Regarding the issue of net positive suction head and required net positive suction head
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I will look up information online about pump net positive suction head and required net positive suction head when I have time these days. It’s completely confusing to watch. I’ve been thinking about this on my own; I hope an expert can give some feedback: 1: Generally, pump nameplates list a value known as the net positive suction head. This value can be used to calculate the suction lift, which is equal to the pump’s installation height above the liquid surface. Some pumps specify a required net positive suction head – is this value equivalent to the pump’s installation height? 2: Is there any way to estimate the value of pipeline loss?
The relationship between the required net positive suction head and the installation height is such that the local atmospheric pressure is converted to meters based on the specific gravity of the fluid being transported; for example, when transporting water at 20 degrees Celsius, with a local atmospheric pressure equal to standard atmospheric pressure, the corresponding height is 10 meters. Required NPSH of the 10mi-pump = maximum installation height. This does not take into account any pipeline losses or safety margins. If it is an alkaline solution at room temperature with a specific gravity of 1.3, the corresponding height is simply 10/1.3, which equals 7.7 meters.
Effective NPSH: Effective NPSH, also known as plant NPSH, represents the excess energy per unit weight of the liquid as it flows from the suction level to the pump inlet, above the saturated vapor pressure. The required net positive suction head is the pressure drop per unit weight of liquid from the pump inlet to the point of lowest pressure at the blade inlet.
I see that some formulas state that the suction head = 10.33 – net positive suction head – pipe losses – 0.5; suction head = installation height
How is the specific gravity calculated? Try sucking up concentrated sulfuric acid by yourself to see if you can pull it up
This formula uses water as a reference, right? As you said, if the specific gravity of the medium is 1.4, then is the final height obtained by dividing the suction lift by 1.4?
You also need to take into account the temperature of the medium, that is, the vapor pressure