Attachment E - MPEX-00-ENG-002.pdf

MPEX-00-ENG-002 Rev 0

Vacuum Handbook

MATERIAL PLASMA EXPOSURE EXPERIMENT

(MPEX)

Prepared by

OAK RIDGE NATIONAL LABORATORY

Oak Ridge, TN 37831-6283

Managed by

UT-BATTELLE, LLC

For the

US DEPARTMENT OF ENERGY

under contract DE-AC05-00OR22725

July 2021

This report was prepared as an account of work sponsored by an agency of the United States government. Neither the United States government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States government or any agency thereof.

MPEX-00-ENG-002 Rev 0 MPEX Vacuum Handbook ii

Material Plasma Exposure Experiment Oak Ridge National Laboratory for the

Material Plasma Exposure Experiment Project

MPEX-00-ENG-002

Jeff Ulreich, Preparer Date

Adam Aaron, Vacuum Systems CAM Date

Christopher Stone, Vacuum SME Date

John Sanseverino, MPEX Project Manager Date

LaTravia Harmon, Quality Assurance Representative Date

Arnold Lumsdaine, MPEX Project Engineer Date

Phillip D. Ferguson, MPEX Project Director Date

7/26/2021

MPEX-00-ENG-002 Rev 0 MPEX Vacuum Handbook iii

Change Log

Revision History

Revision Date Description of Changes

0 [Date] Initial issue

MPEX-00-ENG-002 Rev 0 MPEX Vacuum Handbook iv

CONTENTS

1 OVERVIEW

1.1 GENERAL OVERVIEW

1.2 SCOPE

1.3 TERMINOLOGY AND DEFINITIONS

2 VACUUM DESIGN

2.1 VACUUM DESIGN CONSIDERATIONS

2.2 PERMITTED MATERIALS FOR MPEX VACUUM SYSTEMS

2.3 PROHIBITED MATERIALS FOR MPEX VACUUM SYSTEMS

2.4 MAGNETIC FIELD MATERIAL RESTRICTIONS

2.5 BAKE-OUT REQUIREMENTS

2.6 MICROWAVE CONSIDERATIONS

2.7 VACUUM COATINGS AND FINISHES

2.8 CONDUCTANCE AND PUMPING SPEED REQUIREMENTS

2.9 FABRICATION CONSIDERATIONS

2.10 WELDING

2.11 SEAL DESIGN

2.11.1 Elastomer Seals

2.11.2 O-Ring Vent Grooves

2.11.3 Metal Seals

2.12 VACUUM FLANGES AND FITTINGS

2.13 FASTENERS

2.14 PUMPS

2.15 GAUGES

2.16 VACUUM VALVES

2.17 EXHAUST FOR VACUUM PUMPS

2.18 PRESSURE RELIEF DEVICES

2.19 PRINT NOTATIONS AND STATEMENTS OF WORK

2.19.1 Print Notations for Rough Vacuum Application (Atmosphere to 1.0x10-3 Torr):

2.19.2 Print Notations for High Vacuum Application (1.0x10-3 to 1.0x10-7 Torr):

2.19.3 Print Notations for Ultra High Vacuum Application (1.0x10-7 to 1.0x10-9 Torr):

2.19.4 Statements of Work

2.20 VACUUM VENDOR SELECTION

2.21 LEAK DETECTION

3 FABRICATION, PACKING, AND HANDLING OF VACUUM COMPONENTS

3.1 MECHANICAL OPERATIONS ON VACUUM SURFACES

3.1.1 Preferred Fabrication Processes

3.1.2 Preferable Material Removal Techniques

3.2 LESS PREFERABLE MATERIAL REMOVAL TECHNIQUES

3.3 GUIDANCE FOR PREPARING COMPONENTS FOR WELDING

MPEX-00-ENG-002 Rev 0 MPEX Vacuum Handbook v

3.4 MAGNETIC PERMEABILITY OF WELDS AND WELD AFFECTED AREAS

3.5 TREATMENT OF WELD BURNS

3.6 ALTERNATIVE MANUFACTURING PROCESSES

3.6.1 Additive manufacturing (3D Printing)

3.6.2 EDM (Electrical Discharge Machining)

3.6.3 Castings

3.6.4 Sintered Powdered Metals

3.6.5 Abrasive Honing

3.6.6 Other Processes

3.7 HARDWARE AND FASTENERS

3.8 MARKING AND LABELING

3.8.1 Marking of vacuum components

3.8.2 Proper labeling materials

3.9 QUALITY ASSURANCE

3.10 HANDLING AND PACKING

3.10.1 Proper handling

3.10.2 Cleaning process

3.10.3 Packing

3.11 SHIPPING

4 CLEANING OF FABRICATED COMPONENTS

4.1 GENERAL CLEAINING STEPS

4.2 SMALL COMPONENTS

4.2.1 Machining of small components

4.2.2 Cleaning of small stainless steel components

4.2.3 Cleaning of small non-ferrous metal components

4.2.4 Cleaning of wires

4.2.5 Cleaning of ceramic and machinable glass

4.3 CLEANING OF LARGE COMPONENTS AND ASSEMBLIES

4.3.1 General Guidance

4.3.2 Cleaning of large stainless steel components

4.4 CLEANING OF LARGE NON-FERROUS METAL COMPONENTS

4.5 CLEANING OF VACUUM BELLOWS

4.5.1 General guidance

4.5.2 Cleaning procedure

4.6 CLEANING OF ASSEMBLIES AND SUB-ASSEMBLIES

4.6.1 General guidance

4.7 STORAGE OF ASSEMBLIES AND SUB-ASSEMBLIES

4.7.1 General guidance

5 VACUUM ACCEPTANCE TESTING AND CRITERIA

PREPARATION FOR TESTING

5.1 38

5.2 LEAK TESTING

5.2.1 Use of Dry Pump

5.2.2 Record of leak test

5.3 OUT-GASSING AND RESIDUAL GAS ANALYSIS

5.4 RESERVED RIGHTS

5.4.1 Witnessing for acceptance

5.4.2 Additional rights

6 MPEX VACUUM SYSTEMS TEAM

MPEX-00-ENG-002 Rev 0 MPEX Vacuum Handbook vi

7 REFERENCES

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1 OVERVIEW

1.1 GENERAL OVERVIEW

The performance of a vacuum system is highly dependent on the design of the vessel, pumping scheme, and components within the system. Therefore, it is essential that all components which form part of or are placed within a vacuum system conform to the design and fabrication standards in this document.

