intermediate Point Vent 1

[POLYENGMOR]

Hello,

First of all, excuse me if I don't use the right vocabulary.

I am currently working on updating the calculation of high point vents/low point drains of a 1000mm pipe (drinking water), the pipe has already been commissioned.

In the calculation, there is an intermediate point vent between a high point vent and a low point drain. In the execution, the intermediate point vent was placed 50 meters from where it should be (high point vent side). As a result, we always need an additional intermediate point vent.

Is it possible to size the intermediate point vent already built (put a bigger air valve for example) so as not to have to add an additional intermediate point vent?

 

[LittleInch]

Can you share a profile of this as I'm not sure what you're trying to calculate?

What sort of velocity do you have?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Latexman]

My first thought was, isn't the 50-meters-off intermediate point vent good enough? What's the difference (%) between the performance of the 50-m-off point and the optimum point, and what parameter would you use to compare them? You must know this already, and it's significant if you want to add another intermediatre vent.

Good Luck,
Latexman

 

[POLYENGMOR]

Hello,

Here's the profile :

https://files.engineering.com/getfi...742-4090-adba-4b49f3940db3&file=IP_SIZING.jpg

 

[LittleInch]

Drawing key?

Blue line is ?
Yellow line is?
What is the calculation you're doing?
Velocity?
I've never worked out why water people insist on all these vents myself. Just flow at >1m/sec and it just flushes all the air out...

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[POLYENGMOR]

@LittleInch :
The blue line is the profile of the pipe
The yellow line is the profile minus 3 meters
The magenta line is the hydraulic head

The principle is whenever you have more than 3 meters between the profile of the pipe and the hydraulic head, you need to put an air valve.

 

[Latexman]

You still have not told us the actual velocity/flow rate in this 1 m diameter water pipe.

Good Luck,
Latexman

 

[LittleInch]

So is this a slack line / partially filled line?

Flowing right top left?

I'm still lost as to why you need valves and how you decide where they should be.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[bimr]

Wherever possible, select a profile that minimizes the number of air valves because they constitute an onerous maintenance problem. A manual valve can be used with initial startup to eliminate the air.

The principle is whenever you have more than 3 meters between the profile of the pipe and the hydraulic head, you need to put an air valve.

There is no such principle, who gave you this advice?

If you pipeline is flowing left to right on your diagram, no air vent is required.

If your pipeline is flowing right to left on your diagram, a vent valve may be eliminated by a higher velocity as stated by LittleInch. The velocity will depend on the slope of the pipeline.

 

[katmar]

You have called this an air vent, but it appears to me that it is actually a vacuum breaker. Your statement that the hydraulic pressure should never be more than 3m below the pipe elevation makes it sound like the aim is to protect the pipeline from external pressure. If this is the case then the water velocity is unimportant and there is no need to flush air out - in fact your aim is to bring more air in and increase the pressure drop and therefore increase the hydraulic pressure at the intermediate point.

This is not really a hydraulics problem. You need to investigate the safety factor for the pipe in resisting external pressure. This will enable you to evaluate whether the air that can be drawn in at the as-built "vent" point is sufficient to keep the pressures safe at the point of maximum difference between the pipe elevation and the hydraulic grade line.

Katmar Software - AioFlo Pipe Hydraulics

http://katmarsoftware.com

"An undefined problem has an infinite number of solutions"

 

[pierreick]

Hi,
You may find pointers in the document attached.
Pierre

 

[POLYENGMOR]

Hello,

@Latexman : Velocity is 1,5m/s

@LittleInch : It is a forced pipe (or a discharge line should I say ?), flowing left to right.

My goal is to size triple function air relief valves that allow the evacuation of air when filling the pipes, air entry when emptying the pipes (or breakage) and elimination of air pockets during operation.

 

[LittleInch]

Well your definition of hydraulic head is different to mine.

At that velocity you don't need air valves.

I've never really worked out why water engineers like them so much. PITA mostly.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[bimr]

Agree completely with LittleInch.

"Wherever possible, select a profile that minimizes the number of air valves because they constitute an onerous maintenance problem. In water service, the short valve body (Figure 5-16) is appropriate for combination air valves. Lescovich [15] has discussed the use of air valves in transmission mains.

Lescovich, J. E., "Locating and sizing valves in transmission mains," Journal of the American Water Works
Association, 64, 457^61 (July 1972)."

Pumping Station Design