training - flowserve apm pump cw pump part 2

8/17/2019 Training - Flowserve Apm Pump Cw Pump Part 2

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Q&A

Flowserve Corporation Property and Confidential 39

Understanding Head and Pressure

Centrifugal Pump Basics


Rev-0 CIRCULATING WATER PUMP - O & M TRAINING 20 of 97


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Understanding Head and Pressure



Shows the relationship between head and pressure.

Specific Gravity’s Effect on Head





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Understanding Head and Flow


Head is found in the following forms:

• Static Pressure Head

• Dynamic Velocity Head

• Static Elevation Head

• Friction Head

Flowserve Corporation Property and Confidential


System Head

Head Capacity

Desired Head


System Curve

Desired

Flowrate

-Static Head

-Pressure Head

-Friction and

Other Losses



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System Head




System Head




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Velocity

Where:

GPM = flow rate

=


47

Veloci ty Head


• Is the energy of a liquid as a result of its motion at a velocity

• Equivalent head in feet that the liquid would have to fall to acquire

the same velocity


Where:

hv = velocity head

v = velocity

g = gravity (32.2 ft/s2 or 9.81 m/s2)



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Friction Head and Friction Losses


•Pressure, converted to head, needed to overcome resistance to flow of

a liquid in a piping system

•Resistance:

o Pipe friction

o Valves, fittings


o Heat exchangers

o Filters, orifices, etc.

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Values in feet of water can be found in the Hydraulic Institute pipe

friction manual and other technical manuals.

Where:


hf = fiction head, feet or meters

K = coefficient for the valves and fittings

g = gravitational constant, 32.2 ft/s2 or 9.81 m/s2



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Friction head is determined by the equations:

Where:

f = friction factor V = velocit in ft/sec


L = pipe length (feet)

D = pipe ID (feet)

K = coefficient for the

valve/fitting

Friction


• Viscosity

• Size of pipe

• Roughness of pipe’s interior wall

• Age condition of pipe material


• Total length of pipe

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Friction Head Loss for

Water per 100 ft of Pipe



Friction Head Loss for

Water per 100 ft of Pipe

Notice the difference in

head loss between a one

inch line and a two inch


line at the same flow rate.



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Resistance Coeffic ients (K) Values



Losses Due to Friction

Pipe and fitting condition will have an impact on losses.




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Friction Head and System Changes

For constant pipe diameter

•Friction loss will vary as the square of the capacity ratio. If capacity is

doubled, friction loss will increase 4 times. Capacity varies as the square

root of the total head.

•Doubling the head will increase capacity 1.41 times.



Friction Head and System Changes

For constant capacity

•Friction loss is inversely proportional to the 5th power of the pipe

diameter.

•Reducing pipe size by 50% will increase friction loss 32 times.




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Total Discharge Head and Total Suct ion Head

These total heads can be calculated using the following equations:

total di scharge head discharge surface pressure


static discharge head discharge friction head

Total Discharge Head and Total Suct ion Head


total suction head suction surface pressure


suction static head suction friction head

Note:

The three contributing heads must have been converted previously to feet of

liquid before the above equations can be solved.



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Calculating System Head


Total Head is the difference between the total discharge head and total

suction head.


hd and hs must be expressed in the same units

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training - flowserve apm pump cw pump part 2

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