For the purpose of this document, vacuum regimes are defined as follows:

Regime Range (torr)

Rough Atmosphere to 1.0x10-3

High Vacuum (HV) 1.0x10-3 to 1.0x10-7

Ultra High Vacuum

(UHV)

1.0x10-7 and lower

Following are guidelines for design of components in rough, high, and ultra-high vacuum. As this is not an exhaustive treatment of all aspects of the design process, please contact the

Vacuum Systems Team (Section 6) with any questions not covered in this document.

1.2 SCOPE

This handbook covers design, material selection, fabrication, and special cleaning methods required for components intended for use within the vacuum systems of the MPEX. Vacuum acceptance tests for vessels and assemblies are also included. In the context of this document

“component” means any of the following:

• a vacuum vessel

• any item forming all or part of the wall of a vacuum system

• any item totally immersed in a vacuum containment device

• material classification, use, and restriction for the MPEX device

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1.3 TERMINOLOGY AND DEFINITIONS

Each Vacuum Handbook requirement has a unique and permanent identifier. The interface identifier is indicated at the beginning of the requirement, in square brackets. The convention for requirements identifiers is:

[VH.XXX]

where:

• VH is an abbreviation for Vacuum Handbook so as to distinguish from system requirements

• XXX is the sequential number for the requirement

Requirements are specified as follows:

[identifier] This is an example interface [ref1] [ref2] [ref3]

Where [identifier] is assigned as noted earlier in this chapter and [ref] may be a Project

Requirement, Standard, drawing, schematic, or other reference that informs the interface.

Removed interfaces shall be designed with a strike through in the first revision after removal then completely removed in subsequent versions. The number shall not be re-used.

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2 VACUUM DESIGN

2.1 VACUUM DESIGN CONSIDERATIONS

In order to design a component for vacuum service, there are several details that should be addressed:

• Material Selection and Finish

• Determination of conductance and pumping speed requirements based upon gas loads

• Use of standard equipment including flanges, hardware, seals/gaskets, pumps, gauges, valves

• Proper joint construction and weld design

• Proper seal selection and seal design

The MPEX project has other functional design considerations for components in vacuum service

• Interaction with the plasma beam

• Interaction with magnetic field lines.

• Interaction with microwaves

• Lithium and other alkali metals may be used in experiments on MPEX

• Vacuum bake out conditions

• Handling of irradiated or activated materials

2.2 PERMITTED MATERIALS FOR MPEX VACUUM SYSTEMS

There are limitations on the materials which are allowed inside the space of a vacuum system or create the vacuum boundary on MPEX. Furthermore, there are limitations on materials that interact with the plasma, are near the plasma, are within the influence of the MPEX magnetic fields, are in UHV/HV environments, are in rough vacuum environments, or are in contact with the demineralized cooling water.

Using the correct materials is critical to the proper function of MPEX. The MPEX materials list has been created as a guideline to assist in the correct choice of materials to meet the scientific requirements of the facility.

MPEX materials are classified for use using the following classes:

Class 1 – Plasma Interacting - materials that interact directly with the plasma during operation (High flux components)

Class 2 – Near Plasma – materials that may, but generally do not directly interact with the plasma (low flux components)

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Class 3 – UHV/HV/Plasma Facing – materials that are in UHV or HV but do not interact with the plasma (shadowed/shielded from plasma)

Class 4 – Rough vacuum – materials that are used in the rough vacuum system

Class 5 – Atmosphere – materials used outside of the vacuum systems

Class 6 – Wetted Demin – components with wetted surfaces in the Demineralized

Water loops

Class 7 – Magnetic Field Sensitive - components used inside the influence of the magnetic field lines

Materials are approved, restricted, or prohibited for each class and category using the following qualification system.

Material approved for usage

Material restricted to specific use; program approval required

Material prohibited from use

Blank To be evaluated, material has not been evaluated for use in the classification

Components may fall under the limitations for use of multiple classes. For example, vacuum chambers inside of the magnets, and are water cooled fall under Class 3, 6, and 7 limitations.

Material selection must be compatible with the limitations of all classes the component falls under.

Restricted materials are application specific. Contact the MPEX Vacuum Systems Team for approval of specific uses. The Vacuum Systems Team (Section 6) will review the material for vacuum compatibility and escalate to review with program science compatibility as needed.

Many materials are approved for certain classes but may not meet the temperature or other functional requirements of a specific use. Material selection must take all application specific requirements and environmental conditions into consideration.

Materials not shown on this list are not approved for use in the MPEX vacuum system. If a material is not on the list is needed, contact the MPEX Vacuum Systems Team. The Vacuum

Systems team will review for vacuum compatibility and escalate the material to the science team as necessary for approved, restricted use, or prohibited status.

The MPEX material list is located in Appendix 1. If a material needs to be used that is not on the approved materials list or if there are any concerns as to whether a material is suitable for a particular use contact the MPEX Vacuum Systems Team (Section 6) for approval of specific

MPEX-00-ENG-002 Rev 0 MPEX Vacuum Handbook Page 5 of 41 uses. The Vacuum Systems Team will review for vacuum compatibility and escalate to review for program science compatibility as needed.

2.3 PROHIBITED MATERIALS FOR MPEX VACUUM SYSTEMS

In general, any material containing volatile organic compounds (VOC) should not be used in vacuum. Materials with high porosity or outgassing should not be used in vacuum.

