**Centrifugal pump **** **

These pumps are placed in the category of non-positive displacement pumps, which are transmitted to the fluid by rotating a propeller in that energy. (Including turbo boosters) Like many other pumps, centrifugal pumps transfer energy from the rotating engine to the fluid. Some of this energy appears as kinetic energy in form of speed, as a potential energy in the form of a pressure head can carry the fluid against the gravity of the earth upwards. The energy transfers from a rotating propeller to a fluid to generate pressure and fluid motion is always described as the centrifugal force in the fluid. Centrifugal pumps are the most widely used type of pump in the industry. On average, 75 percent of the pumps used in the industry are centrifuges. Because these pumps always provide a certain amount of water flow at a constant pressure and in every situation, they are ideal pumps These pumps work on the basis of centrifugal force theory. When the blade of the pump runs inside the chamber, it pushes the fluid out of the center. When the fluid is pushed out of the center, the fluid is pulled out under atmospheric pressure or artificial pressure and higher to the center.

The fluid that was pushed out is drained through the outlet. This fluid will have a pressure can be calculated by the step of the pump impeller as well as its rotational speed. As mentioned, these pumps have two main members, the body and the propeller.

Advantages of centrifugr pumps

Availibility

right price

Simple design

Diversity in the impeller

Lower current costs than other pumps

low space

**Disadvantages of centrifugal pumps**** **

Need sealing

Normally do not provide high pressure

Producing of high pressures are very expensive

The centrifugal pump torque at full load

The full load torque is calculated from the following :

T = 30 P / π n

In this case P is the power in Kw.

Suitable flow rate for centrifugal pump suction

The problem is the capacity, cavitation and high energy consumption in the pump resulting from suction conditions. In general, to keep the flow rate down below, it is better to refer to the following table:

If the pressure at any point inside the pump is lower than the liquid vapor pressure in the pump, evaporation or cavitation will occur. For example, the water is boiling or steaming at 28 inHg whit 100 ° F. The problem of cavitation increases at high temperatures.

bubble fluids – due to cavitation – may be pumped with difficulty

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**Best performance point**

The pump can not completely transform the kinetic energy into pressure. A part of the energy is always wasted from the pump and pump out. The efficiency of a pump at the point of its maximum is called BEP. Types of pump losses are:

Hydraulic losses: The friction of the disk in the impeller and the severe drop that occurs due to rapid change in the path and flow velocity.

Volumetric losses: Internal rotation in wear rings

Mechanical losses: internal friction between parts and bearings and external friction of flood and bearings

Minimum flow of centrifugal pumps

Centrifugal pumps and continuous flow minimum:

If the liquid is turned into steam in the pump shell, the centrifugal pump will suffer abrupt breakdown.

To prevent these damages due to excessive fluid heat, the flow should be maintained through the pump to keep the fluid temperature below saturated temperature.

If the temperature rises to 15 ° F or more, the fluid is accepted by the pump and the minimum flow can be calculating by the following equation:

q = PBHP / 2.95 cp SG

In this case, q is the minimum flow rate in terms of (gpm), P input power in terms of (BHP).

Calculate the flow rate of the centrifugal pump

When a fluid flow is transmitted through a pump, the hydrodynamic losses depend on the fluid viscosity

When a fluid is viscous, it is controlled by a centrifugal pump

Increases braking power by horsepower needed

Reduces the produced head

Capacity is reduced

The efficiency of the pump is reduced and the best return point (BEP) is shifted.

Head, flow rate and capacity are corrected in a number of other viscosities relative to reference numbers with a series of coefficients.

To calculate flow flow we use the following equation:** **

qv= cq q

qv is the compensating current for viscosity in terms of (m3 / h, gpm) and q is the main current based on the pump curve (m3 / h, gpm).** **