Where We Go Wrong In Vessel Design

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Where We Go Wrong In Vessel Design

• Dick Hawrelak
• Presented to ES-317Y in 1999 at UWO

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Introduction

• 30 of large property damage losses are caused by
  failures in tanks, process drums and marine
  vessels.
• Average Trended Loss was 40.5MM for tanks alone.

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1984 U.S. National OSHA Record

• 6486 accidents.
• 516 injuries.
• 90 deaths.

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OSHA Record Includes

• Power Boilers
• Water Boilers and Steel Tanks
• Cast Iron Boilers
• Pressure Vessels (poorest record)

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Pressure Vessel Record

• 1310 / 6486 accidents
• 437 / 516 injuries
• 73 / 90 deaths

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Press Vessel Components

• Shell
• Head
• Attachements
• Piping
• Safety Valves
• Misc

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PV Failure Causes

• Operator error or poor maintenance 149 / 933
• Faulty Design 144 / 933
• Corrosion or erosion 132 / 933
• Pressure control failure 41 / 933
• Other 420 / 933

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PV Failure Types

• Cracked 403 / 1087
• Other - 298 / 1087
• Leakage 163 / 1087
• Rupture 158 / 1087
• Explosion 22 / 1087
• Collapsed Inward 15 / 1087

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Obtain Data Analyze

• Search OSHA records On Internet - Google
• Extract records
• Create Excel Database
• Sort and Filter data
• Analyze Data

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Personal Experiences

• Based on 33 Years of Chemical Plant Design at Dow.

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Incomplete Mass Balances

• Normal mass balance.
• Start-up, shut down or upset.
• Recycle conditions.
• Off-loading situations unplanned.

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Residence or Hold-up Time

• Inventory logistics not well defined.
• Flammable or toxic inventories too high.

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Containment

• Dyke dimensions do not meet codes.
• Drainage does not follow NFPA 15.
• Catastrophic failure overwhelms dyke walls.

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Materials Of Construction

• Not suitable for corrosive fluid at high
  temperature.
• Not suitable for low temperature excursions.

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Quantum Explosion - 7 June 89

• A-515-70 grade CS brittle failure of heat
  exchanger shell.
• Start-up, inlet flange leak, isolated exchanger
  and depressured to flare.
• 30 minutes to failure. Two fatalities, seven
  serious burns, major damage to ethylene plant.

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Nozzles

• Level control nozzles in wrong location.
• Nozzles too small creating impingement on far
  wall.
• PSV nozzles not suitable for thrust.

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Visit U.S. EPA CEPP Web Site

• Chemical Emergency Preparedness and Prevention
  Office web site at www.epa.gov/ceppo/acc-his.html
• Check Rupture Hazard of Pressure Vessels.
• Check Catastrophic Failure of Storage Tanks.

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Ammonia Storage Tank Modification

• Oil and Gas Journal, Dec 26, 1998
• Pressure storage in spheres
• Removes bottom unloading lines.
• Converts to overhead siphon system.
• Excellent article on 4 process design options.

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Typical Pressure Vessel
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KO Pot Design
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Internals

• Impingement details not well designed.
• Pump-out sumps act as dirt trap.
• KO Pot internals not designed properly.

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Design Pressure

• Design Pressure not suitable for upset conditions.

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Reactive Chemicals

• PIDs must be examined for reactive chemical
  possibilities.

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Low Pressure API Tanks

• Very easy to bulge or suck-in resulting in loss
  of containment.
• PSV, pad de-pad settings very close.
• Floating roof explosion at Suncor in Sarnia. Roof
  hangs up on pump-out, air sucked into vapor
  phase, lightning ignites flammable vapor.

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Breathing.

• Pumping and temperature change breathing not
  allowed for in combination.
• High breathing losses a cost and an environmental
  problem - Benzene tank.

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Vapor Recovery Options

• Not well understood.
• See BLOSS program for design options.

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Flammable Storage Area

• EO storage bunkers located 1 mile from ISBL.
• 3 independent means of checking quantity to
  prevent overfilling (dual LC, weigh scale flow
  rate x time).
• Refrigeration to prevent polymerization, chart
  temperature.
• Dump contents to pond if runaway reaction takes
  place.

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EO Storage
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Toxic Storage
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Possible Exam Questions

• What are three independent methods for preventing
  overfilling of a storage vessel.
• If a storage product can generate heat by
  polymerization at ambient temperatures, what
  safety measures should be considered?
• What are the main problems with fixed roof, low
  pressure API type storage vessels?

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Exam Questions Contd

• What is one of the main problems with an API,
  floating roof storage tank in flammable service?
• What are the safety measures that should be taken
  for a large chlorine storage sphere to prevent a
  toxic gas release?

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Summary

• This short list is indicative of some of the
  problems caused by poor engineering discipline in
  vessel design.
• Recommend you obtain a copy of the Chemical Plant
  Design programs and follow the procedures built
  into the vessel design spreadsheets.