What dictates the maximum NPSH available for a liquid Ammonia pump?

The maximum Net Positive Suction Head (NPSH) available for a liquid ammonia pump is primarily influenced by the location and operation of the liquid make-up injection connection on the Low Pressure Receiver (LPR).

When determining the NPSH available, the elevation of the liquid source relative to the pump and any potential vaporization of the liquid need to be considered. The make-up injection point ensures that sufficient liquid is available to maintain the necessary head pressure at the inlet of the pump. If the liquid level in the LPR drops below a certain point, the pump may not receive enough liquid, leading to cavitation.

Other options, such as high-level and low-level floats on the High Pressure Receiver (HPR), pertain to monitoring and controlling liquid levels but do not directly dictate the maximum available NPSH in a way that spans the operation of the pump system. Similarly, while having the LPR at 50% full establishes a baseline for liquid storage, it does not uniquely define the maximum NPSH available.

Thus, the liquid make-up injection is a critical factor in ensuring a stable and adequate supply of liquid ammonia reaching the pump, thus dictating the maximum NPSH available for optimal pump performance.