The suspiciously precise 1.83 m/s is 6 ft/s. Which API standard?

6 ft/s is a reasonably sensible rule of thumb limit to balance piping costs with pumping costs, and avoiding erosion by a clean fluid.

Matt

Please reference the standards that you refer to.

I'm pretty sure the max velocity is set to keep static electrical charge buildup below sparking voltages.

1:30 would be better to help keep water out of airplane fuel.

Shouxi,

There are, to my knowledge, no fixed velocities in any code. There are a number of recommended limits or guidance, but no fixed number.

The issues to bear in mind are friction losses, surge pressures and static charge for high velocities. If velocity is low the pipe is bigger than it needs to be and hence costs more, you might not be able to clear air from the line and there is a lot more volume.

For aircraft fuel you want to make sure any water is drained off and not allowed to sit there. A slope of 1:30 allows for good draining.

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

Thanks alot for the replies. Is there any document which shows the details of how to set limits?

Shouxi Wang

The consideration is reasonable and easy to be understand. The problem is how the numbers come from? For example, for the conedown vertical tank bottom, the slope must be larger than 1:30. How the 1:30 comes from? Is 1:25 ok too? Which document defines the 1:30 first and what are the details of getting this number.
Sorry for the question. But now we are bothering by this numbers and trying to find if we can change it little bit for better engieering.

Shouxi Wang

Vaguely recall an IEC standard that discusses static currents and precautions for jet fuel systems design in it.

Flow rate in pipelines is limited on the lower side by the self scouring velocity, typically 1.5 to 2 m/s and on the higher side by erosional velocity, typically 4 m/s or static electricity consideration which is 3 m/s.

http://pipelineandgasjournal.com/jet-fuel-pipeline...

API 2003.

https://law.resource.org/pub/us/cfr/ibr/002/api.20...

Vertical tanks have a cone down bottom with a minimum 1:30 slope to the centre sump, appropriate tank lining, filter/water separators, a manhole chamber if tank is buried Underground tanks are sloped to provide a low point for removal of water and other contaminants.

http://www.unlb.org/showbinarydata.asp?q=U%01%AC~b...'L%14%A0%90%B3%25%0B%1E%95l%04%B5a%7Flg%04%A3%13%FC%3C%FE%E9L%23%92%CA%14%12%92r%E3_%D5

Many thinks to all the responses.
Especially grateful to Bimr. Your imformation are very helpful. Could you please resend the 3rd link please? I couldn't open it.

Shouxi

The BS 5958-2:1991 Code recommends that the product of velocity (m/s) and pipe diameter (m) be less than 0.38 for liquids with conductivities of less than 5 CU, and less than 0.50 for liquids with conductivites above 5 CU. Jet fuel uses Static Dissipator Additives (SDA) to bring the conductivity up to the 150-450 range, but it seems that it is still handled as though the conductivity were very low.

Keeping the velocity below 1.83 m/s (6 ft/s) would match the first of of these criteria (i.e. VxD<0.38) for pipes up to about 8"NB.

Katmar Software - AioFlo Pipe Hydraulics
http://katmarsoftware.com

"An undefined problem has an infinite number of solutions"

The operation standard for aviation fuel JIG 3 calls for a positive low point to collect water and sediment for ease of removal, and requires for vertical storage tanks a cone-down bottom with a continuous slope of 1:30 minimum to a centre sump.

http://www.unlb.org/showbinarydata.asp?q=U%01%AC~b...'L%14%A0%90%B3%25%0B%1E%95l%04%B5a%7Flg%04%A3%13%FC%3C%FE%E9L%23%92%CA%14%12%92r%E3_%D5

• http://files.engineering.com/getfile.aspx?folder=82e07c6b-116e-4732-adb7-ac

Thanks Bimr, I got it.

Shouxi