melhem

2007, ioMosaic Corporation; all rights reservedDo not copy or distribute without the express written permission of ioMosaic Corporation

Selection and Optimization of Isolation Valves for Gas, Liquid, and Multiphase Pipelines

Prepared forPresentation at the Mary Kay OConner Process Safety Center 2007 Symposium

ioMosaic Corporation. All Rights Reserved.

MINNEAPOLIS OFFICE333 Washington Avenue NorthMinneapolis, Minnesota 55401Tel: 612-373-7037Fax:832-553-7283Email: [email protected]: www.iomosaic.com

HOUSTON OFFICE2650 Fountain View, Suite 410Houston, Texas 77057Tel: 713-490-5220Fax:713-490-5222Email: [email protected]: www.iomosaic.com

SALEM OFFICE93 Stiles RoadSalem, New Hampshire 03079Tel: 603-893-7009Fax:603-893-7885Email: [email protected]: www.iomosaic.com


Slide 1

Overview

Pipelines play an important role in energy distribution in the US and Worldwide

U.S. Natural Gas Pipeline Compressor Stations and Distribution Networks


Slide 2

Overview

(AP) PORT ARTHUR October 2007 Many Port Arthur residents have been jolted awake by a pipeline blast that sent flames about 100 feet into the predawn sky.

The blast happened about 2 a.m. Thursday just off U.S. 69, about 1 miles northwest of Texas 73 in the Stonegatesection of Port Arthur.

Witnesses tell The Port Arthur News that the heat of the flames ignited nearby trees, but no injuries or other secondary damage have been reported. Meanwhile, nearby residents are urged to stay indoors.

Port Arthur police say the pipeline is owned by Union Carbide and Dow Chemical. Police say the companies closed the flow through the pipeline about 4 a.m. Now, they're working to stop the remaining leak.

Pipelines accidents continue to occur although overall accident frequency has decreased


Slide 3

Accident Frequency

Pipeline accidents continue to occur although overall accident frequency has decreased

1970-2004

Moving average overlast 5 years

Source: 6th EGIG report 1970-2004


Slide 4

Accident Frequency

Source: 6th EGIG report 1970-2004

Up to 50 % of all gas pipeline incidents are typically caused by external interference


Slide 5

Pipeline flow dynamics are often challenging to model for sub-sea and/or buried pipelines

Sub-sea Pipelines


Slide 6

Buried Pipelines

Crater modeling for buried pipelines requires detailed estimates of temperature, velocity, and release angle

(A) (B)

(C)(D)


Slide 7

For small holes and cracks, flow direction can be estimated from a momentum balance

Flow Angle


Slide 8

Pipeline Consequence and Risk Assessment

Recent independent comparisons of model predictions of buried natural gas pipeline accidents show an excellent agreement with SuperChems Expert

Source: Tonelli, S. M.; Aparcio, L. V. Consequence evaluation in buriednatural gas pipeline. In: MercosurCongress on Chemical Engineering, 2005, Proceeding Empromer 2005, Village Rio das Pedras RJ, 1 CD-ROM.


Slide 9

Initial flow is similar to the expansion side of a shock tube after the membrane is broken

A centered expansion fan propagates into the high pressure gas setting it in motion towards the opening

Initial flow can be estimated without estimation of friction (ideal nozzle like)

As the wave train propagates deep into the gas, the effects of friction will become important

Rapid detection and isolation of pipeline segments depend on the pipeline operating conditions, contents composition, fluid phase, and material of construction

Detection and Isolation


Slide 10

A pressure drop caused by a pipeline break or full bore rupture will propagate with a characteristic acoustic speed through the pipe contents

Detection and Isolation


Slide 11

Sonic velocity of ethylene at saturation conditions

SATURATION TEMPERATURE. K100 150 200 250 300

S

P

E

E

D

O

F

S

O

U

N

D

.

M

/

S

0

500

1000

1500

2000

Liquid

Vapor

Source: SuperChems Expert

The speed of sound for two-phase mixtures depends on the presence of small amounts of dissolved gas


Slide 12

Two-phase sonic velocity of propane

M inimumUgas=218 m/s

Ulig= 732 m/s

Minim umU gas = 2 18 m/s

Ulig = 732 m/s


The speed of sound for two-phase mixtures reaches a minimum at 50 % void fraction


Slide 13

Typical values of E for pipeline materials of construction

For non-rigid piping support, material properties influence the characteristic acoustic speed of the system


Slide 14

Liquid Compressibility

For long pipelines operating under high pressure with sub-cooled liquid contents, a substantial amount of fluid can be released due to contraction of the pipe metal during depressurization


Slide 15

The vessel volume is set to the total pipeline volume

The frictional pipe length is set to 1/3 the total pipeline length (Lf)

The frictional pipe length increases as a function of time at 1/3 the speed of sound in the pipeline

