9 replies to this topic

[snoopie]

Hi,

The inlet stream to the vessel (Vertical Separator with Demister) is as below:

Gas Flow: 340000kg/hr (Density = 70kg/m3)

Liquid Flow: 437kg/hr (Density = 1006kgm3)

 

Based on the conditions above, it is stated that the inlet nozzle recommended velocity is 9.6m/s.

 

As far as I read from the DEP,

For no inlet device, pv2 < 1400

Half open pipe, pv2< 2100

Schoepentoeter, pv2< 8000

 

I do not understand how does the recommended velocity (9.6m/s) is calculated since the type of the inlet device is not stated. Is there anyway to calculate the velocity despite the momentum criteria? Can anyone englighten me on this?..

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[Bobby Strain]

The correct parameter for nozzle sizing is pv² . Be sure you have a good source. If you work for some company, make sure your criteria is in line with theirs. You failed to tell us the reference for the recommended velocity that you state.

 

Bobby

[snoopie]

Hi Bobby, the reference velocity is from an in house calculation sheet, which i m not able to see the related equations in the excel...that's why i m curious how it comes out with that velocity..

[Bobby Strain]

And why can't you see the related equation?

 

Bobby

[shekhar dhuri]

Hi,

As per my understanding, ρv2 is the criteria generally used in the industry for sizing of inlet nozzle (two phase) and gas outlet nozzle. Maximum allowable ρv2 however is based on the design standard we use i.e. DEP or any Company validated calculations. For liquids, nozzle sizes are based on the velocity criteria. Therefore, please size the inlet nozzle and gas outlet nozzle based on ρv2.

Once you size the inlet nozzle, calculate fluid velocity since Higher velocities (> 10 -15 m/s) can impinge directly on shell wall depending on diameter of vessel. If this case arises the vessel should be provided with a suitable impingement plate. Therefore, in my opinion, velocity criteria for the inlet nozzle is used to decide the requirement of impingement /deflector plate. Deflector plate mainly required for no inlet device / half open pipe. I am not sure in case of Schoepentoeter.

Regards,
Shekhar

Edited by shekhar dhuri, 30 March 2014 - 06:33 AM.

[snoopie]

U mentioned that the nozzle sizes are based on velocity criteria. If i understand correctly, the velocity criteria is same as the line sizing velocity criteria?....

[ahyong]

Hi Snoopie,

 

I believe that SHELL DEP recommended to use <=1 m/s for nozzle sizing at new vessel. Since DEP provided the method to calculate for the diameter of the nozzle, you can easily calculate the velocity at nozzle by using the same method too with the criteria that you mentioned above. (Velocity at nozzle = FLowrate (m/s)/0.7854/Diameter of nozzle/Diameter of nozzle). Be sure to include oversize factor at flowrate too.

This is what I use to check the velocity at nozzle

[Steady]

there is a lot of mish-mash in the above few posts.

 

In my opinion, the normal squence of this calc would be -

1. You know the inlet line size and flow conditions that means you know the pv² in the inlet line. The line size must satisfy the general line sizing criteria
2. Is the inlet nozzle size same as the inlet line size. If yes, then you already know the pv² as calculated above otherwise calculate it again
3. Compare that calculated pv² with the standard and decide if you need any inlet device or you need to change the nozzle size.

 

Cheers

Edited by Steady, 31 March 2014 - 08:11 AM.

[snoopie]

Thank you all for the clear info

[amiprocess]

In case of separator inlet nozzle criteria I have got some confusion comparing DEP and GPSA 13th Edition.

 

====Inlet Device Momentum=====

According to DEP

None ρ_mV²_m,in ≤ 1400 kg/m.s2

Half Open Pipe ρ_mV²_m,in ≤ 2100 kg/m.s2
Schoepentoeter ρ_mV²_m,in ≤ 8000 kg/m.s2

 

According to GPSA 13TH Edition (separator section page: 7-25)

• 6000-9000 max. typ, up to 15 000 max kg/m • s2 for diffuser

distributor

• 975-2250 max kg/m • s2 for no inlet distributor

• 1500-3750 max kg/m • s2 for inlet half pipe or elbow distributor

• 1500-3750 max kg/m • s2 for v-baffle or other simple inlet

diverter designs

 

Confusions  on GPSA 13th Data

1. What is the upper momentum limit of the (no inlet distributor)

2. The limit shows that the half pipe, elbow distributor, v-baffle are similar.

3. in between 3750-6000 kg/m.s2 which device should be used.

 

Please advice.