LPG shielded pump
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According to the \"Design Code for Liquefied Petroleum Gas Supply Projects\" GB51142-2015, it is required that shielding pumps be used for filling LPG. I would like to know what the outlet pressure of such shielding pumps should be during filling. Additionally, the LPG storage tank is an underground tank; the lowest level of the LPG liquid is at a depth of -4.0m below the ground level, while the highest level is at -1.0m below the ground level. I would like to know whether shielding pumps can be used under these conditions, what the allowable installation height for such pumps is, and whether it is necessary for the pump’s location to be below the liquid level in the tank ? ? Can the installation height be higher than the tank liquid level, above the floor? ? ? ?
First, one needs to consider the suction lift of the shielded pump; if it is less than 4 meters, it definitely cannot be installed on the ground
I noticed that in the information available online about canned pumps, there is no parameter for suction lift; instead, there are only values such as head of 90 m, flow rate of 15 m3/h, required NPSH of 1.6 m, and power of 11 KW.
To prevent cavitation in the pump, NPSHa must be greater than NPSHr. Exactly how much more, there are empirical values for various types of pumps.
Check the backflow height; it is essential to maintain a safety margin, otherwise cavitation may occur, leading to damage to the sliding bearings and even burnout of the motor. The pressure at the inlet can be calculated based on the head and density of the medium. LPG vaporizes easily, and shielded pumps need to remove not only the heat generated by magnetic losses but also the heat from the motor. With a high load on the medium, cavitation is likely to occur inside the pump, or it may reach a critical point. The lubrication of sliding bearings is not as effective in such cases. In contrast, magnetic pumps only need to handle the heat generated by magnetic losses, which makes them more efficient
I’ve learned it; it’s very helpful! ! !
The consequences of cavitation in shielded pumps are quite severe; the sliding bearings lose lubrication and wear out rapidly.