Surge Tank Sizing 3

[Physics_Nerd]

Hi Guys

I am currently working on a pump Station for which I need to size a surge tank for Water Hammer/pressure variations, I know that we have some standards in AWWA m11 but if u guys have anything like an excel sheet or anything please help me out this is the first time I am sizing a surge tank

I've done expansion tanks for Air Conditioning Systems and Pressure tanks for VFD-Booster Pumps but here we are talking abt a pump station with really high flow like 5000 m3/hr and basically I need to size a surge tank please help me out even if u know any analysis software or manual calculations etc

 

[Physics_Nerd]

U guys have been very helpful Thanks a lot folks for helping me out

 

[LittleInch]

Physics Nerd.

I sense you're not really understanding what me and a few others here are saying.

1) First work out if you actually NEED a surge relief tank. Many places and designs you don't need one or can eliminate it by better control design or slowing down a main valve closure.

2) If you need one then you really need a transient hydraulic analysis to tell you what the volume is to avoid over pressure.

3) The volume for surge tanks is normally quite small as it is a short term event ( say 15 seconds) of fairly high flow ( possible 2-3 times your normal flow) and that's it.

4) You need to avoid having a pump discharge pressure which can exceed the design pressure of the pipeline otherwise you could end up pumping into the relief tank for a long time.

5) If the event causing such surge is common then you really need to do something to avoid it as surge relief like this should be an accidental or occasional event.

6) remember your surge relief is only for pressures above the design pressure by more than 10% normally and the valves will close once that pressure pulse goes away.

7) from what you describe, a tank of about 100m3 or lower should be sufficient to deal with pressure surges. If you need the tank for other events then it might need to be bigger.

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

 

[BigInch]

With the 1.75 m/s velocity he may not need a surge tank at all, but if he does, 100m3 will certainly not be enough. Maybe LI is thinking about hydrotest pressure in a closed pipe. I've filled a 10,000BBL tank off a 24" pipeline before lowering the pressure from 1750 to 1400 psig. True, that was on the end of a rather long pipeline dropping down from the mountains and your's is around a 40" ID.

It's good you don't have a real high velocity. I suspect you may not need a surge tank, but get that hydraulic analysis done soon. Only then will you know.

 

[Physics_Nerd]

@littleinch

I told u guys before this is the first time I am dealing with a project where there could be a problem of surge so yes I dont know much about it and I do not consider myself as highly qualified professional rather I am still just a stundent and will remain so forver, and thats why I am here so that experienced people like you could help me out

English is not my first language and I am sure that is not a problem, is this a rule of the forum that I must not use short words if so please let me know

Storage tanks are really huge man, this site is meant to distribute water in a city..... 163,457 m3 is the Volume of the storage tank (Diameter = 110m, Height = 18.6) and yeah you are right its awkward to use huge... big is better!!! I should not have used huge for surge tank though

I am from INDIA and working in Riyadh, KSA, but our company is ready to buy from abroad its not an issue

Thanks again for your help & apologies for using bad english

 

[BigInch]

Your English is fine. No worries.

Try the Turkish pizza at that place on Thalateen Street, if it's still open.

 

[bimr]

Generally, if the flow rate exceeds around 30 L/s and the dynamic head exceeds 15 m, a surge control analysis should be prepared.

The surge vessel positioned downstream of the pump station is to provide protection against a loss of power to the pump scenario.

What is the elevation difference from the pump station to the discharge point?

Do you have a standby generator in case of power failure?

Is the power reliable?

Controlling a transient response may be less expensive. Possible measures include extending valve opening and closing time periods, coordination of multiple valve closures, addition of quick closing check valves, modifying and extending pump shutdown with motor starters, and/or use of an alternative power supply on some pumps so that the entire system can't fail on loss of power.

