Basic Formula

-: BASIC FORMULAE AND SYMBOLS :-

H = Kg/cm² X 10 h = Head in m.

Liquid sp. Gr.

Vacuum Reading

Metres in liquid column (mlc) when

Vacuum in mm of mercury (Hg) is

Given

mlc = h X 13.6 h = Height of column

1000 X liquid sp. Gr. of Hg in manometer

in mm

13.6 - sp.gr. of Hg.

Valosity head (hv)

Hv = V² in m. V = Flow velocity m/s

2g g = Acceleration due to

Gravity = 9.81m/s²

To find velocity V in a pipe when flow rate Q in given :

V = 1273.2 X l/s d = pipe internal diameter in mm

In m/s D²

V = Q . or Q = V x A =m³/s

A A = Flow area od pipe

In sq. m.

DISCHARGE : l/s X 3.6 = m^3/hr.

Pump Input in kW = WHP in Kw X 100

(BHP) Pump eff. In %

Pump Output in kW = Q X H X Liquid sp.gr.

102***

*** For Engine, Value is 75

for getting HP.

Where, Q = Discharges in l/s.

H = Total Head in m.

Pump Effi. = Pump Output (WHP) X 100

In % Pump Input (BHP)

Pump input = Q (l/s) X H (m) X Liquid sp.gr.

In kW 102 X n%/100

Specific speed (Ns) ( as per IS -5120 )

__

Ns = 3.65 X N X Q

(metric) H^0.75

Where,

Q = Discharge in m^3/s (through one eye)

N = Speed in RPM

H = Total head in m (per stage)

Temperature Conversion

C = 5 X ( F 32)

9

F = 9 C + 32

5

Determation of Total Head (H) at site equipped with gauges. ( Suction pipe larger than delivery pipe ).

Pump with suction lift ( negative suction )

H = hgd + hgs + Z + Vd² Vs²

(in m) 2g

H = hgd - hgs + Z + Vd² Vs²

(in m) 2g

Where,

Hgd & hgs - Readings of Delivery and Suction size gauges respectively in m.

And Z - Gauge correction in m.

With Impeller diameter D held constant and speed change :

For Q = Q1/Q2 = N1/N2

For H = H1/H2 = N1²/N2²

For P = BHP1/BHP2 = N1³/N2³

With speed hold contant & impeller diameter change :

For Q = Q1/Q2 = D1/D2

For H = H1/H2 = D1²/D2²

For P = BHP1/BHP2 = D1³/D2³

Where Q = Flow l/s

H = Head in m.

N = BKW duty

D = Impeller dia. In mm.

VISCOSITY :

Kinematic Viscosity ( cST ) = Abs. viscosity ( in cP) / liquid sp.gr.

SSU = cST X 4.635

FRICTION LOSSES IN PIPES

Hf = (1211 X (10)⁹ / (d^4.87) X ( Q / S) ^1.852

Where, hf = friction losses in 100m. pipe length.

d = Inside dia. of pipe in mm

Q = Discharge in l/s.

C = smoothness co-efficient of pipe materials

150 for RPVC

140 for New GI Pipe

120 for Old GI Pipe