Pump TDH Sizing Calculator

Project

Client

Pump TAG No.

Service

Doc No.

Rev.

Date

Prep. By

FLUID & PUMP DATA

Flow & Fluid Properties

Pump Capacity Q m³/hr

m³/hr

Specific Gravity SG —

—

Fluid / Service —

—

Operating Temperature °C

°C

Viscosity μ mPa·s

mPa·s

Reference only — pipe friction here comes from ΔP1/ΔP2, not from this value

Vapour Pressure Pv bara

bara

Pump Efficiency η —

—

e.g. 0.70 = 70 %

⬇ Suction Side

Vessel Pressure P1 bara

bara

Elevation H1 mlc

mlc

Pressure Loss Suction Line ΔP1 bar

bar

⬆ Discharge Side

Vessel Pressure P2 bara

bara

Elevation H2 mlc

mlc

Pressure Loss Discharge Line ΔP2 bar

bar

PIPE SIZING & VELOCITY

⬇ Suction Line

1. Pipe Size (inch)

2. Schedule

OD -- mm WT -- mm ID -- mm Not available

Suction velocity -- m/s

Select pipe size above.

⬆ Discharge Line

1. Pipe Size (inch)

2. Schedule

OD -- mm WT -- mm ID -- mm Not available

Discharge velocity -- m/s

Select pipe size above.

Velocity guidelines — clean liquids, centrifugal pumps
Suction: 0.5 – 1.5 m/s optimal | up to 2.0 m/s acceptable | >2.0 m/s = cavitation risk
Discharge: 1.0 – 3.0 m/s optimal | up to 5.0 m/s acceptable | >5.0 m/s = erosion & water hammer

📐 Formula Reference — GPSA Method

Ps = P1 + H1·g·SG/100 − ΔP1
Pd = P2 + H2·g·SG/100 + ΔP2
TDH = (Pd − Ps) / (g·SG/100) [mlc]
NPSHav = (Ps − Pv) / (g·SG/100) [mlc]
Pshaft = Q·ΔP·100 / (3600·η) [kW]
P_motor = Pshaft × 1.15 → IEC standard size

SYSTEM SCHEMATIC

Suction Vessel

P1 = -- bara

H1 = -- mlc

ΔP1 = -- bar

suction

discharge

Discharge Vessel

P2 = -- bara

H2 = -- mlc

ΔP2 = -- bar

Enter input data and click ▶ CALCULATE TDH to see results.

TDH — Total Dynamic Head

—

[ metres liquid column — mlc ]

Differential Pressure

—bar

NPSHav

—mlc

Theoretical Power

—kW

Break Power (shaft)

—kW

Motor Size — IEC Standard

—kW

Step-by-step Calculation ▸

Parameter	Symbol	bar(a)		mlc
Pressure conv. g·SG/100	—	—	bar/mlc	1.000	mlc
Pressure suction vessel	P1	—	bara	—	mlc
Elevation suction → pump	H1	—	bar	—	mlc
Pressure loss suction line	ΔP1	—	bar	—	mlc
Suction pressure at pump	Ps	—	bara	—	mlc
Pressure discharge vessel	P2	—	bara	—	mlc
Elevation discharge → pump	H2	—	bar	—	mlc
Pressure loss discharge line	ΔP2	—	bar	—	mlc
Discharge pressure at pump	Pd	—	bara	—	mlc
Differential pressure / TDH	ΔP	—	bar	—	mlc
Vapour pressure	Pv	—	bara	—	mlc
NPSHav = Ps − Pv	NPSHav	—	bar	—	mlc
Hydraulic / theoretical power	Pth	—	kW	—
Break power (shaft)	Pbp	—	kW	—
Suction pipe NPS / Sch / OD / ID	pipe_s	—
Suction velocity	v_s	—	m/s	—
Discharge pipe NPS / Sch / OD / ID	pipe_d	—
Discharge velocity	v_d	—	m/s	—

Sizing note: TDH is the head the pump must develop at rated flow. Always verify NPSHav > NPSHr + 0.5 mlc margin. Motor size selected as the next IEC standard frame above Pshaft × 1.15.

