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| Preface | |
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| Acknowledgments | |
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| How to Use this Book | |
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| Abbreviations | |
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| Distillation Troubleshooting Database of Published Case Histories | |
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| Troubleshooting Distillation Simulations | |
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| VLE | |
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| Close-Boiling Systems | |
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| Nonideal Systems | |
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| Nonideality Predicted in Ideal System | |
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| Nonideal VLE Extrapolated to Pure Products | |
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| Nonideal VLE Extrapolated to Different Pressures | |
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| Incorrect Accounting for Association Gives Wild Predictions | |
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| Poor Characterization of Petroleum Fractions | |
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| Chemistry, Process Sequence | |
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| Does Your Distillation Simulation Reflect the Real World? | |
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| General | |
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| With Second Liquid Phase | |
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| Refinery Vacuum Tower Wash Sections | |
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| Modeling Tower Feed | |
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| Simulation/Plant Data Mismatch Can Be Due to an Unexpected Internal Leak | |
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| Simulation/Plant Data Mismatch Can Be Due to Liquid Entrainment in Vapor Draw | |
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| Bug in Simulation | |
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| Graphical Techniques to Troubleshoot Simulations | |
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| McCabe-Thiele and Hengstebeck Diagrams | |
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| Multicomponent Composition Profiles | |
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| Residue Curve Maps | |
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| How Good Is Your Efficiency Estimate? | |
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| Simulator Hydraulic Predictions: To Trust or Not to Trust | |
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| Do Your Vapor and Liquid Loadings Correctly Reflect Subcool, Superheat, and Pumparounds? | |
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| How Good Are the Simulation Hydraulic Prediction Correlations? | |
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| Where Fractionation Goes Wrong | |
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| Insufficient Reflux or Stages; Pinches | |
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| No Stripping in Stripper | |
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| Unique Features of Multicomponent Distillation | |
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| Accumulation and Hiccups | |
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| Intermediate Component, No Hiccups | |
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| Intermediate Component, with Hiccups | |
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| Lights Accumulation | |
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| Accumulation between Feed and Top or Feed and Bottom | |
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| Accumulation by Recycling | |
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| Hydrates, Freeze-Ups | |
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| Two Liquid Phases | |
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| Azeotropic and Extractive Distillation | |
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| Problems Unique to Azeotroping | |
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| Problems Unique to Extractive Distillation | |
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| Energy Savings and Thermal Effects | |
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| Energy-Saving Designs and Operation | |
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| Excess Preheat and Precool | |
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| Side-Reboiler Problems | |
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| Bypassing a Feed around the Tower | |
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| Reducing Recycle | |
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| Heat Integration Imbalances | |
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| Subcooling: How It Impacts Towers | |
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| Additional Internal Condensation and Reflux | |
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| Less Loadings above Feed | |
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| Trapping Lights and Quenching | |
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| Others | |
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| Superheat: How It Impacts Towers | |
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| Tower Sizing and Material Selection Affect Performance | |
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| Undersizing Trays and Downcomers | |
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| Oversizing Trays | |
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| Tray Details Can Bottleneck Towers | |
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| Low Liquid Loads Can Be Troublesome | |
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| Loss of Downcomer Seal | |
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| Tray Dryout | |
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| Special Bubble-Cap Tray Problems | |
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| Misting | |
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| Undersizing Packings | |
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| Systems Where Packings Perform Different from Expectations | |
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| Packed Bed Too Long | |
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| Packing Supports Can Bottleneck Towers | |
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| Packing Hold-downs Are Sometimes Troublesome | |
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| Internals Unique to Packed Towers | |
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| Empty (Spray) Sections | |
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| Feed Entry Pitfalls in Tray Towers | |
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| Does the Feed Enter the Correct Tray? | |
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| Feed Pipes Obstructing Downcomer Entrance | |
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| Feed Flash Can Choke Downcomers | |
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| Subcooled Feeds, Refluxes Are Not Always Trouble Free | |
