Appendix F tank - Converting PSI to mmH2O

[Syahar1975]

Dear Tank Buiders,

A tank designed as per appendix F has an internal pressure 0.5 PSI.

We have to air tested this tank as required. We are planning to use a water manometer to measure the air pressure above the hydrotest water.

From google we have 0.5 PSI = 351 mmH20.

Is the above equation still remain the same for ambient temperature 30 Celcius.

Or there is an adjustment factor to be considered.

Syah

 

[16548613513]

0,5 psi = 351 mmH2O is the at 4°C
4°C is the temperature of maximum density of water.

Osman YOGUN
Storage Tank and Dome Roof Designer

 

[IFRs]

The density of water changes with temperature and with impurities.
To get 0.5 psig the height of the column of water in the manometer will vary with the density of the water, although the difference may not be significant. At 30 Degc the density of pure water is 0.99669 instead of 1.000 at 4 DegC. The difference is about 1 mm of water column. A larger variation may be seen in the density of the water based on the lack of purity. For this number you'd want to actually precisely weigh a precisely known volume of water. Again this may not be significant, for instance sea water weighs 1.02 to 1.03 times as much as pure water. This would change the manometer from 351 to 362. Rather than split hairs, if you test at 370 mmH2O you should be conservative.

 

[Syahar1975]

Dear Osmanyugun / IFRs,

Thanks for the explanation.

Syah