WINDOWS FOR EXTERNAL OR INTERNAL HYDROSTATIC PRESSURE VESSELS PART II. Flat Acrylic Windows Under Short-Term Pressure Application May 1967 NAVAL FACILITIES ENGINEERING COMMAND NAVAL CIVIL ENGINEERING LABORATORY Port Hueneme, California Distribution of this document is unlimited. WINDOWS FOR EXTERNAL OR INTERNAL HYDROSTATIC PRESSURE VESSELS PART II. Flat Acrylic Windows Under Short-Term Pressure Application Technical Report R-527 Y-FO15-01-07-001 by J. D. Stachiw, G. M. Dunn, and K. O. Gray ABSTRACT Flat, disk-shaped acrylic windows of different thickness-to-diameter ratios have been tested to destruction under short-term hydrostatic loading at room temper- atures, where short-term loading is defined as pressurizing the window hydrostatically on its high-pressure face at a 650-psi/minute rate till failure of the window takes place. Critical pressures and displacements of windows with thickness to effective diameter ratios less than 1.0 have been recorded and plotted. The critical pressures derived from testing flat windows in flanges with 1.5-inch, 3.3-inch, and 4.0-inch openings have been found applicable also to flanges with larger openings, so long as the larger windows are of the same t/D; and Do /D; ratios, where t is thickness of the window, D; is the clear opening in the flange and therefore the effective diam- eter of the window exposed to ambient atmospheric pressure and Dg is overall diameter of the window face exposed to hydrostatic pressure. The performance of flat windows under short-term hydrostatic pressure has been found to be comparable to that of conical windows with included angle equal to, or larger than 90 degrees. Distribution of this report is unlimited. Copies available at the Clearinghouse for Federal Scientific & Technical Information (CFSTI), Sills Building, 5285 Port Royal Road, Springfield, Va. 22151 Price $3.00 The Laboratory invites comment on this report, particularly on the results obtained by those who have applied the information. CONTENTS WERRAIINIOINOLEN CIS GT ele Nee Ocho Olu oO mmmeo m5 oo 6 6 ol dn dele teaho JIN ROIDIIGIICIN 55S Biers pots Gut Cn Fe neo a oo GoD DISGUISSIOUNT (8.6 0a Ste ial Gio 5) Gq ucnieAnitua 6 sa) cao HOMO kn one Vetinn a ea’ Gemenale we wre esis Meh Ayn AN ieee ak GT INNS or tent aire eae ce Efrectzor: Loading GonediihlOmSi ues suerte eit mien savcye ergot cia Tower ke= oyeeteont ore Effech orm Vaniationsiim Flange Designs. sss o cusvele sl ees) ene BINDING Stay cits enaeie suis asp ce ekse mise ei yeurem ucecPet slaerie ee winenicits shave. e APPENDIXES An — Discussion ot Window Mountings 0.) < «cs ss) eo isles) sbe B — Failure Modes of Flat Acrylic Windows. ........-+.2-+--. C — Axial Displacement and Critical Pressures of Flat Acrylic Windows Subjected to Hydrostatic Pressure InmDOEMypegiintlangescn saute. to eee, eae. tated) seeraune vel es REFERENCES WOU wm 0 0301 004038 coe Vl TERMINOLOGY The diameter of the clear opening in the flange and therefore the effective diameter of the window. The overall diameter of the window, or diameter of opening on high-pressure side of flange (minus clearance). Critical pressure or the pressure at which complete failure of the window occurs, resulting in explosive release of pressure from the vessel and frag- mentation of the window. The nominal or exact measured thickness of the acrylic window. INTRODUCTION The Naval Facilities Engineering Command is responsible for the construction and maintenance of underwater structures attached to the ocean floor. Such struc- tures may include instrumented or manned underwater surveillance or observation posts that will rely (at least in part) on visual observation and the transmission and reception of electromagnetic radiation through nonopaque areas of the hull for the performance of their mission. The Deep Ocean Laboratory of the Naval Civil Engineering Laboratory (NCEL) is carrying out studies to provide information on the design of underwater windows. The first report! on these studies discussed the behav- ior of conical acrylic windows under short-term pressurization. The report in hand presents information on the behavior of flat, disk-shaped acrylic windows under short-term pressurization. Flat, disk-shaped acrylic windows for high-hydrostatic-pressure applications have received very limited attention, and only a few facets of their behavior under hydrostatic loading have been investigated.2 Since flat windows possess characteris- tics not inherent in conical acrylic windows currently in use in underwater structures, it was considered desirable to investigate this type of window. The major advantage of flat windows is the commercial availability of glass, acrylic, epoxy, and polycarbonate material in polished transparent sheets or plates. Conical windows require considerable precision machining to adapt flat sheets or plates to the window flange. On the other hand, flat windows require only simple cutting and turning to transform flat material into usable windows. Furthermore, the fabri- cation of the flat-window mounting flange is also much simpler. Since the mating surfaces of both the window and flange are plane, the problem of replacement of windows is simplified when they become defective due to mechanical damage or the cracking which precedes failure under pressure. There may, of course, be some disadvantages associated with flat windows, such as smaller angle of vision for the same flange opening, but there are sufficient advantages inherent in flat windows to make them worthy of investigation for underwater structural applications. The underwater structures in which flat windows could be incorporated may be subjected to a variety of hydrostatic loadings. Thus a series of studies must be con- ducted to determine their behavior under short-term, long-term, cyclic, and dynamic loading. The first of the studies conducted deals with the short-term hydrostatic loading of flat acrylic windows, where short-term hydrostatic loading is defined as pressurizing the window on its high-pressure face at a 650-psi/min rate from zero (atmospheric) pressure to its failure pressure. The purpose