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| Liquid and Unsuitable Distributors Do Not Work with Flashing Feeds | |
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| Flashing Feeds Require More Space | |
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| Uneven or Restrictive Liquid Split to Multipass Trays at Feeds and Pass Transitions | |
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| Oversized Feed Pipes | |
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| Plugged Distributor Holes | |
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| Low [Delta]P Trays Require Decent Distribution | |
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| Packed-Tower Liquid Distributors: Number 6 on the Top 10 Malfunctions | |
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| Better Quality Distributors Improve Performance | |
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| Original Distributor Orifice or Unspecified | |
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| Original Distributor Weir Type | |
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| Original Distributor Spray Type | |
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| Plugged Distributors Do Not Distribute Well | |
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| Pan/Trough Orifice Distributors | |
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| Pipe Orifice Distributors | |
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| Spray Distributors | |
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| Overflow in Gravity Distributors: Death to Distribution | |
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| Feed Pipe Entry and Predistributor Problems | |
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| Poor Flashing Feed Entry Bottleneck Towers | |
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| Oversized Weep Holes Generate Undesirable Distribution | |
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| Damaged Distributors Do Not Distribute Well | |
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| Broken Flanges or Missing Spray Nozzles | |
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| Others | |
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| Hole Pattern and Liquid Heads Determine Irrigation Quality | |
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| Gravity Distributors Are Meant to Be Level | |
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| Hold-Down Can Interfere with Distribution | |
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| Liquid Mixing Is Needed in Large-Diameter Distributors | |
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| Notched Distributors Have Unique Problems | |
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| Others | |
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| Vapor Maldistribution in Trays and Packings | |
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| Vapor Feed/Reboiler Return Maldistributes Vapor to Packing Above | |
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| Chemical/Gas Plant Packed Towers | |
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| Packed Refinery Main Fractionators | |
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| Experiences with Vapor Inlet Distribution Baffles | |
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| Packing Vapor Maldistribution at Intermediate Feeds and Chimney Trays | |
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| Vapor Maldistribution Is Detrimental in Tray Towers | |
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| Vapor Cross-Flow Channeling | |
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| Multipass Trays | |
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| Others | |
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| Tower Base Level and Reboiler Return: Number 2 on the Top 10 Malfunctions | |
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| Causes of High Base Level | |
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| Faulty Level Measurement or Level Control | |
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| Operation | |
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| Excess Reboiler Pressure Drop | |
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| Undersized Bottom Draw Nozzle or Bottom Line | |
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| Others | |
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| High Base Level Causes Premature Tower Flood (No Tray/Packing Damage) | |
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| High Base Liquid Level Causes Tray/Packing Damage | |
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| Impingement by the Reboiler Return Inlet | |
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| On Liquid Level | |
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| On Instruments | |
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| On Tower Wall | |
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| Opposing Reboiler Return Lines | |
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| On Trays | |
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| On Seal Pan Overflow | |
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| Undersized Bottom Feed Line | |
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| Low Base Liquid Level | |
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| Issues with Tower Base Baffles | |
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| Vortexing | |
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| Chimney Tray Malfunctions: Part of Number 7 on the Top 10 Malfunctions | |
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| Leakage | |
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| Problem with Liquid Removal, Downcomers, or Overflows | |
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| Thermal Expansion Causing Warping, Out-of-Levelness | |
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| Chimneys Impeding Liquid Flow to Outlet | |
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| Vapor from Chimneys Interfering with Incoming Liquid | |
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| Level Measurement Problems | |
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| Coking, Fouling, Freezing | |
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| Other Chimney Tray Issues | |
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| Drawoff Malfunctions (Non-Chimney Tray): Part of Number 7 on the Top 10 Malfunctions | |
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| Vapor Chokes Liquid Draw Lines | |
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| Insufficient Degassing | |
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| Excess Line Pressure Drop | |
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| Vortexing | |
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| Leak at Draw Tray Starves Draw | |
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| Draw Pans and Draw Lines Plug Up | |
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| Draw Tray Damage Affects Draw Rates | |
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| Undersized Side-Stripper Overhead Lines Restrict Draw Rates | |
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| Degassed Draw Pan Liquid Initiates Downcomer Backup Flood | |
