Attachment (A1) LT-ENG-RSI-SR-VA-002_Design_Fab_of_Components_UHV_Sys.pdf

NATIONAL SYNCHROTRON LIGHT SOURCE II

BROOKHAVEN NATIONAL LABORATORY

BROOKHAVEN SCIENCE ASSOCIATES

UPTON, LONG ISLAND, N.Y. 11973

QF-043, REV C

PROJECT:

Design and Fabrication of Components for NSLS-II UHV Systems

LT-ENG-RSI-SR-VA-002 12/18/2008 A

DOCUMENT NUMBER DATE REV

RREEVVIISSIIOONN CCOONNTTRROOLL SSHHEEEETT

REV DESCRIPTION OF CHANGE(S) DATE WRITTEN BY APPROVED BY ENTERED BY

A First issue 12/15/08 H.-C. Hseuh H.-C. Hseuh , N.

Gmür, E. Cheswick, F. Willeke

H.-C. Hseuh

B

C

D

E

F

Design and Fabrication of Components for NSLS-II UHV Systems

CONTENTS

1 Introduction 2 Scope of Document 3 Applicable Documents

3.1 Current Revisions

3.2 Order of Precedence

4 Technical Requirements

4.1 Technical Requirements

4.2 Design Options and Design Reviews

4.3 Material Selection

4.3.1 UHV-Compatible Materials

4.3.2 UHV-Incompatible Materials

4.3.3 Flanges and Bi-Metal Material

4.4 Fabrication

4.4.1 Machining

4.4.2 Welding

4.4.3 Brazing

4.5 Cleaning

4.6 Assembly

4.7 Acceptance Tests

4.7.1 Dimensional Inspection

4.7.2 Leak Test

4.7.3 Outgassing Rate and Residual Gas Analysis

4.7.4 Bakeout

5 Quality Assurance Requirements and Provisions 6 Preparation for Delivery

Design and Fabrication of Components for NSLS-II UHV Systems

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Design and Fabrication of Components for NSLS-II UHV Systems

1 INTRODUCTION

The National Synchrotron Light Source-II Project (“NSLS-II,” hereafter) is to design and construct an electron storage ring with a circumference of 792 m. To provide a long beam lifetime for the circulating electron beam, ultrahigh vacuum (UHV) of 10-10 mbar, and absence of hydrocarbon contamination are necessary in storage ring and front end vacuum systems. Therefore the vacuum chambers and components inside or mounted on the vacuum chambers must meet very stringent UHV requirements, starting from the design stage throughout fabrication, installation, and commissioning.

2 SCOPE OF DOCUMENT

The requirements in this document, in conjunction with the associated Statement of Work (SOW), drawings, specification, and other applicable documents, provides the general requirements in the design, material selections, fabrication and workmanship, cleaning, assembly, inspection, quality assurance, and packaging of chambers, parts, and components (“Components,” hereafter) for NSLS-II UHV systems. It is the responsibility of the manufacturers (“Vendor” hereafter) to demonstrate that the Components meet the requirements of this document prior to their acceptance for installation into NSLS-II UHV systems.

3 APPLICABLE DOCUMENTS

The following document forms a part of this requirement to the extent specified herein. Unless otherwise specified, the issue date or revision level shall be that in effect on the date of the Request for Quote (RFQ).

Exceptions must be approved in writing by BNL.

BNL QA-101, Seller Quality Assurance Requirements (4/08).

3.1 Current Revisions

It is the responsibility of the Vendor to determine that the requirements, the technical specification(s) and applicable drawing(s) used in the preparation of quotations by the Vendor and the subsequent execution of the Purchase Order, are the most current revisions. This is emphasized here, in the interest of the Vender.

3.2 Order of Precedence

In the event of conflicting requirements, requirements specifically stated within the applicable SOW and/or other associated technical specification(s) shall take precedence over requirements stated herein. These conflicting requirements shall be emphasized in the applicable documents.

