Download - Detailed Design Review
DETAILED DESIGN REVIEWP13681
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The Team• Austin Frazer
• Role: Lead Engineer - Analysis• Major: Mechanical Engineering
• Eileen Kobal• Role: Lead Engineer – Mixtures
of Gas Fluids• Major: Chemical Engineering
• Ana Maria Maldonado• Role: Team Manager• Major: Industrial Engineering
• Marie Rohrbaugh• Role: Project Manager• Major: Mechanical Engineering
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Agenda for the review• Overview of the Project• Our system designs• Part designs• Lab View layout• Bill of Materials• Test plans• Risk Assessment• Schedule for the rest of the Project
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Problem Statement
To mass spectrometer
UUT
High pressure helium
High pressure helium
Fixturing/leakage similar to other side
Fixtures interface between AGT can and UUT
Fixture leakageUUT leakage
Leakage from Unit UnderTest
Leakage from FixtureLeakage from room through lid and baseplate
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Project Overview
MATLAB/SIMULINK MODEL
The System
3000 psi
Flow Sensor
0 psi (Vacuum)
Case 1) 14.7 psi (ambient)Case 2) 0 psi (Vacuum)Case 3) Variable pressure/vacuum (nitrogen)
• We require a means to distinguish between the top two generated concepts. Consequently, a math model of the system was created.• Results must be an improvement from the baseline
Simplification of the System
3000 psi 0 psi (To Mass Spectrometer)
Orifice 3 : Accurately simulates uniformly mixed flow out of vent.
Orifices 1 and 2: Model Oring Leakage.
Entire Vent Volume
Flow Sensor
• Orings will be models as (very) small orifices• Molar percentages must be taken into consideration for all three cases
(compare apples to apples)
HELIUM MIXTURE
CasesP vent Initial
(N2)P Applied
(N2) Notes1 14.7 psi 14.7 psi This is the baseline
2 14.7 psi 1 psiP vent quickly equalizes to approx 1 psi
3 14.7 psi 120 psi Note this is not a 50% Duty Cycle1 psi
Parameters and Equations
�̇�𝑂𝑟𝑖𝑓𝑖𝑐𝑒 ,𝐻𝑒=𝜌𝑀𝑖𝑥𝐶𝑑 𝐴𝑜
𝑀𝑊 𝐻𝑒 √ 2𝑑𝑃𝜌𝑀𝑖𝑥
�̇�𝐻𝑒 ,𝑡𝑜𝑡=∑ �̇�𝐻𝑒 , 𝑖𝑛−∑ �̇�𝐻𝑒 ,𝑜𝑢𝑡
�̇�𝑁 2 , 𝑡𝑜𝑡=∑ �̇�𝑁 2 ,𝑖𝑛−∑ �̇�𝑁 2 ,𝑜𝑢𝑡
�̇�𝑂𝑟𝑖𝑓𝑖𝑐𝑒 ,𝑁 2=𝜌𝑀𝑖𝑥𝐶𝑑 𝐴𝑜
𝑀𝑊 𝑁 2 √ 2𝑑𝑃𝜌𝑀𝑖𝑥
𝑃=𝜌 𝑅𝑠𝑇
Orifice area, Ao, is adjusted for the oring and vent orifices to produce accurate molar flow rates
Ideal Gas Law:𝑃𝑉=𝑛𝑅𝑢𝑛𝑖𝑣 𝑇
3000 psi 0 psi (To Mass Spectrometer)
Entire Vent Volume
𝜌𝑚𝑖𝑥=𝑃𝑣𝑒𝑛𝑡
𝑇 (%𝑁 2𝑅𝑁 2
+%𝐻𝑒𝑅𝐻𝑒 )
Mixed Density Calculation:
Assumptions• Most Importantly: This is a pressure driven flow
• Permeability considerations were made (Parker equations from design review). The leakage rates predicted through the Orings were too small.
