Post on 25-May-2017
Where We Go Wrong In Vessel Design
Dick Hawrelak
Presented to ES-317Y in 1999 at UWO
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.
1984 U.S. National OSHA Record
6486 accidents. 516 injuries. 90 deaths.
OSHA Record Includes Power Boilers Water Boilers and Steel
Tanks Cast Iron Boilers Pressure Vessels (poorest
record)
Pressure Vessel Record 1310 / 6486 accidents 437 / 516 injuries 73 / 90 deaths
Press Vessel Components Shell Head Attachements Piping Safety Valves Misc
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
PV Failure Types Cracked – 403 / 1087 Other - 298 / 1087 Leakage – 163 / 1087 Rupture – 158 / 1087 Explosion – 22 / 1087 Collapsed Inward – 15 / 1087
Obtain Data & Analyze Search OSHA records On Internet -
Google Extract records Create Excel Database Sort and Filter data Analyze Data
Personal Experiences Based on 33 Years of Chemical
Plant Design at Dow.
Incomplete Mass Balances
Normal mass balance. Start-up, shut down or upset. Recycle conditions. Off-loading situations unplanned.
Residence or Hold-up Time
Inventory logistics not well defined. Flammable or toxic inventories too
high.
Containment
Dyke dimensions do not meet codes.
Drainage does not follow NFPA 15. Catastrophic failure overwhelms
dyke walls.
Materials Of Construction
Not suitable for corrosive fluid at high temperature.
Not suitable for low temperature excursions.
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.
Nozzles Level control nozzles in wrong
location. Nozzles too small creating
impingement on far wall. PSV nozzles not suitable for thrust.
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.
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.
Typical Pressure Vessel
KO Pot Design
Internals Impingement details not well
designed. Pump-out sumps act as dirt trap. KO Pot internals not designed
properly.
Design Pressure Design Pressure not suitable for
upset conditions.
Reactive Chemicals P&IDs must be examined for
reactive chemical possibilities.
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.
Breathing. Pumping and temperature change
breathing not allowed for in combination.
High breathing losses a cost and an environmental problem - Benzene tank.
Vapor Recovery Options Not well understood. See BLOSS program for design
options.
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.
EO Storage
Toxic Storage
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?
Exam Questions Cont’d
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?
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.