Design and Fabrication of Components for NSLS-II UHV Systems

4 TECHNICAL REQUIREMENTS

4.1 Technical Requirements

These technical requirements shall be followed for the design, fabrication, and evaluation of all Components to be installed in NSLS-II UHV systems. Any deviation from the requirements is to be brought to the attention of NSLS-II cognizant engineers/scientists for review and approval in writing.

4.2 Design Options and Design Reviews

The basic design rule for UHV Components is to minimize the gas load, with the benefit of low operating pressure. The gas load arises from outgassing both thermal and desorbed, and diffusion and leaks, which can vary by several orders of magnitude. Gas load is minimized by the selection of proper materials, careful surface treatment, and by minimizing the surface area exposed to vacuum.

An important design criterion is the elimination of trapped volumes, which connect to the main vacuum through very small orifices, capillaries, etc. To this end, the vacuum sealing welds, whenever possible, shall be internal welds. Where this is not possible, full penetration external welds must be specified. Similarly, vacuum brazing should leave a smooth run of braze material on the vacuum side of the brazed joints.

There should never be an attempt to seal a trapped volume under any circumstances, whether it is a sealing weld or a threaded bolt. All volumes should be vented, either to atmosphere or to vacuum. For the same reason a vacuum sealing weld should always be a single weld, never a double weld. All threaded fasteners located in blind holes inside vacuum are to be vented through coaxial vent hole.

It is sometimes a requirement that vacuum surfaces be coated. Extreme care should be taken so that there is no possibility of delaminating or peeling of the coatings. The surface to be coated should be clean and free from defects which could give rise to trapped volumes under the coatings. A high-temperature vacuum bake of > 200oC is recommended to test the adhesion, and the Components shall be rejected with any evidence of peeling. If acid bath is used for coating, vacuum bake at > 400oC shall be applied to remove any acid residues from electroplating.

Cleanliness is important at all times. Frequent cleaning of items before, during, and after manufacturing processes is required. Care should be taken not to cross-contaminate “clean” and “dirty” components.

Proper support of the Components during fabrication and evaluation shall be considered at the design stage to eliminate the possibility of distortion and damaging of the Components. All Components must be designed to safely withstand the loading exerted by atmospheric pressure while under vacuum. Modular Components utilizing bellows or geometries which result in differential loading while under vacuum must include proper restraints that prevent lateral and axial movements due to the differential pressure loading.

The design of the Components shall be submitted for review and approval by NSLS-II, including detailed drawings, bill of materials, applicable fabrication processes, etc. This review shall take place prior to the Vendor’s procurement of material and start of fabrication.

4.3 Material Selection

Only UHV-compatible metal and ceramic materials shall be selected for fabrication of the Components for the NSLS-II UHV systems. Some UHV materials may be excluded based on the specific application, e.g., magnetic permeability, temperature limitation, or radiation resistance.

Design and Fabrication of Components for NSLS-II UHV Systems

The Vendor is to supply material certification traceable to its original sources for each batch of material used, including material specification, chemical analysis report, mechanical properties, etc.

4.3.1 UHV-Compatible Materials

The following materials are UHV-compatible, after proper cleaning and degassing:

Stainless steel – Austenitic, 300-series vacuum arc remelt (VAR) or hot-forged electron slag remelt (ESR). Preferred types are ASTM 304L, 304LN, 316L, 316LN, 321, and 347, where “L” signifies low carbon content (which reduces chromium carbide precipitation in the heat-affected weld areas), and “N” is for high nitrogen content. Carbide precipitation can lead to corrosion, reduced strength, and high magnetic permeability.

Aluminum alloys 2219, 5086, A6061-T6, and A6063-T6 for their high strength, easy weldability, and non-magnetic properties

Copper – Oxygen-free high conductivity, OFHC or OFS grades, Beryllium Copper, GlidCop

Titanium – Commercially pure, aircraft quality, type 50A

Ceramics, Refectories – Alumina (> 96% Al2O3) and similar oxide ceramics (however, beryllia is not allowed without written approval by NSLS-II)

Others – glass, sapphire, Inconel, beryllium windows, Monel, Kovar, Mu Metal, Macor, Kapton

4.3.2 UHV-Incompatible Materials

The following materials are not UHV compatible:

Zinc and zinc alloys with high vapor pressure at elevated temperature, found in bearings, silver solders, brass and bronze components

Cadmium and cadmium alloys with high vapor pressure, found in bearings, solders, and steel rust proofing.

