2010 requirement for Relief valve on all Wet systems 3

[Cidona]

The 2010 edition of NFPA 13 has section 7.1.2.1, which states 'Relief valves will be required on all wet pipe systems that do not have auxilary air reservoirs. Previously, they were only required on gridded systems. The size of the relief valve was increased to 1/2" and the relief valve now needs to be listed'.
I thought I heard that the reason for the relief valve on all wet systems was because there was something in there that was going to require that the air be expelled from the system when filling. And that therefore due to the lack of air in the system to act as a cushion for the expansion and contracton with temperture flucuation, that the relief valve was now required.
However, I can't see anything in '10 requiring any provisions for removing air from the system. 8.17.4.2.4 allows the inspectors test anywhere after the WFS, so they're not trying to enforce it that way. Anyone see anything more in this regards?

 

[pipesnpumps]

Very interesting topic.. Now the obvious question is what makes the pressure go that high? I just can't wrap my brain around that..

If the pressure were uniformly high you could say the evolution of gasses from MIC pressurized the system over time.. but that can't be it, because in the cool evenings the pressure drops back down..

It has GOT to be something related to the difference in solubility of gas at high and low temps... Maybe CO2.. The CO2 breaks out of solution in the heat of the day and dissolves back at night.. It would be interesting if you could somehow capture the water under pressure and check to see what the level of CO2 is.. I'm sure at some point the inside of a pipe goes anaerobic due to bacteria, and has dissolved CO2...

That would explain this issue. You heard it here first folks.. Don't steal my theory, if it turns out to be true I want to be an SFPE fellow for my contributions...

 

[FFP1]

No MIC problems with many/most of the systems which I have resolved the excessive pressure problems due to the trapped air pockets........relatively clean and smooth interior surfaces in most of the systems (minor scale accumulation in a few of the systems, but not MIC) when I have completed internal inspections in addition to removing the trapped air. Removing most of the trapped air has resolved the excessive pressure problem in every instance (100%).

 

[spkreng]

the whole problem would be resolved if an inclution to the code (13) was that wet pipe systems shall have a high point venting relief valve, mostly stick a sprig before you exit the stair/valve room with a AGF drain/relief valve replacing the test drain, areas with multipule high spots, i have always listed tee's to be plugged for venting while filling so much so i don't even think about it anymore, as to how they are installed....don't know, just know my fitters install them whether they use it?????