Mechanical integrity vessels

Mechanical Integrity Vessels and other equipment must meet existing codes and be inspected during manufacture and after installation. Appropriate procedures for maintenance must be developed and followed. 

Some toll processes lend themselves to test runs in the pre-startup phase. Actual materials for the toll may be used in the test or substitute materials, typically with low hazard potential, are often used to simulate the charging, reaction, and physical changes to be accomplished in the toll. Flow control, temperature control, pressure control, mixing and transferring efficiency can be measured. Mechanical integrity can be verified in regard to pumps, seals, vessels, heat exchangers, and safety devices. 

Test run steps can frequently be incorporated into process startup procedures. Two examples would be pulling a vacuum on vessels and verifying it holds, or distilling a solvent and checking for the presence of water to verify the mechanical integrity of the heating and cooling equipment. 

Similarly, a negative pressure differential across the spent catalyst slide valve can allow hot flue gas to backflow to the reactor and the main fractionator, severely damaging the mechanical integrity of these vessels. 

Process Facilities 15 Area electrical classification 16 Accessibility for mechanical integrity (sampling, maintenance, repairs) 17 Protection of piping and vessels from vehicles and forklifts 18 Protection of small-bore lines, fittings from external impact, personnel 19 Routing of process piping, critical controls cable trays, critical utilities 20 Vent, drain, and relief valve discharge locations... 

The Workbook does not deal with fire relief of vessels (except where external fire modifies the relief sizing for runaway exothermic reaction) or with the mechanical integrity of either the process vessels or relief system. Guidance on these is available elsewhere14. 

Covers mechanical integrity programs for piping, pressure vessels, storage tanks, and process piping, including corrosion under insulation problems... 

Mechanical Integrity Programs for Piping, Pressure Vessels, Storage Tanks, and Process Piping... 

The mechanical integrity focus of this section covers stationary existing chemical processing plant equipment and piping. Equipment includes storage tanks, pressure vessels, dryers, heat exchangers, reactors, incinerators, columns, filters, knock-out pots, and so forth. As previously stated, this section assumes the equipment is designed and fabricated to... 

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 previously defined. Here are the highlights of that section specifically for pressure vessels and storage tanks. 

The Role of Mechanical Integrity in Chemical Process Safety 219 Internal Inspections of Vessels... 

The Freeport, Texas, Dow Chemical Plant shared details of their pressure vessel management program several years ago. [19] The Dow Texas pressure vessel program had evolved over 25 years and covered about 12,000 pressure vessels. No doubt with today s PSM Mechanical Integrity element, Dows program has far exceeded the excellent efforts discussed here. 

If pressure-containing parts of a vessel corrode or erode to a thickness less than the minimum allowable, something must be done. The deficient parts must be reconditioned or the equipment will be assigned a lower pressure rating consistent with the new conditions. When a vessel is rerated, engineers review the relief system. [ 19] The Dow Chemical system for vessels, as reported over a decade ago, seemed to be a very practical method to meet the todays OSHA Mechanical Integrity requirements. 

Large safety factors have been built into the design of the EDS vessel and the procedures for its operation. The mechanical integrity of the vessel was evaluated by Sandia National Laboratories using a combination of small-scale failure analysis tests and computer simulations. This evaluation indicated that the EDS-1 containment vessel could withstand several thousand detonations with more than 1 pound of explosive, providing a significant margin of safety for a system with an intended life of 500 detonations (SNL, 2000). 

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