Q/A PROTOCOL FOR THE DAYA BAY 4-METER ACRYLIC VESSELS
August 27, 2008 Revision 1.0
Abstract
A Q/A plan for the construction and delivery of the 4m acrylic vessels (AV’s) for the Daya Bay neutrino experiment is presented. The plan is divided into five parts: material testing, manufacturing facility tests, measurements during defined construction stages, inspection of surface cleanliness, and inspection after delivery to the Surface Assembly Building (SAB) where the vessels will be incorporated into the detector assemblies.
Technical Contact
Tom Wise University of Wisconsin Department of Physics [email protected] Phone: 608 262-3091 Cell: 608 843-8053
1 Table of Content
TABLE OF CONTENT 2
I. INTRODUCTION 3
II. COMPLETENESS DISCLAIMER 3
III. MATERIAL TESTS 4
IV. FACILITY TESTS 7
V. Q/A TESTS DURING CONSTRUCTION STAGES 8
VI. ACRYLIC VESSEL CLEANING AND CLEANLINESS 18
VII. EXTERNAL Q/A INSPECTION BREAKS 19
VIII. REPORTING OF NON-CONFORMING INSPECTIONS 21
APPENDIX A - SURFACE REQUIREMENTS FOR MOUNTING OF 4-M ACRYLIC VESSELS DURING INSPECTION 22
APPENDIX B – ASSEMBLY SEQUENCE AND INSPECTION BREAKS 23
2 I. Introduction
Our goal is to manufacture acrylic vessels as nearly identical pairs. To this end the vessels will be manufactured two at a time. We have been informed that the suppliers of the acrylic sheet have a maximum batch size that does not allow construction of two complete vessels from a single batch. We therefore will split all batches into two halves with each half being used to construct a common portion of the two paired AV’s. For example one batch might be used to construct the lower tier of panels for both AV’s. Another batch might be used to construct the bottom plates and the lids of the paired AV’s. In this way we can more closely preserve identicalness of pairs of detectors. “We”, “us”,“our”, and “UW” refer to the University of Wisconsin who is purchasing the vessels. The terms “Reynolds”,”RPT”, and “fabricator” refer to Reynolds Polymer Technology.
The 4m vessels will be constructed by Reynolds Polymer Technology, located in Colorado, USA and the 3m vessel will be constructed by Nakano, a subsidiary of Gold Aqua, Taiwan. To facilitate communications with the two fabricators the Q/A plan is divided into separate documents for 4m and 3m acrylic vessels. This will facilitate communication with the separate vendors. In most cases the Q/A requirements will be identical but the requirements will differ considerably when the Q/A is related to the vessel geometry.
This document will be attached to the procurement documentation for the 4m vessels and will become part of the procurement contract.
II. Completeness Disclaimer
This document represents our best understanding to date of the inspections required to produce acrylic vessels with properties required for the DayaBay experiment. Unforeseen manufacturing variables may arise that affect the experiment in adverse ways. As a result it may become necessary to modify the procedures or the scope of the inspections described here in order to preserve the quality of the product.
3 III. Material Tests
Construction from any acrylic batch shall not proceed until the samples provided from that batch pass inspections 1-8 below. These specifications are more explicitly enumerated in a document entitled “Acrylic Material Specification for AVs” which will be supplied to the acrylic supplier(s).
1) RPT will supply the document “Acrylic Material Specification for Daya Bay 4- Meter Acrylic Vessels” to the acrylic supplier.
2) RPT will provide UW with a copy of the material certifications from the material suppliers and sheet manufacturers. These items include the sheet thickness measurements, the factory air based optical measurements, and raw material certifications.
3) RPT will send samples to UW from every UVT acrylic batch as they are first removed from stock/storage at the RPT facility. This is to verify that the storage of the material did not degrade the raw acrylic material.
4) RPT will measure thickness and thickness uniformity of the UVT sheets as they are first removed from stock An ultrasonic thickness gage is recommended for these measurements. Such devices are typically accurate to ±0.02mm. We have specified a sheet thickness conforming to ASTM 4802.. For 18 mm acrylic sheet the ASTM thickness tolerance is +.040”/-.090”. For this purpose it will be sufficient for the fabricator to provide us with records of their measurements of the sheet thickness. Additional details concerning the selection and sorting of sheets are given in the separate acrylic document referred to above.
