Design for Overpressure and Underpressure Protection Slide Show Slides with Text Exit

Design for Overpressure and Underpressure Protection SLIDE PRESENTATION NEXT HOME

Design for Overpressure and Underpressure Protection Outline Introduction Introduction Causes of Overpressure and Underpressure Reliefs Effluent Handling Systems for Reliefs Runaway Reactions Overpressure Protection for Internal Fires and Explosions Reliefs Runaways Safeguards

Design for Overpressure and Underpressure Protection For Further Information: Refer to the Appendix Supplied with this Presentation NEXT PREVIOUS Text Home

Causes of Overpressure Design for Overpressure and Underpressure Protection Causes of Overpressure Operating Problem Equipment Failure Process Upset External Fire Utility Failures NEXT PREVIOUS Text Home

Causes of Underpressures Design for Overpressure and Underpressure Protection Causes of Underpressures Operating Problem Equipment Failure NEXT PREVIOUS Text Home

Presentation 1 of 3: Reliefs Design for Overpressure and Underpressure Protection Presentation 1 of 3: Reliefs Causes of Overpressure/Underpressure Presentation 2: Runaways NEXT PREVIOUS Presentation 1: Reliefs Presentation 3: Safeguards Text Home

Pressure Relief Devices Design for Overpressure and Underpressure Protection Pressure Relief Devices Spring-Loaded Pressure Relief Valve Rupture Disc Buckling Pin Miscellaneous Mechanical NEXT PREVIOUS Text Home

Spring-Loaded Pressure Relief Valve Design for Overpressure and Underpressure Protection Spring-Loaded Pressure Relief Valve NEXT PREVIOUS Text Home

Design for Overpressure and Underpressure Protection Rupture Disc NEXT PREVIOUS Text Home

Buckling Pin Relief Valve Design for Overpressure and Underpressure Protection Buckling Pin Relief Valve Closed Pressure Below Set Pressure Full Open Pressure at or Above Set Pressure (Buckles in Milliseconds at a Precise Set Pressure) NEXT PREVIOUS Text Home

Simple Mechanical Pressure Relief Design for Overpressure and Underpressure Protection Simple Mechanical Pressure Relief NEXT PREVIOUS Text Home

Types of Spring-Loaded Pressure Reliefs Design for Overpressure and Underpressure Protection Types of Spring-Loaded Pressure Reliefs Safety Valves for Gases and Vapors Relief Valves for Liquids Safety Relief Valves for Liquids and/or Gases NEXT PREVIOUS Text Home

Design for Overpressure and Underpressure Protection Types of Safety Valves Conventional Balanced Bellows, and Pilot-Operated NEXT PREVIOUS Text Home

Conventional Safety Valve Design for Overpressure and Underpressure Protection Conventional Safety Valve NEXT PREVIOUS Text Home

Balanced Bellows Safety Valve Design for Overpressure and Underpressure Protection Balanced Bellows Safety Valve NEXT PREVIOUS Text Home

Pilot-Operated Safety Valve Design for Overpressure and Underpressure Protection Pilot-Operated Safety Valve NEXT PREVIOUS Text Home

Design for Overpressure and Underpressure Protection Types of Relief Valves Conventional Balanced Bellows NEXT PREVIOUS Text Home

Design for Overpressure and Underpressure Protection Types of Rupture Discs Metal Graphite Composite Others NEXT PREVIOUS Text Home

Rupture Disc and Pressure Relief Valve Combination Design for Overpressure and Underpressure Protection Rupture Disc and Pressure Relief Valve Combination NEXT PREVIOUS Text Home

Design for Overpressure and Underpressure Protection Vacuum Relief Devices Vacuum Relief Valves Rupture Discs Conservation Vents Manhole Lids Pressure Control NEXT PREVIOUS Text Home

Design for Overpressure and Underpressure Protection Conservation Vent NEXT PREVIOUS Text Home

Pressure or Vacuum Control Design for Overpressure and Underpressure Protection Pressure or Vacuum Control Add Air or Nitrogen Maintain Appropriately NEXT PREVIOUS Text Home

Design for Overpressure and Underpressure Protection Relief Servicing Inspection Testing NEXT PREVIOUS Text Home

Design for Overpressure and Underpressure Protection Relief Discharges To Atmosphere Prevented Effluent System NEXT PREVIOUS Text Home

Design for Overpressure and Underpressure Protection Effluent Systems Knock-Out Drum Catch Tank Cyclone Separator NEXT PREVIOUS Text Home

Effluent System (continued) Design for Overpressure and Underpressure Protection Effluent System (continued) Condenser Quench Tank Scrubber Flares/Incinerators NEXT PREVIOUS Text Home

Effluent Handling System Design for Overpressure and Underpressure Protection Effluent Handling System NEXT PREVIOUS Text Home

Presentation 2 of 3: Runaways Design for Overpressure and Underpressure Protection Presentation 2 of 3: Runaways Causes of Overpressure/Underpressure Presentation 2: Runaways NEXT PREVIOUS Presentation 1: Reliefs Presentation 3: Safeguards Text Home

Design for Overpressure and Underpressure Protection Runaway Reaction Temperature Increases Reaction Rate Increases Pressure Increases NEXT PREVIOUS Text Home

Causes of Runaway Reactions Design for Overpressure and Underpressure Protection Causes of Runaway Reactions Self-Heating Sleeper Tempered Gassy Hybrid Characteristics of Runaway NEXT PREVIOUS Text Home

