Impingement Plate, Moss et al

[jeanchile]

Hello all,

I have been asked to design an impingement plate per the horizontal vessel detail on page 390 of the Pressure Vessel Design Manual (top right of page) by Dennis R. Moss. Procedure 5-13 shows a vertical vessel but not a horizontal vessel and in all honesty I'm at a loss as to the entire process (I've never calculated one before).

I have the following questions if you feel inclined to help:
1.) The equation that Moss gives for calculating the Equivalent Static Force From Dynamic Flow (F) is F=(V A d)/g but that should read "vee squared" not just "vee" right?
2.) Does anyone have some example calculations for an impingement plate at a horizontal vessel that I can follow by chance?
3.) I've calculated a flow rate of 534 cubic feet per second and an area of 50 inches squared. I believe this gives me a velocity of +-1536.2 ft/s does it not?

I'm hoping to get enough help with this to create an Excel spreadsheet for these in the future. I know if I calculate this one, they're going to ask me to do it all the time. Thanks in advance for the help!

 

[gr2vessels]

Impingement plate is required for ro x v^2 larger than 6000-8000 in metric values. The HTRI will alert you on the need of impingement plate. The size of the impingement plate is typically 25% larger than the nozzle cross section. For gases you can use perforated plate, but for liquids and droplets carried over it should be solid plate. If impingement forces are so high that they will bend the tubes, then use suspended nozzle inserts, hanged of the nozzle, rather than attached to the tube bundle.
Also, check out the TEMA RCB-4.6 IMPINGEMENT BAFFLES requirements.
TEMA querries have also clarified that: "RCB-4.61 does not require impingement plates for all vapors and gases. It requires impingement plates for non-abrasive, single phase fluids where pv^2 is greater than 1500 and all other vapors and gases (that is, vapors and gases which are not non-abrasive and single phase). It does not require impingment plates for fluids (including gases and vapors) which are nonabrasive, single phase, and pv^2 less than 1500".
I would not bother with the calculation, it's just a simply supported beam structural calculation. Select a thumb rule thickness, include corrosion allowance if needed.
Cheers,
gr2vessels

 

[jeanchile]

I am so sorry gr2vessels. I should have been more clear. This is not for a heat exchanger it's just a natural gas "knock-out drum".

The media is water and hydrocarbon vapors, with a density of 0.064 lb/ft^3. The flow is listed on the data sheet as 95,938 lb/hr and 46.11 MMSCFD. Operating temperature is 50-140 degrees F.

Using that information I calculated the velocity at 1536 ft/second but if I'm honest, I'm not entirely sure that's correct because I've never done this before. I figured the next step was to turn the dynamic flow/velocity into an equivalent static force and then analyze the plate/weld after that but I'm trying to nail down the exact steps.

I certainly appreciate the help, and I apologize for the ambiguity, but this is a new procedure for me and I'm trying to learn how to accomplish the task I've been assigned. Thanks for your help!

 

[gr2vessels]

You can download for free the DEP 31.22.05.12-Gen for the knock-out drum calculations.
There is everything you need for the design of these separators. Obviously, you need to provide a suitable mechanical design in accordance with your applicable code.
Cheers,
gr2vessels