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| Other Problems with Tower Liquid Draws | |
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| Liquid Entrainment in Vapor Side Draws | |
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| Reflux Drum Malfunctions | |
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| Reflux Drum Level Problems | |
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| Undersized or Plugged Product Lines | |
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| Two Liquid Phases | |
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| Tower Assembly Mishaps: Number 5 on the Top 10 Malfunctions | |
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| Incorrect Tray Assembly | |
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| Downcomer Clearance and Inlet Weir Malinstallation | |
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| Flow Passage Obstruction and Internals Misorientation at Tray Tower Feeds and Draws | |
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| Leaking Trays and Accumulator Trays | |
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| Bolts, Nuts, Clamps | |
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| Manways/Hatchways Left Unbolted | |
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| Materials of Construction Inferior to Those Specified | |
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| Debris Left in Tower or Piping | |
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| Packing Assembly Mishaps | |
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| Random | |
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| Structured | |
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| Grid | |
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| Fabrication and Installation Mishaps in Packing Distributors | |
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| Parts Not Fitting through Manholes | |
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| Auxiliary Heat Exchanger Fabrication and Assembly Mishaps | |
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| Auxiliary Piping Assembly Mishaps | |
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| Difficulties during Start-Up, Shutdown, Commissioning, and Abnormal Operation: Number 4 on the Top 10 Malfunctions | |
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| Blinding/Unblinding Lines | |
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| Backflow | |
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| Dead-Pocket Accumulation and Release of Trapped Materials | |
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| Purging | |
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| Pressuring and Depressuring | |
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| Washing | |
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| On-Line Washes | |
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| Steam and Water Operations | |
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| Overheating | |
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| Cooling | |
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| Overchilling | |
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| Water Removal | |
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| Draining at Low Points | |
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| Oil Circulation | |
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| Condensation of Steam Purges | |
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| Dehydration by Other Procedures | |
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| Start-Up and Initial Operation | |
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| Total-Reflux Operation | |
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| Adding Components That Smooth Start-Up | |
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| Siphoning | |
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| Pressure Control at Start-Up | |
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| Confined Space and Manhole Hazards | |
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| Water-Induced Pressure Surges: Part of Number 3 on the Top 10 Malfunctions | |
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| Water in Feed and Slop | |
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| Accumulated Water in Transfer Line to Tower and in Heater Passes | |
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| Water Accumulation in Dead Pockets | |
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| Water Pockets in Pump or Spare Pump Lines | |
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| Undrained Stripping Steam Lines | |
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| Condensed Steam or Refluxed Water Reaching Hot Section | |
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| Oil Entering Water-Filled Region | |
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| Explosions, Fires, and Chemical Releases: Number 10 on the Top 10 Malfunctions | |
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| Explosions Due to Decomposition Reactions | |
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| Ethylene Oxide Towers | |
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| Peroxide Towers | |
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| Nitro Compound Towers | |
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| Other Unstable-Chemical Towers | |
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| Explosions Due to Violent Reactions | |
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| Explosions and Fires Due to Line Fracture | |
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| C[subscript 3]-C[subscript 4] Hydrocarbons | |
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| Overchilling | |
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| Water Freeze | |
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| Other | |
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| Explosions Due to Trapped Hydrocarbon or Chemical Release | |
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| Explosions Induced by Commissioning Operations | |
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| Packing Fires | |
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| Initiated by Hot Work Above Steel Packing | |
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| Pyrophoric Deposits Played a Major Role, Steel Packing | |
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| Tower Manholes Opened While Packing Hot, Steel Packing | |
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| Others, Steel Packing Fires | |
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| Titanium, Zinconium Packing Fires | |
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| Fires Due to Opening Tower before Cooling or Combustible Removal | |
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| Fires Caused by Backflow | |
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| Fires by Other Causes | |
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| Chemical Releases by Backflow | |
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| Trapped Chemicals Released | |
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| Relief, Venting, Draining, Blowdown to Atmosphere | |