5) RPT will visually inspect raw sheet for oversize defects such as pits, bubbles and other inclusions and will omit these defects from the fabrication process during sheet selection and layout.
6) RPT will produce a number of material samples from stock cut from the acrylic batch(es) used in the AV construction. These samples will shadow the experience of the various AV parts and will be sent out for testing one by one as different stages in the construction proceed. For example exposure to excessive UV light could be detected because the shadow samples would always be exposed to the ambient light conditions. The number and timing of the samples will be determined by mutual agreement between UW and the fabricator.
7) UW will provide optical test results within 2 working days after receipt of the samples. Wisconsin has obtained a transmission spectrometer to measure the optical transmission spectrum of each sample from 200nm through the visible. Development of a standardized measurement protocol for the samples is in
4 progress. The transmission of the UVT sheet must meet or exceed the transmission specifications defined in the separate acrylic document referred to above. Plots showing preliminary tests of some samples are shown in Figure 1.
8) RPT will perform or arrange for strength testing of samples of UVT sheet. The tests serve two purposes. First, to verify that the assumptions made during FEA calculations of the vessel structure are representative of the material actually used. Second the tests provide a baseline for later tests of the bond strength. The strength tests will follow standard engineering practice using standardized coupons. Details and responsibilities are enumerated in the separate acrylic document referred to above.
Figure 1: Minimum acceptable and expected optical transmission curves for acrylic material used in construction of the acrylic vessels for the Daya Bay neutrino experiment. Numerical values for acceptable transmission are given in the separate acrylic document referred to above.
5 UVT & SUVT
100
90
80
70
60 UVT 1 50 SUVT 1 40 % Transmission 30
20
10
0 200 300 400 500 600 700 800 wavelength nm
Figure 2: Results from preliminary samples of UVT and a newly available UV exposure tolerant formulation called SUVT. The data are not corrected for surface reflection.
6 IV. Facility Tests
1. Air Quality: Construction of the acrylic vessels must occur in a relatively clean environment to avoid inclusion of particulates in the bond zones. During the last stage of construction when the surfaces will be cleaned a more stringent class 100,000 particle count typical of a clean tent environment must be utilized.
1. UW will inspect the bonding areas and cleaning facility at RPT and monitor the air quality with portable particulate counters. It is expected that air filtration will be needed to maintain the required air quality during the final cleaning process.
2. RPT agrees to provide the space to set up a clean tent that will provide the clean air to meet a 100,000 particle count during the final cleaning of the vessels. The clean tent is not part of the RPT fabrication contract for the 4-m vessels.
2. Exposure to UV Light: It has come to our attention that UVT acrylic is sensitive to excessive exposure to UV light from, for example, exposure to sunlight or long term fluorescent or mercury vapor lighting. This may require that RPT will take steps to reduce the total UV exposure level.
1. UW will quantify the UV exposure problem by using accelerated aging tests of UVT acrylic samples and measuring the UV exposure at Reynolds with electronic sensors.
2. UW will develop recommendations for minimizing the UV exposure and discuss the proposed measurements with RPT.
3. RPT will cover the acrylic material during storage and when not working on it under a light-tight tarp.
4. If necessary, RPT will take preventative steps such as the installation of UV absorbing film over windows, skylights or artificial lighting.
5. If necessary, RPT will take steps to minimize exposure to sunlight by unloading truck shipments at night or moving the vessels in and out of the ovens at night.
7 V. Q/A Tests During Construction Stages
Refer to Appendix B for a description of the construction steps mentioned here. The fabrication procedures and sequencing are still evolving as RPT and UW discuss the details of the fabrication process. The details provided here may need to be modified to reflect those changes. Regardless of the procedures used the controlling document for dimensional specifications is the set of mechanical drawings provided by UW and attached as a separate document.
1. Raw material for panels
A) RPT, Polycast, and UW will follow the QA, selection, and testing of sheets described in the document “Acrylic Material Specification for the 4-m Daya Bay Acrylic Vessels”
2. Cut and formed individual panels
A) RPT will be responsible for control of the panel forming process. No external Q/A required by the Daya Bay collaboration.