• Perfect gas mixture throughout the volume at all times• N2 and He are ideal gases
The Simulation
Calculates % Moles
Calculates Mixed Density
Molar flow rate of gas into/out of vent
Molar flow rate of helium into vent (3000 psi)
Molar flow rate of gas into can calculator
He IntegratorN2 Integrator
Case 1: Ambient Vent Pressure• High vent pressure causes more total leakage than Case 2• More nitrogen is present; concentration of helium grows slower than in
Case 2
Case 2: Vacuum Vent Pressure• Low vent pressure causes less total leakage than Case 1• Less nitrogen is present; concentration of helium grows faster than in
Case 1
*Note: Hein remains (approximately) constant for both cases
≈ 14.8 psi
≈ 14.8 psi
≈ 14.8 psi
≈ 1.1 psi≈ 1.1 psi
Very High % Helium
Moderately High % Helium
Red Dots: HeliumBlue Dots: Nitrogen
≈ 14.8 psi
14.7 psi
14.7 psi
14.7 psi
1 psi1 psi
1 psi
Total Molar Flow Rate Into Can• Question arises: Is it better to have a lower total leakage (lower
vent pressure) or a lower percentage of helium in the vent?• The simulation should answer this question
• Below is a plot of the actual molar flow rates into the can
0 50 100 150 200 250 300 350 4000
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6x 10
-13
Time (seconds)
Tota
l Can
Mol
ar L
eaka
ge (n
dot)
Total Molar Flow Rates
Case 1: Ambient Applied PressureCase 2: Constant 1 psi Vacuum
Note the order of magnitude
As expected, the total molar flow rate is less for Case 2
% Helium in Can
• The concentration of helium grows at a rapid rate when less N2 is present in the vent
• At the beginning of the response, Case 2 exhibits a lower concentration of helium than Case 1
0 50 100 150 200 250 300 350 4000
1
2
3
4
5
6
7x 10
-3
Time (seconds)
% H
eliu
m In
Ven
t
Percentage of Helium In Vent
Case 1: Ambient Applied PressureCase 2: Constant 1 psi Vacuum
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 20
0.5
1
1.5
2
2.5
3
3.5
4
4.5x 10
-6
Time (seconds)
% H
eliu
m In
Ven
t
Percentage of Helium In Vent
Case 1: Ambient Applied PressureCase 2: Constant 1 psi Vacuum
Note the order of magnitude
What Does This Tell Us?Graphed below are the results for the volume of the total leakage for cases 1 and 2:
• Over the full interval, the model predicts that Case 2 • An improvement is not expected for a constant vacuum scenario. A constant vacuum
does show an improvement in can leakage for the full test duration• This duration of this improvement grows as the vent volume is increased
0 0.5 1 1.5 2 2.50
0.2
0.4
0.6
0.8
1
1.2x 10
-11
Time (seconds)
Vol
ume
of L
eaka
ge H
e (c
c)
Beneficial Range of Case 3
Case 1: Ambient Applied PressureCase 2: Constant 1 psi Vacuum
0 50 100 150 200 250 300 350 4000
0.5
1
1.5
2
2.5x 10
-6
Time (seconds)
Vol
ume
of L
eaka
ge H
e (c
c)
Comparison of Cases 1 and 2
Case 1: Ambient Applied PressureCase 2: Constant 1 psi Vacuum
Full 6 Minutes
Early Region (2.5 seconds)
Cases 1 and 2 With Increased Vent Volume
• For a significantly increased volume:
0 20 40 60 80 100 120 140 160 180 2000
1
2
3
4
5
6x 10
-10
Time (seconds)
Hel
ium
Lea
kage
Vol
ume
(cc)
Helium Leakage Volume vs. Time
Case 1Case 2
The positive influence of Case 2 lasts for approximately 175 seconds (as opposed to 2 seconds). That being said, the remainder of the results will assume that the vent volume is the nominal calculated value (8.49E-7 m3)
Cases 1 and 2 Conclusions• Concentration of helium in vent dominates the response
of the simulation• Case 2 would show a significant improvement over Case
1 if:• The % He was allowed to grow near 100% in both cases (within
the allotted time interval)• The vent volume was significantly increased
• A Case is needed which actively reduces the concentration of helium in the vent. A marked improvement over Case 1 is expected
Case 3 Concept1. Nitrogen is forced in at above ambient pressure: % Helium
increases over time
2. Uniform mixture of gas molecules are removed from the vent: % Helium remains about same.
120 psi N2
≈ 120 psi Mixture
≈ 1 psi Mixture
Case 3 Concept Continued3. Nitrogen is once again forced into the vent: % Helium Drops (Note
total percentage still > step 1)
4. Repeat step 2 and 3 throughout the 6 minute external leakage test. The percentage of helium will inevitably grow, but at a slower rate than cases 1 or 2.