Elastomers – O-ring seals for flanges and valves

Organics with high outgassing rates tend to trap hydrocarbon contaminants; and are less radiation resistant. Use of Teflon® is specifically prohibited.

4.3.3 Flanges and Bi-Metal Material

Conflat® flanges with knife-edge sealing surface shall be fabricated from 304L, 316L, or 316LN VAR or ESR stainless steel. Knife edge with 90° angle is preferred over 70° angle.

The leak-check grooves of the Conflat flanges shall be at vertical center when the flange face is vertical;

when not, the grooves shall be parallel to the electron beam direction.

The following bi-metal transition materials have been used successfully in UHV application. However, detailed inspection including, but not limited to, thermal cycling and leak tests, must be made before and after fabrication. Since these materials can vary from lot to lot, all pieces must be 100% inspected and tested.

Design and Fabrication of Components for NSLS-II UHV Systems

Roll-bonded plates and shells between aluminum and stainless steel

Explosion-bonded plates between copper and stainless steel

Explosion-bonded plates between aluminum and stainless steel (e.g., ATLAS® flanges)

4.4 Fabrication

4.4.1 Machining

Only water soluble machining lubricants are allowed. The use of silicone- or sulfur-based machining lubricants is prohibited. All machining is to be carefully controlled to ensure that no foreign matter is embedded in the surface of the material. The use of abrasive wheels or cloths, wire brushes, files, sand, polishing pastes, and the like is prohibited.

Scale removal, etc., shall be performed by careful hand brushing with a clean 300-series stainless steel brush. All Components shall be deburred prior to welding to ensure proper fit at assembly, and to prevent a handling hazard from sharp edges and burrs.

4.4.2 Welding

All parts shall be cleaned prior to welding and brazing. All welding shall be performed in a clean area.

Clean, lint-free gloves shall always be worn. All jigs, fixtures, and heat sinks shall be clean.

Tungsten Inert Gas (TIG) and Electron Beam (EB) welds are recommended for UHV applications. Only clean 300-series stainless steel hand brushes are to be used for removing oxides from welds. Power driven brushes, abrasive papers and abrasive wheels shall not be used.

No welds, brazes, or joints of any kind shall bridge water-cooled channels and vacuum spaces. If possible, the welds are to be on the vacuum side of the joints with single pass seal welding. If not, the welds shall have 100% penetration to eliminate virtual leaks. The inside surface shall be purged with argon or helium throughout the welding operation.

Where high strength requires welding on both sides of thick sections, the side facing the vacuum is to be continuous and the opposite side intermittent. At no time should there be continuous welds on both sides of the joint.

The weld zones shall be free from scale, voids, blow holes, etc. There shall be no visible evidence of inclusions. The welds shall be inspected with X-ray or other non-invasive methods. The use of dye penetrate testing after welding is strictly prohibited. No repair of defective welds is allowed without prior approval from NSLS-II. There shall be no machining or cleaning operations after welding without prior approval in writing from NSLS-II.

4.4.3 Brazing

Hydrogen or vacuum furnace brazing are acceptable for copper to stainless steel joints, for copper alloy cooling tubes to copper alloy absorbers, and for ceramic to metal joints. All brazing joints shall have adequate filler metal to provide a flush, smooth fillet free from voids, blow holes, etc., and there shall be no visible evidence of inclusion.

No silver soldered or soft soldered joints are permitted.

Design and Fabrication of Components for NSLS-II UHV Systems

The proposed brazed joint design and brazing plan shall be submitted to NSLS-II for approval, including the materials, the brazing alloys, etc. No rectification of defective brazed joints is to be carried out without prior approval in writing from NSLS-II. There shall be no machining or cleaning operations after brazing, except alcohol rinse in ultrasonic bath, followed by oven drying.

