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Emergency Relief

Gary Van Sciver

September 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

ERS

Normal Vent

1

23

4

5

1. Normal vent2. Design basis3. Mechanical4. Discharge

5. MOC

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Terminology (ERS)

Emergency

Relief

System

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1. Normal Vent

ERS

Normal 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

ERS

Normal Vent

1

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 - 2005

Truck 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

PFill

T

RDPC

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X X X X X X

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Temperature vs time

time

Tem

pera

ture

or

Pre

ssur

e

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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. Codes

2. 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 (

Btu

/ho

ur)

<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

ERS

Normal Vent

1

23

4

5

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

MAWP

0 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

Flo

w

Rupture Disk

HolderVacuum support goes under the RD

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Compression-loaded RD(Reverse Buckling)

Flo

w

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

ERS

Normal Vent

1

23

4

5

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

ERS

Normal Vent

1

23

4

5

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?