Calculation Of minimum Inlet Pressure

Ako je pritisak u pumpi niži od pritiska pare medija, doći će do kavitacije, što će utjecati na performanse pumpe. Da bi se izbjegla kavitacija i osigurao minimalni tlak na ulazu pumpe, maksimalna usisna visina treba izračunati na sljedeći način:

H = Pbx10.2-NPSH-Hf-hv-Hs

Pb: Atmospheric pressure, bar (In close pipeline system, it can be considered as the system pressure );
NPSH: Net positive suction head, m (Value at maximum flow of Q-NPSH curve);
Hf: Suction pipe line loss (Value at maximum flow of corresponding pipeline);
Hv: Medium vapour pressure, m (Medium vapour pressure at corresponding temperature, the default medium is water, as shown in figure4 on the right );
Hs: Safety margin, m, general value is 0.5.
Rezultat proračuna: ako je H pozitivan, pumpa je instalirana na usisni način, inače je ugrađena na donji način.

Note: It is not necessary to do above calculation under general conditions. Only when we use pump in the following situations do we need to calculate the H:
1. Medium temperature is high;
2. brzina protoka je veća od nominalne vrijednosti;
3.Suction glava je velika ili ulazni cjevovod je dug;
4.Sistemski pritisak je mali;
5.Ulazno stanje je loše.

Selection Of Pumps

Izbor pumpi treba da se zasniva na:
Radna tačka pumpe.
Dimensional data such as pressure loss as aresult of height differences,friction loss in the pipework,
Pump efficiency etc.
Materijali pumpe
Pump connections
Najčešće korišćene tabele za konfiguraciju mehaničkog zaptivača

1. Točka rada pumpe:

Iz radne tačke moguće je izabrati pumpu na bazi krive karte prikazane u "performansama / tehničkim" oznakama. podaci.

2. Dimensional data:

When sizing a pump the following must be taken into accounting: •Required flow and pressure at the draw-off point. •Pressure loss as a result of height differences. •Friction loss in the pipework(Hf) (Refer to Fig.1) It may. •Best efficiency at the estimated duty point. •NPSH value. •For calculation of the NPSH value, see corresponding curves chart.

3. Pump efficiency:

Before determining the best efficiency point, the operation pattern of the pump needs to be identified. If the pump expected to operate as the same duty point, then select a BL pump which is operating at a duty point corresponding with the best efficiency of the pump.
As the pump is sized on the basis of the highest possible flow, it is important always to have the duty point to the right on the efficiency curve(eta) in order to keep efficiency high when the flow drops.

4. Materijal pumpe:

Selection of pump connection depend on the rated pressure and pipe work. the pump offer a wide range of ftexible connection such as:

5. Uobičajene tablice s konfiguracijom mehaničkog brtvljenja

Application Field

Vrsta brtve vratila

Materijal brtve vratila

Normalno

Poseban

1

2

3

4 5

Type key

Rotirajući dio

Kod

Stationary part

Kod

Elastomeri

Kod

Kompresiona opruga

Collor

Kod

0 „do + 90â čiste vode

â—

Grafit

A

SiC

S

FPM

F

SUS304

C

ASFC

0 „do + 90â čiste vode

â—

toalet

W

Grafit

A

FPM

F

SUS304

C

WAFC

+ 90 „do + 120â otpornost na koroziju

â—

SiC

S

SiC

S

EPDM

E

SUS304

C

SSEC

do 0 „

â—

toalet

W

toalet

W

EPDM

E

SUS304

C

WWEC

Tip mehaničke brtve	Model pumpe	d1	d2	h
NJK	BL (T) 2/4	12	12	55
	BL(T)8/12/16/20	16	16	57.5
	BL (T) 32/45/60/90	22	22	72
NDA	BW(J)2/4	12.7	16	32
	BW(J)8/16	17.4	20	33.5