Self-Heating Reaction Design for Overpressure and Underpressure Protection Self-Heating Reaction Loss of Cooling Unexpected Addition of Heat Too Much Catalyst or Reactant Operator Mistakes Too Fast Addition of Catalyst or Reactant NEXT PREVIOUS Text Home

Design for Overpressure and Underpressure Protection Sleeper Reactions Reactants Added But Not Mixed (Error) Reactants Accumulate Agitation Started .. Too Late NEXT PREVIOUS Text Home

Design for Overpressure and Underpressure Protection Tempered Reaction Heat Removed by Evaporation Heat Removal Maintains a Constant Temperature NEXT PREVIOUS Text Home

Design for Overpressure and Underpressure Protection Gassy System No Volatile Solvents Gas is Reaction Product NEXT PREVIOUS Text Home

Design for Overpressure and Underpressure Protection Hybrid System Tempered Gassy NEXT PREVIOUS Text Home

Reliefs for Runaway Reactions Design for Overpressure and Underpressure Protection Reliefs for Runaway Reactions Two Phase (or Three Phases: Liquid, Vapor, and Solid) Flow Relief Area: 2 to 10 Times the Area of a Single Gaseous Phase NEXT PREVIOUS Text Home

Design for Overpressure and Underpressure Protection Two Phase Flow NEXT PREVIOUS Text Home

Relief Valve Sizing Methodology Design for Overpressure and Underpressure Protection Relief Valve Sizing Methodology Special Calorimeter Data Special Calculation Methods NEXT PREVIOUS Text Home

Characterization of Runaway Reactions Design for Overpressure and Underpressure Protection Characterization of Runaway Reactions ARC VSP RSST APTAC PHI-TEC Dewars NEXT PREVIOUS Text Home

Presentation 3 of 3: Safeguards Design for Overpressure and Underpressure Protection Presentation 3 of 3: Safeguards Causes of Overpressure/Underpressure Presentation 2: Runaways NEXT PREVIOUS Presentation 1: Reliefs Presentation 3: Safeguards Text Home

Design for Overpressure and Underpressure Protection Safeguards Safety Interlocks Safeguard Maintenance System Short-Stopping NEXT PREVIOUS Text Home

Design for Overpressure and Underpressure Protection Safety Interlocks Agitator Not Working: Stop Monomer Feed and Add Full Cooling Abnormal Temperature: Stop Monomer Feed and Add Full Cooling NEXT PREVIOUS Text Home

Safety Interlocks (continued) Design for Overpressure and Underpressure Protection Safety Interlocks (continued) Abnormal Pressure: Stop Monomer Feed and Add Full Cooling Abnormal Heat Balance: Stop Monomer Feed and Add Full Cooling Abnormal Conditions: Add Short-Stop NEXT PREVIOUS Text Home

Safeguard Maintenance System Design for Overpressure and Underpressure Protection Safeguard Maintenance System Routine Maintenance Management of Change Mechanical Integrity Checks Records NEXT PREVIOUS Text Home

Short-Stops to Stop Reaction Design for Overpressure and Underpressure Protection Short-Stops to Stop Reaction Add Reaction Stopper Add Agitation with No Electrical Power NEXT PREVIOUS Text Home

Protection for Internal Fires and Explosions Design for Overpressure and Underpressure Protection Protection for Internal Fires and Explosions Deflagrations Detonations NEXT PREVIOUS Text Home

Protection Methods for Internal Fires and Explosions Design for Overpressure and Underpressure Protection Protection Methods for Internal Fires and Explosions Deflagration Venting Deflagration Suppression Containment NEXT PREVIOUS Text Home

Protection Methods for Internal Fires and Explosions (continued) Design for Overpressure and Underpressure Protection Protection Methods for Internal Fires and Explosions (continued) Reduction of Oxidant Reduction of Combustible Flame Front Isolation NEXT PREVIOUS Text Home

Protection Methods for Internal Fires and Explosions (continued) Design for Overpressure and Underpressure Protection Protection Methods for Internal Fires and Explosions (continued) Spark Detection and Extinguishing Flame Detection and Extinguishing Water Spray and Deluge Systems NEXT PREVIOUS Text Home

Design for Overpressure and Underpressure Protection Deflagration Venting Vent Area via NFPA 68 Vent Safely NEXT PREVIOUS Text Home

Vent of Gas Deflagration Design for Overpressure and Underpressure Protection Vent of Gas Deflagration NEXT PREVIOUS Text Home

Vent of Dust Deflagration Design for Overpressure and Underpressure Protection Vent of Dust Deflagration NEXT PREVIOUS Text Home

Deflagration Suppression System Design for Overpressure and Underpressure Protection Deflagration Suppression System NEXT PREVIOUS Text Home

Design for Overpressure and Underpressure Protection Containment Prevent Rupture and Vessel Deformation Prevent Rupture but Deform Vessel NEXT PREVIOUS Text Home

Design for Overpressure and Underpressure Protection Reduction of Oxidant Vacuum Purging Pressure Purging Sweep-Through Purging NEXT PREVIOUS Text Home

Reduction of Combustible Design for Overpressure and Underpressure Protection Reduction of Combustible Dilution with Air NFPA 69 NEXT PREVIOUS Text Home

Design for Overpressure and Underpressure Protection Flame Front Isolation NEXT PREVIOUS Text Home

Spark/Flame Detection and Extinguishing Design for Overpressure and Underpressure Protection Spark/Flame Detection and Extinguishing NEXT PREVIOUS Text Home