1. The following materials that are not specifically formulated for HV/UHV applications shall not be used in vacuum or come in to contact with vacuum components in the form of jigs, fixtures, tools, packing etc.:

• Copper-Zinc alloyed Brass

• Soft Solder, Standard Hard Solder, or Electrical Solder and fluxes

• Plastics (see materials list for acceptable plastic applications)

• Glues, epoxies, and adhesives

• Grease, oils, and other lubricants

• Do not use silicon or sulfur based machining lubricants when machining any components (Use water soluble machining lubricants only)

• GE Varnish

• Anodized surfaces

• Any material containing:

o Zinc, Cadmium, Phosphorus, Sodium, Selenium, Potassium or Magnesium

• Dirt and other contaminants

There are some vacuum compatible plastics, however the use of plastics should be limited and needs to be approved for specific use. Vacuum compatible plastics are listed with a restricted status in the materials list.

See Appendix 1 for specific material approvals, restrictions, and prohibitions.

If a material needs to be used that is not on the approved materials list, or is listed as prohibited but required by design, contact the MPEX Vacuum Systems Team (Section 6).

2.4 MAGNETIC FIELD MATERIAL RESTRICTIONS

The MPEX device uses precise magnetic fields to control the plasma. Materials that are magnetically permeable can alter the field and change the uniformity of the magnetic field lines that control the plasma.

[VH.001] Materials with a relative permeability that is greater than 1.03 at 200 Oersteds shall not be used within the cryostat and the vacuum chamber without formal project approval.

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• NOTE: 304 SST (and several other 300 series alloys) does not meet the MPEX permeability spec in the work hardened form [4]. If 304 SST is to be used inside the influence of the MPEX magnet fields, it must be solution annealed after coldwork and verified that it meets the MPEX magnetic permeability specification. This includes fasteners and hardware. Cold worked 316 SST meets the MPEX magnetic permeability specification and is the preferred alternative to 304 SST

• NOTE: Attention must be paid to selecting the correct alloys of materials. For example, certain alloys of Tungsten are magnetic, and others are not. Sintered

Tungsten alloys that use iron and nickel as a binding agent are magnetic. Non-magnetic alloys use copper and nickel as binding agents. Both materials fall under the same

AMS-T-21014 classifications.

2.5 BAKE-OUT REQUIREMENTS

The main vacuum chamber needs to be vacuum baked during initial pump down from atmosphere to assure a clean vacuum environment. This will be achieved by recirculating heated water through the water jacketed vacuum chambers to bake the main vacuum chamber while the system is pumped down. The water may be up to 150C, at a low flow rate, with a minimum pressure of 55

PSI to abate boiling, and up to 90 PSI to give enough working pressure for flow. Components attached to the main vacuum chamber, or in vessel components (IVC) must meet the following requirements:

[VH.002] The main vacuum vessel and PMI chamber shall be capable of being baked to 150°C.

[PR191-R]

[VH.003] The TEC shall be able to be baked to 150°C. [PR192-R]

[VH.004] The in-vessel high-heat-flux components shall be able to be baked to a minimum of

150°C. [PR193-R]

[VH.005] The capability for baking shall be provided while the superconducting magnets are at any temperature between 5 K and 293 K. [PR194-R]

[VH.006] The main vacuum vessel, PMI chamber, TEC, and in-vessel components shall be capable of being raised from ambient 20°C temperature to the baking temperature with 24 hours.

[PR195-R]

[VH.007] Following baking, the main vacuum vessel, PMI chamber, TEC, and in-vessel components shall be capable of being returned to ambient 20°C temperature within 12 hours.

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[PR196-R]

[VH.008] The rate of change of the temperature of the main vacuum vessel, the PMI chamber, TEC, and in-vessel components shall not be greater than 15 K/hr during warm-up and -15 K/hr during cooldown, considering thermal stresses. [PR197-R]

[VH.009] All MPEX systems shall be designed to accommodate 100 baking cycles from the commissioning phase to the end of life of MPEX. [PR198-R]

2.6 MICROWAVE CONSIDERATIONS

Because of the microwave power that will be used for electron heating in MPEX, components in vacuum must be designed to account for possible stray radiation. Microwave absorptivity is low for permitted metals, and special care will not be required.

Design requirements for materials in the presence of microwaves are:

[VH.010] Non-metals should be shielded from microwave power with metallic shielding with gaps no larger than 1.3mm (0.051 inch).

[VH.011] Any port leading to sensitive components (such as windows and vacuum pumps) must include a screen or other mitigation technology to cut-off microwave power, also with gaps no larger than 1.3mm (0.051 inch).

[VH.012] Any exceptions must be made with the approval of the lead engineer in consultation with the microwave SME.

2.7 VACUUM COATINGS AND FINISHES

In general, no coatings or finishes are required for any vacuum vessel. However, in cases where a coating or finish is required, please contact the MPEX Vacuum Systems Team (Section 6) for recommendations. Some approved coatings for use in vacuum are included in Appendix 1.

Surface finishes can affect vacuum performance. Rough surfaces have more surface area where contaminants and hydroxyl layers can form affecting pump down time and ultimate vacuum pressure of the system. Smooth surface finishes are desirable.

[VH.013] Internal vacuum surfaces shall have a maximum surface roughness of 32 micro-inch Ra.

Exceptions to this requirement must be approved in advance by the MPEX Vacuum Systems Team

(Section 6).

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[VH.014] All stainless-steel vacuum vessels and components in vacuum should be electropolished per ASTM B912 02 Passivation of Stainless Steels Using Electropolishing. Exceptions should be reviewed with the MPEX Vacuum Systems Team (Section 6).

2.8 CONDUCTANCE AND PUMPING SPEED REQUIREMENTS

Gas loads stem from multiple sources, all of which are independent of pumping speed. When designing a vacuum system or component, proper attention must be given to the pressure requirements and expected gas loads in order to determine what conductance and pumping speeds will be required. Overlooking the importance of these items could result in a vacuum system whose original design is ineffective and potentially irreversible.

Please direct questions regarding pumping speeds, pressures, and conductance to the

MPEX Vacuum Systems Team (Section 6), which has the tools and expertise to ensure a successful design.