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| Undesired Reactions in Towers | |
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| Excessive Bottom Temperature/Pressure | |
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| Hot Spots | |
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| Concentration or Entry of Reactive Chemical | |
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| Chemicals from Commissioning | |
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| Catalyst Fines, Rust, Tower Materials Promote Reaction | |
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| Long Residence Times | |
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| Inhibitor Problems | |
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| Air Leaks Promote Tower Reactions | |
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| Impurity in Product Causes Reaction Downstream | |
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| Foaming | |
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| What Causes or Promotes Foaming? | |
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| Solids, Corrosion Products | |
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| Corrosion and Fouling Inhibitors, Additives, and Impurities | |
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| Hydrocarbon Condensation into Aqueous Solutions | |
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| Wrong Filter Elements | |
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| Rapid Pressure Reduction | |
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| Proximity to Solution Plait Point | |
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| What Are Foams Sensitive To? | |
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| Feedstock | |
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| Temperature | |
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| Pressure | |
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| Laboratory Tests | |
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| Sample Shake, Air Bubbling | |
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| Oldershaw Column | |
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| Foam Test Apparatus | |
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| At Plant Conditions | |
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| Antifoam Injection | |
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| Effective Only at the Correct Quantity/Concentration | |
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| Some Antifoams Are More Effective Than Others | |
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| Batch Injection Often Works, But Continuous Can Be Better | |
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| Correct Dispersal Is Important, Too | |
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| Antifoam Is Sometimes Adsorbed on Carbon Beds | |
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| Other Successful Antifoam Experiences | |
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| Sometimes Antifoam Is Less Effective | |
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| System Cleanup Mitigates Foaming | |
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| Improving Filtration | |
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| Carbon Beds Mitigate Foaming But Can Adsorb Antifoam | |
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| Removing Hydrocarbons from Aqueous Solvents | |
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| Changing Absorber Solvent | |
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| Other Contaminant Removal Techniques | |
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| Hardware Changes Can Debottleneck Foaming Towers | |
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| Larger Downcomers | |
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| Smaller Downcomer Backup (Lower Pressure Drop, Larger Clearances) | |
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| More Tray Spacing | |
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| Removing Top Two Trays Does Not Help | |
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| Trays Versus Packings | |
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| Larger Packings, High-Open-Area Distributors Help | |
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| Increased Agitation | |
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| Larger Tower | |
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| Reducing Base Level | |
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| The Tower as a Filter: Part A. Causes of Plugging-Number 1 on the Top 10 Malfunctions | |
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| Piping Scale/Corrosion Products | |
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| Salting Out/Precipitation | |
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| Polymer/Reaction Products | |
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| Solids/Entrainment in the Feed | |
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| Oil Leak | |
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| Poor Shutdown Wash/Flush | |
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| Entrainment or Drying at Low Liquid Rates | |
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| Others | |
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| The Tower as a Filter: Part B. Locations of Plugging-Number 1 on the Top 10 Malfunctions | |
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| Trays | |
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| Downcomers | |
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| Packings | |
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| How Packings and Trays Compare on Plugging Resistance | |
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| Trays versus Trays | |
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| Trays versus Packings | |
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| Packings versus Packings | |
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| Limited Zone Only | |
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| Draw, Exchanger, and Vent Lines | |
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| Feed and Inlet Lines | |
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| Instrument Lines | |
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| |
| Coking: Part of Number 1 on Tower Top 10 Malfunctions | |
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| Insufficient Wash Flow Rate, Refinery Vacuum Towers | |
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| Other Causes, Refinery Vacuum Towers | |
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| |
| Slurry Section, FCC Fractionators | |
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| Other Refinery Fractionators | |
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| Nonrefinery Fractionators | |
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| Leaks | |
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| |
| Pump, Compressor | |
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| Heat Exchanger | |
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| Reboiler Tube | |
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| Condenser Tube | |