Water Spray or Deluge Systems Design for Overpressure and Underpressure Protection Water Spray or Deluge Systems NEXT PREVIOUS Text Home

Design for Overpressure and Underpressure Protection Deluge System NEXT PREVIOUS Text Home

Design for Overpressure and Underpressure Protection Conclusion NEXT PREVIOUS Text Home

End of Slide Presentation Design for Overpressure and Underpressure Protection End of Slide Presentation Causes of Overpressure/Underpressure Presentation 2: Runaways NEXT PREVIOUS Presentation 1: Reliefs Presentation 3: Safeguards Text Home

Design for Overpressure and Underpressure Protection

Design for Overpressure and Underpressure Protection SLIDES WITH TEXT This presentation includes technical information concerning the design for overpressure and underpressure protection. The presentation is designed to help students and engineers to: Slide

Design for Overpressure and Underpressure Protection Understand the technologies, special engineering devices, and methods that are used for the protection against overpressure and underpressure (vacuum) incidents, Slide

Design for Overpressure and Underpressure Protection Understand the root causes of overpressure and underpressure incidents, and Design plants with the appropriate features to protect against overpressure and underpressure incidents. Slide

Design for Overpressure and Underpressure Protection Six Sections 1. Introduction 2. Causes of Overpressure and Underpressure 3. Reliefs 4. Effluent Handling Systems for Reliefs 5. Runaway Reactions, and 6. Overpressure Protection for Internal Fires and Explosions This presentation is divided into six sections: Slide

Design for Overpressure and Underpressure Protection Six Sections 1. Introduction 2. Causes of Overpressure and Underpressure 3. Reliefs 4. Effluent Handling Systems for Reliefs 5. Runaway Reactions, and 6. Overpressure Protection for Internal Fires and Explosions Introduction NEXT The “Introduction” button on your left will lead you to this introduction and an explaination of the Causes of Overpressure and Underpressure Reliefs PREVIOUS Runaways Safeguards Slide Home

Design for Overpressure and Underpressure Protection Six Sections 1. Introduction 2. Causes of Overpressure and Underpressure 3. Reliefs 4. Effluent Handling Systems for Reliefs 5. Runaway Reactions, and 6. Overpressure Protection for Internal Fires and Explosions Introduction NEXT The “Reliefs” Button sends you to Sections 3 and 4, covering Reliefs and Effluent Handling Systems for Reliefs Reliefs PREVIOUS Runaways Safeguards Slide Home

Design for Overpressure and Underpressure Protection Six Sections 1. Introduction 2. Causes of Overpressure and Underpressure 3. Reliefs 4. Effluent Handling Systems for Reliefs 5. Runaway Reactions, and 6. Overpressure Protection for Internal Fires and Explosions Introduction NEXT The “Runaways” Button leads to a discussion on Runaway Reactions, and . . . Reliefs PREVIOUS Runaways Safeguards Slide Home

Design for Overpressure and Underpressure Protection Six Sections 1. Introduction 2. Causes of Overpressure and Underpressure 3. Reliefs 4. Effluent Handling Systems for Reliefs 5. Runaway Reactions, and 6. Overpressure Protection for Internal Fires and Explosions Introduction NEXT The “Safeguards” Button will take you to a section on Overpressure Protection fot Internal Fires and Explosions Reliefs PREVIOUS Runaways Safeguards Slide Home

Appendix Contains Detailed Information Design for Overpressure and Underpressure Protection Appendix Contains Detailed Information This design package includes an appendix with detailed information for each of the sections of this presentation. The appendix also includes an extensive list of relevant references. Slide

Causes of Overpressure Design for Overpressure and Underpressure Protection Causes of Overpressure Operating Problem The major causes of overpressure include: Operating problems or mistakes such as an operator mistakenly opening or closing a valve to cause the vessel or system pressure to increase. An operator, for example, may adjust a steam regulator to give pressures exceeding the maximum allowable working pressure (MAWP) of a steam jacket. Slide

Causes of Overpressure Design for Overpressure and Underpressure Protection Causes of Overpressure Operating Problem Although the set pressure is usually at the MAWP, the design safety factors should protect the vessel for higher pressures; a vessel fails when the pressure is typically several times the MAWP. Slide

Causes of Overpressure Design for Overpressure and Underpressure Protection Causes of Overpressure Operating Problem Equipment Failure Equipment failures; for example a heat exchanger tube rupture that increases the shell side pressure beyond the MAWP. Although the set pressure is usually the MAWP, the design safety factors should protect the vessel for higher pressures; a vessel fails when the pressure is typically several times the MAWP. Slide

Causes of Overpressure Design for Overpressure and Underpressure Protection Causes of Overpressure Operating Problem Equipment Failure Process Upset External Fire Utility Failures Process upset; for example a runaway reaction causing high temperatures and pressures. External heating, such as, a fire that heats the contents of a vessel giving high vapor pressures, and Utility failures, such as the loss of cooling or the loss of agitation causing a runaway reaction. Slide

Causes of Underpressures Design for Overpressure and Underpressure Protection Causes of Underpressures The causes of underpressure or the inadvertent creation of a vacuum are usually due to operating problems or equipment failures. Slide

Causes of Underpressures Design for Overpressure and Underpressure Protection Causes of Underpressures Operating Problem Operating problems include mistakes such as pumping liquid out of a closed system, or cooling and condensing vapors in a closed system. Slide

Causes of Underpressures Design for Overpressure and Underpressure Protection Causes of Underpressures Operating Problem Equipment Failure Equipment failures include an instrument malfunction (e.g. vacuum gage) or the loss of the heat input of a system that contains a material with a low vapor pressure. Slide