3. Bonding of formed panels together to form a cylinder
A) RPT will provide one or more bond samples conducted at the same time and with the same raw materials as the panel bonds.
B) UW will test the bond(s) for optical transmission in the range 200nm through the visible. UW will destructively test the bond for strength. The bond must have a strength at least 85% of the base material to pass. Alternatively the fabricator may submit bond samples to an independent testing lab for analysis.
4. Assembled and bonded free cylinder. UW will inspect the free cylinder before top flange and bottom surface are attached. RPT will provide the support surface for this inspection. The required support surface is described in Appendix A.. The cylinder inspection will be performed by UW and will consist of the following:
A) Inspection of support surface
8 B) Outer circumference measured at 5 equally spaced heights. RPT and UW will make this measurement. The circumference tolerance is specified on drawings provided by UW. We will utilize a PI tape for these measurements. A 4m PI tape is in house and the procedure has been tested on the 4m prototype AV and has been shown to work. A PI tape has also been left with RPT for this measurement.
Figure 3. Pi tape with accuracy better than 0.1mm at 4m diameter.
C) Ellipse error. RPT will locally polish the cylinder surface to accommodate this measurement. Diameter of cylinder measured at three equally spaced angles and at four heights (12 diameters). The diameters at the top and bottom of the cylinder can be measured with a metal tape. We have successfully measured the diameter of the 4m prototype cylinder in the center where a tape cannot be used by using a hand held laser based distance meter. The accuracy of the device (Leica Disto A5) is stated by the manufacturer to be ±1.5mm. However tests of the device on the 4m acrylic prototype vessel indicate a better repeatability than that. These numbers are less than the diameter tolerance given in manufacturing drawings provided by UW. We note that the laser distance measurement is time of flight based and thus the measurement must be corrected for the acrylic thickness using the acrylic index of refraction.
Figure 4. Leica A5 laser range finder
9 We further note that the ellipse measurement at this stage of construction is only for detecting gross errors in the cylinder construction because the free cylinder walls are highly flexible. We expect that at the time of this inspection the cylinder will be pushed into circular shape at the bottom where it contacts the level support surface described above. This measurement requires optically clear paths through the acrylic.
D) Parallelogram error. RPT will measure the perpendicularity of the walls by measuring the distance from the wall to a plumb line. The sides of the cylinder must be perpendicular to level with a tolerance as specified in the construction drawings. The perpendicularity of the cylinder walls will be inspected by sliding a target along the surface or by use of a plumb line. The target position will be determined with respect to a vertical reference line using survey instruments. Alternatively the perpendicularity of the walls can be measured by measuring the distance from the wall to a plumb line.
E) Bond quality. To facilitate this inspection RPT will complete a preliminary polishing of these bonds. In addition to the testing of sample bonds described previously we will visually inspect every cylinder bond for inclusions, bubbles, and other defects.
F) Internal stress. UW will perform this measurement. It is important that internal stresses be relieved at each step of the assembly. Anomalous regions of high internal stress can be identified by the retardation of light passing through the stressed region. To date this diagnostic has been confined to the limited but still useful function of identifying regions of excessively high stress. We are investigating recently available equipment from a manufacturer that is claimed to quantify the stress level in transparent plastics of known thickness. If this equipment can be applied to our work we will utilize it to inspect the panels (and other locations on the acrylic assembly).
G) Panel thickness. UW will perform this measurement. Using an ultrasonic thickness gage we will sample the wall thickness with particular attention paid to the area near the bonds. Tolerances are stated in manufacturing drawings provided by UW.
5. Top flange. The top flange is thicker than the cylinder walls. It is produced by cutting arcs out of plate, bonding them together, and finish machining.
A) RPT will provide a sample of the flange material and the bonds used to connect arcs together. We will test the sample’s optical properties using the criteria stated in the separate acrylic specifications document referred to above. The bond strength will be tested by UW or sent out to an independent testing lab.