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| Auxiliary Heat Exchanger (Preheater, Pumparound) | |
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| Chemicals to/from Other Equipment | |
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| Leaking from Tower | |
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| Leaking into Tower | |
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| |
| Product to Product | |
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| Atmospheric | |
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| Chemicals to Atmosphere | |
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| Air into Tower | |
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| Relief and Failure | |
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| Relief Requirements | |
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| Controls That Affect Relief Requirements and Frequency | |
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| Relief Causes Tower Damage, Shifts Deposits | |
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| Overpressure Due to Component Entry | |
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| Relief Protection Absent or Inadequate | |
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| Line Ruptures | |
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| All Indication Lost When Instrument Tap Plugged | |
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| Trips Not Activating or Incorrectly Set | |
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| Pump Failure | |
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| Loss of Vacuum | |
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| Power Loss | |
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| Tray, Packing, and Tower Damage: Part of Number 3 on the Top 10 Malfunctions | |
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| Vacuum | |
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| Insufficient Uplift Resistance | |
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| Uplift Due to Poor Tightening during Assembly | |
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| Uplift Due to Rapid Upward Gas Surge | |
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| Valves Popping Out | |
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| Downward Force on Trays | |
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| Trays below Feed Bent Up, above Bent Down and Vice Versa | |
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| Downcomers Compressed, Bowed, Fallen | |
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| Uplift of Cartridge Trays | |
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| Flow-Induced Vibrations | |
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| Compressor Surge | |
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| Packing Carryover | |
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| Melting, Breakage of Plastic Packing | |
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| Damage to Ceramic Packing | |
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| Damage to Other Packings | |
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| Reboilers That Did Not Work: Number 9 on the Top 10 Malfunctions | |
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| Circulating Thermosiphon Reboilers | |
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| Excess Circulation | |
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| Insufficient Circulation | |
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| Insufficient [Delta]T, Pinching | |
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| Surging | |
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| Velocities Too Low in Vertical Thermosiphons | |
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| Problems Unique to Horizontal Thermosiphons | |
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| Once-Through Thermosiphon Reboilers | |
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| Leaking Draw Tray or Draw Pan | |
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| No Vaporization/Thermosiphon | |
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| Slug Flow in Outlet Line | |
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| Forced-Circulation Reboilers | |
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| Kettle Reboilers | |
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| Excess [Delta]P in Circuit | |
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| Poor Liquid Spread | |
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| Liquid Level above Overflow Baffle | |
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| Internal Reboilers | |
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| Kettle and Thermosiphon Reboilers in Series | |
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| Side Reboilers | |
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| Inability to Start | |
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| Liquid Draw and Vapor Return Problems | |
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| Hydrates | |
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| Pinching | |
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| Control Issues | |
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| All Reboilers, Boiling Side | |
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| Debris/Deposits in Reboiler Lines | |
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| Undersizing | |
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| Film Boiling | |
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| All Reboilers, Condensing Side | |
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| Non condensables in Heating Medium | |
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| Loss of Condensate Seal | |
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| Condensate Draining Problems | |
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| Vapor/Steam Supply Bottleneck | |
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| Condensers That Did Not Work | |
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| Inerts Blanketing | |
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| Inadequate Venting | |
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| Excess Lights in Feed | |
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| Inadequate Condensate Removal | |
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| Undersized Condensate Lines | |
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| Exchanger Design | |
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| Unexpected Condensation Heat Curve | |
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| Problems with Condenser Hardware | |
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| Maldistribution between Parallel Condensers | |
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| Flooding/Entrainment in Partial Condensers | |
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| Interaction with Vacuum and Recompression Equipment | |
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| Others | |
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| Misleading Measurements: Number 8 on the Top 10 Malfunctions | |
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| Incorrect Readings | |