Design for Overpressure and Underpressure Protection Part 1 of 3: Reliefs Slide

Pressure Relief Devices Design for Overpressure and Underpressure Protection Pressure Relief Devices Pressure relief devices are added to process equipment to prevent the pressures from significantly exceeding the MAWP (pressures are allowed to go slightly above the MAWP during emergency reliefs). Slide

Pressure Relief Devices Design for Overpressure and Underpressure Protection Pressure Relief Devices Spring-Loaded Pressure Relief Valve Rupture Disc Buckling Pin Miscellaneous Mechanical The pressure relief devices include spring-loaded pressure relief valves, rupture discs, buckling pins, and miscellaneous mechanical devices. Slide

Spring-Loaded Pressure Relief Valve Design for Overpressure and Underpressure Protection Spring-Loaded Pressure Relief Valve This is a sketch of a spring-loaded pressure relief valve. As the pressure in the vessel or pipeline at point A exceeds the pressure created by the spring, the valve opens. The relief begins to open at the set pressure which is usually at or below the MAWP; this pressure is usually set at the MAWP. Slide

Design for Overpressure and Underpressure Protection Rupture Disc This is a sketch of a rupture disc. In this case the disc ruptures when the pressure at A exceeds the set pressure. Recognize, however, that it is actually the differential pressure (A-B), that ruptures the disc. Slide

Buckling Pin Relief Valve Design for Overpressure and Underpressure Protection Buckling Pin Relief Valve Closed Pressure Below Set Pressure Full Open Pressure at or Above Set Pressure (Buckles in Milliseconds at a Precise Set Pressure) This sketch shows a buckling pin pressure relief valve. As shown, when the pressure exceeds the set pressure, the pin buckles and the vessel contents exit through the open valve. The rupture disc and the buckling pin relief valves stay open after they are opened. Slide

Buckling Pin Relief Valve Design for Overpressure and Underpressure Protection Buckling Pin Relief Valve Closed Pressure Below Set Pressure Full Open Pressure at or Above Set Pressure (Buckles in Milliseconds at a Precise Set Pressure) The spring operated valves close as the pressure decreases below the “blowdown” pressure. The blowdown pressure is the difference between the set pressure and closing pressure. Slide

Simple Mechanical Pressure Relief Design for Overpressure and Underpressure Protection Simple Mechanical Pressure Relief A simple mechanical pressure relief is a weighted man-way cover as shown in this sketch. Another mechanical relief is a U-tube filled with water (or equivalent). Slide

Types of Spring-Loaded Pressure Reliefs Design for Overpressure and Underpressure Protection Types of Spring-Loaded Pressure Reliefs Safety Valves for Gases and Vapors Relief Valves for Liquids Safety Relief Valves for Liquids and/or Gases There are three types of spring-loaded pressure relief valves: Safety valves are specifically designed for gases. Relief valves are designed for liquids, and Safety relief valves are designed for liquids and/or gases. Slide

Design for Overpressure and Underpressure Protection Types of Safety Valves Conventional Balanced Bellows, and Pilot-Operated There are three types of safety valves; that is: Conventional, Balanced bellows, and Pilot-operated. Slide

Conventional Safety Valve Design for Overpressure and Underpressure Protection Conventional Safety Valve A conventional safety valve is designed to provide full opening with minimum overpressure. The disc is specially shaped to give a “pop” action as the valve begins to open. Slide

Balanced Bellows Safety Valve Design for Overpressure and Underpressure Protection Balanced Bellows Safety Valve A balanced bellows safety valve is specially designed to reduce the effect of the back pressure on the opening pressure. As illustrated in this sketch the differential pressure that is required to open the valve is the pressure inside the vessel minus the atmospheric pressure. Slide

Balanced Bellows Safety Valve Design for Overpressure and Underpressure Protection Balanced Bellows Safety Valve The bellows design allows the outside air and pressure to be on the downstream side of the valve seal. Once the relief is open, then the flow is a function of the differential pressure A-B. Slide

Pilot-Operated Safety Valve Design for Overpressure and Underpressure Protection Pilot-Operated Safety Valve A pilot-operated safety valve is a spring-loaded valve. As illustrated, the vessel pressure helps to keep the valve closed. When the pressure exceeds the set pressure (or the spring pressure), the pressure on top of the valve is vented and the valve opens. Slide

Pilot-Operated Safety Valve Design for Overpressure and Underpressure Protection Pilot-Operated Safety Valve The set pressure of this type of valve can be closer to the operating pressure compared to conventional and balanced bellows valves. The disadvantages, however, are (a) the process fluid needs to be clean, (b) the seals must be resistant to the fluids, and (c) the seals and valves must be appropriately maintained. Slide

Pilot-Operated Safety Valve Design for Overpressure and Underpressure Protection Pilot-Operated Safety Valve These disadvantages are also true for spring operated reliefs. Pilot-operated valves are not used in liquid service; they are normally used in very clean and low pressure applications. Slide

Design for Overpressure and Underpressure Protection Types of Relief Valves Conventional Balanced Bellows Relief valves (for liquid service) are either the conventional or the balanced bellows types. Slide

Design for Overpressure and Underpressure Protection Types of Rupture Discs Metal Graphite Composite Others As illustrated, there are many different types of rupture discs. They are especially applicable for very corrosive environments; for example: discs made of carbon or Teflon coating are used for corrosive service. Slide