10 B) RPT will machine the top flange using CNC methods. One critical feature is a double O-ring groove for sealing the lid. We will inspect the finish and measure the depth of every groove. We will inspect the groove depth with a hand held depth gauge available in any machine shop. We will inspect the ID of the O-ring grooves with a metal tape measure and/or with O-rings manufactured to fit the grooves. We will inspect the groove width with calipers or go/no-go gages. We will inspect the relative feature-to-feature concentricity among the grooves, the 96 clamping holes, and the inner and outer edges of the flange by measuring the radial distances between these features at various locations around the circle. Tolerances for these features will be taken from manufacturing drawings provided by UW. The surface finish requirement for static liquid sealing O-rings is typically 0-32 micro-inch (0-0.8 micro-meter) RMS. UW will inspect the groove surface finish with a portable roughness gage such as the one illustrated here.
Figure 5: Hand held surface finish monitor. The monitor measures surface roughness in the range of 0.1 C) RPT will inspect each hole in the top flange for local cracking and overheating. The top flange and lid (see below) are fastened together with 96 holes on a common bolt circle. Based on experience with the prototype vessel it will be necessary to inspect each hole for local cracking and overheating. 6. Bottom plate. The bottom plate will be assembled by bonding together smaller plate pieces or machining from solid cast. The assembled full sized plate will be rough cut and then finished on a CNC machine. A) RPT will provide a bond sample from scrap generated during rough cutting. 11 B) UW will test the bond for optical transmission in the range 200nm through the visible. Inclusions and visible bubbles not conforming to ASTM4802-02 will not be accepted. Wisconsin will destructively test the bond for strength. The bond must have a strength of at least 85% of the base material to pass inspection. C) It is expected that RPT will use the outer surface of the bottom plate as a reference surface for positioning the cylinder walls. Although we anticipate that the plate will be circular to sufficient accuracy, RPT will inspect the plate diameter before it is removed from the machine bed. 7. Ribs. Flatness and levelness with respect to bottom surface needs to be checked after the ribs are bonded to the bottom surface. The inspection method depends on the construction sequence. The flatness inspection must be done with the bottom surface sitting on a horizontal surface as described in Appendix A. The rib tolerance is specified in the construction drawings A) UW will use a precision level or an optical survey instrument for this inspection of the ribs. 8. Assembled vessel body with ribs, bottom surface, and top flange all bonded to cylinder. The assembly will be placed on the surface specified in Appendix A for the following inspections. A) Parallelogram error and cylindricity. Measurement accomplished using plumb line suspended from top flange outer surface or with an optical survey instrument. UW will measure this. The tolerances are specified in manufacturing drawings provided by UW. B) Height error. Measure height of vessel from bottom surface to top surface of top flange. UW will use a metal tape to measure the height at eight nearly equally spaced positions around the cylinder. We may also use an optical survey instrument. The height tolerance is specified in manufacturing drawings provided by UW. C) Bond quality. Visually inspect all bonds for bubbles, inclusions, and other defects. RPT will provide additional bond samples as additional bond batches are prepared. UW, or an independent lab, will test the optical and mechanical properties of the bond samples as described earlier. D) Circumference as described earlier. E) Ellipse error as described earlier. F) Other inspections described in inspection break #2 under the heading “Details of external Q/A inspection breaks” below. 12 9. Rib pockets for 3m support pads . Pocket diameter and location will be determined with calipers and metal tape or with optical survey equipment. RPT will provide safe access to the center of the vessel for this inspection. The height, co-planarity and levelness of the four rib pockets are important for proper positioning of the 3 meter vessel. UW will inspect the height of the four pockets with respect to the support surface in Appendix A using either the following method shown schematically in figure 5 or a method equivalent to it. A sighting level or theodolite will be set up inside the 4 meter vessel over its center. A survey grade height rod will be placed in the pockets and on the support surfaces to make eight height measurements. Figure 5. Concept for measuring pocket height. 10. Rib mounted stops. RPT will determine the separation distance and centering of the stops with a go/no-go gage provided by UW. The 3 meter vessel is located inside the 4 meter vessel via the pads described above and by stops bonded to the four ribs with pockets. The stops will pass or fail inspection based on the provided gage. The jig measurement may be backed up using optical survey equipment. 