4.5 Cleaning

It is recommended that all parts be chemically cleaned and/or vacuum baked prior to welding, assembly, and testing. The cleaning process shall remove residual surface contaminants such as dirt, grease, oils, etc.

without etching the vacuum side of the surface. Therefore, the cleaning process shall not include strong acid or alkaline etching. Mechanical operations to remove surface stains shall be kept to an absolute minimum. Any metal brushing, sand blasting, or other harsh abrasives on the vacuum side are prohibited.

The exact cleaning process depends on materials, sizes of the Components, and available Vender facilities.

Components shall be carefully inspected so that any areas which might form potential contamination traps (e.g., blind holes, crevices, or cracks) are identified to ensure that they are properly cleaned out.

The recommended cleaning process shall include mild detergent washing baths with ultrasonic agitator, de-ionized water rinsing bath, and air or nitrogen drying oven. Non-invasive cleaning detergents, such as mild-etch alkaline (e.g., Almeco 18, Ridoline 357) or acid (e.g., Citranox) solution are permissible. The Vender is required to specify in detail its cleaning process to NSLS-II for review and approval.

After cleaning, the vacuum surfaces shall not be touched with bare hands. Clean, lint-free gloves shall be worn when handling the cleaned Components. Cap and gown shall be worn while handling the cleaned Components. All parts shall be wrapped in lint-free paper, and then tightly wrapped in vacuum-grade aluminum foil.

4.6 Assembly

Assembly, welding, inspection, and packaging of the Components shall take place in dedicated clean areas.

The areas shall not be located near machine tools, compressors, oily or dirty parts and tools, etc., which can contaminate the work area with hydrocarbons and dirt. No eating, drinking, or smoking shall be permitted in these clean areas.

Unless the Components are being actively worked on or inspected, the Components shall be wrapped in clean vacuum grade aluminum foil and kept covered.

Cleaned Components shall only be handled with clean, lint-free gloves. Clean gloves shall only contact clean parts and tools in the clean work area. If they touch unclean surfaces (hair, face, chair, floor, tools, etc.) they shall be replaced with clean gloves.

It is required that the arms or bodies of the workers coming in contact with the Components shall be covered with a lab coat with elastic-cuffed sleeves, to prevent debris from falling into the Components.

4.7 Acceptance Tests

Acceptance tests include, but are not limited to, dimensional inspection, leak testing, and outgassing measurements. Acceptance tests shall be performed on all Components prior to delivery. Components shall not be marked for identification by any technique other than dry scribing or engraving. Acid etching or marker pen is prohibited.

Design and Fabrication of Components for NSLS-II UHV Systems

4.7.1 Dimensional Inspection

All tools and inspection gages which come in contact with the cleaned Components shall be cleaned accordingly. When the tools are not in use, they shall be covered and stored to prevent their use on dirty parts. Tools shall not be made of materials which could contaminate the cleaned Components, e.g., brass, plastic, zinc, etc.

Work bench surfaces shall be thoroughly cleaned with detergent, rinsed with water, and then wiped with alcohol before their use in the assembly area. The surfaces shall be hard and non-absorbent (stainless steel, Formica, etc.). Wood bench tops or similar materials are not acceptable.

Dimension inspection shall be defined by the applicable drawings. The inspections shall also include the cleanliness and appearance of the Components.

4.7.2 Leak Test

The whole Components shall have a total leak rate < 2x10-10 std.cc/sec He, as measured with a helium mass spectrometer with minimum sensitivity <1x10-10 std.cc/sec He. This mass spectrometer shall be calibrated and data recorded at the beginning and ending of each working shift. Dye penetrate techniques and solvent ingress techniques are strictly prohibited.

