How to troubleshoot centrifugal pump myself




Suction tube too high or too small or suction too long, causing considerable friction loss - check with meter • Aspiration or turbine or the suction inlet fully connected • Wrong direction of rotation Air pocket in suction line • • Worn or stuffing box connected to a siphon, so that air leaks in the casing of the pump • Air leak in suction line. Not enough water supplied • coating and priming the suction pipe is not satisfied with water • The speed is too low • higher prevalence than expected - Check especially friction loss • Suction pipe too high or the suction is too small or too long causing excessive friction loss - check with gauge • Impeller or suction pipe opening, or partially connected to • Wrong direction of rotation • air pocket in suction line, perhaps due to high vertical curvature or concentric reducers suction line • Worn or stuffing box connected to a siphon, allowing an air leak in the pump • Air leak in suction line • Foot valve too small • Foot valve is not immersed deep enough • Mechanical failures - worn wear rings, impeller damaged casing leaks. Not enough pressure • a speed too low • Air to water • The wheel diameter too small • Mechanical failures - worn wear rings, impeller damaged, defective packing box • Wrong direction of rotation • The pressure is measured incorrectly point - to measure pressure at the top of the case of the pump. The pump runs for a while and then closes • Leak in the suction • Housing worn or attached gland seal water when air leaks into the pump Air pocket in suction line • • Not enough to lift the hot water or volatile liquids - check carefully that this is a common cause of problems with hot water, etc. • air or gas in a liquid • Suction lift too high. Pump takes too much power • speed of the motor is too high • Head lower than rating, pumps too much water • mechanical failure - tree bent, a rotating liaison unit, the packing too tight, the pump and the driving misalignment • Wrong direction of rotation. Pump leaks too gland • Packing worn or poorly lubricated • The package is not installed properly or not working properly • Packing type incorrect for the treated liquid • The tree marked. The pump is too noisy • Hydraulic Noise (cavitation) - Suction lift too high - check with manometer • Mechanical failure - the bent axle, rotating parts tie Loose or broken, worn bearings of the pump, and Guide unit of an angle.

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Coupling and Drive of a standard Centrifugal Pump

The turbine is usually driven by an electric motor. The coupling between the motor and the hydraulic system is a weak point, because it is difficult to seal a rotating shaft. In connection with the clutch, which distinguishes between two types of pumps: Dry-runner pumps and canned rotor type pump. The advantage of the rider dry pump compared to the pump, canned rotor type is the use of standard motors. The disadvantage is the seal between the motor and wheel. Dry runner pump and motor shaft are separated from liquid joint, separating long-handled or magnetic coupling. In a pump with a rotor engine is smooth and separated by joints, see Figure 1.9. Mechanical seals are maintenance free and has a minor leak Fill the boxes with packing material compressed. The mechanical life shaft seals depending on the fluid pressure and temperature.

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Centrifugal pump impeller

The design of the turbine depends on the requirements of the pressure, flow and application. The impeller is a primary element of the set pump performance. Pump variants are often created by changing only impeller.
In radial impeller, is a significant difference between the input diameter and the diameter of the exit and the exit diameter and width of output, which is the height of the channel output wheel. In this construction, the result of the centrifugal forces of high and low pressure the flow. The relatively low pressure and high flow, on the contrary, can be found axial fan does not change the title and the opening width large. Semi-axial impellers are used to compromise the increased pressure and flow is required. The turbine has a number of blades of the turbine. The number depends mainly on the desired performance and noise limits and the amount and size of solid particles in the liquid. Scooters with channels from 50 to 10 has been shown give the best performance and is used for the liquid without solid particles. One, two or three-wheel channels are used for fluids with particles such as sewage. The leading edge of the propeller is designed to minimize the risk particles block the wheel. One, two and three channels wheels can the handle of a certain size of the particles through the impeller. Figure 1.7 shows a pump of a channel. Impellers without the shroud is called open impellers. Open impellers is used when you need to clean the impeller, and where there is a risk blockage. Vortex pump with open impeller used in applications of wastewater treatment. This type of pump, the impeller creates a flow similar vortices in a tornado, see Figure 1.8. The vortex pump has a low efficiency compared to pumps with a shroud and seal the turbine. Once the basic shape of the impeller has been decided, the planning turbine is a matter of finding a compromise between the friction losses and losses concequence because it is not uniform velocity profiles. In general, a uniform velocity profiles can be obtained by extending blades, but this means increased friction wall.

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Hydraulic components of centrifugal pump

The principles of the hydraulic components are common for most centrifugal pumps. The hydraulic components are the parts in contact with the fluid. Figure shows the hydraulic components in a single-stage inline pump. The subsequent sections describe the components from the inlet flange to the outlet flange.

