Fluid Velocity In Pipeline

Question

Fluid Velocity In Pipeline

qazx (Chemical)

(OP)

26 Dec 02 02:15

In many texts it is mentioned that normal liquid velocity in the pipes ranges from 4-8 ft/sec.Are there any citeria for determining of fluid velocity in pipelines in corrosion errosion point of view?

mohtogh (Chemical) · Answer 1 · 2002-12-26 05:39:02

RE: Fluid Velocity In Pipeline

mohtogh (Chemical) 26 Dec 02 05:39

refer to this:
Thread116-31921

hacksaw (Mechanical) · Answer 2 · 2002-12-26 07:56:03

gazx,

depends on the fluid. If you are deaaling with hydrocarbon liquids that is one set of explanations, and if you are dealing with corrosive liquids another, and so on.

ukn (Chemical) · Answer 3 · 2002-12-30 01:45:15

qazx
i would add that there is a criteria in API 14E mainly for hydrocarbon fluids on erosion velocity. Its

velocity= C/SqRoot(density)
density in lb/ft3 and velocity in ft/sec. C is a constant, value 100 for continous service and 120 to 150 for discontinous service

ukn

jmw (Industrial) · Answer 4 · 2002-12-30 05:36:34

I think you may find that there is also a limitation on hydrocarbon velocities in pipelines that relates to static electricity generation. I believe there is an ASTM standard on this, maybe some one else can help out here.

johbil (Bioengineer) · Answer 5 · 2002-12-30 15:25:23

When you talk about erosion corrosion a lot depends on the fluid and its properties. For entrained air in water a practical limit of 5 M/S (15 ff/s) has been proposed. At that velocity you will have an appreciable pressure loss per length unit. In my opinion you want to stay away from that high a velocity. (energy and equipment concerns)
If here are however abrasive particles in the liquid, the maximum velocity drops to about 1.5 m/s or 4.5 ft/s). We have arrived at this velocity by trial and error. We have one application in which an 15% ds abbrasive in acidified water is used. The solution is pumped in stainless steel piping. By adhering to this maximum velocity we have succesfully reduced the occurence of erosion corrosion.

SagarSanjeev (Mechanical) · Answer 6 · 2003-01-08 00:18:22

It depends on the fluid you are handling if you are dealing with oil coolers than the normal fluid flow velocity through tubes (water) is 1.5 to 2 m/sec as per API recommendations.

saxon (Chemical) · Answer 7 · 2003-01-09 12:55:13

qazx, Velocity limitation is due primarily to "water hammer" problems that occur when valves and the like are open and closed during system operation. The fundamental equation for the subsequent pressure rise that can occur is as follows:

P=M*dv/dt

where:
P=pressure rise
M=mass of fluid
v= mean velocity of pipe flow
t=time closure of valve

So what happens when the velocity is high? Pressure rise is high. Or What happens when time of closure approaches 0?
Pressure rise approaches infinity. Now what happens when the pressure rise is greater than allowable system pressure? Opps! the system just blew up! I won't mention vibration problems, cyclic pressure loads and fatigue of the piping or system components.

If the fluid stream is abrasive and or corrssive, high velocities will increase erosion/corssion rates.

Hope this this provides an insight into the rational for limiting fluid velocities.

saxon

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Fluid Velocity In Pipeline