Abstract: A compressor surge control system is provided for a compressor system in which recirculation of gas from the discharge outlet of the compressor to the suction inlet of the compressor is utilized to prevent surging of the compressor. The recirculation of gas from the discharge outlet of the compressor to the suction inlet of the compressor is substantially minimized by using a first controller to provide a floating set point for a second controller. This reduced recirculation substantially increases the efficiency of the compressor system.

Abstract: Control of a pumping station is accomplished in such a manner so as to maximize the energy efficiency of the pumping station by utilizing a variable drive pump to maintain the pipeline suction pressure seen at the input to the pumping station at an acceptable level. If the pipeline suction pressure decreases below a level which can be controlled by the variable drive pump, then a control valve located at the output of the pumping station is closed to the extent necessary to maintain the pipeline suction pressure at an acceptable level. If the pipeline suction pressure is greater than can be controlled by the variable drive pump then additional pumps are brought online to prevent overloading of the variable drive pump.

Abstract: In the recovery of natural gas liquids by partial condensation, flashing, and compression, minimum and maximum temperature control of partially condensed feed stream hydrocarbons to a product separator is imposed by a minimum temperature control system which provides the same set point to the pressure controllers on the compressor suction scrubbers for both the product and the flashed vapor produced from the liquid outlet of the product separator with one of the two output signals responsive to the pressure of the product suction scrubber or the flashed vapor suction scrubber manipulating, by way of a selective relay, the engine speed controller of the dual compressor unit taking suction from the two scrubbers; and a maximum temperature controller which controls the rate of by-pass of natural gas feed around the partial condensation-separation system unless, by means of a selective relay, compressor availability is a more limiting criterion.

Abstract: In the recovery of natural gas liquids by partial condensation, flashing, and compression, minimum and maximum temperature control of partially condensed feed stream hydrocarbons to a product separator is imposed by a minimum temperature control system which provides the same set point to the pressure controllers on the compressor suction scrubbers for both the product and the flashed vapor produced from the liquid outlet of the product separator with one of the two output signals responsive to the pressure of the product suction scrubber or the flashed vapor suction scrubber manipulating, by way of a selective relay, the engine speed controller of the dual compressor unit taking suction from the two scrubbers; and a maximum temperature controller which controls the rate of by-pass of natural gas feed around the partial condensation-separation system unless, by means of a selective relay, compressor availability is a more limiting criterion.

Abstract: An apparatus and method for controlling a fluid pressure actuated valve are provided whereby the valve inlet pressure and valve outlet pressure are applied to control and limit the valve outlet pressure and to substantially reduce the fluid pressure applied to the valve actuating means when the valve inlet pressure is below a preselected safe value.