Several issues regarding the protective pipes composed of flexible pipes and galvanized pipes
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Let me share my opinion first; feel free to criticize or correct me: 1. In intrinsically safe systems, it’s okay if there is no sealing gasket at the joint between the flexible tube and the instrument, as galvanized tubes don’t necessarily need to be completely sealed. Sometimes, to prevent water leakage, I add a tee between the flexible pipe and the galvanized pipe; the flexible pipe exits from the side, with the drainage exposed below. Is this in compliance with the regulations? 2. In the flameproof system, I used sealing rubber rings at the instrument inlet; can the protective tube section also be made as described in the first point? 3. Armored cables must be used for sealing with flanged connections; explosion-proof flanges are required on the instrument side. Explosion-proof flanges are not necessary for the ends of galvanized pipes – ordinary flanges can be used, or those ends can simply be sealed with mortar. In short, I think that no matter what type of explosion-proof system is used, as long as the wiring compartment of the instruments is properly sealed and isolated, there is no need for such strict sealing in the protective tubes running from the cable tray to the instruments.
For explosion-proof systems, as long as the wiring compartment of the instruments is properly sealed and isolated, I agree with your view; the flexible tubes in intrinsically safe circuits are mainly used for protection purposes.
It is still necessary to follow the relevant regulations; there are things that, even if they are possible, cannot be done if they do not comply with the standards.
This post was last edited by yu*nyang_01 on 2017-8-5 14:11. I think the current approach might not be appropriate Must electrical and instrumentation wiring in explosion-hazardous areas be enclosed in steel pipes? If it’s to prevent baozha* gas from entering, then how can we explain the cable trays in that area?
Then I’ll complain. 1. Intrinsic safety also requires a sealing ring; otherwise, can it be waterproof? Its explosion-proof connector also has a water resistance rating. The specifications allow the use of tees, but generally no one does this in the field. 2. The protective tube needs to be safeguarded; otherwise it will wear down the cable. It’s generally better to use a waterproof connector, and protective cable caps can also be used. 3. Discontinuous protection does not require armored cables, but armored cables are generally accepted for use. Galvanized steel pipes generally do not require sealant; it’s just a way to cover things up.
In intrinsically safe circuits and flameproof circuits equipped with sealing gaskets, instruments are connected via flexible pipes, galvanized pipes, flameproof elbows or tees to the cable tray. In such a structure, could the removal of the cover on the elbow or tee, or the absence of sufficient screws, affect safety? Is it incorrect to use a tee between the flexible pipe and the galvanized pipe, with the third port of the tee left unblocked for drainage?
How do the experts handle wire protection in instruments?
I think you’ve done the right thing. What truly provides explosion protection (for flameproof types) or water resistance (for intrinsically safe types) is the gland that connects directly to the instrument; the flexible hoses, conduit pipes, tees, elbows, and similar components serve only to protect against mechanical damage. Is it incorrect to use a tee between the flexible hose and the galvanized pipe, with the third port of the tee left unblocked for drainage? ” That’s exactly how the self-control installation manuals are structured; the only difference is that the tee has an additional plug, and water is drained only when needed, while it remains in a fully sealed state at other times
When installing flexible pipes, connecting the instruments from bottom to top prevents rainwater from flowing back into the instruments through the flexible pipes; moreover, a tee should be used between the flexible pipe and the galvanized pipe
The main function of flexible pipes and galvanized pipes is explosion protection; it is acceptable to disregard this function, but if explosion protection is required, sealing is necessary. Sealing theory prevents water ingress