Rotary Pumps

Lekce 1: Centrifugal pumps – horizontal

Kapitola 1: Centrifugal pumps – horizontal

Centrifugal pumps are a type pumps used to convey liquids or gases by the means of a rotating impeller, which increases the pressure of a fluid. The energy is transmitted to the fluid from the impeller driven by an electric or other type of a motor. If the shaft is placed horizontally, we call them horizontal pumps. As the impeller of the pump rotates, it accelerates the fluid, which then flows radially outward into the volute casing and into the manifold system. Centrifugal pumps are most often used, when large discharge through a small head is needed.

Operation

In fact, centrifugal pumps work on the Bernoulli’s principle, converting kinetic energy into potential energy (which can be measured as static fluid pressure at the outlet of the pump). First, kinetic energy is transmitted from an electric motor via the rotation of the pump impeller to the fluid. The fluid is drawn into the impeller, where it is accelerated and pushed outwards through a system of vanes to the volute casing (or diffuser) and from there to the outlet manifold.

The outlet manifold can be open either at a place located higher or lower than the position of the impeller. If it is open higher, the kinetic energy of the fluid is converted into static pressure, otherwise it gains greater speed.

Multistage centrifugal pumps

Sometimes centrifugal pumps can have two or even more impellers. In such a case they are called multistage centrifugal pumps. The impellers can share one shaft or they can be mounted on different shafts. If the impellers are connected in series, fhe fluid gains higher pressure. If they are connected in parallel, we receive a higher flow output.

Vocabulary

Centrifugal pumps – odstředivá čerpadla

Convey – dopravit

Liquid – kapalina

Gas – plyn

Impeller – oběžné kolo; rotor

Pressure – tlak

Fluid – tekutina (tj. kapalina nebo plyn)

Transmitt – přenést

Driven – poháněný

Shaft – hřídel

Rotate – rotovat

Accelerate – zrychlovat

Flow – téct

Radially – směrem od osy

Volute casing – spirálová skříň

Manifold – potrubí

Discharge – výtok, výtlak

Head – hydraulický spád

Bernoulli’s principle – Bernoulliho princip

Convert – přeměnit

Kinetic energy – kinetická energie

Potential energy – potenciální energie

Pressure – tlak

Outlet – výstup

Draw – sát

Vane – lopatka

Diffuser – rozváděč

Speed – rychlost

Mounted – namontovaný, nainstalovaný

In series – sériově

In parallel – paralelně

Obrázky a fotografie použité v této kapitole pochází ze stránek {Wikimedia Commons XH http://commons.wikimedia.org}, kde byly zveřejněny pod licencí {GNU FDL XH http://commons.wikimedia.org/wiki/Commons:GNU_Free_Documentation_License}.

Kapitola 2: Cvičení

Studenti zpracují na téma Centrifugal Pumps – Horizontal powerpointovou prezentaci.

Kapitola 3: Kontrolní otázky

Can you briefly describe horizontal centrifugal pumps?
How do they operate?
How do single stage and multistage centrifugal pumps differ?

Kapitola 4: Autotest

Centrifugal pumps can convey
liquids
gases
both
Horizontal centrifugal pumps have
horizontal manifold system
horizontal shaft
horizontal casing
What happens, when the fluid is discharged at a position higher than the impeller?
Its kinetic energy is converted into static pressure.
Its potential energy is converted into static pressure.
It gains higher speed.
What happens, when the fluid is discharged at a position lower than the impeller?
Its kinetic energy is converted into static pressure.
Its potential energy is converted into static pressure.
It gains higher speed.
Multistage centrifugal pumps have
two or more impellers.
two or more shafts.

Lekce 2: Centrifugal pumps – vertical

Kapitola 1: Centrifugal pumps – vertical

Deep wells

Vertical pumps are especially convenient to pump water from deep drilled wells to the surface. They can be single stage or multistage. Single stage pumps have just one impeller by which the water is accelerated and then ejected. Multistage pumps have a series of impellers: after the water is ejected from one impeller, it flows into another one and thus its pressure is increased. During the pumping process the impeller has to be under the water level (in the case of multistage pumps just the first of the series of impellers). The bowl bearings usually do not require any lubrication, they are lubricated by the pumped water.

Other applications

Vertical pumps can be also used in wet pits. These types are usually also lubricated just by the pumped water, but they can also have a forced lubrication system. Sometimes they are also mounted in barrels, cans or other enclosed containers. In this case they are usually used to pump other liquids than water.

Submersible pumps

A special type of vertical pumps are submersible pumps. They have an electric drive motor which is coupled directly to the bowl assembly. They are designed to work under the surface of the pumped liquid, usually water, which also serves as a coolant (which means that the temperature of the pumped liquid must not exceed a certain value). Most often they are used in wells and wet pits.

Vocabulary

Centrifugal pump – odstředivé čerpadlo

Convey – dopravit

Liquid – kapalina

Gas – plyn

Impeller – oběžné kolo; rotor

Pressure – tlak

Fluid – tekutina (tj. kapalina nebo plyn)

Transmit – přenést

Application – použití

Well – studna

Drilled well – vrtaná studna

Surface – povrch

Accelerate – urychlit

Single stage – jednostupňový

Multistage – vícestupňový

Eject – chrlit

Bowl – těleso rozváděče

Bearings – ložiska

Lubricate – mazat

Forced lubrication system – nucený mazací systém

Mounted – namontovaný, nainstalovaný

Barrel – sud

Container – nádrž

Wet pit – mokrá jímka

Submersible pump – ponorné čerpadlo

Drive – pohon

Coolant – chladící médium

Temperature – teplota

Exceed – překročit

Value – hodnota