Transcript Design Basis

Selecting
an ERS
Design Basis
SACHE Workshop
Gary Van Sciver
September 20, 2005
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Emergency
Relief
System
Rupture
Disk
Reactor
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Vessel Overpressure
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Concept Sciences
1999 Allentown, PA 5 fatalities
high concentration and temperature of hydroxylamine 4
Hazardous Release
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Phillips
Pasedena, Texas
1989
23 fatalities
Vapor cloud explosion of ethylene and other gases
Explosion occurred ~ 2 minutes after release started
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Bhopal
Union Carbide
1984
2,500 fatalities
large ERS release of methyl isocyanate
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Venting Policy:
ERS must protect
on-site people AND
off-site people
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Balance:
On-site
Risk
Off-site
Risk
$
Economics
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What is a
Design Basis?
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Design Basis:
Simple way to express
system capacity
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Failure
Scenario
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Fire Scenario
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Runaway Scenario
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Failure Scenario:
Series of events
leading to high vessel
pressure.
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How high?
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Codes require that the maximum
pressure not exceed the vessel
design pressure
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Design Basis:
Most severe failure
scenario which complies
with the Codes.
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How do we do it?
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Procedure:
1. Identification
2. Selection
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1. Identification
(of all important failure
scenarios)
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ideas
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Non-reactive
Systems
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Product Tank Example
RD
Heating/Cooling
From Reactor
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Non-Reactive
Checklist
1. Heat addition
a. Normal breathing
b. Fire
c. Excessive heating
2. Pressurized liquid addition
3. Pressurized gas addition
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1a. Normal breathing
(atmospheric temperature and pressure changes)
RD
Heating/Cooling
From Reactor
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1b. Fire Exposure
RD
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1c. Excessive heating
(steam valve failures, coil leaks)
RD
Steam wide open
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2. Pressurized liquid addition
(usually accompanied by some flashing, especially if hot)
RD
Liquid
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3. Pressurized gas addition
(line blowing, pressure transfers, pads or purges)
RD
Air, Nitrogen or Steam
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Reactive
Systems
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Is there an exothermic or
gas-generating
reaction?
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Generic Emulsion Compatibility Matrix
activator
bactericide
catalyst
chain transfer
agent
miscellaneous
additive
monomer
neutralizer
preform
promoter
soap
water
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Reactive Chemistry
Worksheet
developed by EPA and NOAA
(National Oceanic and Atmospheric Administration)
http://response.restoration.noaa.gov/chemaids/react.html
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OSHA Chemical
Reactivity Website
http://www.osha.gov/dep/reactivechemicals/
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Bretherick’s
Handbook of Reactive
Chemical Hazards
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Lab
Experiments
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Emulsion Reactor Example
Reactant
Miscellaneous
Catalyst/
Activator
Cooling
Water
TIC
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Normal
Reaction Checklist
1. Inadequate cooling
2. Inadequate heat sink
3. Excessive reactant
4. Poor reactivity
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1. Inadequate cooling
Cooling
water
fails
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2. Inadequate heat sink
Water NOT
charged
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3. Excessive reactant (continuous)
Bypass open
Reactant
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3. Excessive Reactant (batch)
Reactant
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4. Poor reactivity
Agitator off
Reactant
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Abnormal
Reaction Checklist
1. Too hot
2. Wrong composition
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1. Too hot
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2. Wrong composition
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System ________________
1. Non-Reactive Scenarios
Apply?
Description & Size
XXX
XXXXXXXXXXX
XXX
XXXXXXXXXXX
1a. Normal Breathing
1b. Excessive Heating
1c. Fire Exposure
1d. Liquid Addition
1e. Gas Addition
2. Normal Reaction Scenarios
2a. Inadequate Cooling
2b. Inadequate Heat Sink
2c. Excessive Reactants Fed
2d. Excessive Reactant Buildup
3. Abnormal Reaction Scenarios
3a. Too Hot
3b. Wrong Composition
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2. Selection
(of a design basis from the
important failure scenarios)
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Selection
Approaches:
A. Codes/Standards
B. Tradition/Analogy
C. Risk
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List scenarios by
ERS size
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Example Scenario List:
1.Liquid filling
2.Fire case
3.Half charge runaway
4.Full charge runaway
5.Full charge runaway without
water heel
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A. Codes/ Standards
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NFPA 30 requires
ERS protection against
fire exposure
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B. Tradition/ Analogy
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Traditional
Designs
Non-reactive: Fire Case
Reactive: Full-charge
Runaway
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Traditional Design
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ERS Database
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C. Risk
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Probability
of
consequences
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Consequences
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Probability
(of high vessel pressure)
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Plot Plan
Fenceline
Hospital
Process
Neighbors
Offices
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Risk Contours
Fenceline
Hospital
Process
Neighbors
Offices
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Rohm and Haas
Risk Criteria
On-site Risk - once per 40,000 years
Off-site Risk - once per 100,000 years
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