Design for Overpressure and Underpressure Protection Types of Rupture Discs Metal Graphite Composite Others A rupture disc that is used for pressure reliefs may need a specially designed mechanical support if it is also used in vacuum service. Slide

Rupture Disc and Pressure Relief Valve Combination Design for Overpressure and Underpressure Protection Rupture Disc and Pressure Relief Valve Combination Rupture discs, as illustrated, are sometimes used in combination with a spring operated relief device. In this case the disc gives a positive seal compared to the disc-to-seal design of a spring operated valve. Slide

Rupture Disc and Pressure Relief Valve Combination Design for Overpressure and Underpressure Protection Rupture Disc and Pressure Relief Valve Combination This is useful when handling very toxic materials where even a very small release (through the seal) may be hazardous, or when handling materials that polymerize. The spring operated relief following the rupture disc reseats when the pressure drops below the blow-down pressure. Slide

Rupture Disc and Pressure Relief Valve Combination Design for Overpressure and Underpressure Protection Rupture Disc and Pressure Relief Valve Combination This design, therefore, stops the discharge from the vessel. The discharge is not stopped if only a rupture disc is used. This design (rupture disc followed by a spring-operated relief) is discouraged by some practitioners. Slide

Rupture Disc and Pressure Relief Valve Combination Design for Overpressure and Underpressure Protection Rupture Disc and Pressure Relief Valve Combination In this design, as illustrated, a pressure detection device (per ASME Code), e.g., a pressure indicator, needs to be placed between the disc and the spring-operated valve. This pressure reading is checked periodically to be sure the rupture disc has its mechanical integrity. Slide

Rupture Disc and Pressure Relief Valve Combination Design for Overpressure and Underpressure Protection Rupture Disc and Pressure Relief Valve Combination A pin-hole leak in the rupture disc could increase the pressure on the discharge side of the disc. This is a major problem because it increases the relief pressure, that is: the differential pressure across the disc is the rupturing mechanism. Slide

Rupture Disc and Pressure Relief Valve Combination Design for Overpressure and Underpressure Protection Rupture Disc and Pressure Relief Valve Combination Another major problem with this design is the possibility that a piece of the rupture disc could plug the discharge orifice of the spring operated relief. This problem is prevented by specifying a rupture disc that will maintain its integrity when it is ruptured; that is, non-fragmenting. Slide

Design for Overpressure and Underpressure Protection Vacuum Relief Devices Vacuum Relief Valves Rupture Discs Conservation Vents Manhole Lids Pressure Control Vacuum relief devices are: vacuum relief valves, rupture discs, conservation vents, manhole lids designed for vacuum relief, and pressure control. Slide

Design for Overpressure and Underpressure Protection Conservation Vent A conservation vent is illustrated in this sketch. As shown, it is designed to relieve a pressure usually for pressures in the region of 6 inches of water. It is also designed to let air into the vessel to prevent a vacuum, usually a vacuum no more than 4 inches of water. Slide

Pressure or Vacuum Control Design for Overpressure and Underpressure Protection Pressure or Vacuum Control Add Air or Nitrogen Maintain Appropriately Sometimes pressure or vacuum control systems are used to add air or nitrogen to the vessel to maintain a slight pressure. In this case, the system needs to be appropriately maintained because a malfunction could result in an overpressure or underpressure. In either case the consequence could be a ruptured vessel. Slide

Design for Overpressure and Underpressure Protection Relief Servicing Inspection Testing Every relief device needs to be inspected and tested before installation and then at predetermined intervals during its lifetime. The interval depends on the service history, vendor recommendations, and regulatory requirements, but it is usually once a year. Slide

Design for Overpressure and Underpressure Protection Relief Servicing Inspection Testing Operating results and experience may indicate shorter or longer intervals. Records must be carefully maintained for every inspection and test, and for the entire life of the plant. Slide

Design for Overpressure and Underpressure Protection Relief Discharges To Atmosphere Discharges from pressure relief devices may be sent directly to the atmosphere if they are innocuous, discharged in a safe manner, and regulations permit it. Slide

Design for Overpressure and Underpressure Protection Relief Discharges To Atmosphere Prevented An additional option is to prevent releases by (a) designing vessels with high MAWPs to contain all overpressure scenarios, or (b) add a sufficient number of safeguards and/or controls to make overpressure scenarios essentially impossible. Slide

Design for Overpressure and Underpressure Protection Relief Discharges To Atmosphere Prevented Effluent System The third option is to design an effluent system to capture all nocuous liquids and gases. Slide

Design for Overpressure and Underpressure Protection Effluent Systems Knock-Out Drum Catch Tank Cyclone Separator An effluent system may contain a Knock-out drum Catch tank Cyclone separator Slide

Effluent System (continued) Design for Overpressure and Underpressure Protection Effluent System (continued) Condenser Quench Tank Scrubber Flares/Incinerators Condenser Quench tank Scrubber, and/or Flares or incinerators An effluent handling system may have any combination of the above unit operations. Slide

Effluent Handling System Design for Overpressure and Underpressure Protection Effluent Handling System One effluent handling system is illustrated in this sketch. Every element of an effluent system needs to be designed very carefully. The design requires detailed physical and chemical properties, and the correct design methodology for each unit operation. Slide

Effluent Handling System Design for Overpressure and Underpressure Protection Effluent Handling System It should also be recognized that it is important to size the relief appropriately, because the size of the entire effluent system is based on this discharge rate. The design methodology is in the references noted in the Appendix of this package. Slide

