Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here


Storage tank defect spray distance

Storage tank defect spray distance

Storage tank defect spray distance


I don't know if I should ask this question here, or in the proccess engineering forum, but let me start by asking it here.

I have to calculate the spray distance resulting from a small defect (say 10 or 20 mm) in a storage tank shell.

My first assumption was to calculate the outlet velocity using the hydrostatic pressure:
velocity = (2*g*Head)^0.5
where Head = the liquid height above the defect

Then calculate the time it takes for gravitation to get the liquid down:
droptime = (2*height of defect / g)^0.5

Then using droptime * velocity to get the horizontal distance of the spray.

However if I compare my results to the example results I have from someone elses calculation my distances are much larger (about 1.6 times).
I know I calculated the distance with constant horizontal speed of the flow which may not be accurate.

Can any of you help me to get a more accurate calculation method for this problem?

Thanks in advance for the help.

RE: Storage tank defect spray distance

What you've posted is how I would calculate it. Of course, the following items could change the calculation:
1. Pressure (if it's a pressurized tank, the velocity would increase, v = (2*g*Head + pressure/density)^0.5
2. Viscosity, if the fluid is more viscous than water then you may have more losses due to friction.
3. The calculation is assuming no losses occurring at the defect.

All in all, if you are wanting to find the worst case scenario, then your calculation (unless the tank is pressurized) are correct.

Note: I noticed you double posted this in the Chemical Process Engineering forum as well, which is against the forum rules. I would suggest you request one of them to be deleted.

RE: Storage tank defect spray distance

The velocity, and the flowrate, are affected by the shape of the 'orifice', so you apply a coefficient.
It's around 0.7 for a round orifice without burrs or edge radii.
It's around 1.0 for a round orifice without burrs and with a generous radius on the inlet.
Of course you can't assume a round orifice, and you don't know anything about the defect's shape in any direction, so 1.0 is conservative. I'm guessing your friend used a less conservative value.

Mike Halloran
Pembroke Pines, FL, USA

RE: Storage tank defect spray distance

Thanks for the replies.

@MikeHalloran: Where to use this coefficient? Is it in velocity = (2*g*Head)^0.5, becoming velocity = (2*g*Head*coefficient)^0.5?

RE: Storage tank defect spray distance

It's the 'flow coefficient' Fc in the orifice equation here:
used as a factor to estimate the orifice's effective area relative to its measured area.

... which is unnecessary for your method. Sorry.

Mike Halloran
Pembroke Pines, FL, USA

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close