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1. TITLE BOX
The title box provides information about the pump model, size, speed, and other identifying criteria specific to the pump. If checking the performance of an existing pump, confirm that you are matching the pump to the associated curve.
2. FLOW
To start your selection, identify the amount of flow required from the pump. For this example, we chose 300 gallons per minute. The horizontal axis of the curve indicates flow.
3. HEAD
You will also need to know the total head the pump needs to overcome at the specified flow. For this example, we will use 100 ft. The vertical axis indicates the head. Follow 100ft across the curve intersects your flow line which indicates your performance point.
4. IMPELLER TRIM
Sometimes, performance points cannot be met with maximum impeller sizes. To accommodate for those performance points, centrifugal pumps allow for trimmed impellers.
Reducing impeller size limits the pump to your specific performance requirement. The curve lists the impeller diameters on the left side of the curve and the performance for each trim across as a bold line. Our selection is between 10” and 11” so a trim of 10.5” is appropriate.
Centrifugal pumps can also be limited by variable speed, which is the ideal means of control when several performance points are required by a single pump and not achieved by a single trim without system modification. Variable speed curves will be covered in a later post.
Reducing impeller size limits the pump to your specific performance requirement. The curve lists the impeller diameters on the left side of the curve and the performance for each trim across as a bold line. Our selection is between 10” and 11” so a trim of 10.5” is appropriate.
Centrifugal pumps can also be limited by variable speed, which is the ideal means of control when several performance points are required by a single pump and not achieved by a single trim without system modification. Variable speed curves will be covered in a later post.
5. HORSEPOWER
Horsepower is indicated across the curve as a dotted line in this case at a downward angle. Our performance point is between the 10hp and 15 hp lines, we estimate this selection to require 12 hp.
6. NPSHR
Net Positive Suction Head Required (NPSHR) is important for proper pump operation. This is the minimum amount of pressure on the suction side of the pump to overcome pump entrance losses.
The pump curve identifies the NPSHR, not Net Positive Suction Head Available (NPSHA). NPSHA is a calculation of the head the system is able to deliver. If sufficient NPSH is not met, the pump will cavitate, affecting performance and pump life.
More information about how system changes affect NPSH can be found in this blog post: “9 System Changes that Screw with NPSH”.
The pump curve identifies the NPSHR, not Net Positive Suction Head Available (NPSHA). NPSHA is a calculation of the head the system is able to deliver. If sufficient NPSH is not met, the pump will cavitate, affecting performance and pump life.
More information about how system changes affect NPSH can be found in this blog post: “9 System Changes that Screw with NPSH”.
7. EFFICIENCY
When selecting the best pump for an application, efficiency is an important factor. On the pump curve, efficiency is the ratio of energy delivered by the pump to the energy supplied to the pump. The higher the efficiency, the less energy required to operate for a specific performance point. Pump efficiency numbers of 60-80% are normal.
8. MINIMUM FLOW
A centrifugal pump requires a minimum amount of flow to be moving through the pump to dissipate the heat created. On the left side of the curve, minimum flow is indicated by a vertical bold line; operation to the left of this line is not recommended and can significantly decrease the life of the pump.
Knowing how to read a centrifugal pump curve is essential to the health of your system. Running too far out on the curve, or too far back, can cause damage to the pump, excessive energy consumption, and overall poor performance.
Having a pump that won’t working, loses its efficiency, or is slow to prime? Ask us about it at water pump dubai We gladly provide technical assistance to businesses
Knowing how to read a centrifugal pump curve is essential to the health of your system. Running too far out on the curve, or too far back, can cause damage to the pump, excessive energy consumption, and overall poor performance.
Having a pump that won’t working, loses its efficiency, or is slow to prime? Ask us about it at water pump dubai We gladly provide technical assistance to businesses
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