13 11. Lid. The 4m lid has a conical shape and is reinforced with ribs bonded to the top surface. There are three penetration holes with bonded tubes for insertion of calibration sources. At present there are two possibilities for construction of the lid-- bonded and machined from solid. Therefore we provide two different Q/A inspections. Items A-E apply to the bonded lid. Items AA to FF apply to the machined lid. A) Plate to plate bonds. The available sheets are too small to make the lid from single sheets. RPT will provide samples of the bonds used to combine sheets. UW or an independent testing lab will inspect them. B) Lid to rib bonds. RPT will provide additional bond samples as additional bond batches are prepared. UW will test the optical and mechanical properties of the bond samples as described earlier. C) Lid thickness. UW will measure the lid thickness using the ultrasonic thickness gage described earlier. Tolerances are stated in manufacturing drawings provided by UW. D) Lid profile and rib flatness. UW will measure the lid profile and rib accuracy by scanning a target in contact with the lid top surface and recording the position with a survey instrument. During these measurements the lid will be placed on a flat surface with continuous support or clamped to the main vessel top flange. RPT may provide center support for this inspection at their discretion. RPT will provide a working surface capable of supporting the live load from two workers and allowing targets to be slid along the top surface of the lid. Tolerances are stated in manufacturing drawings provided by UW. E) Penetration holes and clamping holes. UW will measure the location and rotational accuracy of holes on the lid by placing targets in contact with the lid and recording the positions with a survey instrument. Levelness and height of the attached tube flanges will be measured with calipers and precision level. During these measurements the lid will be placed on a flat level surface with continuous support or clamped to the main vessel top flange. Tolerances are stated in manufacturing drawings provided by UW. The holes will be visually inspected for overheating and local cracking. AA) Plate to plate bonds. The available casting size is too small to make the lid from single plates. . RPT will provide samples of the bonds used to combine sheets. UW or an independent testing lab will inspect them. 14 BB) Lid thickness . UW will measure the lid thickness using the ultrasonic thickness gage described earlier. Tolerances are stated in manufacturing drawings provided by UW. CC) Lid profile and rib flatness. UW will measure the lid profile and rib accuracy by scanning a target in contact with the lid top surface and recording the position with a survey instrument. During these measurements the lid will be placed on a flat surface with continuous support or clamped to the main vessel top flange. RPT may provide center support for this inspection at their discretion. RPT will provide a working surface capable of supporting the live load from two workers and allowing targets to be slid along the top surface of the lid. Tolerances are stated in manufacturing drawings provided by UW. DD) Penetration and clamping holes. UW will measure the location and rotational accuracy of holes on the lid by placing targets in contact with the lid surface and recording the positions with a survey instrument. Levelness and height of the attached tube flanges will be measured with calipers and precision level. During these measurements the lid will be placed on a flat level surface with continuous support or clamped to the main vessel top flange. Tolerances are stated in manufacturing drawings provided by UW. The holes will be visually inspected for overheating and local cracking. EE) Penetration hole bonds. The machined design requires tube to tube bonds for mounting the penetration hole flanges. Those bonds will be inspected in the usual manner. FF) Machining induced stresses. RPT will take steps to reduce the stress in the base material by careful annealing. However additional stress will be induced after the machining process. We will inspect the lid for residual stress using optical instruments. 12) Lid to top flange compatibility and seal quality. A) Bolt circle compatibility. During the inspection process RPT will attach the lid to the top flange. That attachment will serve as a check of the bolt circle compatability. B) O-ring sealing quality. To inspect the sealing surfaces RPT will place the lid onto the top flange with the O-rings in place and with the 96 fastening bolts, and corresponding washers, and sleeves in place but not tightened down. Specification of the top flange and the lid lower surface where the two parts interface for the O-ring seal is not adequately addressed solely by specification of surface finish (see above) and overall flatness (see mechanical drawings). Pockets, bulges, 15 or steps on either of the two mating surfaces occurring over a scale of zero to about 20cm can induce excessive internal stresses in the acrylic. Irregularities over sub-mm length such as might be caused by dripped bonding syrup or machining errors are also problematic. 