### How to calculate steam & water pipe line size???

What are the factors needed to calculate steam & water pipe line sizes?

Quantity of maximum & minimum flow through the line

Pressure & temperature of the fluid

Pressure drop allowed

Velocity of the fluid in pipe

Density & specific volume of the fluid

How do you measure the steam flow through the pipe?

Steam flow is measured with the help of orifice plate, flow nozzles etc

How do you measure the water flow through the pipe?

Water flow is measured with the help of orifice plate, vortex meter, Rota meter & turbine meters installed in pipe lines.

What is the importance for calculating pipe line size for particular fluid flow?

To provide correct required flow

To avoid pressure drop of fluid

To avoid starvation

Why the velocity is the important factor while calculating the line size?

Flow = Area of the pipe X Velocity

By looking at the above relation, velocity is the critical & important parameters, as miss judgment of velocity may lead to wrong result.

Fluid having high pressure will be having high velocity & hence require lesser pipe line size & vice versa

And also fluid having lower density will be having high velocity & hence lesser pipe size and vice versa

What are the assumed velocity for various fluids flow?

Velocity of water at the suction of pump = 0.7 to 0.9 m/sec

Feed water flow at pressure 87 kg/cm2 = 2 to 4 m/sec

Saturated steam = 25 to 50 m/sec

Super-heated steam = 30 to 70 m/sec

What will happen if a 6” pipe line carrying hot water at the rate of 100 TPH suddenly contracts to 4”?

Following shall be observed

Velocity in the pipe will increase suddenly

Head or pressure loss will occur

Energy required to pump the water will increase

What are the factors that can cause the pressure drop in a pipe line?

Friction factor of pipe (pipe internal wall roughness)

Length of the pipe

Diameter of the pipe (size of the pipe)

Velocity of fluid in the pipe line

Pipe line fittings like valves, bend, tee etc. present in the pipe line

What are the effects of over sizing the pipe lines?

The cost of pipe lines & related fittings like valves, bend, Tee etc. will increase accordingly

Higher installation cost including pipe line supports & insulations

For higher sized steam pipe lines more condensate will tend to form & hence more number of steam traps are required

For higher sized steam pipe lines, there is more possibility of carryover wet steam to end user

More heat loss due to more exposed heat/hot surface area

What are the effects of under sizing the pipe lines?

For under sized pipe lines low pressure will be available for end user

In steam lines more pressure drop may cause starvation in pipe lines

Chance of erosion

Chance of water hammer & noise

Calculations:

1. Calculate the pipe line size required to pump 100 m3/hr of water at pressure 85 kgg/cm2 to the Boiler.

As discussed in the above theory part, velocity of the feed water at pressure 85 kg/cm2 is around 3 m/sec

Then flow, Q = Area of pipe line in M2 X Velocity in meter

(100/3600) m3/sec = (3.142 X D2/4) X 3 m/sec

D = 0.108 m = 108 mm

Looking at the above value, the pipe line size required should have internal diameter 108mm.

Then pipe line size = Pipe ID + 2 X thickness

For feed water pipe line having above pressure needs minimum 80 schedule, so refer carbon steel pipe line chart & select the required schedule & thickness.

2. Calculate the main steam pipe line size required for connecting Boiler out let steam to distribution header. Maximum steam flow is 125 TPH at pressure 110 kg/cm2 & temperature 540 deg C, assume velocity of steam in pipe line is 52 m/sec

Steam flow = 125 TPH = 125000 kg/hr

Density of steam at pressure 110 kg/cm2 & 540 deg C = 32 kg/m3...Refer steam table

Steam flow in m3/sec = 1250000 / (32 X 3600) = 1.08 m3/sec

We have,

Q = AV

1.08 = A X 52

A = 0.02 M2

A = 3.142 X D2/4

0.02 = 3.142 X D2/4

D = 0.159mm = 160 mm

So need pipe line of internal diameter 150 mm

Note: Outer diameter of the pipe line is standard, need to select schedule based on operating pressure & temperature to get desired line size.

3-Calculate the velocity of 55 TPH saturated steam flowing in 500 NB pipe line at pressure 1.7 kg/cm2 & 135 deg C

Density of steam at pressure 1.7kg/cm2 & temperature = 1.5 kg/m3

Steam flow in m3/sec = 55 X 1000 / (1.5 X 3600) = 10.18 m3/sec

We have,

Q = AV

10.18 = (3.142 X 0.92/4) X V

V = 15.99 m/sec

Following are the various cases taken as case study for pipe line size

Case-1

 Pressure (kg/cm2) 2.7 Temperature (deg c) 135 Density (kg/m3) 1.4 Flow TPH 135 Flow M3/sec 26.79 Line size-mm 800 Area M2 0.5 Velocity m/sec 53.28

Case-2

 Pressure (kg/cm2) 2.7 Temperature (deg c) 135 Density (kg/m3) 1.4 Flow TPH 160 Flow M3/sec 31.75 Line size-mm 900 Area M2 0.64 Velocity m/sec 49.9

Case-3

 Pressure (kg/cm2) 2.7 Temperature (deg c) 135 Density (kg/m3) 1.4 Flow TPH 80 Flow M3/sec 15.87 Line size-mm 600 Area M2 0.28 Velocity m/sec 56.13

Case-4

 Pressure (kg/cm2) 2.7 Temperature (deg c) 135 Density (kg/m3) 1.4 Flow TPH 40 Flow M3/sec 7.94 Line size-mm 450 Area M2 0.16 Velocity m/sec 49.9

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Hi all,