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| Meter or Taps Fouled or Plugged | |
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| Missing Meter | |
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| Incorrect Meter Location | |
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| Problems with Meter and Meter Tubing Installation | |
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| Incorrect Meter Installation | |
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| Instrument Tubing Problems | |
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| Incorrect Meter Calibration, Meter Factor | |
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| Level Instrument Fooled | |
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| By Froth or Foam | |
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| By Oil Accumulation above Aqueous Level | |
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| By Lights | |
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| By Radioactivity (Nucleonic Meter) | |
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| Interface-Level Metering Problems | |
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| Meter Readings Ignored | |
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| Electric Storm Causes Signal Failure | |
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| Control System Assembly Difficulties | |
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| No Material Balance Control | |
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| Controlling Two Temperatures/Compositions Simultaneously Produces Interaction | |
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| Problems with the Common Control Schemes, No Side Draws | |
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| Boil-Up on TC/AC, Reflux on FC | |
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| Boil-Up on FC, Reflux on TC/AC | |
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| Boil-Up on FC, Reflux on LC | |
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| Boil-Up on LC, Bottoms on TC/AC | |
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| Reflux on Base LC, Bottoms on TC/AC | |
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| Problems with Side-Draw Controls | |
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| Small Reflux below Liquid Draw Should Not Be on Level or Difference Control | |
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| Incomplete Material Balance Control with Liquid Draw | |
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| Steam Spikes with Liquid Draw | |
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| Internal Vapor Control makes or Breaks Vapor Draw Control | |
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| Others | |
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| Where Do Temperature and Composition Controls Go Wrong? | |
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| Temperature Control | |
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| No Good Temperature Control Tray | |
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| Best Control Tray | |
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| Fooling by Nonkeys | |
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| Averaging (Including Double Differential) | |
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| Azeotropic Distillation | |
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| Extractive Distillation | |
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| Other | |
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| Pressure-Compensated Temperature Controls | |
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| [Delta]T Control | |
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| Other Pressure Compensation | |
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| Analyzer Control | |
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| Obtaining a Valid Analysis for Control | |
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| Long Lags and High Off-Line Times | |
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| Intermittent Analysis | |
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| Handling Feed Fluctuations | |
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| Analyzer-Temperature Control Cascade | |
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| Analyzer On Next Tower | |
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| Misbehaved Pressure, Condenser, Reboiler, and Preheater Controls | |
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| Pressure Controls by Vapor Flow Variations | |
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| Flooded Condenser Pressure Controls | |
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| Valve in the Condensate, Unflooded Drum | |
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| Flooded Drum | |
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| Hot-Vapor Bypass | |
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| Valve in the Vapor to the Condenser | |
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| Coolant Throttling Pressure Controls | |
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| Cooling-Water Throttling | |
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| Manipulating Airflow | |
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| Steam Generator Overhead Condenser | |
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| Controlling Cooling-Water Supply Temperature | |
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| Pressure Control Signal | |
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| From Tower or from Reflux Drum? | |
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| Controlling Pressure via Condensate Temperature | |
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| Throttling Steam/Vapor to Reboiler or Preheater | |
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| Throttling Condensate from Reboiler | |
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| Preheater Controls | |
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| Miscellaneous Control Problems | |
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| Interaction with the Process | |
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| [Delta]P Control | |
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| Flood Controls and Indicators | |
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| Batch Distillation Control | |
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| Problems in the Control Engineer's Domain | |
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| Advanced Controls Problems | |
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| Updating Multivariable Controls | |
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| Advanced Controls Fooled by Bad Measurements | |
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| Issues with Model Inaccuracies | |
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| Effect of Power Dips | |
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| Experiences with Composition Predictors in Multivariable Controls | |
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| References | |
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| Index | |
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| About the Author | |