The leak test shall be carried out in a clean area. A vacuum bakeout prior to leak checking is recommended, to drive out any cleaning solution, machining fluids, or water vapor that might otherwise plug a leak. The leak test shall be carried out with internal vacuum of < 1x10-4 mbar while the leak check zone is immersed in one atmosphere helium. All-metal manifolds and valves shall connect the Components and the test equipment. Viton O-rings may be used as temporary seals for the leak test. No lubricants or greases of any kind are to be used on the O-ring seals. Greases or oil are prohibited on any internal or external surfaces, which could block the leak passage.

The leak test shall be performed with the Components pumped with turbomolecular pump backed by oil-free dry mechanical pump, or other UHV equivalent pumps. After leak testing, the Components shall be vented to atmospheric pressure with dry nitrogen from an evaporated liquid source or from a high-purity water-pumped nitrogen bottle. A suitable leak test certificate shall be prepared for each Component.

4.7.3 Outgassing Rate and Residual Gas Analysis

The outgassing rate of the interior surfaces of the Components depends on types of material and treatment.

It shall not exceed 1x10-9 mbar.l/sec/cm2 for all the materials, and 1x10-10 mbar.l/sec/cm2 for smooth metal surface, after under vacuum for 100 hours. Conventional all-metal UHV practices shall be used in making these measurements.

The assembled Components shall be measured for residual gas composition using quadrupole mass spectrometer with sensitivity down to 10-12 mbar partial pressures. The predominant gas component shall be hydrogen and be at least 60% of the total pressure after under vacuum for 100 hours. Masses greater than 28 amu shall be less than 10% of the total pressure. The sum of peak heights at mass locations 39, 41, 43, 45, and greater shall be less than 1% of the total pressure.

4.7.4 Bakeout

All Components shall be bakeable under vacuum to the designated temperatures. Typically, stainless steel shall be bakeable to 250°C and aluminum to 150°C. The exact temperature, duration, and ramping rate of

Design and Fabrication of Components for NSLS-II UHV Systems the bakeout shall be considered at the design stage to ensure that the thermal stress is manageable and not causing any damage to the Components.

5 QUALITY ASSURANCE REQUIREMENTS AND PROVISIONS

The following Quality Assurance requirements apply to the Components defined by this specification.

Failure of the Components to meet any of the requirements of this specification shall constitute non-conformance and be cause for rejection.

The following BNL-QA-101 clauses apply: 1, 2, 3, 3.1, 3.1.2, 3.2 thru 3.7, 4.0, 4.2 thru 4.4, 4.4.1 thru 4.4.3, 4.5 thru 4.7, 4.7.1, 4.7.3, 4.10, 4.10.1, 4.10.2, 4.10.4, 4.13, 4.15, 4.16, 4.18, 4.18.2, 4.18.4, 4.19, 4.21, 4.22, 4.23, 4.24 (only where applicable), 4.31, 4.34, 4.39, and 4.42.

With each Component delivered, the Vender shall supply to NSLS-II a Certificate of Conformance, in accordance with section 4.16 of BNL QA-101.

NSLS-II reserves the right to carry out inspections and to witness Vender tests specified herein prior to delivery to NSLS-II. The Vender shall inform NSLS-II at least three (3) weeks prior to conducting the Vender tests specified herein, such that arrangements can be made for NSLS-II representatives to witness the Vender tests.

6 PREPARATION FOR DELIVERY

The Components shall be packaged individually suitable to their dimensions and intended application. Any water in cooling channels must be completely removed, and back-filled with dry nitrogen. If possible, the Components shall be sealed with blank flanges and back-filled with clean, dry nitrogen. If this is not possible, the Components shall be wrapped in lint-free paper and vacuum-grade aluminum foil and put into clean transparent polyethylene bags back-filled with clean, dry nitrogen. Knife-edge flanges and other vacuum-sealing faces shall be protected to prevent damage during transit.

The Components must be properly supported and contained to prevent damage and contamination during transit. Durable material, such as clean wood, bubble wraps, or similar non-contaminating materials are to be used to support and protect the Components from one another during transit and storage. No peanut-type material shall be used for packaging.