2.9 FABRICATION CONSIDERATIONS

Proper vacuum fabrication requires more detail to cleanliness than does typical fabrication performed in most standard machine shops. Grease, grit, grime, fingerprints, etc. can lead to leaky vessels or hamper the ability of vacuum pumps to work effectively. The single most effective way of ensuring that proper vacuum fabrication practices are done is to use shops that primarily focus on vacuum fabrication. Please consult with the MPEX Vacuum Systems Team (Section 6) for guidance on external fabrication vendors.

Moreover, the best practice for insuring quality construction of a vacuum vessel or component is to have it physically separated from the environment where tasks are being performed on other materials (carbon steel) where the shavings and dust can contaminate weld prep areas causing micro-inclusions that can lead to leaks.

The surface finishes of vacuum chamber walls and components contribute to the ability to adequately clean those components, as well as the ability to pump the vacuum system down to the desired pressure. Stainless steel components can be electropolished to achieve higher quality surface finishes than conventional manufacturing processes. Refer to section 2.7 for surface finish requirements.

Abrasive techniques to clean or attempt to improve the appearance of the surfaces of vacuum components must be kept to an absolute minimum and preferably avoided. The use of grinding wheels, wire brushes, files, harsh abrasives, sand, shot or dry bead blasting, polishing pastes and the like is prohibited under normal circumstances.

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Preferred techniques are slurry blasting with alumina or glass beads in a water jet; gentle hand use of a dry fine stone or a fine stone lubricated with IPA, ethanol or alcohol and hand polishing with fine mesh alumina or silicon carbide in an IPA or ethanol carrier on a lint free cloth; hand polishing with Scotch-Brite (Alumina loaded, Grade A).

2.10 WELDING

Dirt, oil and other contaminates in the vicinity of the weld prep area will lead to inclusions in the weld and outgassing under vacuum. Therefore, ALL welded components MUST be cleaned to vacuum standards, using the appropriate method described in section 4, BEFORE being welded together.

Welding materials with a relative permeability that is greater than 1.03 should not be used within the cryostat and the vacuum chamber without formal project approval.

Although weld burns may be removed by using acid pastes; in general, such burns do not affect vacuum performance and are best left alone. Any scaling must be removed using the techniques outlined in the section 4 regarding cleaning below. If it is desired to remove burns, then slurry blasting with alumina in water or hand burnishing with alumina powder is a satisfactory alternative. Hand finishing with Scotch-Brite or a dry stone is also permissible. Heavy abrading, grinding or wire brushing on surfaces exposed to vacuum is prohibited.

To avoid the potential for creation of trapped volumes which could adversely affect vacuum performance, vacuum components must be fabricated using weld joint designs which involve single pass, full penetration welds or internal seal welds with external partial penetration or fillet skip welds to ensure adequate structural strength while allowing for effective leak testing. See figure 2.1 for the appropriate vacuum weld types and drawing callouts.

The use of internal seal welds with external skip welds is not directly addressed by ASME Section

VIII, Division 1, but may be accepted if the design has been demonstrated by an engineering analysis to be capable of withstanding the anticipated loads under the provisions of paragraph U-

2(g). The use of multiple pass full penetration welds which potentially contain voids or inclusions capable of becoming trapped volumes must be avoided. For more specific guidance regarding welding for vacuum systems, please consult the MPEX Vacuum Systems Team (Section 6).

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Figure 2.1 – Internal Seal Welds

2.11 SEAL DESIGN

Depending upon the desired pressure within a vacuum vessel among other considerations, a variety of sealing techniques are possible. However, special attention must be made between the selection of rough, High Vacuum (HV), and Ultra High Vacuum (UHV) seals.

2.11.1 Elastomer Seals

Elastomer seals are most often used in rough and HV vacuum applications (Atmosphere to 1.0x10-

7 Torr) but are forbidden on UHV applications. Viton ® is the MPEX material choice for elastomer seals. It has a temperature range of -20C to 205C (230C for short durations). Viton® elastomer seals should only be used in applications that fall within the temperature ratings noted. If a different material is required, it must be approved for the specific use by the MPEX Vacuum

Systems Team (Section 6).

Please note that in areas of high temperature and/or elevated radiation that elastomer seals may not be the most suitable seal because of reduced life and/or complexity of replacement.

The MPEX Vacuum Systems Team highly recommends the use of standard flanges, rather than designing custom flanges and seals. However, if a custom flange must be made, please refer to the

Parker Handbook (5705A) [1] on elastomer o-ring seal design. Figure .2 is a chart detailing gland design for static vacuum o-ring seals (taken from Parker 5705A O-Ring Vacuum Sealing

Handbook, Chart IV, page 9). Furthermore, the o-ring groove itself should be vented on both the vacuum and atmosphere sides to eliminate trapped volumes of gas as well as facilitate leak testing.

A surface finish of 16 micro-inches or better is recommended.

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Figure 2.2 – Gland design for static vacuum o-ring seals [1]

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2.11.2 O-Ring Vent Grooves

The purpose of an o-ring vent groove is to provide means for leak checking and/or venting trapped gas from a trapped volume. Vent grooves are required when an o-ring is used to isolate vacuum or gas(s). Vent grooves would not be required on the side of the o-ring that is isolating a liquid – shown below in Figure 2.3.

Figure 2.3 – Vent grooves

• Reference “ORD 5700 Parker O-Ring Handbook” [1] for gland/groove design.

• Width of the vent groove are ½ times the o-ring diameter

• The depth of a vent groove should be 90-95% the depth of the o-ring groove

Figure 2.4 – O-ring groove with vent groove

The following specifies the minimum recommended quantity of vent grooves for circular or 4-sided o-ring flange design:

• For a circular o-ring flange design it is recommended to have a minimum of 2 vent grooves at 0º and 180º for flange diameters under 12 (inches). Flange diameters greater than 12 (inches), but less than 48 (inches) require 4 vent grooves at 0º, 90º, 180º, and

270º. Flange diameter greater than 48 (inches) would require grooves every 36 (inches) around the circumference of the flange.

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• For non-circular o-ring flanges, vent grooves are recommended every 36 (inches), with a minimum of 2 vent grooves per seal design.

