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Becht Engineering Blog

In this section of the site contributing authors submit interesting articles relating to the various services, industries and research & development efforts of Becht Engineering.

Design/Specification of FCC Replacement Parts and Upgrades

Design/Specification of FCC Replacement Parts and Upgrades
Overview Fluid Catalytic Cracking (FCC) units were first developed in the 1930s. Over the years this technology has evolved and it is one of the most important processes used in refineries. The FCC units are used to convert high boiling point, high molecular weight hydrocarbon fractions of crude oils to gasoline, olefinic gases, and other products. There are a number of process technology providers who license proprietary FCC technology; however, the equipment is basically the same ─ a reactor vessel where the hydrocarbon feed and hot catalyst contact and react (~950F) producing hydrocarbon vapors for further processing, and a regenerator vessel where the carbon laid down on the surface of catalyst from the reaction is burned off (regenerated and heated) in a fluidized bed (~1350F). The regenerated catalyst is returned to the reactor. The catalyst circulation between the reactor and regenerator is continuous. Large diameter refractory lined piping (transfer lines) circulate the...
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State Approval of Used or Relocated Pressure Vessels

State Approval of Used or Relocated Pressure Vessels
Achieving “State Special” designation for a pressure vessel can require a fair amount of effort in documentation development.   This process is warranted – for example – when a company wants to move a pressure vessel from one facility for operation in a facility located in another state, or when they purchase a used vessel located in another country or state for use in the United States.   The vessel may or may not have been constructed to the rules of the ASME Boiler and Pressure Vessel Code or ASME Code stamped.   A question that typically arises, “Are there regulations governing the relocation/reuse of such vessels?” The answer is “Yes” and the regulations are found within the state agency, e.g.  the Department of Public Safety, the Department of Labor that has jurisdiction over both the construction of new boilers and pressure vessels, and inspection and repairs of existing equipment.  It is headed by...
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Refrigerated Storage Tanks – Managing Operational Integrity

Refrigerated Storage Tanks – Managing Operational Integrity
Refrigerated Liquefied Storage Tanks have been used for over 60 years in the industry. A significant number of these tanks store liquefied Propane and Butane, Ethylene and LNG and Ammonia. The stored fluids are at atmospheric pressures with temperatures which range from -45 F to -270 Failures of refrigerated tanks have been quite infrequent over the past 50 years. However, in each of these incidents there was catastrophic damage to the tank and its environment. In view of this history, Industry Standards and Operating & Maintenance practices place a rigorous emphasis in managing tank safety and integrity. Background At a major Refrigerated Storage Tank Terminal, the Operators were confronted with a need to remove a large dome roofed LPG tank from service to internally inspect the bottom plates for structural integrity. The concern arose from the discovery of “cold zones” (icing up) at localized areas in the tank foundation - which...
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Explosive Failure of Vessels

FAILURE MODE - When an explosion (either a subsonic deflagration, or a supersonic detonation) occurs in a metallic vessel, one of three things can happen: Case 1 – Containment: The vessel can contain the explosion, elastically as if nothing happened, or with plastic bulging. Case 2 – Rupture: The vessel can rupture, without ejecting fragments. The rupture can be a fish-mouth ductile tear, or a more brittle running crack. Case 3 – Fragmentation: The vessel can rupture and fragment. There can be as little as a single fragment, for example when the top of a ground-anchored vessel takes off like a rocket, leaving behind the its anchored bottom, or as many as dozens of fragments of different sizes. PREDICTION - Can we predict which of the three failure modes will take place? In most cases, yes. Let’s explain what we mean by “in most cases”: CONTAINMENT - We can predict analytically...
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