Propane Burner Train Area Classification

[PPerez]

I could use some help on a classification issue. We have a low pressure (30 psi max supply, reduced down to 1-2 psi at the blower unit) propane burner skid with two blowers, flow and pressure control intrumentation, and two burner heads. THe skid has a pressure relief vent at the blower units. NFPA 497 Fig 5.9.2(a) would appear to apply but the box in the figure shows that it is only applicable to medium or high pressure conditions. I can't find any reference or diagram for a low pressure condition.

API RP 500 Fig. 14 and 18 show a 10' radius but the pressures referenced are nearly 300 psi.

This is outdoors in an area with 10mph wind regularly and often times higher.

Any advise? Do the pipe connections (flanges, valves, etc.) even qualify at these lower pressures? Is the system non-classified due to such low pressures?

Thank you in advance.

 

[rbalex]

At low pressures, closed piping even with valves and flanges, usually don?t require any special electrical area classification treatment; however, as a general rule, relief valves and vents that discharge to atmosphere imply at least a modest requirement.

I do recommend reading the text that goes with the various figures you cited ? not only the text in the figures themselves but the Sections they referred back to as well. You will find the figures should be considered a minimum.

Since you referenced API RP500, I suggest you also consider reviewing Appendix D. Read the whole Appendix; it isn?t that long. Give special attention to D.5.6.

 

[PPerez]

Thanks Bob. D.5.6 does help.