Figure 2.5 – Example of o-ring groove with vent groove

2.11.3 Metal Seals

Since most vacuum systems do not exceed high vacuum, the use of metal seals will probably be limited to use on systems that are at high temperatures, located in areas of elevated radiation or in areas of Ultra High Vacuum.

Conflat (CF) flanges and gaskets are the most common combination for UHV systems. CF assemblies utilize an OFHC copper gasket that is pierced by a knife edge between two mating flanges. CF assemblies are robust, reliable, and can withstand a wide range of temperatures.

Other metal sealing options are available such as the EVAC Ce-Fix assembly and HelicoFlex spring energized metal seal. However, please consult with the MPEX Vacuum Systems Team

(Section 6) on the best metal seal to use.

2.12 VACUUM FLANGES AND FITTINGS

Table show types of flanges and fittings that will achieve various pressures indicated in the

“Application/Notes” column.

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Table 2.1 – Types of flanges

FLANGE

TYPE

FASTENER TYPE SEAL TYPE APPLICATION /

NOTES

PICTURE

VCR Custom male/female nut system

Custom crush gasket, typically copper or silver

1000’s of PSI to UHV

(size dependent)

1/16” to 1” sizes Swagelok Custom male/female nut system

Custom single-use ferrule, typically stainless steel, brass, or Teflon.

1000’s of PSI to Atm

(size dependent)

1/16” to 2” sizes

Valco GC fittings

GC high pressure fitting

Zero dead volume fittings for gas chromatography

10,000 PSI to UHV

1/32” to 1/4“ tubing

ISO-LF Type

K

Single or Double Claw

Clamps

Viton Seal on an aluminum centering ring

Atm to 1.0x10-7 Torr.

Vacuum tubing greater than 2” in diameter.

Bakeable with appropriate seal to

150°C.

ISO-LF Type

F

Double Claw Clamps

Viton Seal on an aluminum centering ring

Atm to 1.0x10-7 Torr.

greater than 2” in

ISO-CF Standard ¼” or 5/16” fine-thread SS hardware, silver-plated to prevent galling.

CF Gasket, typically copper.

Atm to 1.0x10-13 Torr.

greater than 1” in

(-)200°C to 450°C.

CeFix CeFix custom chain-clamping system

CeFix custom metal seals, typically aluminum.

Atm to UHV

16mm to 250mm

Bakeable to 200°C

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If there is a need to use another type of flange, seal, or fastener please consult with the MPEX

Vacuum Systems Team (Section 6) concerning other options.

2.13 FASTENERS

All fastener materials with a relative permeability that is greater than 1.03 should not be used within the cryostat and the vacuum chamber or any area that may influence the MPEX magnetic field lines without formal project approval (see section 2.4). 304 and 18-8 stainless steel fasteners are typically cold rolled, and work hardened. Work hardened 304 and 18-8 stainless steels can have a relative permeability between 1.05 and 10 [4]. 310 stainless steel, 316/316L stainless steel, Grade 660 (UNS S66286, A286) stainless steel, or titanium are the preferred material choices for fasteners.

Trapped volumes and virtual leaks due to the use of fasteners must be avoided to prevent contamination and pump out problems. Blind tapped holes, and blind holes for pressed in pins create trapped volumes and virtual leaks. Furthermore, blind holes are traps for contaminants and the solvents used to clean the contaminants, both of which are undesirable in a vacuum environment. In general, blind holes for fasteners should not be used in vacuum systems or components. The pilot drill for a tapped hole should drill through the material to provide a vent.

This is the preferred method for venting fastener holes. The threaded contacts do not have 100% engagement (typically ~75%) and allow both volumes shown in Figure 2.6 to be pumped out through the threads. In special cases such as roll formed threads in place where 100% thread engagement is possible, additional venting precautions should be taken

Blind holes create trapped volumes Through holes eliminate trapped volumes

Figure 2.6

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In some instances, there is no option other than a blind hole. In these cases, the design must provide a vent path for trapped volumes. Special attention needs to be placed on cleaning contaminants and solvents from blind tapped holes. Vented hardware allows trapped gas to escape when being pumped. Several types of vented hardware exist. These range from vented screws

(small hole through the center) and slotted screws (a long slot cut the length of the screw) to vented washers and nuts.

Figure 2.7 - Center Hole Vented and Slot Vented Screws

(Image from UC Components)

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Figure 2.8 – Vented Nut and Washer

(Image from UC Components)

Vent path for center hole vented screws Vent path for slot vented screws

Figure 2.9

Figure 2.9 shows how vented screws relieve the trapped volume. Caution should be taken when using vented hardware. Vented screws with a hole through the center reduce the cross-sectional tensile area. Hole vented screws cannot use standard torque specifications. The standard torque of 90% proof strength of a full cross section will cause the vented screws to fail. Slot vented screws have a much smaller impact on the tensile cross-sectional area. Vented screws are not recommended for use in structural or load bearing joints requiring graded hardware.

MPEX-00-ENG-002 Rev 0 MPEX Vacuum Handbook Page 18 of 41

Alternatives to vented hardware are to provide either a small, axial, or cross drilled vent hole into the pilot drill of the tapped hole (figure 2.10), or to provide a vent path for the trapped volume between the mating components (figure 2.11). These methods are preferred for structural joints using graded hardware when blind holes are necessary.

Axially drilled vent hole Cross drilled vent hole

Figure 2.10

Mating face vent groove

Figure 2.11

MPEX-00-ENG-002 Rev 0 MPEX Vacuum Handbook Page 19 of 41 similarly, a vent hole or groove, hole vented dowel pins, dowel pins with one flat edge, and slotted

(not coiled) spring pins can be used to vent blind pin holes.

