Detailed Design Review

DETAILED DESIGN REVIEWP13681

2

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

3

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

4

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

5

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


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


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


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


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

44

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

Documents

Detailed Design Review