≈ 120 psi Mixture
Determining the Frequency of Pulse/Purge
• Previous slides indicated that pulling a vacuum is only beneficial for approximately 2 seconds. Consequently the following duty cycles for varying input signal periods were calculated:
• Values of 120 psi pulse pressure and 1 psi purge pressure were selected
Period (s) Duty Cycle (%)
10 20
20 10
30 6.7
40 5
1 Period
1 psi
120 psi
Case 3 Results
0 50 100 150 200 250 300 350 4000
1
2
3
4
5
6
7x 10
-13
Time (seconds)
He
Can
Lea
kage
(cc/
s)
Volumetric Flow Rate of Helium into Can Over Time
Period = 10 sPeriod = 20 sPeriod = 30 sPeriod = 40 s
0 50 100 150 200 250 300 350 4000
0.2
0.4
0.6
0.8
1
1.2
1.4x 10
-10
Time (seconds)
He
Can
Lea
kage
Vol
ume
(cc)
He Can Leakage Volume Over Time
Period = 10 sPeriod = 20 sPeriod = 30 sPeriod = 40 s
Integration
Case 1 to Case 3 Comparison• The best curves of Case 3 are now compared to baseline:
• A significant improvement is noted for Case 3
0 50 100 150 200 250 300 350 4000
0.5
1
1.5x 10
-9
Time (seconds)
He
Can
Lea
kage
Vol
ume
(cc)
He Can Leakage Volume Over Time
Case 3Case 1 (Baseline)
0 50 100 150 200 250 300 350 4000
0.2
0.4
0.6
0.8
1x 10
-11
Time (seconds)
He
Can
Lea
kage
(cc/
s)
Volumetric Flow Rate of Helium into the Can Over Time
Case 3Case 1 (Baseline)
Simulation Conclusion• A case 3 scenario shows a marked improvement over the
current setup• This model will be used as a tool in MSDII to fine tune the
system to optimize can leakage prevention
Areas of Desired Feedback• After seeing the results, is the magnitude of can leakage
accurate?• If not, the size of the orifices will be adjusted accordingly
• Is the 8.49E-7 m3 vent volume accurate? Note that this is 84.7 mm3
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System Layout
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Cycling Valve
GN2
Vacuum
To the small o-ring
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Enclosure
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Pipeline model
Some type of relief structure will be in place here
Wires exit rear
To small vent
From Vacuum Source
To large o-ring
From Nitrogen Source
3-way valve
2-way valve
2-way valve
Regulator
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Mounting to the can
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Through the Manifold
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Port Blocks
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The Plug
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Mounting to the side of the can
Pressure Vessel Analysis: Plug• A pressure vessel analysis was ran for the plug geometry.
This geometry was selected due to the thin walls• Due to the thin walls this is considered the worst case geometry
• Failure margins were calculated with a 1.1 factor of safety. Note all margins are positive.
Material Properties• Plugs assumed to be machined from structural steel
(properties taken from ANSYS library):• Fty = 36.3 ksi• Ftu = 66.7 ksi• μ = 0.3• E = 2.9E7 psi
Mesh
2 cells through thickness achieved
• 472699 Nodes• 311215 Tetrahedral
Elements (Overkill)
Loads and Boundary ConditionsNominal Loading Worst Case Loading
Fixed Support
Nominal Loading Results
Maximum stress: 9675 psi
Worst Case Loading Results
Maximum stress: 9675 psi
Margin Calculation• Margin for yield in the worst case loading scenario is
negative. All others are positive
• This is due to a high stress at the part surface. The net section stress will now be studied.
Margin TableLoad Case Yield/Ulimate Allowable Actual F.S. Margin
Nominal Yield 36.3 9 1.1 0.72Ultimate 66.7 9 1.1 0.85
Worst Case Loading Yield 36.3 33.9 1.1 -0.03Ultimate 66.7 33.9 1.1 0.44
𝑀𝑎𝑟𝑔𝑖𝑛=𝜎𝑎𝑙𝑙𝑜𝑤𝑎𝑏𝑙𝑒−𝐹 .𝑆 .∗𝜎𝑎𝑐𝑡𝑢𝑎𝑙
𝜎𝑎𝑙𝑙𝑜𝑤𝑎𝑏𝑙𝑒
Worst Case Loading: Net Section Stress
Load Path
Average stress is calculated for the load path shown. New margins are calculated
Net Section Margins• Net section margins are positive
• The part is deemed to be safe for cleanroom usage
𝑀𝑎𝑟𝑔𝑖𝑛=𝜎𝑎𝑙𝑙𝑜𝑤𝑎𝑏𝑙𝑒−𝐹 .𝑆 .∗𝜎𝑎𝑐𝑡𝑢𝑎𝑙
𝜎𝑎𝑙𝑙𝑜𝑤𝑎𝑏𝑙𝑒
Margin TableLoad Case Yield/Ulimate Allowable Actual F.S. Margin
Worst Case Loading Yield 36.3 8.6 1.1 .74Ultimate 66.7 8.6 1.1 .85
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LabView Layout
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Wire Diagram
Each valve has 2 leads for a circuit. They will be connected to a terminal block and then to a terminal block on the AGT system
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Bill of materials
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Test plansSpec. # Function Test Nominal Pass/Fail Units Order of Testing
1 Reduction of Test gas Leakage
Run external leakage test at Moog with their current system using a blank instead of a valve and new O-
rings. Run external leakage test with the new system under the same conditions. Verify the reduction
percentage of helium comparing both results. Redo both tests using used O-rings.
