Pressure Vessels and Storage Tanks

The intent of the mechanical integrity section of the OSHA Process Safety Law is to prevent or reduce catastrophic releases. [1] An equipment classification system is a requirement of the law. Earlier in the chapter, a simple system involving three classes was defined. Here are the highlights of that section specifically for pressure vessels and storage tanks. 

Critical Consequences—Class 1. Containment equipment whose failure would result in uncontrolled catastrophic releases of dangerous materials resulting in accidental 

Serious Consequences —Class 2. Containment equipment whose failure could pos.sibIy cause uncontrolled releases of dangerous materials, situations that could result in accidental fires and explosions, with minimal off-site problems. Such a failure could have revSulted in serious conditions involving environmental releases, property nr production losses, or other non-life-threatening situations. This equipment is given a slightly lower priority. However, the equipment is also inspected and tested on a regular schedule, but may be allowed to have some leniency in compliance. 

Nomud Consequences—Class 3. All other containment equipment serving the operation whose failure could not create serious conditions involving recordable environmental releases, or injury to personnel. However, such a failure could create some property losses or production interruptions. 

API 510, Pressure Vessel Inspection Code Maintenance, Inspection, Rating, Repair, and Alteration, June 1989, is an owner/user code and an excellent inspection reference. 117] Some countries, provinces, and states require pressure vessels to be inspected by govem-ment agents. In those cases, the goveniing agency s rules should be the standard reference. 

Normal Consequences—Class 3. All other containment equipment serving the operation whose failure could not create serious conditions involving recordable environmental 

Visual external inspections (or in-service inspections) should be made regularly to operating vessels to help ensure the integrity of the vessel. The frequency of this inspection should 

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The important property of high mechanical strength of duplex stainless steels has been profitably used in the fabrication of pressure vessels, and storage tanks. The digesters in the pulp and paper industry are made of duplex stainless steels of wall thickness of 19-21 mm compared with 31 mm thickness of carbon steel. Some typical wall thickness values of steels calculated for pressure vessels are noted below ... 

Pressure Vessels and Storage Tanks 143 Carbon Steel... 

The preventive maintenance/predictive program covers pressure vessels and storage tanks, valve and piping systems, relief and vent systems, emergency shutdown systems, fire suppression systems, controls, and pumps. 

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