Air meter leakage

[mikeofBelAir]

For Type B Air Meter, how much leakage is acceptable?
I know that as the cir cools, it will lose a little pressure, but after allowing some time for the air to cool, how much leakage is acceptable? If the gauge needle drop 0.1 % in a say 30 seconds, is that OK? Most air meters I see have a little leakage, but 20-30 seconds seems like a reasonable time to run the test.Did i miss something in the Standard?

 

[Ron]

ASTM C231 "Air Content of Freshly Mixed Concrete by the Pressure Method" contemplates only the use of a fully sealed chamber. There is no allowance for leakage. If you have leakage, you need to repair your pressure meter.

 

[mikeofBelAir]

Thanks, Ron,
That makes sense. The big leaks are easy; its the very minor ones that are difficult. I have 3 that don't have any leakage, and one that just has that very slow leak.

 

[darthsoilsguy2]

i don't think most of the industry would notice a 0.1% leak over 30 seconds during calibration. i would think most of the industry would not notice and likewise ignore a 0.1% over 30 secs. i suspect the threshold for noticing leakage is around 0.2% over 10 seconds.

 

[mikeofBelAir]

I found a US government document on air meter calibration that specifies, " Check for pressure loss exceeding 1/2 IPL mark in 90 seconds."

 

[Ron]

Mike...that's probably defensible, but check THEIR sources as well. If you say that you are meeting ASTM standards and those are the referenced standards in the specs, then those are the ones you have to meet...not a nebulous government spec that is not traceable (unless it is, of course!)

 

[mikeofBelAir]

Ron,
Always good advice.
Its amazing how easy it is to get lazy. I constantly remind technicians to "check the Standards". Everyone, it seems wants to have their own method of doing something. They complain that "your" method takes too long/ is too hard/etc. I remind them, it is not "your" method, or "my" method--there is only the method described by ASTM or AASHTO or whatever other agency.
Thanks for the reminder.

 

[labboss]

Mike,

As Ron said. There is no allowance for leakage. I have even had some CCRL inspectors pump up to initial pressure, leave meter on the bench overnight and check the next day. If you are having trouble finding the leak, i have found that if you pump it up, then submerge in water ( say a curing tank or other water bath) you can usually find the leak pretty quickly. Good luck.