Design for Overpressure and Underpressure Protection Part 2 of 3: Runaways Slide

Design for Overpressure and Underpressure Protection Runaway Reaction Temperature Increases Reaction Rate Increases Pressure Increases A runaway reaction is an especially important overpressure scenario. A runaway reaction has an accelerating rate of temperature increase, rate of reaction increase, and usually rate of pressure increase. The pressure, of course, increases if the reaction mass has a volatile substance, such as, a solvent or a monomer; or if one of the reaction products is a gas. Slide

Causes of Runaway Reactions Design for Overpressure and Underpressure Protection Causes of Runaway Reactions Self-Heating Sleeper Tempered Gassy Hybrid Characteristics of Runaway In general, there are two causes of runaway reactions (self-heating and sleeper) and three characteristics of runaways (tempered, gassy, and hybrid). Slide

Causes of Runaway Reactions Design for Overpressure and Underpressure Protection Causes of Runaway Reactions Self-Heating Sleeper Tempered Gassy Hybrid Characteristics of Runaway When protecting a system for overpressures due to runaway reactions the engineer needs to know the type of runaway and needs to characterize the behavior of the specific runaway with a special calorimeter. This specific methodology is described in this section of this presentation. Slide

Self-Heating Reaction Design for Overpressure and Underpressure Protection Self-Heating Reaction Loss of Cooling Unexpected Addition of Heat Too Much Catalyst or Reactant Operator Mistakes Too Fast Addition of Catalyst or Reactant One self-heating scenario occurs when the reaction is exothermic and a loss of cooling gives an uncontrolled temperature rise. A few causes of self-heating scenarios are shown. Slide

Design for Overpressure and Underpressure Protection Sleeper Reactions Reactants Added But Not Mixed (Error) Reactants Accumulate Agitation Started .. Too Late Sleeper reactions are usually the result of an operator error. Two examples include: (a) the addition of two immiscible reactants when the agitator is mistakenly in the off position, and (b) the addition of a reactant to the reaction mass when the temperature is mistakenly lower than that required to initiate the reaction. Slide

Design for Overpressure and Underpressure Protection Sleeper Reactions Reactants Added But Not Mixed (Error) Reactants Accumulate Agitation Started .. Too Late In these cases the runaway is initiated by starting the agitator and adding heat respectively. Slide

Design for Overpressure and Underpressure Protection Tempered Reaction Heat Removed by Evaporation Heat Removal Maintains a Constant Temperature Tempered runaway reactions maintain their temperature when the energy exiting the relief device is equal to the energy generated in the reactor due to the exothermic reaction. The reaction heat is absorbed by the evaporation of the volatile components. The vapor pressure in a tempered system can typically be characterized by an Antoine type equation. Slide

Design for Overpressure and Underpressure Protection Gassy System No Volatile Solvents Gas is Reaction Product A system that is characterized as “gassy” has no volatile solvents or reactants. The pressure build-up is due to the generation of noncondensible gas such as N2 or CO2. Slide

Design for Overpressure and Underpressure Protection Hybrid System Tempered Gassy A hybrid system is the combination of a tempered and a gassy system. Under runaway conditions, the pressure increases due to the vapor pressure of the volatile components as well as from the generation of noncondensible gaseous reaction products. Slide

Reliefs for Runaway Reactions Design for Overpressure and Underpressure Protection Reliefs for Runaway Reactions Two Phase (or Three Phases: Liquid, Vapor, and Solid) Flow Under runaway conditions, when the relief device opens, the relief discharge is a foam; that is, the gases are entrained with the liquid. Slide

Reliefs for Runaway Reactions Design for Overpressure and Underpressure Protection Reliefs for Runaway Reactions Two Phase (or Three Phases: Liquid, Vapor, and Solid) Flow To maintain a constant temperature in the reactor (i.e. control the runaway reaction), the relief valve is sized to remove all the heat generated from the exothermic reaction via the heat removed with the discharged mass, which is typically a foam. Detailed information on runaway reactions is found in the appendix. Slide

Reliefs for Runaway Reactions Design for Overpressure and Underpressure Protection Reliefs for Runaway Reactions Two Phase (or Three Phases: Liquid, Vapor, and Solid) Flow Relief Area: 2 to 10 Times the Area of a Single Gaseous Phase The required relief area to remove this heat with the foam is two to ten times the area that would be required by releasing a single gaseous phase. Slide

Design for Overpressure and Underpressure Protection Two Phase Flow This is a picture that illustrates the two-phase flow characteristics of a relief discharge due to a runaway reaction. As illustrated, the discharge is similar to the release of foam from a freshly opened bottle of pop after being shakened. If the relief is not designed for two-phase flow, the pressures would increase rapidly and the vessel could rupture. Slide

Relief Valve Sizing Methodology Design for Overpressure and Underpressure Protection Relief Valve Sizing Methodology Special Calorimeter Data Special Calculation Methods The relief valve sizing methodology for runaway reactions is very complex. It requires the characterization of the runaway reaction using a specially designed calorimeter. Relief valve sizing, additionally, requires special calculation methods that are described in the Appendix of this package. Slide

Characterization of Runaway Reactions Design for Overpressure and Underpressure Protection Characterization of Runaway Reactions The characterization of runaway reactions includes the determination of the rates of rise of the temperature and pressure under adiabatic conditions. The test results also characterize the reaction type, that is, tempered, gassy, and/or a hybrid system. Slide

