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MECHANICAL HAZARDS - Pressure Vessel Safety

The presentation used to aid the lecture "Mechanical Hazards - Pressure Vessel Safety" as a part of the course OME 754 Industrial Safety handled by Prof. Rathnavel Ponnuswami for Akshaya College of Engineering and Technology

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MECHANICAL HAZARDS - Pressure Vessel Safety

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  1. PRESSUREVESSEL SAFETY

  2. PRESSUREVESSEL SAFETY Introduction to Pressure Vessels UPV Safety

  3. INTRODUCTION TO PRESSURE VESSELSakaUPV or UFPUnfired Pressure Vessels

  4. PRESSURE VESSELS • Pressure vessels are containers for fluids under high pressure. • They are used in a variety of industries like • Petroleum refining • Chemical • Power • Food & beverage • Pharmaceutical

  5. TYPES OF PRESSURE VESSELS There are three main types of pressure vessels in general • Horizontal Pressure Vessels • Vertical Pressure Vessels • Spherical Pressure vessels However there are some special types of Vessels like Regeneration Tower, Reactors etc. But these names are given according to their use only.

  6. TYPES OF PRESSURE VESSELS

  7. HORIZONTAL PRESSURE VESSEL

  8. VERTICAL PRESSURE VESSEL

  9. SPHERICAL PRESSURIZED STORAGE VESSEL

  10. Constructed in a wider range of shell diameter and height. They can be relatively small in dia. and very large (e.g. 4 ft dia. And 200 ft tall distillation column. They can be very large in dia. and moderately tall (e.g. 3 ft dia. And 150 ft tall tower). Internal trays are needed for flow distribution. TALL VERTICAL TOWER

  11. Figure shows a typical reactor vessel with a cylindrical shell. The process fluid undergoes a chemical reaction inside a reactor. This reaction is normally facilitated by the presence of a catalyst which is held in one or more catalyst beds. VERTICAL REACTOR

  12. MAIN COMPONENTS OF PRESSURE VESSEL Following are the main components of pressure Vessels in general • Shell • Head • Nozzle • Support

  13. SHELL • It is the primary component that contains the pressure. • Pressure vessel shells in the form of different plates are welded together to form a structure that has a common rotational axis. • Shells are either cylindrical, spherical or conical in shape.

  14. SHELL • Horizontal drums have cylindrical shells and are constructed in a wide range of diameter and length. • The shell sections of a tall tower may be constructed of different materials, thickness and diameters due to process and phase change of process fluid. • Shell of a spherical pressure vessel is spherical as well.

  15. HEAD • All the pressure vessels must be closed at the ends by heads (or another shell section). • Heads are typically curved rather than flat. • The reason is that curved configurations are stronger and allow the heads to be thinner, lighter and less expensive than flat heads. • Heads can also be used inside a vessel and are known as intermediate heads. • These intermediate heads are separate sections of the pressure vessels to permit different design conditions.

  16. NOZZLE • A nozzle is a cylindrical component that penetrates into the shell or head of pressure vessel. • They are used for the following applications. • Attach piping for flow into or out of the vessel. • Attach instrument connection (level gauges, Thermowells, pressure gauges). • Provide access to the vessel interior at MANWAY. • Provide for direct attachment of other equipment items (e.g. heat exchangers).

  17. SUPPORT • Support is used to bear all the load of pressure vessel, earthquake and wind loads. • There are different types of supports which are used depending upon the size and orientation of the pressure vessel. • It is considered to be the non-pressurized part of the vessel.