of this report is to document the first experimental study. EXPERIMENTAL PROCEDURE The objective of the experimental study was to generate a set of performance curves that would serve as the basis for designing flat acrylic windows for use under short-term hydrostatic pressure. Also the critical pressures for windows had to be determined before further optical studies could be undertaken. Therefore, experi- mental data not only had to cover the whole range of depths encountered in the ocean, but also had to be applicable to flat windows of different thicknesses and diameters. To meet these objectives, window test specimens had to be designed that upon testing would provide the necessary data on which generalized window design curves could be based. This was accomplished by selecting two nondimensional parameters for dimensioning the windows. Use of the t/D; ratio and the Do /D; ratio (see "Terminology" and Figure 1) permitted not only the adequate description of any window, but also scaling window dimensions up or down. In order to cover the whole depth range in the ocean, the thickness component (t) of the t/D. ratio was varied from 0.125 inch to 2 inches, while to prove the applicability of experimental data to all possible window sizes the flange opening diameter (D;) component of the ratio was varied from 1.5 inches to 4.0 inches (Table 1). Flanges and some of the windows are shown in Figures 2, 3, and 4. The flange seat diameter ratio (Dg /D;) was not varied during the generation of the experimental data serving as basis for generalized design curves because there were indications (see Appendix A) that varying this param- eter would unduly complicate the study. For the same reason the various methods for retaining the window in the flange were not investigated, although earlier explor- atory experimental data shows’ that for some t/D; and t/Dg ratios, the type of edge restraint used on the window has a considerable influence on the critical pressure of the window. To avoid confounding the data, the windows in this study were not clamped or lapped in place, but simply sealed with grease into the flange cavity with approximately 0.005 to 0.010 inch radial clearance between them and the flange. This type of flat acrylic window mounting (shown in Figure 1) will be referred to in this report as the DOL type III flange. Although in designing a flat acrylic window to be safe for underwater application it is necessary to know the behavior of such windows under various types of hydrostatic loading, only the short-term strength of windows was considered in this study. The experimental evaluation of long-term and cyclic hydrostatic loading was relegated to future studies on this subject. In the present study it is considered sufficient for design purposes to have reliable data on only the magnitude of the displacement of the center on the window's low-pressure face and the critical pressure at which a window of any t/D. ratio fails under short-term loading. high-pressure face under hydrostatic pressure low-pressure face under ambient shoulder atmospheric pressure D, = 1.5 x Dj * Indicates maximum and minimum dimensions allowable. Figure 1. DOL type III flange configuration for short-term testing of flat acrylic windows. ie) i 4 5 6 | DeepOceanLab. © “= DeepOceanEng.Div. Figure 2. Flat acrylic windows and 1.50-inch (D,) flange used to determine the relationship between the window's critical pressure and t/D; ratio. Figure 3. Flat acrylic windows and 3.33-inch (D;) flange used to determine the relationship between the window's critical pressure and t/D; ratio. Laboratory ~-*» Deep 0 Figure 4. Flat acrylic windows and 4.00-inch (D;) flange used to determine the relationship between the window's critical pressure and t/D; ratio. 4 Table 1. Flat Disk Window Test Specimens (* represents a test group of five window specimens) Nominal Thickness (in.) * * * * * * * * In order to simulate the loads encountered by flat acrylic windows in underwater structures, window specimens were subjected to hydrostatic pressure loading in a hydrospace simulation chamber. The pressurization of the windows was conducted in a 16-inch naval gun shell converted into a pressure vessel4 with water at room temperature serving as the pressurization medium. The water was pressurized by two air-driven, positive-displacement pumps whose pumping rate was controlled within +50 psi/minute. Since previous studies! have shown that critical pressure of windows depends on water temperature as well as on pressurization rate, an effort was made to hold these variables constant for all the window tests. The standard pressurization rate was 650 psi/minute, and water temperature was held between 65°F and 75°F. The window test specimens for this study (Table 1) were fabricated by lathe turning Plexiglas grade G sheet stock. The circular disks (Figure 1) thus formed had an overall diameter (D,) of 0.010 inch to 0.020 inch less than the flange's high- pressure opening diameter (Do), permitting the window to seat in its flange cavity with 0.005 to 0.010 inch radial clearance. The manufacturer's tolerances for varia- tion in the nominal thickness of commercial sheets were accepted for the thickness tolerance of the finished circular flat windows. The finish of the disk edges was held to 32 rms. Dimensions recorded were the average of micrometer measurements taken at three different locations for the window's diameter and for its thickness. The hydrostatic testing consisted of pressurizing a flange-mounted window (Figure 5) until failure occurred. Since the window flange is open on one side to the atmosphere, window fragments were ejected upon its failure (Figure 6). The displacement of the window's low-pressure face during pressurization was measured to 0.001 inch by means of a wire that transmitted the displacement of the window to a mechanical dial indicator over a pulley system without any mechanical ampli- fication (Figures 5 and 7). To permit the attachment of a displacement indicator wire to the center of the window's low-pressure face, a short acrylic rod with a small transverse hole