Issues with explosion-proof hoses for field instruments
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Hello everyone. To save costs on our project, we are considering removing the explosion-proof metal hoses from the field instruments and replacing them with isolation joints. Is this in compliance with the **regulations? Are there any relevant regulations? Urgent, need a solution. Thank you all for your effort.
We’re often told by experts about these explosion-proof hoses; they never show us any relevant regulations, and they don’t really check whether we have intrinsically safe equipment. In zones 0 and 1, it’s better to use explosion-proof hoses in all cases – otherwise, if the inspection fails, we’ll have to redo the work, which will be a lot of trouble
Explosion-proof metal hoses: 20 or 30 years ago, many instruments followed electrical standards, as those instruments were operated at 220V at that time. Such hoses are consumable items; they get damaged due to exposure to wind and sun, as well as from being knocked, and they are also prone to water intrusion, with holes forming in the lower parts. Nowadays, many instrument valves operate at 24V, so such hoses are no longer necessary. I seem to have seen the guidelines; I can’t find them now. Ask the design institute
I’ve checked many instrument specifications on this issue, and none mention any problems with the gland fittings. Currently, when experts come for inspections, they refer to electrical specifications; the absence of explosion-proof hoses means that the device is considered non-explosion-proof. They don’t take into account gland connections, even though such connections can provide explosion-proof sealing – but the experts ignore this. Therefore, this issue requires the instrument installation specifications to be updated and clarified.
The clear specifications regarding instruments are outlined in the installation manual of HG/T21581-2012. For example, 7.4.8 of GB50093-2013, 8.4.7 of SHT3521-2013, 7.3.6 of SHT3019-2016, and so on; the fundamental standard is GB3836.
There are no issues with using explosion-proof glands; they meet the specification requirements. When in use, just ensure the construction quality of the instrument inlet is satisfactory. The friend on the 7th floor is absolutely right. The so-called experts who come to conduct inspections these days actually don’t understand much. Basically, it’s all about taking things out of context and interpreting the standards in a dogmatic manner; some people don’t even understand the principles behind explosion prevention.