1. The lid bottom surface must make continuous contact with the top surface of the O-rings in the un-tightened condition. Visible skip zones are permissible provided continuous contact can be achieved by application of no more than 400 Newtons downward force (90 pounds) on any one bolt. For this inspection step multiple bolts may be utilized to achieve continuous contact. This force will be determined by specifying a torque value to the clamping hardware. 2. The squeeze of the O-rings after fully tightening the flange bolts is determined by the difference between the O-ring diameter and the groove depth further reduced by any residual gaps between the mating acrylic pieces. The squeeze can be no less than 0.036” ( 0.91mm) and no more than 0.053” (1.36mm). UW will determine this squeeze by measuring the depth of the O-ring groove and subtracting it from the minimum and maximum diameters of the O-ring specification. Any gaps present between the flange and the lid after fully clamping the lid to the flange with O-rings installed will be further subtracted from the squeeze calculated above. The minimum and maximum squeezes given above are calculated from the groove depth dimension and tolerance on the mechanical drawings of the 4m vessel and from the O-ring cross-section dimension and tolerance from the O-ring manufacturer. 13) Completely assembled vessel with all stress relief cycles completed, all surfaces polished, and lid fully clamped and sealed with an O-ring. A) Penetration hole locations. RPT will place the vessel on a flat level surface as specified in Appendix A during these measurements Locations of penetration holes with respect to the bottomand top flanges of the acrylic vessel will be measured by placing targets at the relevant locations and measuring their positions with a survey instrument.. The acceptable errors are stated in the construction drawings. B) Polishing quality. RPT and UW will visually inspect the finish of the vessel surfaces. We note here that the main purpose of requiring polished surfaces is to enable visual inspection of bonds, examination for inclusions or other defects and for transmission of polarized light for detecting regions of high internal stress and for detection of undesirable 16 surface crazing over time. A good surface polish will also make cleaning of the surfaces easier and more complete. The optical performance of the vessel will not be significantly affected by small regions of imperfect polishing in difficult to reach locations because the index of refraction of both liquid scintillator types and the mineral oil are closely matched to the refraction index of UVT acrylic. We will use a specification of “optically clear” for this inspection. C) Stress relief check with polarized light. UW will inspect bonds and regions of higher stress as determined by FEA analysis of the structure (such as near the top flange bolt holes) for evidence of excessive stress. This will be accomplished using a visible light source and crossed polarizers. D) Lifting test. Vessel will be lifted from support points and statically tested to 1.1 g equivalent. Flat acrylic sheet or other material sufficient to provide this extra load will be provided by the manufacturer and placed inside the vessel on the ribs. RPT will provide crane and working space for this test. UW will provide a lifting jig for this test. Stress inspection with polarized light will be performed during the static load portion of the lifting process. E) Leak tightness. UW will provide the leak detection equipment and will provide the argon gas required for one fill of a 4meter vessel. Vessel will be leak tested using diffusion of an argon atmosphere from the inside of the vessel to the outside. For these tests the internal volume will be filled with at least 80% argon. The overpressure of the argon atmosphere will be limited to <1cm water column. Portable argon based leak chasers with a sensitivity of 1x10-8 stdcc/s and a response time of 3 s are commercially available. For example see the model MS-50 manufactured by Vacuum Instrument Corp. at http://www.vicleakdetection.com/PDF/MS50ARGON.pdf At a leak rate of 1x10-8 stdcc/s it will take 77,000 years to pass one mole of gas. Even accounting for the inefficiency of the sniffing technique we must use there is sufficient sensitivity for our purposes. If any leaks are found that are due to vessel construction not meeting specifications RPT will be responsible for providing additional argon as required to verify that a repair has been successfully executed. F) Volume estimation. UW will survey the overall external dimensions of the vessel will be surveyed using a “total station” or other optical survey device. That information will be combined with a survey of the wall thickness using an ultrasonic thickness gage to calculate the inner volume of the vessel. There is no explicit tolerance on the vessel volume. The volume tolerance will be derived from other construction tolerances. 