+2 votes
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Surge forces definitions of the process vessels

asked Sep 2, 2014 in Downstream-Midstream by judyp (2,700 points)
Surge forces definitions for fluidized solids process vessels and support structures that are subject to surge vibration.

3 Answers

+2 votes
answered Sep 2, 2014 by judyp (2,700 points)

Surge Forces: Static lateral forces that account for the dynamic loads generated by surge vibration.

Surge Vibration: Movement induced by the action of fluidized solids contained in process vessels and piping.

Normal Surge Forces: The forces corresponding to the maximum fluid-bed height and density in the process vessels and piping during normal operation of the equipment.

Abnormal Surge Forces: The forces corresponding to the most severe combination of fluid-bed height and density in the process vessels and piping during startup or upset of the equipment.

 

+1 vote
answered Sep 2, 2014 by Tadd Pham (5,620 points)

The surge force applied to a single process vessel and its support structure for process equipment is:

  • Fluid Catalytic Cracking: 0.075W
  • Flexicracking: 0.075W
  • Fluid Coking: 0.15W
  • Flexicoking: 0.15W
  • Gas Conversion Fixed-bed Syngas Generator: 0.15W

Where;
W, for normal surge force, is the maximum weight of fluid-solids in a single vessel and associated piping during normal operation.
W, for abnormal surge force, is the maximum weight of fluid-solids in a single vessel and associated piping during abnormal (startup or upset) conditions resulting in the most severe combination of fluid-bed height and density in the vessel.

0 votes
answered Sep 2, 2014 by pasmith (3,320 points)
  • The total surge force should be divided between the vessel and the portion of the support structure extending above the base of the vessel skirt according to their relative weights.
  • The total surge force should be the sum of the surge force for the structure and the surge force for the vessel.
  • The surge force for the structure should be distributed over the portion of the support structure located above the base level of the vessel support according to the mass weighted by its height above the vessel support level.  The surge force for the structure should not exceed 20% of the total surge force.
  • Surge forces should be considered to act in any horizontal direction that causes the largest stresses, overturning moments, or deflection.
  • Surge forces applied to the vessel and to the support structure should be considered to act simultaneously in each of the following combinations:
    • The surge forces on the vessel and on the support structure acting in the same direction
    • The surge forces on the vessel acting in the opposite direction of the surge forces on the support structure
    • The surge forces on the support structure and on the vessel above the skirt acting in the opposite direction of the surge forces on the vessel below the skirt to produce the maximum base rotation
  • Relative stiffness of the vessel, the support structure, and vessel to support structure connections should all be considered when determining how the surge forces are transmitted between the vessel and the support structure.
  • If two or more vessels are supported by or connected to a common support structure, all surge forces should be considered to act simultaneously.  However, only feasible combinations of fluid-bed height and density that could simultaneously occur in all the vessels for a particular normal or abnormal condition should be considered.
  • Members and connections should be checked for fatigue assuming two million loading cycles using stresses from normal surge loads.
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