Other fastener considerations for vacuum include addressing galling of mating components. When fasteners and tapped holes are cleaned for vacuum service, lubricants from manufacturing processes that would otherwise prevent galling are removed. This makes vacuum hardware particularly susceptible to galling. Stainless steel hardware in stainless tapped holes will gall and seize in place after tightened. It is difficult, if not impossible to remove the hardware once this happens. One seized fastener can ruin an entire assembly. Mitigation steps need to be taken. There are several ways to prevent this problem:

1. Silver plated hardware – Silver plated hardware tends to be limited to a single use, as tightening the hardware causes the plating to come off

2. MoS2, WS2, Tin, and graphite coated screws provide better gall protection than silver.

However, there are many processes to apply these coatings. Any processes using organic binders are not permitted. PVD and high-pressure spray coatings are preferred. These coatings typically can be used for multiple insertions but should be discarded and replaced at the first sign of galling. Care must be taken with dry coatings such that particulate migration does not become a problem.

3. A small amount of low vapor pressure vacuum grease such as Apiezon L, can be applied to screws prior to insertion to prevent galling. This is a proven, effective technique;

however, vacuum greases do not have high operating temperatures. The use of vacuum grease must be approved for each individual use by the MPEX Vacuum Systems Team

(Section 6). Vacuum grease may be used on bolts that connect flanges at atmosphere, but the maximum flange temperature must not exceed the temperature rating of the grease.

Any use of vacuum grease must consider what temperature the grease will see during

MPEX operation and the MPEX vacuum bakeout process. The grease must be rated for the highest temperature it will be exposed to.

Vented hardware is available through McMaster Carr (www.mcmaster.com) and U-C

Components (www.uccomponents.com) and Extreme Bolt (https://www.extreme-bolt.com/vented-screws.html).

[VH.015] - 302, 303, 304, 321, and 347 sst, as well as 18-8 sst shall not be used where class 7 materials are required (refer to section 2.2)

[VH.016] - Vented screws shall not be used in structural or load bearing joints requiring graded hardware.

[VH.017] - All fasteners and corresponding tapped holes shall meet UNC, UNF, or UNEF 2A

(internal thread) or 2B (external thread) standards.

MPEX-00-ENG-002 Rev 0 MPEX Vacuum Handbook Page 20 of 41

2.14 PUMPS

Although there are a variety of pumps and pumping systems available by a myriad of vendors, the

Vacuum Systems Team has standardized on a list of particular pumps. By standardizing on specific pumps, it is much easier and cost effective to maintain spares and maintenance kits as well as train technical staff on operation, installation, and maintenance. Listed below in Table .2 are the standard pumps supported by the Vacuum Systems Team. If uncertain of needs or questions about the performance or use of a particular pump, please contact the MPEX Vacuum Systems Team

(Section 6).

Table 2.2– Standard pumps

PUMP Manufacturer TYPE APPLICATION /

NOTES

PICTURE

TriScroll

300/600 Agilent (Varian) Dry Scroll

1E-2 Torr Base Pressure

9/18 CFM

110/220 VAC 60Hz

ACP 15/28 Pfeiffer Vacuum Multi-Stage Roots

7.5E-2 Torr Base

Pressure

14-27 m3/hour

110 VAC 60Hz

Screwline

SP250/SP630

Oerlikon (Leybold) Dry Screw

~1E-2 Torr Base Pressure

177/371 CFM

240/480 VAC 60Hz 3Ph

RUVAC

WS1001/WS

Oerlikon (Leybold)

Roots-Type Blower

(Used in series with SP250/630)

~1E-3 Torr Base Pressure

589/1207 CFM

Titan Series Gamma Vacuum Ion Pump

<1E-11 Torr Base

~10 – ~1000 L/s

110 or 208/240 VAC

60Hz

MPEX-00-ENG-002 Rev 0 MPEX Vacuum Handbook Page 21 of 41

Cryo-Torr

Series

Brooks (CTI

Cryogenics) Cryogenic Pump

UHV Base Pressure, dependent on load

1000’s L/s for condensable gases

MaxCool

4000 Series Brooks (Polycold) Cryo-Cooler

UHV Base Pressure, dependent on load

1000’s L/s for condensable gases

HiPace Series Pfeiffer Turbomolecular

<1E-10 Torr Base

~80 – ~2300 L/s

2.15 GAUGES

In order to standardize gauging on all vacuum systems, gauges have been selected for use within the MPEX vacuum systems).

[VH.018] All gauges in rough vacuum systems utilize a KF25 connection.

[VH.019] All vacuum gauges shall be as defined in table 2.3

Table 2.3 – Standard gauges

VACUUM

LEVEL

GAUGE TYPE MANUFACTURER MODEL

NUMBER

Rough(1) Convection-Enhanced Pirani MKS 10-3170027SH

Rough(2) Capacitance Manometer MKS 626 Series

High and Ultra-

High

Cold Cathode MKS 104210004

(1) For indication only. Use only where qualitative pressure data is required.

(2)

Use where accurate pressure data (< ±50%) is required.

MPEX-00-ENG-002 Rev 0 MPEX Vacuum Handbook Page 22 of 41

2.16 VACUUM VALVES

There are a large variety of vacuum valves that will be used across the ORNL site. Please consult with the MPEX Vacuum Systems Team (Section 6) regarding the use of vacuum valves. (What is the intention of this section?) Is it to specify the functional requirements for the vacuum valves or performance requirements relative to the I&C system?

2.17 EXHAUST FOR VACUUM PUMPS

The use of Victaulic Press pipe is highly recommended on exhaust systems primarily because of its low installation cost and ease of installation. To terminate the exhaust, a KF flange should be used. The vacuum valve of choice for isolating the exhaust system is the VAT Series 22 vacuum valve.

[VH.020] All throughput pumps exhausting to atmosphere shall be HEPA filtered on the exhaust port.

2.18 PRESSURE RELIEF DEVICES

Due to the variability and complexity of each vacuum system, it is impossible to settle on a single standard for pressure relief. The Vacuum Systems Consensus Guideline for Department of Energy

Accelerator Laboratories – BNL-81715-2008-IR Section VI, Part D [2] contains pressure relief device guidance that is applied at other facilities. Please consult the MPEX Vacuum Systems Team

(Section 6) for sizing and implementation of a Pressure Relief Device for each specific project. A

PRD is required for any system that can be potentially connected to a pressurized source such as process gas and nitrogen purge or vent gas supply (and internal volumes of LHe from the superconducting magnet systems. Please consult the MPEX Vacuum Systems Team (Section 6) for sizing and implementation of a Pressure Relief Device for each specific project.

