Abstract: A backflow prevention device includes a main pipe body extending along a first center longitudinal axis, at least one check valve disposed within the main pipe body, an inlet pipe connected to an inlet side of the main pipe body, and an outlet pipe connected to an outlet side of the main pipe body. The inlet pipe and the outlet pipe extend along a second center longitudinal axis. The first center longitudinal axis is offset with respect to the second center longitudinal axis in a direction perpendicular to the first and second center longitudinal axes. A center of the valve seat of the at least one check valve is offset with respect to the second center longitudinal axis in the direction perpendicular to the first and second longitudinal axes.

Abstract: A check valve may include: a check seat defining a flow path; a clapper assembly hingedly connected to the check seat and configured to obstruct the flow path, including: a clapper and a seal retainer detachably mounted to the clapper; a first extension extending from the clapper assembly in an upstream direction and having a roller; a cam arm rotatable relative to the clapper assembly and configured to engage with the roller; and a torsion spring operatively connected to the cam arm so as to apply a biasing force to the cam arm in the upstream direction. The biasing force may be imparted to the clapper assembly via the cam arm and roller, so that the clapper assembly obstructs the flow path.

Abstract: A spring stop arrangement for a check valve may include: a check seat defining a flow path; a clapper assembly connected to the check seat and configured to obstruct the flow path, the clapper assembly including: a clapper; and a seal retainer detachably mounted to the clapper; a cam arm connected to the check seat, the cam arm including a stopper; and a torsion spring operatively connected to the cam arm so as to apply a biasing force to the cam arm against the direction of fluid flow. When the seal retainer is dismounted from the clapper, the stopper may be configured to contact the check seat so as to prevent rotation of the cam arm.

Abstract: A circuit and method are provided for detecting a power of a signal amplified in a power amplifier. A diode and a voltage bias source are used to shift a voltage of the signal taken at a base of an amplifying transistor of the power amplifier, to generate a positive signal. The positive signal is provided to a base input of an emitter follower exhibiting high input impedance to generate a power detector output which follows the positive signal.

Abstract: A circuit and method are provided for detecting a power of a signal amplified in a power amplifier. A diode and a voltage bias source are used to shift a voltage of the signal taken at a base of an amplifying transistor of the power amplifier, to generate a positive signal. The positive signal is provided to a base input of an emitter follower exhibiting high input impedance to generate a power detector output which follows the positive signal.

Abstract: A flat-formed arch ring unit includes a linear array of voussoir portions connected along their upper edges. The unit is then archable. A method is provided for forming an archway including the steps of arching one or more the flat formed arch ring units and locating them between two or more foundation blocks or the like. This provides a simple yet effective process and unit for forming an archway. With ease of production, shaping and transportation, making new archways or carrying out repairs of existing bridge archways is significantly faster and cheaper, minimizing disruption and delay to traffic.

Abstract: Method for the recovery of hydrogen and carbon monoxide from a feed gas mixture containing hydrogen, carbon monoxide, methane, and hydrocarbons heavier than methane. The method comprises utilizing a cryogenic methane wash column to recover hydrogen from an intermediate feed stream containing hydrogen, carbon monoxide, methane, and hydrocarbons heavier than methane, wherein the methane wash column utilizes a methane wash stream which contains less than about 5 mole % of hydrocarbons heavier than methane, and wherein the methane wash stream consists of components obtained from the intermediate feed stream.