VESSEL PIPE NOZZLE

0 at t =0

1 at t >031 at localsteadystateconditions3

f

f

f

L

L u t

L L

==

=

[1] Single phase or multiphase blowdown of vessels and pipelines, H. L. Norris and C. Puls, 1993 SPE Annual Technical Conference and Exhibition

We can effectively model the time dependent release rate of pipelines containing gases, two-phase, and sub-cooled fluids using a method proposed by Norris et al.[1]

Flow Dynamics Modeling


Slide 16

The following is an example that illustrates the importance of discharge flow area /

total pipe flow area

Flow Diameter (in) Flow Area (in2) Flow Area / Pipe Area

4.00 12.73 100.00%3.00 7.39 58.08%2.00 3.36 26.36%1.00 0.86 6.79%0.50 0.30 2.39%

Pipe outside diameter. in 4.00Pipe flow area. in2 12.73Initial temperature. F 19.75Initial pressure. psig 493.00Total mass of ethylene in pipe. lbs 19,842Pipe length. ft 13,124


Slide 17

Vessel solution vs. pipeline solution. Ah/Av = 100 %

100

TIME. s0 20 40 60 80

P

R

E

S

S

U

R

E

.

p

s

i

g

300

400

500

Pipeline

Vessel



Slide 18


TIME. s

Pipeline

Vessel

0 20 40 60 80 100

P

R

E

S

S

U

R

E

.

p

s

i

g

300

400

500



Slide 19


Pipeline

Vessel

TIME. s0 20 40 60 80 100

P

R

E

S

S

U

R

E

.

p

s

i

g

300

400

500



Slide 20


Pipeline

Vessel

TIME. s0 20 40 60 80 100

P

R

E

S

S

U

R

E

.

p

s

i

g

300

400

500



Slide 21

Vessel solution vs. pipeline solution. Ah/Av = 2.4 %

Pipeline

Vessel

TIME. s0 20 40 60 80 100

P

R

E

S

S

U

R

E

.

p

s

i

g

300

400

500



Slide 22

A similar conclusion was reached by reference [1].

Reference [1] indicated that the friction effects will important, even at flow area to total pipe area ratios as low as 25 %

The influence of pipe friction becomes important if the break flow area over the total pipe flow area is larger than 10 %

Fluid Dynamics Modeling


Slide 23

SuperChems Expert Modeling

Define mixture

Define reaction (if applicable)

Define piping segments

Define a horizontal cylindrical vessel with flat heads consisting of the entire pipe length as a vessel and designate as a pipeline

Select the number of divisions to use for the initial wave propagation and flow establishment duration. Typically 25 points are adequate

Define a piping layout consisting of piping segments equivalent to 1/3 of the total piping length starting from the flow point

Attach piping layout to vessel

Load scenario

Run simulation using dynamic gas or two-phase vessel module

OR Run WIZARDS!


Slide 24

Releases Under Water

Bubble formation

Bubble distribution

Bubble rise, volume, and velocity as a function of water depth

Mass transfer between bubble gas and water

Pipeline flow dynamics are often challenging to model for sub-sea and buried pipelines


Slide 25

Crater Modeling

Guess crater diameter

Maximize hazard distance as a function of crater diameter / flow diameter

Maximum hazard zones are usually established at a 10 degree flow angle

Flow is choked here

Crater modeling for buried pipelines requires detailed estimates of temperature, velocity, and release angle

Depending on the ratio of crater flow areato pipeline break flow area, the flow will eitherbe choked or subsonic.

For subsonic flow, the shockdiscontinuity influences the fluid exitdensity, velocity, and temperature

P=?


Slide 26

How Hazards Develop from Natural Gas Pipelines

Consider a range of failure scenarios including:

Full bore rupture ID Hole 80 mm Leak 20 mm

Flow is typically isothermal since the thermal inertia of the pipe is larger than tat of the gas

Hole size is determined by pipe fracture mechanics theory to be the maximum sustainable hole size that does not propagate into a full bore rupture

100.00%1.02E-03Total

42.61%4.34E-04Pin hole Crack (=2 cm)

42.87%4.36E-04Hole (>2cm


Slide 27


Quantitative Risk Analysis should be used to assess if the use of isolation valves will reduce the risk


Slide 28

1.00E-08

1.00E-07

1.00E-06

1.00E-05

1.00E-04

-500 -400 -300 -200 -100 0 100 200 300 400 500Distance from centre of pipeline (m)

Individual Risk of fatality (per year)

`


Pipeline is above surface Full bore, Hole and Leak:

Flow from both ends of pipe for full bore rupture

Flow is momentum driven and not likely to be obstructed

Hazard footprints are Omni directional and do not strongly depend on wind direction

Flame Jets Usually oriented along the path of the pipeline

Fireballs Caused by delayed ignition, usually 30 seconds of peak flow

Overpressure Impact area is often smaller than that of the fireball

Dispersion without ignition

Possible hazard outcomes from natural gas pipelines depend on whether the pipeline is buried or not