 

[Physics_Nerd]

@bimr

thanks for your help, the thing is I dont think client will agree on us not installing the surge vessel as it is included in the BOQ & there are other such sites and I saw one em had a very big pressure tank for surge.... and the thing is these pumps are meant to distribute water in the city and I have the drawing of the distribution plant and not the city.... I am attaching a picture of what I have at this stage as this also our end of contract but the thing is that pressure vessel is within our contract limits and I do not have the excavation details at this stage either

all I know is Water is coming from 6 Tanks (each 163,457 m3) into a header with 5000 m3/hr flow & then the pump station and then to the discharge point out of the plant toward the city.... and I need to install this surge vessel after the pump station..... I dont know the elevation difference as I dont have the excavation details

@BigInch

I ll definitely check that Turkish Pizza....

 

[Physics_Nerd]

http://files.engineering.com/getfil...file=8b7cf548-458c-4ecd-813a-06e00c697cd4.jpg

 

[LittleInch]

PN -

Lets be clear here what it is you are thinking off.

Is this a Pressure vessel to accommodate surges / high pressure / fluctuations without removing any water ( like an expansion vessel on a closed loop system) or a large tank (not a pressure vessel) which is connected to relief valves which open at high pressure and dump water into the tank?

I'm beginning to think you mean the first one, which is a completely different thing than what we've been talking about so far. Please explain / define further.

Your picture of an empty space on the drawing is not helpful and provides no information, sorry.

BI - Was that the Turkish place where they baked an enormously long single piece of bread if you went in with a dozen people?

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

 

[Physics_Nerd]

@littleinch

its not a closed system, its open.... this pump station will deliver water to the city & to some other reservoir (I am working on getting information on this reservoir)

 

[LittleInch]

I know that, my question is whether this "surge tank" is actually a pressure vessel (i.e. water goes in and out held under pressure or is it an atmospheric tank??

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

 

[BigInch]

That's the one. (Turkish pizza) I remember you being there on occasion. I always liked that place.

 

[bimr]

LittleInch,

This project is utilizing a closed pressure surge vessel to protect the pump station from power failure. It is shown on his sketch.

Physics_Nerd:

This pump station and pipeline are considered to be closed systems.

 

[Physics_Nerd]

This is the exact situation... this tank is not atmospheric.... so I did'nt know if it was a closed system but anyway thanks for the guidance so thats abt it..... @BIMr what are he most important points I would need to find an approximation of this tank size???

obviously I am still working on getting drawings of te city & the his other reservoir

@bimr thanks for the picture

@littleinch
bro that picture is exactly what I have

 

[LittleInch]

OK,

given we are now looking at a pressure vessel, you're in a completely different place than where I was originally coming from.

This is primarily there to inject water under pressure at a big flow rate ( so will need pipes close to the size of the delivery pipes) for a very short time if the pumps all turn off together.

In those circumstances, the water downstream of the pumps can create a low pressure / vacuum due to the water in the pipeline continuing to move. When that vacuum then collapses as water rushes back the pressures can be very high. Hence designers often require some means of putting water into the pipeline to avoid the low pressure.

It is not really possible to estimate this volume without proper transient analysis, but if you want an initial size work on flowrate of the pipeline for 30 seconds - in your case 40m3. However a lot of the tank will need to be pressurized gas (50% say) so the volume of your pressure vessel comes to around 80m3. Depending on the pressure that's a big pressure vessel which costs a lot of money (compared to a "tank").

Your use of a consultant will be well worth the money because he or she might say you don't need one, or the volume is only 10m3.

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

 

[Physics_Nerd]

@LittleInch

Thanks a lot man

 

[Physics_Nerd]

@LittleInch

if you worked here in Riyadh then you should know abt DONGO & METITO, they are the people who are mainly involved in these projects, I saw their sites the surge vessel looks big man, its horizontal & super huge so you see we quote good price for the vessel we can pay for it no problem lets see, I am still trying to get full information on the pipeline this is NWC we are working for, they dont reply fast and DONGO wont help obviously unless you have a friend inside