What exactly is the air supply requirement for a positive-pressure explosion-proof box?
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I have a few questions regarding the gas supply for positive-pressure explosion-proof enclosures: I was looking at a sample from SIPAI, and in the technical specifications for the \"positive-pressure explosion-proof dashboard\", it states that the gas supply pressure should be 0.4~0.8 MPa. The gas consumption is listed as 10~20 m3/h when the gas pressure is 0.3 MPa, while the gas usage rate is given as 2~5 m3/h under the same gas pressure. 1. Does the gas consumption need to be adjusted based on the actual gas supply pressure? 2. How should I understand this gas consumption and usage amount? Do I need to supply 20, 25, or 5? 3. This is the gas consumption of the dashboard on the sample. If I use an explosion-proof cabinet instead, will the gas consumption remain the same?
The gas consumption is the flow rate at 0.3 MPa. The gas consumption figures provided by the manufacturers are merely reference values for specific products (values obtained under specific experimental conditions); just like the power consumption figures for air conditioners and refrigerators, they are intended only for reference, and the actual values can differ significantly. It is only meaningful during selection comparisons. There are three important criteria regarding the volume of air required for positive pressure explosion protection: the first is the internal pressure ； The second is the consumption during normal gas supply (positive pressure explosion protection requires ventilation to dilute the combustible gas to below the specified concentration within 30 minutes) ； Third, it specifies the air replenishment volume at the maximum allowable leakage. In fact, as long as the internal pressure is maintained, there are no major issues in achieving the latter two. The positive pressure explosion protection requirement is that the internal pressure must be no less than 50 Pa (Zone 1, Px type) and 25 Pa (Zone 2, Pz type), with a normal maximum of up to 200 Pa. The actual gas consumption is proportional to the internal volume; if it is just a small box, the gas consumption will decrease accordingly. As long as it is sealed as required, gas consumption will not be high.
The gas consumption refers to the amount of gas used to fill the control box when it is turned on; in our case, if this amount falls below the specified value, the system automatically resets and starts filling again. Gas consumption during normal operation refers to the amount of gas used while maintaining pressure after the filling is complete. So I think the gas supply volume should be no less than 10; otherwise, repeated inflation will occur.
I checked another sample for reference: Gas consumption (m3/h), Air exchange rate (m3/h), Air exchange time (min), Operating positive pressure (Pa), Automatic air supply pressure (Pa): 2-8, 10-20, 10-30 (determined by the explosion-proof testing agency), 250±100, <150
So what problems will occur if I supply too much air?
Inflatable explosion protection involves inflating it using a pressure-stabilizing (pressure-reducing) device. The pressure regulator is only responsible for maintaining the pressure; the amount of gas flow depends on leaks – if there are no leaks, then there is no gas flow.