in one end was bonded to the window's surface with solvent- type cement. The displacement of the window under hydrostatic pressure was read directly from the dial indicator with a closed-circuit television system that permitted the operators to be in a safe location during the ejection of the window from its retaining flange when critical pressure was reached (Figures 8 and 9). As discussed in Appendix A, silicone grease was used as a pressure seal between the window and flange. The grease was spread by hand on the contact area of the low-pressure face and edge of the window. Sealing was completed when the window was placed in the flange cavity, rotated in place and pushed inward against the flange. This was done to distribute the grease uniformly over the area of contact and also to eliminate any small air bubbles trapped between the window and flange. This procedure proved to be adequate as it allowed no leakage of water to occur between the window and the flange. Care was exercised to insure that both the flange cavity and window were clean, since the flange was used for successive testing and tended to retain small fragments of previously tested specimens. Since the ejection of windows in many cases fragmented them into very small pieces, a reconstruction of the mechanism of material failure was usually impossible. To provide data that would give an insight into the mechanism of failure, some of the windows were pressurized only to a fraction of the window's critical pressure and then removed for inspection of their deformation and cracks (Appendix B). The explosive release of energy which accompanied window failure at higher critical pressures was quite harmful to O-rings, bolts, and flanges. To decrease the shock effects of this energy release, the cylindrical passage in the flange and the adaptor flange was filled with water after the window was in place. At the moment the window failed the water was forced through a 1/2-inch-diameter restrictive opening in the adaptor flange. This shock-damping method was sufficient to prevent the breaking of the eight 1/4-inch-diameter high-strength bolts connecting the window flange and adaptor flange. y pulley 7 0.007-in.-diam stainless steel wire flow restrictor 0.046-in.-diam wire 4 iT gS, Z 4 i (2 / eitccas 4 la end closure _@) guide filled y A j h eavity 7 V y) i eeient t/ t= ff eee j yy) y gs | ZL i flange My “ys of Ga lS Yj meus Li BO ~— 0.001-in. dial indicator Ws low- J, pressure ‘7 ©m VAG. face (a a x & NEEX \ ES = = deflection indicator js SSSR LMG MILA, a Figure 5. Schematic drawing of deflection measuring apparatus and flange mounting used in the testing of windows. 7 Figure 6. Ejection of window fragments by a high-pressure jet of water upon failure of the window. Figure 7. Deflection-measuring apparatus in place on pressure vessel. Air-driven positive displacement pumps (1) supply water under pressure to the Mk | 9-in. pressure vessel (2). Pressure is monitored by gage (3) and recorded. Dial indicator (4) is watched via closed-circuit television camera (5) and monitor (6). Operator is thus enabled to record data behind safety barricade. Figure 8. Schematic plan of experimental setup. Figure 9. Pressure gages, pumps, and closed-circuit television monitor used behind barricade during testing. 10 DISCUSSION General The flat acrylic windows failed either in flexure or in shear, depending on their t/D; ratio. The failure modes and mechanisms are discussed in detail in Appendix B, and deflection data are presented in Appendix C. In most cases, the center of the window was ejected in the form of small fragments, while in few cases in the low t/D; ratio range the center was not ejected, as the formation of large cracks in the window at low pressure vented the pressurized water, and thus removed the energy required for ejection of the window. The critical pressures of windows were found to vary exponentially with their t/D; ratio. When the critical pressures of windows with the same D,/Dj and t/D; ratios, and effective diameters of 1.50, 3.33, and 4.00 inches were plotted on the same graph (Figure 10) they were found to fall in the same failure region. This indicates that the critical pressure of a flat acrylic window is dependent only on the t/D; ratio (and the mounting of the window in the flange). The displacement of the windows also varied with their t/D; ratio. Comparison of displacements of windows having effective diameters (D;) of 1.50 inches (Figure 11), 3.33 inches (Figure 12), and 4.00 inches (Figure 13) shows that the displacements, besides being a function of t/D: ratio are also a function of Dj. Although there are insufficient experimental data to establish a reliable relationship between the magni- tude of displacement and the D; of the window in DOL type III flange, it appears that the displacement is directly proportional to the D; of the window. The critical pressures of flat acrylic windows when compared to the critical pressures of conical acrylic windows investigated in previous studies! were found to be approximately of the same magnitude as the critical pressures of conical windows of same t/D; ratio and having an included angle equal to, or larger than 90 degrees. Thus, it would appear that the flat acrylic windows mounted in the DOL type III flange are as resistant to short-term hydrostatic loading as the conical windows with included angle equal to, or larger than 90 degrees. A technical discussion of the relationship between the critical pressure, Do /Dj ratio, radial clearance between the window and the flange, and the method of sealing is presented in detail in Appendix A. A technical discussion of the mode of failure of flat acrylic windows is presented in detail in Appendix B. 11 "G*| OF ponba o1yos 'q/°q YyIm smopulm o1)A190 fO]4 JO} C144 ‘a/3 pun ainsseid {po!4149 UBseMjoq diysuol4yoye1 pOyUsWIiedxe ayy “Q{ aunBiy onpy 'q/t Ol 60 8°0 £0 90 S‘0 v0 £0 c'0 L°0 0 Epes: | AS GinG9. ainjosadwa} 194d ui /isd 997-909 Uolsoztunssaid yo ayoy SSa@UHdIIY} |OUIWOU YC F a2uD1a|O¥ ssaUuxrIYy] y F 9 svjBixalgq [Dl4ayow | wnWwiuly SMOPUIM BAI} Wod} DJOp 8 aboiaay |DyUauiadxa WAWIxDW JO 1844095 smopulm (!q) ° al 9L 02 eee of @uUOZ aiN| ID} V7. 