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1. A pressure testing system for pressurizing and testing a test vessel using a pump driven by pneumatic pressure and having a pressurized hydraulic fluid outlet to the test vessel, the pressure testing system comprising: a hydraulic pressure transducer configured to be coupled to the hydraulic fluid outlet to generate a hydraulic pressure signal indicative of the hydraulic pressure at the test vessel; and a pneumatic control unit configured to drive the pump via a supply of pressurized air from a pneumatic source, the pneumatic control unit comprising: a pressurized air inlet from the pneumatic source, and a pressurized air outlet to the pump; a pneumatic regulator disposed between the pressurized air inlet and the pressurized air outlet to modulate a pneumatic pressure of the pressurized air toward a target pneumatic pressure by metering airflow from the pressurized air inlet to the pressurized air outlet; control circuitry configured to receive the hydraulic pressure signal, set the target pneumatic pressure based on a target hydraulic pressure at the test vessel, and iteratively increase the target pneumatic pressure until the hydraulic pressure signal exceeds the target hydraulic pressure; wherein the pneumatic regulator comprises a pneumatic valve, the pneumatic valve disposed between the pressurized air inlet and the pressurized air outlet and actuatable open or close in response to a control signal from the control circuitry; a pneumatic pressure transducer disposed between the pneumatic valve and the pump to sense a pneumatic pressure of the pressurized air provided by the pneumatic control unit to the pump; and wherein the pneumatic regulator is configured to iteratively adjust a position of the pneumatic valve based on a comparison of the sensed pneumatic pressure with the target pneumatic pressure, independently of the target hydraulic pressure or the sensed hydraulic pressure.
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