Is it necessary to equip positive-pressure explosion-proof cabinets with pressure switches for interlocked power shutdown?
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The PLC cabinets installed on site are of positive-pressure explosion-proof type. May I ask: 1. Is it necessary to install a pressure switch for these cabinets, so as to cut off the power supply to them in case the pressure of the instrument air is low? 2. Are there any relevant standards or specifications that address this issue? 3. If a pressure switch interlock for power shutdown is installed, how should the potential production disruptions caused by power loss when opening the switchgear door be addressed? Thank you!
This post was last edited by Niumiu on 2019-8-9 at 11:55. 1. Check the relevant provisions in GB 3836.5-2017. 2. Positive-pressure explosion-proof designs do not allow the cabinet doors to be opened while the equipment is powered on; if both safety and production needs to be taken into account, consider adopting a \"three-out-of-two\" approach. However, most of the instruments in positive-pressure explosion-proof cabinets are analytical devices, so they probably have little impact on production
The on-site PLC cabinet is designed as a positive-pressure explosion-proof type, with process control, monitoring, and interlock functions. What does three-out-of-two mean?
Aren’t you still worried that a power outage could affect production? Use three pressure transmitters to measure the pressure inside; two of them will indicate low pressure, at which point the system will shut down as a safety measure. This reduces the likelihood of false alarms compared to using just one transmitter
It would be sufficient for the manufacturer to provide a bypass switch; during maintenance, it can be set to the bypass position, as turning off the power is indeed troublesome.
It is certainly necessary to consider relevant safety measures. Wind pressure interlock power shutdown is the common practice