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Everything about Centrifugal Pump


A centrifugal pump is a pump that uses a spinning rotor to create a flow rotodynamic by adding energy to a fluid. Centrifugal pumps are commonly used to move fluids in pipes. The fluid enters the pump impeller along or near the axis of rotation and is accelerated by the impeller, flowing radially outward into a diffuser or volute room (housing), where in the pipe downstream. Centrifugal pumps are used to remove large, with smaller heads. Liquid enters the pump suction, and then the impeller eye. When the impeller rotates, spins the liquid sitting behind the scenes of grease to the outside and the creator of centrifugal force. As the fluid leaves the eye of the impeller a low pressure area is a basic understanding of the eye to allow more fluid pump.


Centrifugal pumps are classified in three categories:


Radial flow - a centrifugal pump where the pressure has been developed entirely centrifugal.

Mixed flow - a centrifugal pump where the pressure is developed partly by centrifugal force and partly by raising the turbine blades in the liquid.

Axial Flow - a centrifugal pump where the pressure developed by the propelling or lifting action of the vanes of the impeller on the liquid.


And head pressure

If the issuance of a centrifugal pump is pointed up in the air is pumped into the liquid should be a certain height - or head - has suspended the head. This decision is mainly determined by the maximum diameter of the pump impeller and shaft rotation speed. The head turns the pump flow is changed.

The kinetic energy of a liquid that comes out of a wheel is blocked by the creation of a flow resistance. The first resistance is created by the pump house that catches liquid and it slows down. When the fluid slows down the kinetic energy is converted into pressure energy.

* This is the flow resistance of the pump that reads a meter connected to the discharge line

A pump does not create pressure, it only creates flow. The pressure is a measure of the resistance to flow.

In Newtonian fluids (non-viscous liquids such as water or gasoline), the term head is used to measure the kinetic energy that creates a bomb. The head is a measure of the height of the column of fluid from the pump creates the kinetic energy of the pump provides fluid.

* The main reason for using the head instead of pressure to measure the energy of a centrifugal pump is the pump pressure will change if the specific gravity (weight) of the liquid changes, but the head does not

The pump performance on any Newtonian fluid can always be described using the head term.

Different types of pump heads

* Total Static Head - Total head when the pump is not working

* Total head (Head Total System) - Total height when the pump is running

* Static Suction Head - Head of aspiration, with the pump, if the head is larger than the pump impeller

* Static Suction - Suction Head, with the pump, if the head is below the pump impeller

Discharge head * - Head of the discharge side of the pump with the pump

* Dynamic Suction Head / Lift - Head on the suction side of pump, pump

* Head of the dynamic pressure - Head of the discharge side of the pump with the pump

The head is measured in feet or meters, and can be converted into common units of pressure psi or bar.

* It is important to understand that the pump pump all fluids to the same height as the shaft rotates at the same regime

The only difference between the fluids is the amount of energy it takes to get the hub of a proper diet. The higher the specific gravity of the fluid more power is required.

* Centrifugal pumps are "constant load machine"

Note that not a machine at constant pressure, because pressure is a function of the head and density. The head is constant, even if the density (and pressure) changes.



The head of a pump in metric units can be expressed in metric units as:
h = (p2 - p1)/(ρ  g) + v22/(2 g)         (1)
where
h = total head developed (m) 
p2 = pressure at outlet (N/m2)
p1 = pressure at inlet (N/m2)
ρ =   density (kg/m3)
g = acceleration of gravity (9.81)  m/s2
v2 = velocity at the outlet (m/s)
Head described in simple terms
  • pump vertical discharge "pressure load" is the vertical lift height - usually measured in feet or meters of water - in which a bomb can not exert enough pressure to move water. At this point, the pump can be said to have reached its "off" head pressure. In the flow curve in the bank pump "head" is the point on the graph, where the flow is zero

Pump Efficiency

Pump efficiency, η (%) is a measure of the efficiency with wich the pump transfers useful work to the fluid.
η = Pin/Pout   (2)
where 
η = efficiency (%)
Pin = power input
Pout = power output  



Centrifugal Pumps: Basic Concepts of Operation, Maintenance, and
Troubleshooting


User any centrifugal pump often starts with a general statement,"Your centrifugal pump will give you completely trouble free and satisfying as provided they are installed and used with care and stay well. "Despite all the care in the operation and maintenance engineers are often faced with the statement "The pump has failed ie can not be kept in service." Inability to deliver the desired flow and head is just one of the most common conditions to take a pump out of service. There are many other circumstances in which a pump, despite suffering no loss of flow or head is considered failed and must be removed from service as soon as possible. These includes a gasket problems (leaks, loss of irrigation, cooling, fire protection systems, etc.), The problems associated pump and motor bearings (loss of lubrication, cooling, air pollution oil, abnormal noise, etc.), leakage of the pump housing, high noise and vibration levels or the driver (motor or turbine) related problems.




sources:

 http://www.maintenanceworld.com/Articles/engresource/centrifugalpumps.pdf
www.engineeringtoolbox.com/centrifugal-pumps-d_54.html
en.wikipedia.org/wiki/Centrifugal_pump

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