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Emergency Relief

Gary Van SciverSeptember 16, 2008

         

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Gary Van Sciver

Process Engineer – 8 years

Risk Analyst – 22 years

ETC – 2 ½ years

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Presentation Overview

ERSNormal Vent

1

23

4

5

1. Normal vent2. Design basis3. Mechanical4. Discharge

5. MOC

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Terminology (ERS)

EmergencyReliefSystem

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1. Normal Vent

ERSNormal Vent

1

23

4

5

1. Normal vent2. Design basis3. Mechanical4. Discharge

5. MOC

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What is the difference between the normal vent & the

emergency vent?EmergencyVent

Normal Vent

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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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VPRV (conservation vent)

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VPRV(vacuum pressure relief valve)

To/fromvessel

Fromatmosphere

Discharge

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ManifoldsOne pollution abatement device will normally

handle the discharge of multiple vessels

PollutionAbatement

Device

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VPRV(vacuum pressure relief valve)

To/fromvessel

Fromatmosphere

Discharge

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Storage Tank Under Vacuum

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Plastic Bag Over Vent

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2. Design Basis

ERSNormal Vent

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23

4

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1. Normal vent2. Design basis3. Mechanical4. Discharge

5. MOC

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Upset Scenario...

Series of events leading to high vessel pressure

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What do we want the ERS to protect against?...

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Concept Sciences1999 Allentown, PA 5 fatalities hydroxylamine

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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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Concept Sciences

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Flammable Discharge

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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 - 2005Tower – 170 feet tall Blowdown drum – 115 feet tall

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BP - 2005Truck parked,

but idling about 25 feet from

blowdown drum

Eyewitness saw engine over-revving and

backfiring sparks

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BP - 2005

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Toxic Discharge

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Bhopal - 1984

>2000 off-site fatalities due to toxic relief valve discharge

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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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Bhopal - 1984

MICStorage Refrigeration Scrubber Flare

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Design Basis Procedure

1. Identification  2. Sizing 3. Selection

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How do we identify upsets?

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2 important upsets

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Fire ExposureRD

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Runaway reactionHigh

temperatureor unusual

composition

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Some other non-reactive upsets

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Excessive heating(steam valve failures, coil leaks)

Steam wide open

RD

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Pressurized liquid addition

Liquid

RD

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Pressurized gas addition(line blowing, pressure transfers, pads or purges)

RD

Air, Nitrogen or Steam

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Some reactive upsets

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Inadequate cooling

Coolingwaterfails

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Inadequate heat sinkWater NOT

charged

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Excessive reactant

Reactant

Bypass open

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Poor reactivityAgitator off

Reactant

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Design Basis Procedure

1. Identification  2. Sizing

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Sizing vents is straightforward but we do need kinetics

data for reactive scenarios

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Types of runaway reaction

• Vapor Pressure• Gas Generating .

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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

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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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MAA Rail Car

July 1988 (R&H) Deer Park, Texas

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VSP(Vent Sizing Package)

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VSP

120 cctest cell

P FillT

RDPC

XXXXXXX

XXXXXXX

X X X X X X

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Temperature vs time

time

Tem

pera

ture

or P

ress

ure

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P vs T

Temperature

Pre

ssur

e

Heat up

Cool down

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Design Basis Procedure

1. Identification  2. Sizing 3. Selection

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List the scenarios in

order of increasing relief

device size requirement

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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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Selection Approaches

1. Codes2. Tradition3. Risk .

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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 (B

tu/h

our)

<1 psig

>1 psig

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Tradition

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Take advantage of our previous experience

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For example: batch reactor ERS sized for a full-charge

runaway

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Risk

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Risk Management Services(RMS)

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Rohm and Haas Risk Criteria

Community 1 in 100,000 per year

Employees 1 in 40,000 per year

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3. Mechanical

ERSNormal Vent

1

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4

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1. Normal vent2. Design basis3. Mechanical4. Discharge

5. MOC

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Vessel Failure

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Vessel FailureWith increasing pressure, flat surfaces become rounded,

vessel resembles a sphere.

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Bottom Seam Failure

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Hold Down Lug - Older

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Hold Down Lug - Newer

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Hold Down Lug - Newer

Vessel

Concrete

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Failure Pressure

Safety Factor

HydrostaticTest Pressure

MAWP0 1X 1.5X 2X 3X 4X

Pressure

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Relief Devices

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Rupture Disk

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Tension-loaded RD

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Tension-loaded RD

Flow

Rupture Disk

HolderVacuum support goes under the RD

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Compression-loaded RD(Reverse Buckling)

Flow

Rupture Disk

Holder

Knife blade (if necessary) goes on top of the RD

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Relief Valves

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Weak Seam Roof(part of API 650)

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Weak Seam RoofWeak seam roof should prevent this

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Weak Seam Roof

Install with relief device to protect the roof

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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

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Thrust forces

RuptureDisk

Reactor

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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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Piping – Thrust forces(initial & established)

Initial load

Established load

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4. Discharge

ERSNormal Vent

1

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4

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1. Normal vent2. Design basis3. Mechanical4. Discharge

5. MOC

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Dispersion Zones1. High momentum2. Less momentum3. Gravity4. Atmospheric

turbulence

1

2 3

4

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2-phase Flow

1 3

4 5 6

2

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2-phase Flow

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PHAST – Emulsion Reactor RD

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Gooseneck

Toatmosphere

From vessel

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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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Toll Incident

2002 runaway

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Toll Incident2002 runaway

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TNP(Thrust Neutralization Plate)

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TNPThrust Neutralization Plate

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TNP or Gooseneckwind

typical flammable region

buildingair inlet

With an obstruction

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Catch TankGravity Separator

Vapors still escape from a separator,

but at a lower

velocity.

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Catch Tank

From reactor Cyclone separator

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Catch Tank Incident

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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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Catch Tank Incident

Catch tank roof failed

Low-pressure vessel with

insufficient vent

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Catch Tank Incident

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Quench Tank

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Straight up

wind

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Rain Protection - Cover

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5. MOC

ERSNormal Vent

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4

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1. Normal vent2. Design basis3. Mechanical4. Discharge

5. MOC

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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

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Questions?