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Flanges employed in investigation of window mountings. youl-g"z ‘uolsoBiyseau! Bulyunow mopulm euy ul pasn (‘q youl-c*|) sebunjy *Z- e4nBi4 7s i= res in. (nominal) 1/64 in. radius 1.960 1.960 in. () 1.940 in. 940 in. 0.160 in. a omISohins in. = t= 3/4 in. (nominal) (b) t= 3/4 in. (nominal) 3.960 in. (c) 3.940 in. 0.125 in. 0.160 in. { 0.120 in. 0.150 in. J t = 3/4 in. (nominal) a ee 999 in. (d) 3.998 in. * Indicates maximum and minimun dimensions allowable. Figure A-3. Details of flat acrylic windows used in investigation of window mountings. 22 Figure A-4. Flat acrylic windows used with O-ring sealing technique in the investigation of window mountings. Deep OceanLab. «‘a%/; DeepOceanEnsg.Dw. Figure A-5. Flat acrylic windows used with plane surface (grease) sealing technique in the investigation of window mountings. 23 The influence of window fit on the critical pressure was investigated with windows having the same D,/D; ratio and thickness (Figures A-3a and A-3b) fitted into flanges with different major diameters (Figures A-la and A-1b). In one of the flanges (Figure A-la) the pretest radial clearance between the windows and the flange was either 0.001 inch (Figure A-3b) or 0.025 inch (Figure A-3a), while in the other flange (Figure A-1b) the clearance was 0.125 inch. A radial clearance of 0.001 or 0.025 inch when the window is subjected to hydrostatic pressures above 10,000 psi is calculated to result in an interference fit between the window and the flange, thus resulting in a lateral constraint of the window. The flange (Figure A-1b) and window (Figure A-3a) assembly with the initially larger radial clearance of 0.150 inch, even when subjected to hydrostatic pressures that destroyed the window, did not cause it to be wedged inside the flange opening. With such an arrangement it was possible to determine whether the wedging in of the window in the flange under hydrostatic pressure had any measurable influence on the critical pressure of flat windows. DISCUSSION Relationship Between Critical Pressure and D,/D; Ratio Tests to determine the relationship between critical pressure and D,/D; ratio were conducted with five 2-inch (D,) windows ina 1.5-inch (D;) flange and five 4-inch (D,) windows in a 1.5-inch (Dj) flange. The windows were sealed in the flange with the aid of silicone grease, which was liberally applied to the bearing as well as the radial surfaces of the flat circular window. For both the 2-inch and the 4-inch (D_) windows, the radial clearance between the window and the flange was 0.025 inch. When tested to destruction, the average critical pressure of 2-inch (D,) windows was 18,490 psi (Table C-1), while the critical pressure of 4-inch (D,) windows was 19,190 psi (Table C-16). The small difference between the average critical pressures of the 2-inch and the 4-inch (D,) windows with a 0.5 t/D; ratio seemed to indicate that varying the D,/D; ratio from 1.33 to 2.67 did not signifi- cantly influence the critical pressure of flat acrylic windows, since the maximum collapse pressure found in 2-inch (D,) windows (18,900 psi, Table C-1) overlapped the minimum collapse pressure found in 4-inch (D,) windows (18,800 psi, Table C-16). Since the critical pressures of windows with 1.33 and 2.67 D, /D; ratios are approximately the same so long as their t/D; ratios are identical, a flange with an intermediate D, /Dj ratio of 1.5 was selected for the conduct of the main flat- window study program. 24 Relationship Between Critical Pressure and Sealing Technique The evaluation of window sealing methods was conducted with a total of 20 windows (10 untested windows in addition to the 10 already tested in the evalua- tion of D,/D; ratio study). Five of the additional windows had a 1.33 D,/D; ratio and a 0.5 t/D; ratio and a Dy of 2 inches (Figure A-3b), while the five others had a 2.67 Do /D; ratio and a 0.5 t/D; ratio with a Do of 4 inches (Figure A-3d). All 10 windows had a nominal 1/8-inch-diameter radial O-ring seal located in a groove machined in the window 0.125 inch below its high-pressure face. When the windows were tested to destruction in appropriate flanges (Figures A-la and A-Ic), the critical pressures of the O-ring-equipped acrylic flat windows were 19,060 (Table C-2) and 19,270 psi (Table C-17) — reasonably close to the pressures (18,490 and 19,190 psi, Tables C-1 and C-16) of the corresponding windows sealed in the flange with silicone grease. The displacements of the O-ring-equipped win- dows were approximately the same as the displacements of grease-sealed windows with the identical D,/Dj; and t/Dj; ratios (Table A-1). Thus, both seal designs are of equal desirability, so long as the sole criterion for their selection is their influence on the critical pressure of the flat acrylic window. For the main body of the flat window study program, where the relationship between the t/D. ratio and critical pressure is investigated, the grease-seal design was selected. This design permitted the investigation of very thin, flat windows into whose body an O-ring seal could not be incorporated. Relationship Between Critical Pressure and Window Fit Evaluation of the effect on critical pressure of radial clearance between the flat acrylic window and the steel flange was conducted with a total of 25 windows (5 untested windows in addition to the 20 tested in previous tests). The radial clear- ance between the acrylic window and its flange varied from one group of window specimens to another. One group of 10 windows tested previously had a radial clearance of 0.001 inch (Figures A-3b and A-3d); another previously tested group of 10 had a clearance of 0.025 inch (Figures A-3a and A-3c). The group of 5 win- dows tested in addition to the 20 windows tested previously had a radial clearance of 0.150 inch (Figure A-3a). Appropriate flanges (Figures A-la, A-1lb, and A-1c) were used with the windows to result in 0.001-inch, 0.025-inch, and 0.150-inch clearances. When the critical pressures of all the window groups were