Similar to specific speed, both the flowate and NPSHr are calculated at the Best Efficiency Point (BEP) on the maximum available impeller diameter for the pump in question. NPSHr = Net Positive Suction Head required
N = the speed of the pump in revolutions per minute (rpm) On the other hand, suction specific speed is defined as follows: However, the disadvantage is that the pump will operate at the highest speed where abrasive wear and cavitation damage start to become an issue. In general, whenever we are faced with a specific speed value between 500 and 15,000, we know that such a pump exists and can be purchased from various pump suppliers.įor a given head and capacity, the pump meeting the requirements and having the highest specific speed will most often be the smallest size and the least expensive. NS international not only offers the traveler speed and convenience in booking. NS International services include high speed trains such as Thalys, ICE International, Eurostar and TGV. On the other hand, low head, high capacity pumps may have a specific speed of 15,000 or even bigger (US scale). International passenger rail transport (NS International) NS International is the international subsidiary of NS, offering train travel to destinations abroad. Pumps for high head, low capacity usually occupy the range between 500 to 1,000 (US scale). Impellers towards the right side are more efficient than those near the left side.
Generally speaking, as the number of specific speed increases, the size of the impeller goes from radial vane shape (for values between 500 and 1,000 in the US scale) to axial flow shape (for values between 10,000 and 20,000 in the US scale). Picture 1 - Typical flow classification of pump impellers as per specific speed
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