3
Presentation Overview
ERS
Normal Vent
1
23
4
5
1. Normal vent2. Design basis3. Mechanical4. Discharge
5. MOC
5
1. Normal Vent
ERS
Normal Vent
1
23
4
5
1. Normal vent2. Design basis3. Mechanical4. Discharge
5. MOC
7
What are the differences? (between the normal & emergency vents)
• No blocking devices in ERS• No flame arresters in ERS• ERS usually bigger• Normal vent also handles vacuum• Pollution abatement for normal vent• Normal vent opens first• Manifolding for normal vent .
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ManifoldsOne pollution abatement device will normally
handle the discharge of multiple vessels
PollutionAbatement
Device
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2. Design Basis
ERS
Normal Vent
1
23
4
5
1. Normal vent2. Design basis3. Mechanical4. Discharge
5. MOC
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Concept Sciences
• The plant was designed to concentrate hydroxylamine (HA) up to 50%
• HA is known to be explosive above 70% concentration
• Due to startup problems, the actual concentration was 86% HA .
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BP - 2005
Texas City, Texas 15 fatalities
Vapor cloud explosion of hexane/heptane (44ºC)
7700 gallons released < 2 minutes from 35 m height
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BP - 2005
Truck parked, but idling about
25 feet from blowdown drum
Eyewitness saw engine over-revving and
backfiring sparks
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Bhopal
Taloja
Delhi
Kolkata(formerlyCalcutta)
Chennai(formerlyMadras)
Mumbai(formerlyBombay)
Bhopal
IndiaNH 12
NH 12
Upper Lake
NH 86NH 86
UnionCarbide
Toxic GasCloud
Highly-Populated Region of Bhopal
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Bhopal1984
•Relief valve on an MIC storage tank lifted in the middle of the night releasing 80,000 lbs
•>2,000 people died within a short period
•~30,000 people were permanently or totally disabled
•MIC reacted with water, source of contamination uncertain
•Incident had long-term ramifications for Union Carbide and the chemical industry as a whole .
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Pressurized gas addition(line blowing, pressure transfers, pads or purges)
RD
Air, Nitrogen or Steam
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Vapor PressureRunaway Reaction
• Pressure related to temperature• Control temperature by
evaporative cooling .
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Emulsion Runaway
• 1995, one-shot emulsion process• Water charging system failed• New operator being trained, batch not stopped• 2,000-gallon, 120-psig reactor • Broke 35-psig, 18-inch rupture disk
• ~1200 lbs ethyl acrylate released.
35% EA 70% EA
Normal Upset
90C max 190C max
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Emulsion Runaway
France
Germany
Rohm & Haas Karlsruhe
RheinRiver
Odor complaints 13 miles away in
Karlsruhe, Germany
France
Germany
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Gas GeneratingRunaway Reaction
• Pressure related to amount of gas
• Can’t control temperature by venting
• Only control is depletion of reactants .
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Example Scenario List
2” 1.Liquid filling 3” 2.Fire case12” 3.Half charge runaway18” 4.Full charge runaway24” 5.Full charge runaway, no
water heel .
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NFPA 30 requires ERS protection against fire for
aboveground storage tanks of flammables &
combustibles
Codes
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Fire Case Requirement
Fire Case Heat Input
1.0E+05
1.0E+06
1.0E+07
1.0E+08
10 100 1,000 10,000
Area (sq feet)
Q (
Btu
/ho
ur)
<1 psig
>1 psig
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3. Mechanical
ERS
Normal Vent
1
23
4
5
1. Normal vent2. Design basis3. Mechanical4. Discharge
5. MOC
81
Compression-loaded RD(Reverse Buckling)
Flo
w
Rupture Disk
Holder
Knife blade (if necessary) goes on top of the RD
86
Design Temperature
ERS
Vessel
Temperature
Des
ign
Pre
ssur
e
Am
bien
t Tem
pera
ture
Des
ign
Tem
pera
ture
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Thrust forces
For 24” RD, Area = 452 sq in
Pmax = 165 psi
Thrust = 2 Pmax A = 150,000 lbs
Opposing forces onsupport lugs
& structural steel
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4. Discharge
ERS
Normal Vent
1
23
4
5
1. Normal vent2. Design basis3. Mechanical4. Discharge
5. MOC
97
Toll Incident
• Wisconsin - 2002
• Leaky steam valve heated a completed batch from 40C to 150C in 3 hours
• Resulting decomposition (>200 psig)
• MSDS: “This material is considered stable”
• No fatalities or injuries .
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Toll Incident
DistillateReceiver
Condenser
4000 GallonReactor
RuptureDisk
Building
Building Roof
Steam
2002 runaway
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Catch Tank Incident• Illinois 2001• Runaway reaction
broke 135 psi RD• Blew off catch tank
top & damaged piping
• No injuries or fatalities .
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Why document?
• Required by OSHA PSM (Process Safety Mgmt)
• Required by EHS 536 (Process Safety Mgmt)
• For future Management of Change (MOCs)
• For future HAZOPs
• Avoid reconstructing the design
• Information can be used on other systems .
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Vent System Analysis
Follow the ERS procedure for every vessel & every relief device
Store the results in a safe place