3 replies to this topic

[zatish]

Can anyone suggest how to determine venting requirements for atmospheric water storage tanks (below ground and above ground). API 2000 is exclusively for petroleum products I guess!! So this query!
Thanks and Regards

[ankur2061]

Zatish,

Your guess is not correct. The normal and emergency venting requirements as given in API STD 2000 for Atmospheric & Low-Pressure storage tanks is applicable to other liquids with a small rider that is given in the scope of the standard. It says and I quote:

This International Standard is intended for tanks containing petroleum and petroleum products but it can also be applied to tanks containing other liquids; however, it is necessary to use sound engineering analysis and judgment whenever this International Standard is applied to other liquids.

Without causing any alarm it simply means that the physical properties of liquids other than petroleum liquids need careful evaluation while applying this standard. If we consider water, the vapor pressure of water is definitely lower than that of petroleum products such as crude oil and motor gasoline at the ambient temperature range. Vapors from petroleum liquids will cause a flammable mixture with air between the lower and upper flammability limit thus necessitating the requirement of inert gas blanketing in the tank. The same is not applicable for a mixture of air-water vapor. Another example would be that for petroleum liquids storage in atmospheric tanks the atmospheric vent would require an in-line or end-of-line flame arrestor to prevent flame propagation as explianed in API 2000, but it certainly would not be required in the case of a water storage tank.

The methodology for calculating the inbreathing (liquid movement out + thermal inbreathing) and the outbreathing (liquid movement in + thermal outbreathing) will remain the same as given in API STD 2000 irrespective of the liquid.

For emergency venting also the methodology for calculating the emergency relief rate will remain the same except that in this case the latent heat of vaporization of the stored liquid comes into the calculation.

To conclude, you can use the venting calculations given in API STD 2000 for the purpose of a water tank also.

Regards,
Ankur.

[proinwv]

While the standard was written for petroleum products, the Scope acknowledges other liquids. Have you reviewed the standard and its assumptions?

If you look at the equations, you will first see that in and out breathing is based upon displacements.

Thermal considers latitude and insulation.

Emergency considers tank areas, latent heat of evaporation of the liquid, environmental conditions, and molecular weight.

Perhaps other members on this forum will post a reply to your question.

You might also query API to see what they might say. If you receive an answer, kindly post it here.

[zatish]

Thank you Ankur and Paul.
Ankur, I could locate the excel file you posted sometime back. It's very useful handy tool.