90% ±5% cm3/sec
3
2 Amount of Nitrogen Measure the amount of nitrogen flowing into the
system using a flowmeter while the external leakage test is in operation with the new system
<100 N/A scc/min
3 Constant Leak DetectionRun external leakage test using a blank instead of a valve and record the leakage value reading the mass
spectrometer every 30 seconds.±5% N/A cm3/sec
4 Training Time
An overview document will be created in order to explain the new system and how it works. In addition, a short presentation will be given to an operator and
questions will be answered. This process will be timed from beginning to end.
<30 N/A min 4
5 Pressure ConditionEach part model will be run through finite element analysis to verify that all parts can work together
under this pressure <3500 N/A psi 1
6 Cost Create Bill Of Materials and verife that the Total cost for one System doesn't exceed the budget <=8000 N/A $ 2
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ID Risk Item Effect Cause Like
lihoo
d
Seve
rity
Impo
rtan
ce
Action to Minimize Risk Owner
1 Concept ideas do not workStart over, beg to have some constraints l ifted, Concepts do not fit Moog constraints 1 3 3
Pay attention to constraints, leave room for error team
2 Complexity is too high
We wont be able to find a concept idea that would work successfully.
We do not have the sufficient skills to solve the problem on our own. 2 2 4
Do enough research and analysis and talk to experts like professors special ized in those areas. Ei leen
3 Can't physical ly test conceptWe don’t know if the system actually works or how well Moog is in buffalo 2 3 6
Build a working model and have constant communication Marie
4
Parts do not arrive on time or purchased parts are not what we ordered
Schedule is affected, we possibly do not meet deadline Vendors/Moog have high lead times 2 2 4
Constant communication and good specifications/ research lead times before purchase Ana Maria
5Mechanical failure post manufacture
No physical product for customer Manufacturing error 1 3 3 Marie
6 Bad design 1 3 3 Design reviews, annoys, cad modeling, Austin
7Customer requirement or priority changes
Scope changes, schedule issues, go over budget and we would need to justify it
Economy plummets/ internal priority shifts 1 1 1 cant Marie
8 Software Bug Doesn’t workPoor design and not experts in Lab view 1 1 1
Verify with experts in Lab view and have a comprehensive layout for what we want Labview to perform Austin
9High pressure gas gets into the vacuum system
damage to the lab's vacuum system
heavily damaged/ missing O-ring or some sort of system bypass 1 3 3
insert burst disk before vacuum system entrance Marie
10High pressure gas gets into the 3-way valve
damage to the valve and the Nitrogen supply system
heavily damaged/ missing O-ring or some sort of system bypass 1 3 3 insert burst disk before the valve Marie
11All system components wil l not fit into the desired space
parts not organized/ cannot access them as needed
parts ordered do not fit as well as planned when actually mounted 1 1 1
plan a layout and purchase parts so that they fit into the assigned electronic shelving space Marie
12System parts do not work cohesively together
the system cannot perfom as desired parts are poorly designed 1 3 3
model the designs together and run through some finite element analysis Ana Maria
13purchased parts are not integrated with the designed parts 1 3 3
research as much information as possible for each purchased part to be sure it corresponds to the existing system Ana Maria
14Team disconnect over the "off" quarter
Have to spend unnecessary time re-learning the project
lack of preparation for the "off" quarter 1 2 2
take well documented notes during the fall , and keep each other (team members, customer, and guides) updated throughout the winter Eileen
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Our schedule for MSDII