Parameter	Symbol	Value	Unit	Note
Fluid / service	—	—
Pump capacity (flow rate)	Q	—	m³/hr
Specific gravity of liquid	SG	—	—	water = 1.000
Operating temperature	T	—	°C
Viscosity	μ	—	mPa·s	reference only
Vapour pressure	Pv	—	bara
Pump efficiency	η	—	—	—
SUCTION SIDE
Suction vessel pressure	P1	—	bara
Elevation suction vessel → pump centreline	H1	—	mlc	+ above pump, − below
Pressure loss suction piping	ΔP1	—	bar
Suction pipe: NPS / Sch / OD / ID	pipe_s	—
DISCHARGE SIDE
Discharge vessel pressure	P2	—	bara
Elevation discharge vessel → pump centreline	H2	—	mlc
Pressure loss discharge piping	ΔP2	—	bar
Discharge pipe: NPS / Sch / OD / ID	pipe_d	—

Parameter

Symbol

Value

Unit

Note

Fluid / service

—

Pump capacity (flow rate)

—

m³/hr

Specific gravity of liquid

—

water = 1.000

Operating temperature

—

°C

Viscosity

—

mPa·s

reference only

Vapour pressure

—

bara

Pump efficiency

—

SUCTION SIDE

Suction vessel pressure

—

bara

Elevation suction vessel → pump centreline

—

mlc

+ above pump, − below

Pressure loss suction piping

ΔP1

—

bar

Suction pipe: NPS / Sch / OD / ID

pipe_s

—

DISCHARGE SIDE

Discharge vessel pressure

—

bara

Elevation discharge vessel → pump centreline

—

mlc

Pressure loss discharge piping

ΔP2

—

bar

Discharge pipe: NPS / Sch / OD / ID

pipe_d

—

Parameter	Symbol	bar(a)	unit	mlc	unit
Pressure conversion factor g·SG/100	—	—	bar/mlc	1.000	mlc
Pressure suction vessel	P1	—	bara	—	mlc
Elevation head suction → pump	H1	—	bar	—	mlc
Friction loss suction line	ΔP1	—	bar	—	mlc
Suction pressure at pump: Ps = P1 + H1·conv − ΔP1	Ps	—	bara	—	mlc
Pressure discharge vessel	P2	—	bara	—	mlc
Elevation head discharge → pump	H2	—	bar	—	mlc
Friction loss discharge line	ΔP2	—	bar	—	mlc
Discharge pressure at pump: Pd = P2 + H2·conv + ΔP2	Pd	—	bara	—	mlc
Differential pressure / TDH: ΔP = Pd − Ps	ΔP / TDH	—	bar	—	mlc
Vapour pressure	Pv	—	bara	—	mlc
Net positive suction head available: NPSHav = Ps − Pv	NPSHav	—	bar	—	mlc
Theoretical / hydraulic power: Pth = Q·ΔP·100 / 3600	Pth	—	kW	—
Break power (shaft): Pbp = Pth / η	Pbp	—	kW	—
Suction pipe: NPS / Sch / OD / ID / velocity	pipe_s	—
Discharge pipe: NPS / Sch / OD / ID / velocity	pipe_d	—
Required motor size (Pbp × 1.15, next IEC standard)	P_motor	—	kW	—

Parameter

Symbol

bar(a)

unit

mlc

unit

Pressure conversion factor g·SG/100

—

bar/mlc

1.000

mlc

Pressure suction vessel

—

bara

—

mlc

Elevation head suction → pump

—

bar

—

mlc

Friction loss suction line

ΔP1

—

bar

—

mlc

Suction pressure at pump: Ps = P1 + H1·conv − ΔP1

—

bara

—

mlc

Pressure discharge vessel

—

bara

—

mlc

Elevation head discharge → pump

—

bar

—

mlc

Friction loss discharge line

ΔP2

—

bar

—

mlc

Discharge pressure at pump: Pd = P2 + H2·conv + ΔP2

—

bara

—

mlc

Differential pressure / TDH: ΔP = Pd − Ps

ΔP / TDH

—

bar

—

mlc

Vapour pressure

—

bara

—

mlc

Net positive suction head available: NPSHav = Ps − Pv

NPSHav

—

bar

—

mlc

Theoretical / hydraulic power: Pth = Q·ΔP·100 / 3600

Pth

—

Break power (shaft): Pbp = Pth / η

Pbp

—

Suction pipe: NPS / Sch / OD / ID / velocity

pipe_s

—

Discharge pipe: NPS / Sch / OD / ID / velocity

pipe_d

—

Required motor size (Pbp × 1.15, next IEC standard)

P_motor

—

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