  18. HAZARDS The potential danger associated with pressure vessels failure if not properly designed, constructed, operated, inspected, tested, or repaired are Blast Effects Fragmentation damage Suffocation Poisoning Fire Explosion Chemical burns Thermal burns

  19. UPV— SAFETY The safety of unfired pressure vessels can be ensured by • Internal inspection • Vessel history documents • Entry • Cleaning and Purging • Testing • Operator Training and Supervision • Safety Devices • Pressure Gauges

  20. UPV—Internal Inspection • Internal inspection • Periodic internal inspections to evaluate integrity of equipment. • Inspections should be carried out by NB licensed inspectors to ensure compliance with jurisdictional or insurance requirements. • Preventive maintenance

  21. UFP—Vessel History Documents • Inspection or maintenance department should keep file or log of original design documents, records of inspections, and vessel history documents. • blueprints • manufacturer’s data reports and instructions • design data, including location of dimensional checkpoints • installation information • records of process changes • vessel’s historical profile, including records of all repairs and conditions found during inspections

  22. UPV—Entry • Develop safe policy and procedure for entering tanks • Confined space with permit and lockout/tagout safety procedures required by OSHA • Potential hazards of confined spaces: • toxic materials including inert gases • flammable vapors which may be ignited • insufficient oxygen • heat or smoke from fire inside vessel • introduction of hot gases or fluids from external sources • start up of agitators or putting confined space in motion

  23. UPV Entry (Cont.) • Prior to entry into pressure vessel: • Ensure it is properly drained, ventilated, and cleaned • Test atmosphere for oxygen content, explosiveness, and toxic levels • Disconnect and blank all connecting pipelines, or close, lock out, and tag valves on the line • All power-driven devices—disconnected, locked out, and tagged • Confined-space permit issued • Provide access for safe entry and exit from vessel • Use safety harnesses and lifelines • Put on proper PPE

  24. UPV—Cleaning and Purging • Clean and purge the vessel’s internal surfaces prior to entry. • Use specific methods based on the substance contained inside the vessel. • Forced ventilation is required to ensure all potentially harmful or dangerous gases and vapors have been removed. • Test atmosphere prior to entry as well as routinely throughout work processes inside a vessel.

  25. UPV—Testing • Hydrostatic tests • Can be used for vessels constructed without access for an internal inspection to ensure the vessel is fit for continued service. • Targeted for the maximum allowable working pressure, the set pressure of the lowest installed safety valve, or the normal operating pressure of the boiler or pressure vessel at discretion of the authorized inspector. • Testing should follow ASME Code and NBIC Codes. • Minimize hazards to personnel during testing, isolate test area from operations, and provide suitable barricades.

  26. UPV—Testing (Cont.) • Detecting cracks/measuring thickness • Ammonia released inside vessel and compressed air applied to a maximum pressure 50% of working pressure is obtained; swab soaked in hydrochloric acid passed over all seams and suspect areas; presence of white vapor (ammonium chloride) indicates leakage • Burning sulfur stick • Non-destructive methods (NDE)—radiography (RT) and ultrasonic examination (UT)—detect cracks, wastage, and other adverse conditions • Lacquer method—apply lacquer to clean system, then conduct hydrostatic test, and examine for cracking of lacquer

  27. UPV—Operator Training and Supervision • Thoroughly train employees working with pressure vessels in routine duties and emergency procedures. • Supervisors should be qualified and knowledgeable. • Review potential hazards of processes and systems. • Written detailed procedures should be reviewed periodically and made available to personnel. • Use a checklist in the training process for start-up, shutdown, or routine processing cycle. • Communication between all staff and personnel is critical. • Proper labeling of valves, piping systems, and control equipment prevents accidents caused by operator error.

  28. UFP—Safety Devices • UFP vessels used in processes with various materials and chemicals, equip each vessel with appropriate safety devices for the type of vessel and work performed. • Safety devices are installed for a purpose: • protect against overpressure • chemical reactions • abnormal conditions

  29. UFP – Safety Devices (Cont.) • Types of safety devices: • safety valves • rupture disks • vacuum breakers • water seal • vents • regulating or reducing valves

  30. UFP - Pressure Gauges • Pressure gauges used at 1800 psi or more should have these properties: • full size • blowout backs • integral sides • front designed to withstand internal explosion • have multi-ply plastic or double-laminated safety glass cover for gauge faces • install substantial shield in front of high-pressure gauges

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