17 VI. Acrylic Vessel Cleaning and Cleanliness After passing inspection steps 1-13 above RPT will clean the acrylic surfaces according to their standard procedures. Currently the plan is to gently wipe the surfaces with suitable soft wipes soaked in a mild Alconox detergent solution followed by generous deionized water rinse. General cleaning of the vessels as for all RPT products is part of this fabrication contract. Specialized cleaning procedures, methods, or requirements specific to the Daya Bay project are not part of the vessel fabrication contract. 1. For the cleaning of the vessel RPT will not use any other liquids besides deionized water and Alconox without informing UW and having approval of the Daya Bay Project. 2. UW will develop tests for determining surface cleanliness of the acrylic surfaces and will develop specific cleaning procedures if needed. . 3. RPT agrees to provide the space for a clean tent or clean working space for the vessel cleaning. The air quality requirement for that space is discussed in an earlier section. The clean tent is not part of this contract. 18 VII. EXTERNAL Q/A INSPECTION BREAKS Appendix B describes the manufacturing and assembly sequence of the 4m AV’s as explained to UW by RPT. We have identified four milestones during this process where hands on inspection by Daya Bay representatives will be required. These inspections are in addition to the testing of various samples described previously. In this section we outline the scope of these four external inspections. Inspection #1 - At this stage a free standing cylinder has been bonded and trimmed to size. UW will inspect the following properties at this time: 1) circumference 2) wall thickness 3) eccentricity 4) plate inspection (no inclusions bubbles or other imperfections) 5) bond inspection (no inclusions bubbles or other imperfections) 6) parallelogram error 7) stress scan using polarized light Inspection #2 - At this stage the top flange and the bottom plate have been bonded to the cylinder. The internal ribs and central spider have been bonded to the tank bottom. UW will inspect the following properties of the vessel at this time: 1) circumference 2) eccentricity and cylindricity 3) parallelogram error 4) parallelness of top flange to mounting surface 5) parallelness of top of internal ribs to mounting surface 6) co-planarity of four Viton “puck” pockets and their parallelness to the mounting surface. 7) distance between and concentricity of opposite stops on four ribs 8) operation and dimensional accuracy of the four anti-buoyancy rib fittings 9) clocking error between ribs and the 96 clamping bolt holes on top flange 10) O-ring groove surface finish and dimension 11) hole quality of 96 bolting holes. Inspect for overheating, local crazing, and local pitting. 12) Feature to feature concentricity among o-ring groves, bolt holes, inner, and outer surface. 13) Bond quality of all bonds added since previous inspection 14) Internal stress inspection 15) height UW will also inspect the following properties of the lid either at this time or when it is completed. For these measurements the lid will be placed on a flat surface meeting th requirements in appendix A or it will be placed on the top flange 1) flatness of top surface of lid ribs 19 2) angular relation of the three penetration holes to the 96 bolt holes 3) height and parallelness of penetration hole flanges compared to support surface. If necessary the lid may be supported in its center from below. 4) thickness of lid plate. 5) surface finish and flatness of lower surface of lid where it contacts O-ring. 6) hole quality of 96 bolting holes. Inspect for overheating, local crazing, and local pitting. 7) internal stress inspection. Inspection #3 - At this stage the lid has been attached to the cylinder with bolts and sleeves in place but not tightened down. The lifting hooks have been attached to the outside walls. UW will perform the following inspections: 1) Check for uniform contact between O-ring and under side of lid as described in sections 11 and 12 above. 2) Tighten 96 clamping bolts, fill vessel with argon and leak check O-ring seal and all bonds communicating from inside to outside of the vessel. 3) Lifting test with 1.1 g sustained. Test includes optical stress test with polarized light. RPT will provide flat materials and lay them on the inside of the 4m vessel to simulate 1.1g lifting force. 