Tie in point - Big diameter difference 2

[Tuga29]

In the project that I’m involved we are now in the design phase. I’m more from quality control and assurance but I want to help. We have right now an issue regarding the tie in point of our pipeline and a pipeline of other facility. The question is that the flow rate is the same and our pipe diameter is much bigger than the one that we will tie in. This will cause a velocity problem isn’t it? How can we solve this?

 

[LittleInch]

Velocity difference, of course, velocity problem, don't know. Give us a few details, but beware there are no fixed rules on velocity. What is acceptable in one situation may be unacceptable in another.

Make the pipe bigger??

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

 

[Tuga29]

Our pipeline is 18 inches and will tie in on a 8 inches from an existing facility.
Flow rates 1000m3/s.

 

[BigInch]

You can at least expect a large pressure drop there, as excess static pressure, if available, will be used to accelerate the fluid to that higher velocity.

 

[Tuga29]

But it's expected to have cavitation and turbulence problems right? Is there any way to solve this?
Maybe to reduce our pipe diameter before the tie-in?

 

[zdas04]

Gas or liquid? Let's assume gas (if it is water then the velocity is on the order of 20,000 ft/s in the 18 inch). Let's assume that your m3/s is SCM/s. Without knowing pressures or the flow rate in the 8-inch it is really hard to predict if there is a problem or not.

At that rate (call it 3 BSCF/day) at a nominal 1000 psig you would have 290 ft/s in the 18 inch and nearly 1470 ft/s in the 8-inch (assuming your gas is the only thing in the line). 1470 ft/s is 1.06 Mach and it isn't happening. You would need pressure on your 18-inch well above 1500 psig (with nothing else in the 8-inch) for this to work with compressible flow calculations.

David Simpson, PE
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist

 

[Bernoulli31]

1000m3/s? What is the application?

If the flowrate is the same, how come you're designing a much larger pipe? Also, I don't understand how you can tie-in a large diameter into a small diameter. Hydraulics are not going to look good.

 

[Tuga29]

My mistake, sorry. 1000m3/h.
We are talking about a new depot (ULP, ADO, JET and HFO), those are the dimensions of the pipelines to the new tank farm.
But we must connect the pipelines from the ships offloading directly to other private terminals and there we have the problem with the existing pipes dimensions.

 

[Tuga29]

And 500kPag at our tank farm.

 

[EmmanuelTop]

For 8" line and 1,000 m3/hr, velocities are in the range of 8 m/sec and pressure drop anywhere between 1-2 bar (100-200 kPa) for densities between 800-900 kg/m3 and dynamic viscosity between 1 and 5 cP. Long-distance 8" line is simply not going to work (massive pressure losses) at 1,000 m3/hr design flow, as pointed by everyone in this thread.

18" line results in velocities <2 m/sec and that looks good from design point of view.

Dejan IVANOVIC
Process Engineer, MSChE

 

[LittleInch]

This post is getting out of control very fast.

Tuga29 - draw out your schematic and add numbers and check them - flowrate, pressures, distances then come back.

1000m3/hr of liquid in an 8" pipe is just stupid. Can be done but makes no sense and you can generate significant surge forces or static charge.

However your description is all over the place and doesn't make sense.

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

 

[Tuga29]

Thank you for all your answers and interest and sorry about my explanations.

The 1000m3/h was a client requirement and today we see that it was wrong since the existing network distribution works with 500m3/h. Now we just need to see if with the cargo pumps (100 to 130m head) we could reach the furthest tank, about 8km of pipeline.