2.19 PRINT NOTATIONS AND STATEMENTS OF WORK

2.19.1 Print Notations for Rough Vacuum Application (Atmosphere to 1.0x10-3 Torr):

All parts shall be fabricated in accordance with good vacuum practice which shall, as a minimum include the following:

1) Removal of all contamination e.g., scale, dirt, grease, and oil prior to fabrication.

2) Use only water soluble, non-sulfurous bearing cutting oils for machining.

MPEX-00-ENG-002 Rev 0 MPEX Vacuum Handbook Page 23 of 41

3) Washing of all parts with detergent to remove cutting oils prior to final washing and rinsing with de-ionized water.

4) Helium leak testing of all fabricated parts which shall show a total leak rate less than

1.0E-7 Torr-L/second using a MSLD.

5) Fabricated components shall be packaged in a way to protect all sealing surfaces and to stop contamination from entering vacuum volume. Use of aluminum foil over flanges and sealing small items in a polyethylene bag is preferred.

6) Please refer to sections 3, 4, and 5 for specifics on the fabrication and handling of vacuum components.

7) [For stainless steel components]

a. Electropolish per ASTM B912 02 Passivation of Stainless Steels Using

Electropolishing

2.19.2 Print Notations for High Vacuum Application (1.0x10-3 to 1.0x10-7 Torr):

All parts shall be fabricated in accordance with good vacuum practice which shall, as a minimum include the following:

1) Removal of all contamination e.g., scale, dirt, grease, and oil prior to fabrication.

2) Use only water soluble, non-sulfurous bearing cutting oils for machining.

3) Washing of all parts with detergent to remove cutting oils prior to final washing and rinsing with de-ionized water.

4) Metal seals should be used (where utilized in end-use) when performing the final helium leak test.

5) Helium leak testing of all fabricated parts which shall show a total leak rate less than

1.0E-8 Torr-L/second using a MSLD.

6) Fabricated components shall be packaged in a way to protect all sealing surfaces and to stop contamination from entering vacuum volume. Use of aluminum foil over flanges and sealing small items in a polyethylene bag is preferred.

7) Please refer to sections 3, 4, and 5 for specifics on the fabrication and handling of vacuum components.

8) [For stainless steel components]

OR,

b. Tin coating by PVD (Physical Vapor Deposition) per AMS2444A

9) [Optional if component is within the MPEX magnetic field lines] Supplier must verify that all materials and fabrication process steps result in all components (including hardware) having a magnetic permeability of <1.03 at 200 Oersteds

MPEX-00-ENG-002 Rev 0 MPEX Vacuum Handbook Page 24 of 41

2.19.3 Print Notations for Ultra High Vacuum Application (1.0x10-7 to 1.0x10-9 Torr):

All parts shall be fabricated in accordance with good vacuum practice which shall, as a minimum include the following:

1) Removal of all contamination e.g., scale, dirt, grease, and oil prior to fabrication.

2) Use only water soluble, non-sulfurous bearing cutting oils for machining.

3) Washing of all parts with detergent to remove cutting oils prior to final washing and rinsing with de-ionized water.

4) Metal seals shall be used when performing the final helium leak test.

5) Helium leak testing of all fabricated parts which shall show a total leak rate less than

1.0E-9 Torr-L/second using a MSLD.

6) The vessel or assembly total out-gassing rate shall be measured after 10 hours of pumping from atmosphere. The out-gassing rate must not exceed 1.0E-9

Torr/liter/sec/cm2.

7) Fabricated components shall be packaged in a way to protect all sealing surfaces and to stop contamination from entering vacuum volume. Use of aluminum foil over flanges and sealing small items in a polyethylene bag is preferred.

8) Please refer to sections 3, 4, and 5 for specifics on the fabrication and handling of vacuum components.

9) [For stainless steel components]

10) [If component is within the MPEX magnetic field lines] Supplier must verify that all materials and fabrication process steps result in all components (including weld affected areas and hardware) having a magnetic permeability of <1.03 at 200 Oersteds

2.19.4 Statements of Work

It is recommended for complicated assemblies or large vessels that a Statement of Work (SOW) is written to provide guidance to vendors more detailed than print notations or more specific than a specification. For assistance in detailing important vacuum information in a SOW, please contact the MPEX Vacuum Systems Team (Section 6).

2.20 VACUUM VENDOR SELECTION

It has been the experience of the SNS Vacuum Systems Team (who have informed the MPEX team) that a limited number of capable vacuum fabricators exist in the United States. Moreover, MPEX-00-ENG-002 Rev 0 MPEX Vacuum Handbook Page 25 of 41 each fabricator tends to have a niche as it relates to materials and sizes of vacuum vessels and components. It is highly recommended that the MPEX Vacuum Systems Team (Section 6) be consulted when choosing potential vendors.

2.21 LEAK DETECTION

Any vessels and/or vacuum components covered by this document will be required to pass a helium leak test of appropriate sensitivity. The specific leak detection procedure and/or technique to be used is highly dependent upon the size, construction, and intended use of each item. Refer to section 5 for guidelines on leak detection.

Employing the wrong testing methodology can result in an invalid test result. Please consult with the MPEX Vacuum Team (Section 6) to determine the appropriate testing methodology to use.

MPEX-00-ENG-002 Rev 0 MPEX Vacuum Handbook Page 26 of 41

3 FABRICATION, PACKING, AND HANDLING OF VACUUM

COMPONENTS

3.1 MECHANICAL OPERATIONS ON VACUUM SURFACES

3.1.1 Preferred Fabrication Processes

Conventional machining (milling, drilling, and turning), sheet metal fabrication (stamping, punching, forming, laser cutting, water jet cutting), forging and welding are the preferred methods for fabrication of approved materials.

[VH.021] Only water-soluble cutting fluids are permissible.