Slide 29

1.00E-08

1.00E-07

1.00E-06

1.00E-05

1.00E-04



`


Pipeline is buried Full Bore Rupture Crater is formed maximum hazard

footprint will depend on crate diameter and flow angle

Flow from both ends of pipe for full bore rupture

Flow is momentum driven, choked at the pipe hole exit, not likely to be obstructed

Hazard footprints are Omni directional and do not depend on wind direction

Flame Jets Usually oriented along the path of the pipeline

Fireballs Caused by delayed ignition, usually 30 seconds of peak flow

Overpressure Impact area is often smaller than that of the fireball

Dispersion without ignition



Slide 30

1.00E-08

1.00E-07

1.00E-06

1.00E-05

1.00E-04



`


Pipeline is buried Hole and Leak Flow is usually obstructed and

momentum is lost

Dispersion is directional and will depend on wind speed, atmospheric stability class, and wind direction

Main hazard is a flash fire



Slide 31

Recommended Conditional Probabilities

0.90 to 0.990.10 to 0.01Leak0.40 to 0.600.60 to 0.40Hole0.10 to 0.010.90 to 0.99Full Bore Rupture

Obstructed Release Leading to Loss of Momentum, Passive Dispersion, and Flash Fires / Deflagrations

Momentum Release Leading to Flame Jets and Fireballs



Slide 32

A Typical Gas Pipeline Flame Jet

3.44 inch ID


Slide 33

Use of Emergency Shutdown Valves

TIME. s0 2 4 6 8 10

M

A

S

S

F

L

O

W

R

A

T

E

.

k

g

/

s

0

20

40

60

80

100

The maximum impact hazard zones are established very quickly following a pipeline release


Slide 34

Impact of Thermal Radiation Exposure Time

EXPOSURE TIME. SECONDS0 1000 2000 3000 4000 5000 6000

P

R

O

B

A

B

I

L

I

T

Y

O

F

I

M

P

A

C

T

.

%

0

10

20

30

40

50

60

70

80

90

100

TNO; Unprotected; Fatality 5.00 kW/m2

TNO; Protected; Fatality 5.00 kW/m2

TNO; 1st Degree Burn; 5.00 kW/m2

TNO; 2nd Degree Burn; 5.00 kW/m2


Slide 35

Impact of Thermal Radiation Exposure Time

TNO; Unprotected; Fatality 12.5 kW/m2

TNO; Protected; Fatality 12.5 kW/m2

TNO; 1st Degree Burn; 12.5 kW/m2

TNO; 2nd Degree Burn; 12.5 kW/m2

EXPOSURE TIME. SECONDS0 600 1200 1800

P

R

O

B

A

B

I

L

I

T

Y

O

F

I

M

P

A

C

T

.

%

0

10

20

30

40

50

60

70

80

90

100


Slide 36

Use of Emergency Shutdown Valves

In general, the use of emergency shutdown valves will not significantly reduce the inherent pipeline risk

In general, the use of emergency shutdown valves can reduce the release time, and enable quicker emergency response


Slide 37

Founded by former Arthur D. Little Inc. executives and senior staff, ioMosaic Corporation is the leading provider of safety and risk management consulting services. ioMosaic has offices in Salem, New Hampshire and Houston, Texas, and Minneapolis, Minnesota.

Since the early 1970's, ioMosaic senior staff and consultants have conducted many landmark studies including an audit of the Trans-Alaska pipeline brought about by congressional whistle blowers, investigation of the Bhopal disaster, and the safety of CNG powered vehicles in tunnels. Our senior staff and consultants have authored more than ten industry guidelines and effective practices for managing process safety and chemical reactivity and are recognized industry experts in LNG facility and transportation safety.

ioMosaic Corporation is also the leading provider of pressure relief systems design services and solutions. Its pressure relief system applications are used by over 250 users at the world's largest operating companies. It holds key leadership positions in the process industries' most influential and active pressure relief system design, and chemical reactivity forums, and plays a pivotal role in defining relief system design, selection, and management best practices.

MINNEAPOLIS OFFICE333 Washington Avenue NorthMinneapolis, Minnesota 55401Tel: 612-373-7037Fax:832-553-7283Email: [email protected]: www.iomosaic.com

HOUSTON OFFICE2650 Fountain View, Suite 410Houston, Texas 77057Tel: 713-490-5220Fax:713-490-5222Email: [email protected]: www.iomosaic.com

SALEM OFFICE93 Stiles RoadSalem, New Hampshire 03079Tel: 603-893-7009Fax:603-893-7885Email: [email protected]: www.iomosaic.com

About ioMosaic Corporation

melhem

Documents

symposium iomosaic corporation

rights reserveddo

port arthur police

port arthur residents

pipeline blast

port arthur news

gas pipeline incidents

overview ap port arthur