Characterization of Runaway Reactions Design for Overpressure and Underpressure Protection Characterization of Runaway Reactions ARC VSP RSST Various calorimeters are used for this characterization: The accelerating rate calorimeter (ARC) The vent sizing package (VSP) The reactive system screening tool (RSST) Slide

Characterization of Runaway Reactions Design for Overpressure and Underpressure Protection Characterization of Runaway Reactions ARC VSP RSST APTAC PHI-TEC Dewars The automated pressure-tracking adiabatic calorimeter (APTAC) The Phi-Tec, and Dewars. Each of these calorimeters have advantages and disadvantages that need to be understood when studying a specific system. Slide

Design for Overpressure and Underpressure Protection Part 3 of 3: Safeguards Slide

Design for Overpressure and Underpressure Protection Safeguards This section of the presentation covers safeguards. Safeguards include the methods and controls used to prevent runaways. As illustrated previously, a containment system (a safeguard), can be very complex and expensive. Alternatively, a series of safeguards may be justified. Slide

Design for Overpressure and Underpressure Protection Safeguards Safety Interlocks Safeguard Maintenance System Short-Stopping Safeguards include safety interlocks, safeguard maintenance system, and/or short-stopping. Slide

Design for Overpressure and Underpressure Protection Safety Interlocks Agitator Not Working: Stop Monomer Feed and Add Full Cooling Abnormal Temperature: Stop Monomer Feed and Add Full Cooling The list of alternative interlocks is fairly extensive. Usually more than one interlock and some redundancy and diversity is required for each runaway scenario. As the number of interlocks increases, the reliability of the system increases. These are examples of safety interlocks for a semibatch polymerization reactor. Slide

Safety Interlocks (continued) Design for Overpressure and Underpressure Protection Safety Interlocks (continued) Abnormal Pressure: Stop Monomer Feed and Add Full Cooling Abnormal Heat Balance: Stop Monomer Feed and Add Full Cooling Abnormal Conditions: Add Short-Stop This is a list of additional interlocks. Other interlocks (manual) that are not on this list include: gages with manual shutdowns, and alarms with manual shutdowns. Slide

Safeguard Maintenance System Design for Overpressure and Underpressure Protection Safeguard Maintenance System Routine Maintenance Management of Change Mechanical Integrity Checks Records A safeguard maintenance system includes routine maintenance, management of change, mechanical integrity checks, and the appropriate records. These are the steps that are required to be sure the safeguards and interlocks perform appropriately under emergency conditions and/or potential runaway reaction scenarios. Slide

Safeguard Maintenance System Design for Overpressure and Underpressure Protection Safeguard Maintenance System Routine Maintenance Management of Change Mechanical Integrity Checks Records The maintenance of safeguard systems is especially important, because: Safeguards and interlocks do not operate on a day-to-day basis, but When they are required to operate (emergency conditions) they need to operate flawlessly. See ISA SP 84.01 for details for the design of safety instrumented systems. Slide

Short-Stops to Stop Reaction Design for Overpressure and Underpressure Protection Short-Stops to Stop Reaction Add Reaction Stopper Add Agitation with No Electrical Power A short-stopping system, stops a runaway reaction by adding a reaction stopper solution to the reacting mass. The reaction-stopper stops the reaction in time to short-circuit the progress of the reaction. A reaction stopper needs to be added when the reaction mass is relatively cold. If the mass is too hot, a short-stopper will not work. Slide

Short-Stops to Stop Reaction Design for Overpressure and Underpressure Protection Short-Stops to Stop Reaction Add Reaction Stopper Add Agitation with No Electrical Power Good agitation, of course, is required to adequately mix the reaction mass with the inhibitor. Since a power failure is often the initiating event of a runaway, an alternative method of agitation needs to be included in the design. A compressed nitrogen system together with a sparge ring is one alternative. Slide

Protection for Internal Fires and Explosions Design for Overpressure and Underpressure Protection Protection for Internal Fires and Explosions Deflagrations Detonations This section of the presentation covers protection methods for internal fires and explosions. Overpressure protection is needed for process equipment that can potentially explode due to an internal deflagration or detonation. Slide

Protection for Internal Fires and Explosions Design for Overpressure and Underpressure Protection Protection for Internal Fires and Explosions Deflagrations Detonations A deflagration is defined as the propagation of a combustion zone at a velocity in the unreacted medium that is less than the speed of sound. A detonation has a velocity greater than the speed of sound in the unreacted medium. Slide

Protection for Internal Fires and Explosions Design for Overpressure and Underpressure Protection Protection for Internal Fires and Explosions Deflagrations Detonations The burning material can be a combustible gas, a combustible dust, a combustible mist, or a hybrid mixture (a mixture of a combustible gas with either a combustible dust or combustible mist). The reaction actually occurs in the vapor phase between the fuel and the air or some other oxidant. Slide

Protection Methods for Internal Fires and Explosions Design for Overpressure and Underpressure Protection Protection Methods for Internal Fires and Explosions Deflagration Venting Deflagration Suppression Containment The protection methods used for fires or explosions include Deflagration venting Deflagration suppression Containment Slide

Protection Methods for Internal Fires and Explosions (continued) Design for Overpressure and Underpressure Protection Protection Methods for Internal Fires and Explosions (continued) Reduction of Oxidant Reduction of Combustible Flame Front Isolation Reduction of the oxidant Reduction of the combustible Flame front isolation Slide

Protection Methods for Internal Fires and Explosions (continued) Design for Overpressure and Underpressure Protection Protection Methods for Internal Fires and Explosions (continued) Spark Detection and Extinguishing Flame Detection and Extinguishing Water Spray and Deluge Systems Spark detection and extinguishing Flame detection and extinguishing Water or foam spray deluge systems Slide

