Abstract: A roof support for an underground mine which has a hydraulic cylinder positioned between a roof engaging support and a ground engaging base and has a flexible gas barrier or enclosure surrounding surfaces of said hydraulic cylinder which are subject to corrosion by gases present in the underground mine. Continuous flowing non-corrosive gas such as nitrogen is supplied to a space between the gas barrier and the hydraulic cylinder for preventing corrosion of cylinder surfaces by corrosive gases present in the mine which may include hydrogen sulfide.

Abstract: A method for detecting loss of SF6 gas from electrical utility apparatus determines a molar ratio of gas in a container at an initial time and of gas in the container at a subsequent time. Measurement of temperature is determined by averaging ambient temperature and temperature of the surface of the container. The initial values of pressure and temperature define the initial value of n as follows: no=Pgas o/Tgas o The value at a subsequent time is nn=Pgas n/Tgas n The molar ratio can be defined as nn/no or as no/nn.

Abstract: A roof support for an underground mine which has a hydraulic cylinder positioned between a roof engaging support and a ground engaging base and has a flexible gas barrier or enclosure surrounding surfaces of said hydraulic cylinder which are subject to corrosion by gases present in the underground mine. Continuous flowing non-corrosive gas such as nitrogen is supplied to a space between the gas barrier and said hydraulic cylinder for preventing corrosion of cylinder surfaces by corrosive gases present in the mine which may include hydrogen sulfide.

Abstract: A method for repairing power plant boilers provides for a water mist insertion into the furnace to provide for more rapid cooling, which allows personnel to enter into the furnace to conduct repairs in a shorter time. Water mist is provided by air-water mixing atomizing sprayers that are inserted into the boiler. Existing power plant oil igniter lighters may be switched from oil to water to provide the air-water mixed atomized mist.

Abstract: An apparatus for measuring phase angle difference between two conductors uses a hot stick, a field unit, and reference unit. Voltage is sensed at a conductor, and the voltage is passed through an automatic gain control which adjusts the voltage input to a voltage detector to a level which prevents saturation of the voltage detector. Non-saturation of the voltage detector enables detection of all of the data in a detected sine wave. Pulse width modulation and pulse width modulation RF transmission are used to provide for data transmission from a hot stick to a field unit.

Abstract: A method for detecting loss of SF6 gas from electrical utility apparatus determines a molar ratio of gas in a container at an initial time and of gas in the container at a subsequent time. Measurement of temperature is determined by averaging ambient temperature and temperature of the surface of the container.

Abstract: A variable potentiometer with a wiper terminal and first and second terminals has relay switches for shorting or for unshorting resistors. When resistance is reduced between the wiper and one of said terminals, resistance is increased between the wiper and another terminal. In one embodiment two strings of resistors with the same nominal values are used between the wiper and the terminals. In another embodiment, a single string of resistors are used and are switched into either the electrical connection between the wiper and the first terminal or between the wiper and the second terminal. When resistance is lowered between the wiper and one of said first or second terminals a first resistor is replaced with a first short circuit and when resistance is increased between said wiper and another of said first and second terminals a second short circuit is replaced with the first resistor.

Abstract: A roof support for an underground mine which has a hydraulic cylinder positioned between a roof engaging support and a ground engaging base and has a flexible gas barrier or enclosure surrounding surfaces of said hydraulic cylinder which are subject to corrosion by gases present in the underground mine. Continuous flowing non-corrosive gas such as nitrogen is supplied to a space between the gas barrier and said hydraulic cylinder for preventing corrosion of cylinder surfaces by corrosive gases present in the mine which may include hydrogen sulfide.

Abstract: A variable potentiometer with a wiper terminal and first and second terminals has relay switches for shorting or for unshorting resistors. When resistance is reduced between the wiper and one of said terminals, resistance is increased between the wiper and another terminal. In one embodiment two strings of resistors with the same nominal values are used between the wiper and the terminals. In another embodiment, a single string of resistors are used and are switched into either the electrical connection between the wiper and the first terminal or between the wiper and the second terminal. When resistance is lowered between the wiper and one of said first or second terminals a first resistor is replaced with a first short circuit and when resistance is increased between said wiper and another of said first and second terminals a second short circuit is replaced with the first resistor.

Abstract: An inductive bridge circuit using mutual inductances to transform impedances is used for detection of wall-thinning defects in metals. The bridge circuit has a first test coil placed adjacent to a good metal section and a second test coil placed adjacent to a metal to be tested. The bridge circuit compares the inductance in the first coil and inductance in the second test coil to compare wall thinning defects. The apparatus may also include first and second measuring transformers which are connected between the bridge circuit and the test coils where the transformers provide for impedance matching and reduced current requirements in the bridge. The circuit may also include one or more potentiometer circuits connected across the bridge which are used for compensating for imbalance of impedance between the first and second test coils when the coils both have known good metal sections adjacent to them.

Abstract: System for tracking or identifying the phase designation, and/or measuring the phase angle or the power angle of electrical conductors at a remote location relative to a reference location, by measuring a time delay between an external clock source such as GPS and a zero crossing or other specified part of the waveform, associating a ‘time tag’ with each measurement, transmitting the time tags and measurement values over a bi-directional link between a field unit and a reference unit, and calculating and displaying a relative phase angle and/or a phase designation. The system finds application, for example, in identifying the phase of conductors, and optionally comparing their phase angle and/or their power angle, before making connections between conductors in a multi-phase electrical power distribution system.

Abstract: An inductive bridge circuit using mutual inductances to transform impedances is used for detection of wall-thinning defects in metals. The bridge circuit has a first test coil placed adjacent to a good metal section and a second test coil placed adjacent to a metal to be tested. The bridge circuit compares the inductance in the first coil and inductance in the second test coil to compare wall thinning defects. The apparatus may also include first and second measuring transformers which are connected between the bridge circuit and the test coils where the transformers provide for impedance matching and reduced current requirements in the bridge. The circuit may also include one or more potentiometer circuits connected across the bridge which are used for compensating for imbalance of impedance between the first and second test coils when the coils both have known good metal sections adjacent to them.