Abstract: A conventional fluid density balance beam measurement instrument used for measuring fluid density at atmospheric pressure is converted for use to measure fluid density at super-atmospheric pressure. The conversion is made without modifying the structure of the conventional instrument. A pressure lid, placed over the open mouth of the instrument's sample cup, is held in place by a removable retaining structure that wraps around the base of the cup. A screw ring at the top of the retainer applies a retaining pressure against the lid. Pressure is applied to the cup through a check valve stem extending through the lid. An adjustable flange on the rim of the lid permits the lid to advance into the cup to change the cup volume for sizing the cup to obtain a precisely known volume for measurement. A counterweight is removably connected to the balance beam to compensate for the weight added by the lid and retaining structure.

Abstract: A replaceable primary rupture disk placed in the main body of a cylindrical test chamber functions as a safety device and ruptures to relieve pressure from the chamber when the pressure exceeds a selected maximum value. A free piston that is moveable within the cylindrical to separate the chamber into two variable volume compartments is equipped with a replaceable secondary rupture disk that limits the pressure differential across the piston. The secondary disk ruptures at a pressure differential lower than that required to rupture the primary disk. The maximum pressure that can be contained in any chamber is a pressure equal to the sum of the secondary and primary rupture pressures. The maximum pressure that can be contained in one compartment, if the other is at atmospheric pressure, is the burst pressure of the secondary disk.