Abstract: A new method and apparatus is described for conducting an integrity test on porous membranes and membrane filters and for conducting a pore-size characterization of membrane. The method and apparatus apply to membrane integrity tests and pore-size characterizations which are based on the dependence on the pore size of the pressure required to intrude a non-wetting, electrically conductive liquid into and through the pores. Electrical-measurement methods are described for identifying the pressure at which intrusion occurs.

Abstract: A muffler for a percussive drill is provided consisting of a casing of general prismatic shape adapted for mounting on the drill. An inlet is present in the casing for receiving exhaust from the drill, the drill exhaust port and muffler inlet having the same cross-sectional area. Resilient rectangular baffles are mounted within the casing and are rigidly fastened at two opposite edges to the casing wall. The two other edges, which are longer than the fastened edges, are in contact with casing walls. Staggered holes are present in the baffles, so the gas flow through the muffler follows a sinusoidal path. The sides of the casing tapers down after the last baffle to a fraction of its height and then extend for a given length at the lessened height to form a narrow rectangular exhaust port. One face of the casing adjacent the exhaust port consists of resilient sheet material. The flow of gas through the muffler causes strong vibration of the baffles and resilient face near the exhaust port.