compared to each other, no significant difference in critical pressures could be found between the groups of windows possessing radial clearances of 0.001 inch and 0.025 inch, respectively. There was, however, a significant difference between the 16,960-psi (Table C-3) critical pressures of the window group with a radial clearance of 0.150 inch and the 25 pressures of two window groups with the 0.001-inch (19,060 psi and 19,270 psi) and 0.025-inch (18,490 psi and 19,190 psi) radial clearances. The difference in the average critical pressure was approximately 10%, the windows with the 0.150-inch radial clearance failing at the lower critical pressures. It would thus appear that it is to the designer's advantage to epecihy small clearances between the flat acrylic window and its flange, since by doing this he accomplishes two desirable objectives. His design not only results in a window that has superior critical pressure, but also is easier to seal in the flange. The small radial clearances are ideal for sealing the window in the flange with a radial O-ring seal, or silicone rubber potting-type seal. Because of these findings, the main body of window test program was conducted with windows that fit into the steel flanges with a 0.005- to 0.010-inch radial clearance. FINDINGS The exploratory tests in the window mounting investigation seemed to indicate that (1) varying the D,/Dj ratio from 1.33 to 2.67, (2) changing the radial clearance between the window and the flange from 0.001 inch to 0.025 inch, and (3) substituting a radial O-ring seal for a grease seal have no significant influence on the critical pressures of flat acrylic windows with a 0.5 t/D; ratio. When the radial clearance is increased to 0.150 inch, the critical pressure of the 0.5 t/D; ratio window is reduced. Whether these conclusions are applicable to flat acrylic windows with t/D. ratios other than 0.5 is unknown. Some of the data generated in the main body of the flat window program have raised serious doubts that the conclusions hold for the whole t/D; range. For example, the critical pressure of windows with a nominal 0.167 t/D; ratio and a 1.5 Dg/D; ratio was discovered to be 723 psi for a radial clearance of 0.005 inch and 2,100 psi for a radial clearance of 0.001 inch. Thus, it would appear that for t/D, ratios less than 0.5, any change in radial clearance below 0.005 inch influences its critical pressure considerably. Future studies will attempt to clarify this problem. 26 Appendix B FAILURE MODES OF FLAT ACRYLIC WINDOWS DISCUSSION In nearly all cases for all sizes of windows tested, failure began with radial cracking on the window's low-pressure face. Radiating outward from near the center, the cracks commonly formed a nonsymmetrical, three- or four-pointed figure. This form of cracking preceded failure in nearly all cases and is assumed to be the beginning of failure (Figures B-1 and B-2). Depth of cracking was found to be a function of the thickness, t/D; ratio of the window, and the pressure of the fluid. Since audible cracking was noted during testing, it is postulated that these radial cracks were rapidly formed, terminating at the window's D;. Depth of cracking in the low-pressure face in most cases was found to be a small fraction of the window's thickness. With additional pressurization, a second stage of failure began to develop. A conchoidal or "cupped cone" fracture was established, emanating from the base of the radial cracks and proceeding radially inward and circumferentially (Figures B-3 and B-4). The formation of a conchoidal fracture surface preceded failure in all cases observed. Simultaneously, as the conchoidal fracture surface was formed, the radial cracks increased slightly in depth (Figures B-5 and B-6). Cracks did not deepen uniformly and new cracks developed with further pressurization. The additional cracking gave rise to formation of new and deeper conchoidal fracture surfaces. Additional pressurization caused the circumferential expansion and coalescence of the conchoidal fracture surfaces into one conical fracture surface as well as an increase in fracture depth (Figures B-7 and B-8). Cracking and formation of con- choidal fracture surfaces continued (Figures B-9 and B-10) deeper into the window's thickness until the critical pressure was finally reached resulting in the fragmentation and expulsion of the window's low-pressure face (Figures B-11 and B-12). The size of the central hole was a function of t/D; ratio and Dj. The conical cavity resulting from the expulsion of the center portion of the window consistently assumed an approximate angle of 30 degrees with the high-pressure face. Cracking between the window's D; and Dg occurred concentrically with the window's circumference, nearly perpendicular to and emanating from the low-pressure face. This cracking was sometimes accompanied by small radial intersecting cracks (Figure B-9). This form occurred with larger t/D; ratios, failure still assuming the conical surface form. The circumferential cracks sometimes penetrated the window's thickness but still did not constitute a plane of failure. 27 “isd 79 uolfoOZluNsseid wNnwIxDW) “| 80°O 4O O1}DJ ‘q/4 D YFIM MOPUIM D144 -YOUI-ZZ 1° Paj!oy Ul Usa4yod 49D *Z-g eunBiy *"SMOPUIM JO 89D} a1Nsseid-Mo| Ul UJayfod 4ODID |DIpoI jO!yluy *|-g aunBi4 uoly3aS [O4seawdIp 2D} ainssaid-moj Buimous Mala do} °d 28 "isd Q66’Z uolyoziinsseid wnwixoy ! “ZEZO JO C144 *q/t DO YYIM MopUlM 4O1YJ-YOuI-Gce"Q pay!ny Ayjorysod ul Usa4yod 24INJDDAY |OP!OyYDUO y-q e4n614 *yuaudojanap Aj10e ‘use44od BINJODAY JOPIOYDUOD eBHpjs puodeg ‘E-g e1nbi4 uoljdaS |[DIJaWDIP at Pet FL LL 82D} ainssaid-mo; Buimoys mata do} 2q 29 “isd QOL ‘OZ uolyOZIINSseid WNWIxDW *Z/G°O "yuowdojerap jo eBoys paouDApo JO O14DA ‘/} D UJIM MOPUIM 49144 ‘usajyod einyopiy joproyouoy = *G-g einbi4 -YOUI~/Gg"Q Ul Usa4yod aunyoD.y JOproysuos yo ebpys peouDApy “9-q ainBi4 UOI}IES |DAJSWDIP ae LF ST 2D} einssaid-mo| Buimoyus mata doy 30 “isd 0098 | UolfOZLINsseid WNWIxOW ‘Ogp7"0 JO 014041 'G/4 D YJIM MOPUIM HOIU4 -YOUI-GE7"*0 DU! aIN|!D} OF JOL4d 4snl SOINJODIy JOPIOYDUOD BHulosajpo0> + *g-g eunbi4 *payspnoiddo S] Binsseid ;OOI}1ID SH SEINJODIJ JOPloyouos jo aduadse;po5 yusulWWW| *7-g eunBi4 Uo!l}IaS |DIJSWDIP Ss 2D} ainsseid-moj Buimoyus mata doy 31 *MOPUIM OYJ OJU! BANJODIY |OPIOYDUOS sy 4oO ysdep uolyo1youed pun 'g s mopuim ay} JO UOISNIYX® BION) “ISd QO0‘6L 04 peziinssoid OSp"Q 4O O14D1 -q/t YIM MOPUIM 4D14I-4OUI-GE/"0 YW “OL-@ 21614 *payopoiddn si aunsseid JDOIF14D SO SB4NJODIy |OPIOYDUOD Jo 99U99S9|D09 4o eBpjs paouDApD uy *6-g ainbi4 uoljoas |D4JJaWDIP a2Dj ainssaid-mo} Bulmoys mala do} °d 32 "isd QQO’EL 4° P2}!0} YOIUM QOP"O JO O14D4 'q/} D YJIM MOPUIM }91UJ-YOUI-EQ9'0 Y “ZL-g e4nb!4 390; ainssaid—yBiy 29D} ainsseid— Mo} *SOODJINS DINJODIAY JO91U09 yO adUEDsa}/D09 a4a;dwWos SMO}JO} YO!YM ONy toy yo addy ay] “| [-g a1NBI4 uoljaas [O4seuDIp a2D} ainssaid-mo; Buimoys maid doy 33 Considerable cold-flow cratering occurred on the high-pressure face before the critical pressure was reached (Figure B-13). Both elastic and plastic extrusion on the low-pressure face were also experienced by the window at this time (Figure B-14). Windows whose t/D; ratios exceeded about 0.50 failed predominately by shear; the conical fracture surface was unable to penetrate the thickness of the material (Figures B-15 and B-16). At the critical pressure, the entire window was penetrated by discontinuous cracks and the central portion (bounded by D;) was completely ejected. RESULTS OF TESTS 1.5-Inch (D;) Windows The 1.5-inch (D;) windows were tested in groups of five; the nominal t/D; ratios included the range from 0.083 to 0.667. For each group, critical pressure was plotted against the t/D; ratio (Figure B-17) and pressure was plotted against the window's central displacement. The windows having t/D; ratios less than 0.2 exhibited both flexural and conical failures. Parametric considerations were the window's radial clearance, pressurization rate, and grease-seal thickness. No attempt was made to isolate these effects in this study. For a t/D; ratio between 0.2 and 0.4 the principal failure was conical, the cone's apex reaching the high-pressure face toward the upper limit of critical pressure (Figure B-12). Audible cracking during pressurization occurred mostly at levels above 75% of critical pressure and occurred fairly consistently between 90% of critical pressure and failure. Windows of t/Dj; ratios greater than 0.4 failed predominantly by shear, fragmentation being so complete that sometimes none of the window material was retained in the flange. Extrusion of these windows caused audible cracking to occur many times before critical pressure was reached. For t/D; ratios of less than about 0.25 pressurization to approximately 70% of critical pressure resulted in no visible evidence (to the naked eye) that the windows had been pressurized. For t/D; ratios between 0.25 and 0.55, the extrusion of the window at 70% of critical pressure caused a shallow impression of the flange seat to appear (Table B-1); however, on examination after release of pressure no visible impairment of optical quality inside this impression was apparent to the naked eye. For windows of t/D; ratios greater than 0.55, the development of cracks accompanied extrusion and depression. Details of flanges used in testing the 1.5-inch (D;) windows are shown in Figure B-18 and an in-place schematic is shown in Figure B-19. 34 “ainssaid isd QQ9’8| Of peyoalqns mopulm O14D4 ‘a/s 067°0 4yO1UJ-YOUI-CE/*Q D JO adn} aiNssoid -Mo| payioddnsun ayy yo uolsnsyxg i $ 4 4 Al q 2e41n6i 4 “ainssaid isd QQ9’g| O4 peyoalqns mopulM Ol4p4 ‘d/s 0447°0 ‘D14J-YOUI-Ge/*GQ BJO apis ainsseid -yBiy ayy uo Bulsayosd MO]} D14S0]q El q e1inbi4 35 "Isd QOE’G| 42 Pay!ny Yorum MopulM 1404 !G/4 Q0G'O ‘42144 -YoUul=ZEep" | BD Ul SIN|IDJ addy-speys °91-g eanbi4 "solyo4 !q/4 aBiny YyIM SMopUIM 0} UOWWOS ainjioy adAy-spEeYg “cG{-g einBi4 uoljaesS [O4saWDIp 92D} a4nssaid-mo; Buimoys mata doy 36 "SMOPUIM 91|A190 4O]4 (1G) YOUI-QG"| 4O C1404 'q /} pu a.insso.d jooI4119 UBamjog diysuolyojey *7Z[-g e1nB14 oupy iq/t ol 60 8°0 £0 9°0 S‘0 v'0 €°0 Z'0 ‘0 0 WOWULW, SMOPUIM DAI} woiy DJOP josUSWIadxe wnwWIxDW JO 4044095 eBboisay eUOSal faces MOPUIM NIA NRAAE A ANDNTN RARE RANAANNANANASS “Ul OVeZ | | 40SZ-S9 ainjosadway 1940) uiwisd 997-009 uolfozZIuNssaid yo a4Dy SSOUHIIYY [DUIWOU % GF adupjajO4 SSOUxIIY | 9 svjBixald [OlueyOW ‘ALON 37 (gOL * isd) ainssaig [DII}1I5 Table B-1. Extrusions of Some Flat Disk Windows Measured After Pressurization % of Group Specimen Measured2/ Average No. Set (in.) Critical Pressure Jy Thickness measured prior to pressurization. 2/ Measured 7 days after pressurization. 3/ See Figure B-26. Note: The maximum pressure was immediately relieved by either (a) bleeding pressurized fluid from the vessel or (b) the development of leaks around the window caused by deformation of the window under pressure. 38 \ | f 9/32-in. diam, 4 places, SS 2.248 in. 64 we 90 degrees apart 7 L 1.501 nd 1.499 in. Test Flange (mild steel) 7.25 in. 8.0 in. — 2.750 in 9/32-in. diam, 4 places, i “ . 90 degrees apart 32 0.070 in Ve Vs, Wh: W. 33 L | ee in. chamfer edge 1.498 in. 1.497 in. Alignment Pin 4 in. * Indicates maximum and minimum dimensions allowable. Backup Plate (mild steel) Figure B-18. Details of flange assembly used to determine the relationship between the window's critical pressure and t/D; ratio for 1.50-inch (D;) windows. 39 7) ae eeneeeenn Ni 0D SL of KN 3.33-Inch (D;) Windows The 3.33-inch (D;) windows were tested in groups of five and had t/D; ratios ranging from 0.036 to 0.600. For each group the critical pressure was plotted against the t/D; ratio (Figure B-20) and the pressure was plotted against deflection. Windows with t/D: ratios of less than 0.1 exhibited both the conical and flexural failure modes, whereas windows with t/D; ratios between 0.1 and 0.4 failed only in the conical fracture mode previously described. Concentric cracking was observed toward the upper t/D: limit. These cracks propagated from the low-pressure face. Shear failures were characteristic of windows whose t/D: ratios were greater than about 0.4 (Figure B-16). Combined with the shear failure pattern were the various combinations of radial and circumferential cracks discontinuous throughout the window. Details of flanges used in testing the 3.33-inch (D-) windows are shown in Figure B-21 and an in-place schematic is shown in Figure B-22. 