Restriction Orifice Thickness Sizing 2

[Krejcirs]

Sonic Flow and Restriction Orifice Thickness
Thickness of the restriction orifice plate needs careful consideration as the differential pressure across the orifice plate is generally higher as compared to measurement orifice, particularly for the sonic flow application where high differential pressure is desired to be maintained to achieve the sonic condition(Note 3).
Sonic flow through restriction orifice plate in quite common in chemical process plants as well as oil and gas industries. The design of the restriction orifice plate will be such that sonic flow is maintained(Note 4). Restriction orifice bore selection(Note 5) for sonic conditions are generally done on trial and error basis in process simulation software. Upstream pressure of the orifice plate is calculated in such a way that flow through the restriction orifice is sonic until the vessel pressure has reached 50% of its design pressure. When a gas flows from one point to other through an orifice, it is obvious that as the down pressure is reduced, the flow rate steadily increases until the velocity at the orifice reaches sonic velocity. Any further reduction of downstream pressure, the flow rate is unaffected and the excess pressure is dissipated in shock waves downstream of the orifice. It should be noted that square
root formula used for normal orifice flow measurement is not valid for sonic flow.


Thickness Calculation Formula
Thickness of any orifice plate, as defined in the R.W.Miller's handbook, depends on the following parameters l Line size
Differential Pressure
Yield Stress of Plate
ß Ratio

Can anyone finish this article? It was cut off right at the most critical point.

 

[danw2]

You might try emailing a couple of people on the contact list to see if you can buy the backissue or an electronic copy. Sometimes major universities will have access to periodicals.

http://www.etinstrumentation.com/contactus.html