[VH.022] Internal vacuum surfaces shall achieve a surface roughness no greater than 32 micro-inches Ra.

3.1.2 Preferable Material Removal Techniques

Finish machining by conventional turning or milling is preferred. Other permitted techniques to meet surface finish requirements are slurry blasting with alumina or glass beads in a water jet;

gentle hand use of a dry fine stone or a fine stone lubricated with IPA, ethanol or alcohol and hand polishing and lapping with fine mesh alumina or silcon carbide (600 grit or higher) in an IPA or ethanol carrier on a lint free cloth; hand polishing with Scotch-Brite (Alumina loaded, Grade A);

electropolishing.

3.2 LESS PREFERABLE MATERIAL REMOVAL TECHNIQUES

Abrasive techniques to clean or attempt to improve the appearance of the surfaces of vacuum components must be kept to an absolute minimum and preferably avoided.

[VH.023] The use of grinding wheels, wire brushes, files, harsh abrasives, sand, shot or dry bead blasting, polishing pastes and the like is prohibited under normal circumstances without the prior approval of MPEX in writing.

3.3 GUIDANCE FOR PREPARING COMPONENTS FOR WELDING

Pay attention to the cleanliness of fabricated parts that are to be welded. Dirt, oil and other contaminates in the vicinity of the weld prep area will lead to inclusions in the weld and out-gassing under vacuum. Therefore, ALL welded components MUST be cleaned to vacuum standards, using the appropriate methods described in this specification, BEFORE being welded together.

MPEX-00-ENG-002 Rev 0 MPEX Vacuum Handbook Page 27 of 41

Moreover, the best practice for insuring quality construction of a vacuum vessel or component is to have it physically separated from the environment where tasks are being performed on other materials (carbon steel) where the shavings and dust can contaminate weld prep areas causing micro-inclusions that can lead to leaks.

[VH.024] All vacuum seal welds shall fall into one of three classifications for proper vacuum welding (reference section 2.8):

1) Full penetration weld

2) Seal weld on the interior of the vessel only

3) Seal weld on the interior of the vessel with skip (stitch) welds on the exterior

[VH.025] Vacuum welds shall NEVER be on the exterior and not fully penetrate, nor should there be a full weld on both the interior and exterior of the joint.

3.4 MAGNETIC PERMEABILITY OF WELDS AND WELD AFFECTED AREAS

MPEX uses magnetic fields to control the plasma used during experiments. MPEX therefore has a magnetic permeability requirement for all materials in the magnetic field sensitive areas of the machine (refer to section 2.4) to assure magnetic field uniformity. This includes weld materials and weld affected zones.

[VH.026] All base materials, weld materials, welds, and weld affected areas that fall under material classification 7 (refer to section 2.2) shall meet the MPEX program magnetic permeability requirement of 1.03 or less (refer to section 2.4).

[VH.027] All welding materials and processes for welds that fall under material classification 7

(refer to section 2.2) shall have the magnetic permeability of the process validated with a test sample prior to the start of fabrication.

[VH.028] All final welds that fall under material classification 7 (refer to section 2.2) shall be verified to have met the MPEX magnetic permeability requirement (refer to section 2.4).

3.5 TREATMENT OF WELD BURNS

Although weld burns may be removed by using acid pastes; in general, such burns do not affect vacuum performance and are best left alone. Any scaling must be removed using the techniques outlined in Section 3.1.1 and 3.1.2. If it is desired to remove burns, then slurry blasting with alumina in water or hand burnishing with alumina powder is a satisfactory alternative. Heavy

MPEX-00-ENG-002 Rev 0 MPEX Vacuum Handbook Page 28 of 41 abrading, grinding or wire brushing is prohibited. Hand finishing with Scotch-Brite or a dry stone is also permissible.

3.6 ALTERNATIVE MANUFACTURING PROCESSES

3.6.1 Additive manufacturing (3D Printing)

Additive manufacturing is a rapidly developing technology and industry. There are vastly different fabrication processes that all fall under the additive manufacturing umbrella. Many metal additive manufacturing processes use laser sintering. Depending on the supplier and processes used, the components can be porous, have inherent virtual leaks, have rough surface finishes, and are difficult to clean.

[VH.029] Any components for use in vacuum that will be fabricated using additive manufacturing processes must be qualified and approved by the MPEX Vacuum Systems Team (Section 6)for each specific application, supplier, and process.

3.6.2 EDM (Electrical Discharge Machining)

EDM processes should be approved for specific applications by the MPEX vacuum systems team

(section 6) and should only use processes that use DI water as the dielectric.

3.6.3 Castings

The use of castings is not permitted.

3.6.4 Sintered Powdered Metals

Sintered powdered metals should be avoided. Use of sintered powdered metals must be approved on a case-by-case basis by the MPEX vacuum systems team (section 6) for specific uses.

Exceptions are listed in Appendix 1.

3.6.5 Abrasive Honing

Abrasive honing is not permitted

3.6.6 Other Processes

Other processes not listed here should be reviewed with the MPEX vacuum systems team (section

6)

MPEX-00-ENG-002 Rev 0 MPEX Vacuum Handbook Page 29 of 41

3.7 HARDWARE AND FASTENERS

Refer to section 2.12 for guidelines on the use of fasteners.

3.8 MARKING AND LABELING

3.8.1 Marking of vacuum components

Marking out or marking for identification should be carried out with clean dry scribers or vibrating engravers only, never by acid etching or marker pen. Laser etching is permitted on exterior, non-vacuum surfaces. Vacuum surfaces should only be marked if it is essential to do so and never on sealing surfaces.

3.8.2 Proper labeling materials

Self-adhesive labels, tapes etc. should only be used if essential to do so and may only be fixed to non-vacuum surfaces. Ensure the adhesive used is soluble in acetone and alcohol.

3.9 QUALITY ASSURANCE

[VH.030] All components, materials, and deliverables shall follow the quality requirements identified in the MPEX Quality Assurance Program Plan (MPEX-12-PLAN-001).

3.10 HANDLING AND PACKING

3.10.1 Proper…