4) Optical stress test of area around flange and O-ring seal and any other areas of interest. Inspection #4 - At this stage the AV has been cleaned and is ready for packaging 1) Final visual inspection looking for scratches or other imperfections not previously noticed. Traces of evaporated water droplets will be searched for. 2) Test of surface cleanliness. The test will include spot inspection with distilled water to test contact angle. Other tests may be developed but are not defined at this time. They may include wipe tests or tests with UV light or visible laser light. As stated earlier special cleaning requirements specific to Daya Bay and beyond the scope of normal cleaning provided by RPT are not in the scope of this contract. Inspection #5 - We may inspect the packing of the vessels. Alternatives to inspection in person may also be considered such as photographs of the packaging process. 20 VIII. REPORTING OF NON-CONFORMING INSPECTIONS 1. Any inspections performed by either UW or by RPT that are non-conforming must be reported to the other party in a timely manner. 2. Any impacts on the integrity of the product or on the schedule, and the advisability of repairing or ignoring the non-conforming defect(s) discovered by the inspection must be discussed by the two parties. 3. A plan of action agreeable to both parties must be decided upon before further action is taken on the part(s) affected by the non-conformity. 21 Appendix A - Surface Requirements for Mounting of 4-m Acrylic Vessels During Inspection The mounting surface shall be located between two horizontal planes separated by 1.0mm. The surface will consist of four (4) equally spaced individual pads centered on a circle of diameter 3860mm or a continuous horizontal surface. Each pad will have a maximum horizontal dimension of 350mm and a minimum horizontal dimension of 250mm. The pads will have a stiffness of at least 1500 Kg/mm. In the case of free standing cylinder inspections the mounting surface shall consist of a continuous flat surface as above or eight (8) equally spaced individual pads. Each pad shall contact the cylinder over a distance no less than 100mm and no more than 350mm. The pads will have a stiffness of at least 1500 Kg/mm. 22 Appendix B – Assembly Sequence and Inspection Breaks This appendix outlines the four meter AV construction sequence, as understood by UW, with milestones triggering on-site external Q/A inspection. This sequence is not a requirement for the fabricator. Rather it is a means to identify the four external inspection milestones. Typical Bonding Sequence 1. clean, prebond bake 2. dry fit 3. establish vacuum tight dam 4. apply syrup 5. cure ~ 2 days 6. anneal (180° F) See next page for the vessel assembly sequence…. 23 Vessel Assembly Sequence 9) Cylinder Panels A) Cut four plate pieces B) Dry fit C) Bond four pieces together D) Anneal E) Thermoform into quadrant F) Trim to size 10) Complete three more quadrants 11) Dry fit quadrants into free standing cylinder A) Dry fit and bond three panels together B) Trim 4th panel to size to match perimeter requirement, and dry fit. C) Bond final cylinder panel D) Anneal E) Trim top and bottom to size >> EXTERNAL ON-SITE Q/A INSPECTION BREAK #1 << 24 12) A) Top Plate (If made from thin sheet) A) Cut plates B) Dry fit C) Bond D) Anneal E) Cut into circle F) Thermoform into cone G) Invert onto mold for support, bond ribs, bond rim reinforcement H) Anneal I) CNC machine outer edge, three penetration holes and (possibly) drill 96 holes. B) Top plate (if made from cast) A) cast plates & anneal B) Bond plates together to get desired size C) Anneal D) CNC top surface E) Invert piece and CNC bottom surface F) Anneal 25 G) Bond penetration flanges 13) Top flange A) Cut 6 arcs from plate B) Dry fit into circle C) Bond D) Anneal E) CNC machine—face, O-ring groove 14) 96 holes on bolt circle A) Mount lid & top flange together on CNC machine B) Drill 96 holes C) Machine outer diameters D) Remove lid, machine inner diameter of top flange 15) CNC machine central spider for bottom plate 26 16) Bottom plate (made from panels) A) Cut panels to size B) Dry fit C) Bond D) Anneal E) CNC machine into circle, add fiducial marks, remove central hole for central spider. F) Bond central spider. G) Anneal 17) Top flange and bottom plate bonded to free cylinder A) Dry fit top plate to cylinder using CNC top flange OD surface as a positioning guide for top of cylinder. Use (temporary) internal spider arms to push/pull top region of cylinder wall into place. B) Bond top flange to cylinder C) Bring 8 custom support jigs into position under bonded top flange to generate a bond gap between bottom plate and cylinder walls. D) Use plumb lines suspended from top flange OD surface to position bottom plate. E) Use bottom plate OD surface to position bottom of cylinder wall. Use (temporary) internal spider arms to push/pull on cylinder wall. F) Bond bottom plate to cylinder 27 G) Remove all excess bond material H) Anneal 18) Add bottom ribs and external lifting tabs >> EXTERNAL ON-SITE Q/A INSPECTION BREAK #2 << 19) Mount O-ring seal, attach lid to top flange with 96 bolts >> EXTERNAL ON-SITE Q/A INSPECTION BREAK #3 << 20) Final polish and final anneal 21) Final cleaning >> EXTERNAL ON-SITE Q/A INSPECTION BREAK #4 << 28 22) Packaging for shipping >> OPTIONAL ON-SITE Q/A INSPECTION BREAK #5 << 29