Other

Hypro Corporation

Gas Research Institute

C Richard Gerlach

Edgar C Schroeder

Rodney T Heath

Ralph E Harris

Anthony J Smalley

A computer-based system and method detects and specifies valve and ring leaks in reciprocating compressors of the type used in natural gas transmission networks. The system employs a method comprising the following steps. The cylinder pressure is measured as a function of cylinder volume to obtain a measured PV card. A predictive model then calculates a predicted PV card for the subject compressor cylinder without including effects of simulated leaks. The predicted PV card is them compared to the measured PV card. The nature and character of the differences between the measured and predicted PV cards indicates whether a leak in the subject compressor cylinder is a suction valve leak, a discharge valve leak, or a piston ring leak. The predictive model is then iterated with simulations of the indicated leak included until the resulting predicted PV card matches the actual measured PV card for the compressor cylinder. The final value of the leak parameters in the model required for the match indicate the nature and magnitude of a corresponding actual leak in the compressor cylinder. Other useful information such as the efficiency of the compressor system with and without the leak and the economic impact of the leak are also derived from the iterative match process.

Method for detecting and specifying compressor cylinder leaks

A positive displacement pump especially designed for home use comprises a crankcase housing and a cylinder block joined thereto, the cylinder block containing a cylindrical bore whose longitudinal axis is at a predetermined angle relative to the longitudinal axis of the pump's drive shaft journaled in the crankcase housing. A piston having a central longitudinal bore formed inward from one end thereof and which includes a timing window extending through its side surface, is fitted into the cylindrical bore and coupled to the drive shaft by a pin which is journaled in a spherical bearing. A suction port is formed through the wall of the cylinder block on one side surface thereof and on the opposite side surface, 180.degree. away, is a high pressure discharge port. When the pump is driven, the piston both rotates and reciprocates causing the timing window in the piston to sweep by the inlet or suction port where a charge of liquid at low pressure is allowed to enter the hollow piston. As the piston rotates, the timing window moves to a point where it is ultimately in line with the discharge port when the piston is at a top dead center position. By canting the pin of the piston relative to its longitudinal axis compensation for the unequal hydraulic forces acting in the transverse direction on the piston results. An improved lubrication system incorporating grease as the lubricant is also employed.

Positive displacement pump with rotating reciprocating piston and

Positive displacement pump with rotating reciprocating piston

A cylindrical shell with a double acting piston, having a high pressure area and a low pressure area on each side thereof, is provided with a valve for alternately injecting high pressure gas to each small area to provide an initial piston drive, and valving for injecting gas under the pressure, opposite from the first high pressure end to the opposite larger area providing a secondary piston drive using expansion of the high pressure expanded gas from the opposite end of the piston. In reversing the piston, the opposite end becomes the drive end in the same manner. In one form, a two position slide valve, initially actuated by piston movement and completed by gas pressure movement, provides a transfer means for gas streams internally of the motor and for exhaust of the secondary expanded gas. The valve is arranged for an initial mechanical movement from one position toward the other position by contact with the end wall of the low pressure cylinder and then completely moved to other position by gas pressure. This arrangement permits a very slow piston reciprocation without stalling.

Dual pressure gas motor, and method of operation

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San Antonio, TX, United States of America

C Richard Gerlach