Large Steel Vessel Design

[MDDSI]

I am a chemical engineer working on a rather mechanical/structural engineering oriented project - sizing explosion venting for a future spray dryer. NFPA does a good job of explaining how to come about the needed venting area, but the thing I am hung up on is how to calculate the design pressure of a vessel. Spray dryers would be a large cylinder and truncated cone. I can calculate the hook and longitudinal stresses easy enough for a given pressure, but I am looking for any resources on standards and codes associated with vessel design. The dryer would operate at about -0.5 inches of water, so I don't believe this is technically a pressure vessel. Are there any books or documents you can recommend that discusses things like stiffener ring placement, supports, wall thickness or general design of large steel enclosures at pressures near atmosphere?

Thank you!

 

[mk3223]

Pressure vessel can be designed under either internal pressure or external pressure conditions. ASME BPVC may be applied to the spray dryers design. I believe it has a minimum external pressure as required for calculating the wall thickness and stiffening rings, as well as the hydrotest.

 

[SlideRuleEra]

MDDSI - The vessel you describe is like certain ductwork for fossil fuel power plants. I don't know of any standards that cover this type (negative pressure) design. Negative pressure is much different than positive pressure. For example, hoop stress may have meaning at a pressure of +0.5 inches of water, but is meaningless at -0.5 inches of water.

I suggest designing for the worst (lowest) possible negative pressure, not the operating negative pressure. Mechanical engineers should be able to define the worst case from fan/blower specs. Don't want an operating excursion or error to collapse the vessel.

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[SAIL3]

The following publication which may be out of print has some usefull info..
"Useful Information on the Design of Plate Structures" Vol 2,,AISI

 

[JStephen]

Also see Annex V of API-650, which covers vacuum design of tanks up to 1.0 PSI. If structure is large enough, wind may have a significant impact as well.

You mention "how to calculate the design pressure". The tank and pressure vessel standards all assume you're given the pressure and you take the design from there. The pressure used may be based on flow considerations, may be based on the set points or flow characteristics of the relief valves, etc.

 

[WARose]

I've typically used the 'Pressure Vessel Design Handbook' (2nd Edition, 1991) by Henry H. Bednar for such calculations. Such handbooks allow you to calculate pressures from localized loads on walls and heads independent of the external/internal pressures.