Useful Information
Volume And Buoyancy
Net buoyancy is obtained by subtracting the weight of the float itself from the gross buoyancy. Refer to the buoyancy formula to the right.
The weight of water at maximum density at 39.1°F., is generally taken as 62.425 lbs. per cubic foot. The figure 62.5, while approximate, is commonly used. The weight of water per cubic foot varies with temperature, from 62.42 lbs. at 32°F. and 62.30 lbs. at 70°F. to 59.76 lbs. at 212°F.
At the temperature corresponding to the commonly used saturated steam pressures the weight of water varies considerably. At 25 lbs. gauge pressure the weight is 58.36 lbs. per cubic foot. At 50 lbs. pressure weight is 57.40 lbs.; at 100 lbs. pressure, 56.02 lbs.; and at 150 lbs. pressure, 54.95 lbs.
>For steam pressure service, calculations of gross buoyancy should include a factor for the weight of water at the maximum operating pressure and temperature. For liquids other than water the effect of the specific gravity should be included in calculations of buoyancy.
Since buoyant force depends on the weight of liquid displacement and not directly on the pressure, it makes no difference whether the float is submerged far below the surface or not, provided the float has sufficient strength to withstand the compression pressure without distortion.
