for week of February 7, 2005:
Mud Balance (noun) An API (American Petroleum Institute)-specified apparatus for determining the density of a circulating fluid (mud slurry). The balance consists of a base and a graduated arm with a constant volume cup and lid, knife-edge, rider, built-in spirit level, and counterweight on the opposite end. The mud weight (density) is reported as pounds per gallon (ppg or lb/gal), which can be converted to pounds per square inch (psi) by multiplying ppg x 0.052 = psi/foot, and to hydrostatic head by multiplying psi/foot x column length in feet.