Where We Go Wrong In Vessel Design Dick Hawrelak Presented to ES-317Y in 1999 at UWO

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

1984 U.S. National OSHA Record n 6486 accidents. n 516 injuries. n 90 deaths.

OSHA Record Includes n Power Boilers n Water Boilers and Steel Tanks n Cast Iron Boilers n Pressure Vessels (poorest record)

Pressure Vessel Record n 1310 / 6486 accidents n 437 / 516 injuries n 73 / 90 deaths

Press Vessel Components n Shell n Head n Attachements n Piping n Safety Valves n Misc

PV Failure Causes n Operator error or poor maintenance – 149 / 933 n Faulty Design – 144 / 933 n Corrosion or erosion – 132 / 933 n Pressure control failure – 41 / 933 n Other – 420 / 933

PV Failure Types n Cracked – 403 / 1087 n Other / 1087 n Leakage – 163 / 1087 n Rupture – 158 / 1087 n Explosion – 22 / 1087 n Collapsed Inward – 15 / 1087

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

Personal Experiences n Based on 33 Years of Chemical Plant Design at Dow.

Incomplete Mass Balances n Normal mass balance. n Start-up, shut down or upset. n Recycle conditions. n Off-loading situations unplanned.

Residence or Hold-up Time n Inventory logistics not well defined. n Flammable or toxic inventories too high.

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

Materials Of Construction n Not suitable for corrosive fluid at high temperature. n Not suitable for low temperature excursions.

Quantum Explosion - 7 June 89 n A grade CS brittle failure of heat exchanger shell. n Start-up, inlet flange leak, isolated exchanger and depressured to flare. n 30 minutes to failure. Two fatalities, seven serious burns, major damage to ethylene plant.

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

Visit U.S. EPA CEPP Web Site n Chemical Emergency Preparedness and Prevention Office web site at n Check Rupture Hazard of Pressure Vessels. n Check Catastrophic Failure of Storage Tanks.

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

Typical Pressure Vessel

KO Pot Design

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

Design Pressure n Design Pressure not suitable for upset conditions.

Reactive Chemicals n P&IDs must be examined for reactive chemical possibilities.

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

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

Vapor Recovery Options n Not well understood. n See BLOSS program for design options.

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

EO Storage

Toxic Storage

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

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

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