4,00-Inch (D;) Windows The t/D; ratios of the 4.00-inch (D;) specimens ranged from 0.058 to 0.498. Four groups consisting of five windows each were used in the comparative study. Critical pressure was plotted against the t/D; ratio (Figure B-23) and pressure was plotted against deflection. Results of limited testing of 4.00-inch (D;) windows were consistently comparable with those for the 1.50-inch, and 3.33-inch (D;) specimens. Flexural and conical surface failures were witnessed for t/D; ratios less than 0.1 and conical failures were observed for t/D; ratios between 0.1 and about 0.4. Shear failure was dominant for t/D; ratios greater than about 0.4. Details of flanges used in testing the 4.00-inch (D-) specimens are shown in Figure B-24 and an in-place schematic is shown in Figure B-25. Extrusion, retained as permanent set in the specimens (Figure B-26), is summarized in Table B-1 for specimens which were not pressurized to critical pressure. SUMMARY Failure mechanisms characteristic of the 1.50-inch (D;) windows were found also to be characteristic of the 3.33-inch and 4.00-inch (D;) windows so long as t/D; ratios were similar. Critical pressures derived from testing of windows having a different D; in the DOL type III flange design were found to be comparable so long as the D,/D; ratio was maintained at 1.5, temperatures were within the 65°F to 75°F range, and the radial clearance was kept to less than 0.010 inch. Al “sMOpUIM 91[A190 4O]J (1G) Youl-EE'E JO 1401 'G/} pu ounsseid Joo! 1119 UBEeMjaq diysuo!iD}ay “OZ-q e461 4 ooy iq /s Ol 60 8°0 £0 S°0 4oS2-S9 ainposadwia}y 1940 M uiw/isd 9Q/-009 uol}pZlunsseaid jo ayDy sSaUHdIYF [OUIWOU YC Fz a2up1a{O} SSOUxHDIY] 95 svj6ixaly |DluayoW *dLON jopusuiadxs JO 4944095 ee a ue DEB A SMOPUIM BAI} aBboiaay Wot OIeP wnwixoWw f | -u! 086'7 x U4! 0667 87 "a/qDMO||D SUC!SUAWIP WNWIUIW PUD WNWIxDW sa}D>!Pul , ce (cOL xX Isd) ainssaig [DI14145) 42 ssembly used to determine the relationship between the window's Seat 7) Figure B-21. Details of a e and +/Dj ratio for 3.33-inch (D;) windows. ou £ oO SS (oe) » KN oe MWS SERS. nfj000 ISS ofan Figure B-22. Schematic of 3.33-inch (D;) window and flange in e Mk | 9=inch pressure vesse "SMOPUIM D1]AIDD 40]} Ol 60 WOU UW aBboiaay winwixDW SMOPUIM SAlf Woy DJDp [OyUSWIadxa JO 1a4j09¢ OlyDy ‘ays “@[QDMoO||D suOoISUSWIp WNWiulw pup winwWixpw sajpsIpuy , doSL-S9 uiw/isd QQ/-009 SS@UHDIYS |DUIWOU YC + 5 svjbixayy "UL 86'S _. | PemsnOS S535) ainjosaduiay 1940M uolypzlunsseaid jo ayDy a2uDI9a}0} sseuyd1Y4] [Ol4sLOW “LON (‘q) youl-go"p Jo Olpu ‘d/4 pup oinsse.id joo14149 ay} UaaMmjeq diysuoijojay “ez—g ainbi4 so = oO N v~ 87 cE ig OL * isd) ainssaigq [DII4ID nd +/D; ed to determine ratio for 4.00-inch (D;) windows. the relationships between the window's critical pressure a Figure B-24. Details of flange us Figure B-25. Schematic of 4.00-inch (D;) window and test flange assembled to the end closure of the Mk | sse 9-inch pressure ve Figure B-26. Permanent extrusion of low-pressure face of a flat acrylic window having a 0.490 t/D; ratio; window pressurized to 67% of ultimate critical pressure. 47 Appendix C AXIAL DISPLACEMENT AND CRITICAL PRESSURES OF FLAT ACRYLIC WINDOWS SUBJECTED TO HYDROSTATIC PRESSURE IN DOL TYPE III FLANGES 48 Table C-1. Hydrostatic Test Data for Nominal 1.50-Inch (D;) -2.00-Inch (Do) Flat Acrylic Windows, Test Specimens 1-5 (Sealed with grease; radial clearance 0.020 to 0.030 inch; nominal DEAD; ratio 1.33) Specimen Number Parameter Thickness (in.) De (actual, in.) Temperature (CF) t/D; Ratio (actual) Pressure at Failure (psi) 17,500 | 18,600 | 18,600 | 18,900 } 18,850 | 18,900 | 18,490 } 17,500 17 Not included in average pressure value. 49 Table C-2. Hydrostatic Test Data for Nominal 1.50-Inch (Dj) - 2.00-Inch (Do) Flat Acrylic Windows, Test Specimens 6 - 10 (Sealed with O-ring; radial clearance 0.0005 to 0.0010 inch; nominal Dg /Dj; ratio 1.33) Specimen Number Parameter Thickness (in.) D acftua ns 9 (actual, in.) Temperature (CF) t/D; Ratio (actual) Pressurization Rate (psi/min) Pressure (psi) Pressure at Failure (psi) 50 Table C-3. Hydrostatic Test Data for Nominal 1.50-Inch (D;) -2.00-Inch (Do) Flat Acrylic Windows, Test Specimens 11 - 15 (Sealed with grease; radial clearance 0.145 to 0.155 inch; nominal Dg /D; ratio 1.33) Specimen Number Parameter Thickness (in.) D, (actual, in.) Temperature (°F) t/D; Ratio (actual) Pressurization Rate (psi/min) Pressure (psi) Pressure at Failure (psi) 17,700 | 16,700 | 15,650 | 17,900 | 16,850 | 17,900 | 16,960 | 15,650 51 | Table C-4. Hydrostatic Test Data for Nominal 1.50-Inch (D;) -2.25-Inch (Do) Flat Acrylic Windows, Test Specimens 16 -20 (Sealed with grease; radial clearance 0.005 to 0.010 inch; nominal Dg /Dj; ratio 1.5) Specimen Number Parameter Thickness (in.) Do (actual, in.) Temperature (°F) t/D; Ratio (actual) Pressurization Rate (psi/min) Pressure (psi) 0.010 | 0.026 0.017 | 0.042 400 450 Displacement at Failure (in.) | 0.067 0.060 0.050 re 0.083 0.083 0.065 0.050 1. Pressurized slowly to facilitate taking displacement data. Notes: 2. Grease sealing and pressurization procedure may have caused erratic results. a2 Table C-5. Hydrostatic Test Data for Nominal 1.50-Inch (D;) -2.25-Inch (D,) Flat Acrylic Windows, Test Specimens 21 -25 (Sealed with grease; radial clearance 0.002 to 0.005 inch; nominal D,/Dj ratio 1.5) Specimen Number Parameter Thickness (in.) Dg (actual, in.) Temperature (°F) t/D; Ratio (actual) Pressurization Rate ( (psi/min) Axial Displacement of Center Point on Window's Low-Pressure Face (in. 0.012 | 0.021 0.008 | 0.033 | 0.030 | 0.033 | 0.021 0.008 100 0.047 0.047 Displacement at Failure (in.) | 0.028 | 0.038 ina te 0.044 | 0.049 | 0.049 | 0.040 | 0.028 meewme fe fete[=[m[m>e]« Note: Grease seal was thin. 53 Table C-6. Hydrostatic Test Data for Nominal 1.50-Inch (Dj) -2.25-Inch (Do) Flat Acrylic Windows, Test Specimens 26 - 30 (Sealed with grease; radial clearance 0.002 to 0.005 inch; nominal D,/Dj; ratio 1.5) Specimen Number Value Parameter Thickness (in.) D s (actual, in.) Temperature (°F) t/D; ratio (actual) Pressurization Rate (psi/min) Note: Grease liberally applied. 