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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
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2007, ioMosaic Corporation; all rights reservedDo not copy or distribute without the express written permission of ioMosaic Corporation
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
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2007, ioMosaic Corporation; all rights reservedDo not copy or distribute without the express written permission of ioMosaic Corporation
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
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2007, ioMosaic Corporation; all rights reservedDo not copy or distribute without the express written permission of ioMosaic Corporation
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
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2007, ioMosaic Corporation; all rights reservedDo not copy or distribute without the express written permission of ioMosaic Corporation
Slide 4
Accident Frequency
Source: 6th EGIG report 1970-2004
Up to 50 % of all gas pipeline incidents are typically caused by external interference
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2007, ioMosaic Corporation; all rights reservedDo not copy or distribute without the express written permission of ioMosaic Corporation
Slide 5
Pipeline flow dynamics are often challenging to model for sub-sea and/or buried pipelines
Sub-sea Pipelines
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2007, ioMosaic Corporation; all rights reservedDo not copy or distribute without the express written permission of ioMosaic Corporation
Slide 6
Buried Pipelines
Crater modeling for buried pipelines requires detailed estimates of temperature, velocity, and release angle
(A) (B)
(C)(D)
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2007, ioMosaic Corporation; all rights reservedDo not copy or distribute without the express written permission of ioMosaic Corporation
Slide 7
For small holes and cracks, flow direction can be estimated from a momentum balance
Flow Angle
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2007, ioMosaic Corporation; all rights reservedDo not copy or distribute without the express written permission of ioMosaic Corporation
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.
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2007, ioMosaic Corporation; all rights reservedDo not copy or distribute without the express written permission of ioMosaic Corporation
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
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2007, ioMosaic Corporation; all rights reservedDo not copy or distribute without the express written permission of ioMosaic Corporation
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
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2007, ioMosaic Corporation; all rights reservedDo not copy or distribute without the express written permission of ioMosaic Corporation
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
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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
Source: SuperChems Expert
The speed of sound for two-phase mixtures reaches a minimum at 50 % void fraction
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2007, ioMosaic Corporation; all rights reservedDo not copy or distribute without the express written permission of ioMosaic Corporation
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
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2007, ioMosaic Corporation; all rights reservedDo not copy or distribute without the express written permission of ioMosaic Corporation
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
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2007, ioMosaic Corporation; all rights reservedDo not copy or distribute without the express written permission of ioMosaic Corporation
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
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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
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2007, ioMosaic Corporation; all rights reservedDo not copy or distribute without the express written permission of ioMosaic Corporation
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
Source: SuperChems Expert
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2007, ioMosaic Corporation; all rights reservedDo not copy or distribute without the express written permission of ioMosaic Corporation
Slide 18
Vessel solution vs. pipeline solution. Ah/Av = 58 %
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
Source: SuperChems Expert
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2007, ioMosaic Corporation; all rights reservedDo not copy or distribute without the express written permission of ioMosaic Corporation
Slide 19
Vessel solution vs. pipeline solution. Ah/Av = 26 %
Pipeline
Vessel
TIME. s0 20 40 60 80 100
P
R
E
S
S
U
R
E
.
p
s
i
g
300
400
500
Source: SuperChems Expert
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2007, ioMosaic Corporation; all rights reservedDo not copy or distribute without the express written permission of ioMosaic Corporation
Slide 20
Vessel solution vs. pipeline solution. Ah/Av = 7 %
Pipeline
Vessel
TIME. s0 20 40 60 80 100
P
R
E
S
S
U
R
E
.
p
s
i
g
300
400
500
Source: SuperChems Expert
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2007, ioMosaic Corporation; all rights reservedDo not copy or distribute without the express written permission of ioMosaic Corporation
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
Source: SuperChems Expert
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2007, ioMosaic Corporation; all rights reservedDo not copy or distribute without the express written permission of ioMosaic Corporation
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
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2007, ioMosaic Corporation; all rights reservedDo not copy or distribute without the express written permission of ioMosaic Corporation
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!
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2007, ioMosaic Corporation; all rights reservedDo not copy or distribute without the express written permission of ioMosaic Corporation
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
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2007, ioMosaic Corporation; all rights reservedDo not copy or distribute without the express written permission of ioMosaic Corporation
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=?
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2007, ioMosaic Corporation; all rights reservedDo not copy or distribute without the express written permission of ioMosaic Corporation
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
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2007, ioMosaic Corporation; all rights reservedDo not copy or distribute without the express written permission of ioMosaic Corporation
Slide 27
How Hazards Develop from Natural Gas Pipelines
Quantitative Risk Analysis should be used to assess if the use of isolation valves will reduce the risk
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2007, ioMosaic Corporation; all rights reservedDo not copy or distribute without the express written permission of ioMosaic Corporation
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)
`
How Hazards Develop from Natural Gas Pipelines
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
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2007, ioMosaic Corporation; all rights reservedDo not copy or distribute without the express written permission of ioMosaic Corporation
Slide 29
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)
`
How Hazards Develop from Natural Gas Pipelines
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
Possible hazard outcomes from natural gas pipelines depend on whether the pipeline is buried or not
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2007, ioMosaic Corporation; all rights reservedDo not copy or distribute without the express written permission of ioMosaic Corporation
Slide 30
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)
`
How Hazards Develop from Natural Gas Pipelines
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
Possible hazard outcomes from natural gas pipelines depend on whether the pipeline is buried or not
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2007, ioMosaic Corporation; all rights reservedDo not copy or distribute without the express written permission of ioMosaic Corporation
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
Possible hazard outcomes from natural gas pipelines depend on whether the pipeline is buried or not
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2007, ioMosaic Corporation; all rights reservedDo not copy or distribute without the express written permission of ioMosaic Corporation
Slide 32
A Typical Gas Pipeline Flame Jet
3.44 inch ID
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Slide 33
Use of Emergency Shutdown Valves
TIME. s0 2 4 6 8 10
M
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W
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k
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s
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20
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60
80
100
The maximum impact hazard zones are established very quickly following a pipeline release
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2007, ioMosaic Corporation; all rights reservedDo not copy or distribute without the express written permission of ioMosaic Corporation
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
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F
I
M
P
A
C
T
.
%
0
10
20
30
40
50
60
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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
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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
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30
40
50
60
70
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90
100
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2007, ioMosaic Corporation; all rights reservedDo not copy or distribute without the express written permission of ioMosaic Corporation
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
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2007, ioMosaic Corporation; all rights reservedDo not copy or distribute without the express written permission of ioMosaic Corporation
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