ZR-KVVRP cable is a control cable with flame-retardant properties, and it is commonly used in applications where flame resistance is required but explosion protection is not a strict necessity. The DJYVPR cable is specifically designed for the transmission of instrument signals in explosion-proof environments. This cable is not only flame-retardant, but also offers superior anti-interference performance and mechanical protection, making it more suitable for use in environments where flammable and explosive gases may be present. If your application environment truly requires high security standards, including explosion protection, then it may be more appropriate to follow the design institute’s recommendation and use DJYVPR cables. Although there have been no problems using ZR-KVVRP cables in the past, from the perspective of improving safety and preventing potential risks, it is a more prudent choice to opt for specialized flame-retardant cables. When selecting instrument cables, it is recommended to carefully examine the requirements of the specific application environment as well as the relevant performance specifications of the cables, in order to ensure safety and reliability. .
Personal understanding: For ZR flame retardancy, it needs to be determined based on the area; information can be found online. There are distinctions between areas that require flame retardant types A/B/C – type C is generally used for instruments, while type B is sufficient for areas with high levels of risk. KVVRP: Copper core, soft PVC insulation, shielded. DJYVPR: Twisted-pair construction with polyethylene insulation and shielding; it is soft in nature. For general-purpose instruments requiring interference resistance, twisted-pair cables should be used. Both materials can generally be used for instrument cables.
Was it supposed to be replaced anyway? Then it makes sense to replace the DJ cable; its interference resistance is generally better.
The insulating materials differ slightly; otherwise, everything else is the same
KVVRP is a control cable, while DJYVPR is a computer cable. In early projects where requirements were not strict, KVVRP was used in circuits such as solenoids where signal interference was not a major concern. Over the years, computer cables have been commonly used for instrument signal cables. The interference resistance of the shielding in computer cables is superior to that of control cables (computer cables can have both individual screening and overall screening, whereas control cables only have overall screening). The price difference between the two should not be significant; it is recommended to follow the requirements of the design institute.
Article 7.2.1 of HG/T 20512-2014 \"Code for Design of Instrument Piping and Wiring\": Instrument signal cables should preferably be flexible cables with multiple copper cores, polyethylene insulation, PVC sheathing, and shielding.
In fact, for ordinary analog current signals or digital signal, KVVRP is sufficient; for voltage signals or communication signals, the latter can be chosen. There’s no need to use DJYVPR
When designing, we use computer cables for instrument signals; one reason is their good resistance to interference, and the other is that chemical industry standards require the use of twisted pairs, which must be taken into consideration during the design review process. So, computer cables are generally chosen. Sometimes, for small projects in boiler rooms, in cooperation with the manufacturers, the cables provided by those manufacturers are all control cables, and it is said that they can also resist interference in terms of performance.
1. First, the design institute must carry out the design in accordance with the standards: JB/T 13486-2018 for computer and instrument shielding cables；
Both KVVRP and DJYVPR are flexible cables with multiple copper cores, polyethylene insulation, PVC sheathing, and shielding; in my opinion, the main differences lie in the way the overall shielding is divided when there are multiple cores, as well as in their voltage tolerance levels