Impeller diameter is a crucial design parameter of high-speed rescue pumps because it affects the performance and inner flow characteristics of these pumps. In the performance test, the head and efficiency of the pump decreased as impeller diameter was reduced.

TipSpeed = Π × D × n

1. Tip Speed – impeller tip speed (rpm)
2. D – impeller diameter (ft)
3. n – impeller rotation speed (fpm)

Calculations

1. The ratio of impeller spreeds N1/N2 = 2 and the ratio of impeller diameters D1/D2= 1/2. The ratio of capacities is given by. (4.24)
2. The ratio of total heads is. (4.25)
3. The ratio of powers is. (4.26)
4. The ratio of required net positive suction heads is. (4.27)

IMPELLER DESIGN: Design of centrifugal impeller is done using K. M. Srinivasan method. Impeller design parameters are calculated using his procedure by giving head, volume flow rate and pump speed as input as mentioned in specifications of pump.

centrifugal pump

An open impeller has vanes that are attached to a center hub and mounted directly onto a shaft. There is no wall surrounding the vanes which makes open impellers weaker than closed or semi-closed valves. Open impellers are generally faster and easier to clean and repair.

The Pump Design Steps

1. Calculate the Flow Rate. The flow rate is the amount of fluid going through the discharge per unit time. Accuracy is of utmost importance here.
2. Calculate the Friction Head. In this step, the designer considers the head lost because of friction.
3. Calculate Total Head.

Positive displacement pumps use a mechanical means to vary the size of (or move) the fluid chamber to cause the fluid to flow. On the other hand, centrifugal pumps impart momentum to the fluid by rotating impellers that are immersed in the fluid. The momentum produces an increase in pressure or flow at the pump outlet.

The steps to follow to select a centrifugal pump are:

1. Determine the flow rate. To size and select a centrifugal pump, first determine the flow rate.
2. Determine the static head.
3. Determine the friction head.
4. Calculate the total head.
5. Select the pump.

100 km

NPSH (A) = (Pressure on the liquid surface) (ha) ± (suction head/lift) (friction loss) (vapour pressure) (hvp) NPSH (A) = 9.02 + 4-1.2 – 0.25 = 11.57 Mts.

Total Head is the measure of a pump’s ability to push fluids through a system. Total Head is proportional to the difference in pressure at the discharge vs. the suction of the pump.

The first is the static head across the pump and the second is the frictional head loss through the suction and discharge piping systems.

1. Total differential head = static head difference + frictional head losses.
2. Static head difference = discharge static head – suction static head.

In simple terms, the mathematical constant 2.31 converts a unit of energy against gravity into a unit of force against any other area. This constant converts a foot of head of water into pressure: Head in feet of water divided by 2.31 equals pressure in psi, and pressure in psi times 2.31 equals head in feet.

How many meter of head in 1 bar? The answer is 84. We assume you are converting between meter of head and bar. You can view more details on each measurement unit: meter of head or bar The SI derived unit for pressure is the pascal.

Water companies have to deliver 1 bar. 1 bar is 10 metres from the ground.

Pressures near the pump are often measured in PSI, however operating system pressures and pump curves use Feet of Head. To convert PSI to Feet of Head, multiply measured PSI times a 2.31 conversion factor. Example: 13.1 PSI times 2.31 equals 30.3 Feet of Head.

Maximum Head Lift is the total height from the source of the water to the destination or drainage point. This provides the power to move water over a distance.

Explanation: To calculate NPSH Available, take the source pressure , add the atmospheric pressure , subtract the losses from friction within the pipeline and subtract the vapor pressure of the fluid . The result equals the NPSHA (or Net Positive Suction Head Available) of your system.

Determine the pump flow rate, head, and power requirements if the pump speed is increased to 3600 rpm. It is possible to develop the characteristic curve for the new speed of a pump based on the curve for its original speed….Pump Laws.

Pump efficiency is the “water horsepower” divided by the “brake horsepower” and multiplied by 100 to present it as a percentage (see formulas in Image 1).

1. Triplex Pump Output = 0.000243 × (Liner Diameter ) 2 × (Stroke Length) Where, Triplex pump output in bbl/stk.
2. Triplex Pump Output = 2.3576 × 10-9× (Liner Diameter ) 2 × (Stroke Length) Where,
3. Duplex Pump Output = 0.000162 × S × [2(D)2 – d2] Where:
4. Duplex Pump Output =1.57172 × 10-9 × S × [2(D)2 – d2] Where: