# Velocity in a pipe via a pressure test.

• mcarrigan
In summary, the conversation is about designing a thrust block for a water supply system with a new 250mm line. The operating head is 30m from water towers, and the speaker has set up a thrust block program in excel. They are unsure about the flow rate/velocity of the water in the new pipeline to calculate the thrust and are considering using Bernoulli's equation. They also have a pressure test from a current 65mm line in the area, but are unsure if it can be used to calculate the velocity in the 250mm line. The speaker may need to get more information from the council.
mcarrigan
Okay I'm currently doing a thrust block design for a water supply system. The new line is a 250mm line. The water is fed from water towers where council has said the operating head is about 30m. I've set up my thrust block program in excel and it is all working fine. The only trouble is I'm unsure on exactly what flowrate/velocity of the water in the new pipeline to calculate the thrust.

Now i was thinking the best way to do it was to solve with bernouli's with two unknown V's.

and simultainiously solve for v1 = v2a2/a1 and vice versa. but was thinking maybe there might be a better way.

I do have a pressure test from a current line in the area where the new line is going. The information from the pressure test is as follows:

65mm line

Flow rate/second (L/s) Pressure (kpa)
0 220
5 185
10 125
15 0
16.5 (open) 0

So using this pressure test, is it possible to gain the velocity of water in a 250mm line under similar conditions? or do i use the approximate 30m head in there to calc it instead? I may have to go to council and get more info off them but i struggled enough to get the pressure test.

If anyone can help that would be great! Cheers.

Sorry i just relised that the pressure test formatting didnt come out right...

So it was a 65mm pipe

fully closed valve = 220kpa
running 5 l/s = 185 kpa
running 10 l/s = 125 kpa
running 15 l/s = 0 kpa
Fully open running 16.5 l/s = 0 kpa

So what I'm chasing is a velocity in a 250mm line in order to accurately calculate thrust in the pipe. We have an estimated head in water towers of 30m and the pressure test in the above.

Can anyone help?

Hope this has clarified things a bit.

Cheers!

## 1. What is velocity in a pipe?

Velocity in a pipe refers to the speed at which a fluid is flowing through the pipe. It is typically measured in feet per second or meters per second.

## 2. How is velocity in a pipe calculated?

Velocity in a pipe can be calculated by dividing the volumetric flow rate by the cross-sectional area of the pipe. It can also be calculated using the Bernoulli's equation, which takes into account factors such as pressure and elevation changes.

## 3. What is a pressure test?

A pressure test is a method used to determine the strength and integrity of a pipe or pipeline system. It involves pressurizing the system with a liquid or gas and monitoring for any leaks or changes in pressure.

## 4. How does a pressure test determine velocity in a pipe?

A pressure test can determine velocity in a pipe by measuring the pressure and flow rate of the fluid being used to pressurize the system. By comparing these values to the known properties of the fluid, the velocity can be calculated.

## 5. Why is velocity in a pipe important to measure?

Velocity in a pipe is important to measure because it can affect the performance and efficiency of a pipeline system. High velocities can lead to increased pressure drops and potential damage to the system, while low velocities can result in sediment buildup and reduced flow rates.

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