Separator Vessel Nozzle Velocity and Momentum

[bmp28]

Hi guys,

I'm checking 2 phase separator vessel inlet nozzle velocity and momentum,, using various guidelines and refereces, but nothing conclusive.

One company internal guideline for separator inlet nozzle rho v2 suggests,
-No inlet device rho-v2 <1000 kg/ms²
-Pipe inlet device rho-v2 <1500 kg/ms²
-Vane type inlet device rho-v2 <6000 kg/ms²

When used inconjunction the velocity limits of 10-25 m/s for vapor and 8-15 for mixed phase flow, the rho v2 limits are breached.

Is there a guideline like API RP or Shell DEP that suggest the maximum velocity and momentum limitation in separators?

Which is governing, velocity or the momentum?

Thanks in advance,
bmp28

 

[katmar]

One free standard that is available is the NORSOK P-100

http://www.standard.no/pronorm-3/data/f/0/01/41/0_10704_0/P-100.pdf

Katmar Software
Engineering & Risk Analysis Software

http://katmarsoftware.com

 

[sethoflagos]

bmp28,

The DEP reference is 31.11.05.11-Gen which gives rho-v2 limits identical to those you quote (december 1996 revision).

It's very conservative.

 

[roker]

hello bmp28,

beside the rov^2 a very useful design is a tangential inlet.

regards,
roker

 

[skyporker]

So is separation efficiency reduced if momentum is above these guidelines? or are the concerns excessive pressure loss and erosion?

Regards,

skyP

 

[25362]

Please note that kg/(ms²) = N/m² = Pa, a pressure unit.

Wear by erosion depends on the impacting particle velocity and the angle of impingement. At a 20^o angle erosion may already be considerable.

For liquid droplets impinging on a solid surface at 90^o the pressure on impact is:

p = [&rho;] [&times;] v_s [&times;] v​

where:

p = pressure on impact [Pa];
[&rho;] = liquid density [kg/m³];
v_s = sound velocity in liquid [m/s];
v = liquid droplet velocity [m/s].

As an example, for water droplets travelling at 100 m/s,

p = 1000[&times;]1500[&times;]100 = 150 [MPa] !​

Wear by impact can form holes or pits, and may even cause fracture if the material is brittle. This is a subject covered -among others- in tribology engineering books.

The following threads and the links therein may show to be helpful with regard to corrosive-erosive wear of piping:

thread794-57906
thread378-66050
thread378-64478
thread378-30500
thread338-23463
thread124-70976