Design for Overpressure and Underpressure Protection Deflagration Venting Vent Area via NFPA 68 The technology required for venting deflagrations is given in NFPA 68. Deflagration venting is usually the simplest and least costly means of protecting process equipment against damage due to the internal pressure rise from deflagrations. Slide

Design for Overpressure and Underpressure Protection Deflagration Venting Vent Area via NFPA 68 Vent Safely If equipment is located inside a building, the vents must be discharged through a vent duct system to a safe location outside of the building. The design of the vent duct system is critical to avoid excessive pressures developed during the venting process. See NFPA 68 for details. Slide

Design for Overpressure and Underpressure Protection Deflagration Venting Vent Area via NFPA 68 Vent Safely A safe location will avoid injury to personnel and minimize damage to equipment outside of the building. The next two pictures illustrate that the “safe venting” may not be trivial. Slide

Vent of Gas Deflagration Design for Overpressure and Underpressure Protection Vent of Gas Deflagration This is a picture of the venting of a gas deflagration. As illustrated, the flame propagates a significant distance from the vessel. The length of the flame is estimated using an equation found in NFPA 68. The main purpose of venting is to protect the mechanical integrity of the equipment. As illustrated, even when it is vented safely, this is a major event. Slide

Vent of Dust Deflagration Design for Overpressure and Underpressure Protection Vent of Dust Deflagration This is a picture of the venting of a dust deflagration. As illustrated, the burning dust continues to burn at great distances from the vent. With dusts, this burning zone is larger because the container has a larger fuel-to-air ratio compared to the gas deflagration scenario. These pictures clearly illustrate the problems with venting deflagrations. Slide

Deflagration Suppression System Design for Overpressure and Underpressure Protection Deflagration Suppression System One alternative to venting a deflagration is suppression. This sketch illustrates a deflagration suppression system that includes (a) a flame or pressure detector, (b) a quick opening valve, and (c) the addition of a flame suppressant. Slide

Deflagration Suppression System Design for Overpressure and Underpressure Protection Deflagration Suppression System The commonly used suppression agents include water, potassium acid phosphate, sodium bicarbonate, and Halon substitutes. The technology for deflagration suppression is described in NFPA 69. Slide

Design for Overpressure and Underpressure Protection Containment Prevent Rupture and Vessel Deformation Prevent Rupture but Deform Vessel The thickness of vessel walls may be increased to contain the pressure of a deflagration. The wall thickness can be large enough to prevent the deformation of the vessel, or The wall thickness may be large enough to prevent a rupture, but allow the vessel to deform. Slide

Design for Overpressure and Underpressure Protection Reduction of Oxidant Vacuum Purging Pressure Purging Sweep-Through Purging Protection for overpressures is also provided with an inert gas blanket to prevent the occurrence of a deflagration. Before introducing a flammable substance to a vessel, the vessel must also be purged with an inert gas to reduce the oxidant concentration sufficiently so that the gas mixture cannot burn. Slide

Design for Overpressure and Underpressure Protection Reduction of Oxidant Vacuum Purging Pressure Purging Sweep-Through Purging The purging methods include vacuum purging, pressure purging, and sweep-through purging. See NFPA 69 and the book by Crowl and Louvar for more details. Slide

Reduction of Combustible Design for Overpressure and Underpressure Protection Reduction of Combustible Dilution with Air NFPA 69 A deflagration can also be prevented by reducing the concentration of the combustible material so that the concentration is below the lower flammability limit (LFL). This is usually accomplished by dilution with nitrogen. The specifications for this type system are given in NFPA 69. Slide

Design for Overpressure and Underpressure Protection Flame Front Isolation As illustrated, isolation devices are used in piping systems to prevent the propagation of a flame front. The method illustrated has a fast-acting block valve. This isolation system prevents the propagation of the flame front; more importantly it prevents deflagration transitions to detonations. Slide

Spark/Flame Detection and Extinguishing Design for Overpressure and Underpressure Protection Spark/Flame Detection and Extinguishing Another method of preventing the propagation of deflagrations in pipelines is the early detection and extinguishment of sparks or flames. In this type system, a detector activates an automatic extinguishing system that sprays water or other extinguishing agents into the fire. This system is similar to the deflagration suppression system discussed previously. Slide

Water Spray or Deluge Systems Design for Overpressure and Underpressure Protection Water Spray or Deluge Systems Process equipment and structures are very effectively protected against fire by water spray or deluge systems. They can be activated manually or automatically. They are designed to cool the equipment or structural members so that the heat from a fire will not weaken them. Slide

Design for Overpressure and Underpressure Protection Deluge System This picture shows a typical deluge system in operation. In this example, the deluge system is automatically activated when the concentration of the flammable gas below the vessel is detected to be at or over 25% of the lower flammability limit. Slide

Design for Overpressure and Underpressure Protection Conclusion This concludes our technology package covering overpressure and underpressure protection. The appendix of this package contains more detailed information. The enclosed references contain the state-of-the-art technology to assist engineers and students with their detailed designs. Slide

End of Slide Presentation (with text) Design for Overpressure and Underpressure Protection End of Slide Presentation (with text) Causes of Overpressure/Underpressure Presentation 2: Runaways HOME PREVIOUS Presentation 1: Reliefs Presentation 3: Safeguards Slide Exit

Design for Overpressure and Underpressure Protection