54 Table C-7. Hydrostatic Test Data for Nominal 1.50-Inch (D;) -2.25-Inch (D,) Flat Acrylic Windows, Test Specimens 31 -35 (Sealed with grease; radial clearance 0.005 to 0.010 inch; nominal D,/D; ratio 1.5) Specimen Number Parameter Thickness (in.) Dg (actual, in.) Temperature (CF) t/D; Ratio (actual) Pressurization Rate (psi/min) Pressure (psi) Pressure at Failure (psi) 1,430 1,210 1,430 1,240 | 1,100 | Note: Erratic deflection. 55 Table C-8. Hydrostatic Test Data for Nominal 1.50-Inch (D;)-2.25-Inch (Dj) Flat Acrylic Windows, Test Specimens 36 - 40 (Sealed with grease; radial clearance 0.005 to 0.010 inch; nominal D,/Dj ratio 1.5) Specimen Number Parameter Thickness (in.) D, (actual, in.) Temperature (°F) +/D; Ratio (actual) Pressurization Rate (psi/min) (in.) Displacement at Failure (in.) | 0.046 | 0.045 | 0.048 | 0.053 | 0.064 | 0.064 | 0.051 | 0.045 1. Thin grease seal coating. Notes: 2. Amount of cement used on deflection pin may have significant effect on thin windows. 56 Table C-9. Hydrostatic Test Data for Nominal 1.50-Inch (D;) -2.25-Inch (Do) Flat Acrylic Windows, Test Specimens 41 -45 (Sealed with grease; radial clearance 0.000 to 0.005 inch; nominal D,/D; ratio 1.5) Specimen Number Value Thickness (in.) D, (actual, in.) Temperature (°F) t/D; Ratio (actual) Pressurization Rate (psi/min) Pressure (psi) Axial Displacement of Center Point on Window's Low-Pressure Face (in.) Displacement at Failure (in.) Pressure at Failure (psi eae 0.142 | 0.100 | 0.085 | 0.093 | 0.142 | 0.105 | 0.085 ee 2,000 | 2,100 | 2,100 | 2,200 | 2,200 | 2,100 | 2,000 1. Abort caused by use of 1,000-psi gage. 2. Grease liberally applied. 3. Audible cracking at about 900 psi and 1,600 psi. Notes: oF, Table C-10. Hydrostatic Test Data for Nominal 1.50-Inch (D;) -2.25-Inch (Do) Flat Acrylic Windows, Test Specimens 46 - 50 (Sealed with grease; radial clearance 0.005 to 0.010 inch; nominal D,/Dj ratio 1.5) Specimen Number Parameter Thickness (in.) Dg (actual, in.) Temperature (°F) t/D; Ratio (actual) Pressurization Rate (psi/min) Pressure (psi) Note: Grease liberally applied. 58 Table C-11. Hydrostatic Test Data for Nominal 1.50-Inch (D;) -2.25-Inch (Do) Flat Acrylic Windows, Test Specimens 51-55 (Sealed with grease; radial clearance 0.005 to 0.010 inch; nominal Dg /D; ratio 1.5) Specimen Number Parameter Thickness (in.) Dg (actual, in.) Temperature (°F) t/D; Ratio (actual) Displacement at Failure (in.) 0.152 0.146 0.122 0.152 0.130 0.122 Pressure at Failure (psi) 85550: || 8,450 | 7,450: || 7,300 | 8,550 |) 7,810) |- 7,300 Jy Deflection wire became disengaged. Notes: 1. Grease liberally applied. 2. 500-psi preload. 3. Audible cracking at about 7,000 psi. Sy) Table C-12. Hydrostatic Test Data for Nominal 1.50-Inch (D;) -2.25-Inch (Dg) Flat Acrylic Windows, Test Specimens 56 - 60 (Sealed with grease; radial clearance 0.005 to 0.010 inch; nominal D,/D; ratio 1.5) Specimen Number Parameter Thickness (in.) D, (actual, in.) Temperature (°F) t/D; Ratio (actual) Pressurization Rate (psi/min) Pressure (psi) Saioemevoroiets)fose| | | || |_| Pressure at Failure (psi 13,300 | 13,800] 13,075 | 13,150 | 13,000 | 13,800 | 13,265 } 13,000 J/ Deflection wire became disengaged. Notes: 1. Grease liberally applied. 2. 500-psi preload. 3. Cracking at about 9,000 psi and 13,000 psi. 60 Table C-13. Hydrostatic Test Data for Nominal 1.50-Inch (D;) -2.25-Inch (Do) Flat Acrylic Windows, Test Specimens 61-65 (Sealed with grease; radial clearance 0.005 to 0.010 inch;'nominal D,/D; ratio 1.5) Parameter Thickness (in.) Dy (actual, in.) Temperature (°F) t/D; Ratio (actual) Pressure (psi) 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000 11,000 12,000 13,000 14,000 15,000 16,000 17,000 18,000 19,000 Pressurization Rate (psi/min) Specimen Number Value 62 63 64 65 Max Avg 0.733 0.734 0.735 0.735 0.735 0.734 2.239 2.241 2.24] 2.240 2.24] 2.240 69 7\ 66 68 71 0.488 0.489 0.490 0.490 0.490 0.489 670 682 669 637 682 Axial Displacement of Center Point on Window's Low-Pressure Face (in.) 0.001 0.000 0.002 0.001 0.002 0.002 0.001 0.000 0.001 0.000 0.011 0.002 0.003 0.011 0.005 0.000 0.013 0.012 0.018 0.016 0.003 0.018 0.012 0.003 0.021 0.012 0.023 0.017 0.004 0.023 0.015 0.004 0.022 0.018 0.029 0.026 0.017 0.029 0.022 0.017 0.029 0.025 0.034 0.026 0.017 0.034 0.026 0.017 0.029 0.033 0.035 0.027 0.018 0.035 0.028 0.018 0.036 0.033 0.040 0.039 0.035 0.040 0.036 0.033 0.043 0.038 0.048 0.039 0.035 0.048 0.041 0.035 0.046 0.045 0.053 0.052 0.036 0.053 0.046 0.036 0.052 0.052 0.061 0.053 0.047 0.061 0.053 0.047 0.059 0.059 0.068 0.065 0.048 0.068 0.060 0.048 0.071 0.064 0.075 0.065 0.063 0.075 0.068 0.063 0.078 0.090 0.095 0.072 0.076 0.095 0.082 0.076 0.097 0.099 0.106 0.084 0.095 0.106 0.096 0.084 0.112 0.121 0.129 0.107 0.109 0.129 0.116 0.107 0.143 0.145 0.125 0.131 0.145 0.135 OMIZ5: 0.174 0.185 0.143 0.164 0.185 0.161 0.143 0.236 0.177 0.236 0.202 0.177 0.256 0.256 0.253 0.252 19,650 19,650 | 19,1001/} 18,600 Displacement at Failure (in.) 0.252 0.255 ) Pressure at Failure (psi gee 19,200 | 18,600 Jy Averaged with preliminary tests. Notes: 1. Abort due to pump failure at 16,600 psi. 2. Audible cracking at about 14,000 psi. 61 Table C-14. Hydrostatic Test Data for Nominal 1.50-Inch (D;) -2.25-Inch (Do) Flat Acrylic Windows, Test Specimens 66 - 70 (Sealed with grease; radial clearance 0.005 to 0.010 inch; nominal D; /Dg ratio 1.5) Specimen Number Value Parameter ee ae Thickness (in.) Dg (actual, in.) Temperature (°F) t/D; Ratio (actual) Pressurization Rate (psi/min) Pressure (psi) Axial Displacement of Center Point on Window's Low-Pressure Face (in.) 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000 11,000 12,000 13,000 14,000 15,000 16,000 17,000 18,000 19,000 20,000 21,000 22,000 23,000 Displacement at Failure (in.) 0.325 | 0.330 0.330 | 0.328 | 0.325 Pressure at Failure (psi) 23,400 | 23,350 | 22,800 23,400 | 23,160 | 22,800 J) Abort due to leak at 20,100 psi, not averaged. 62 Table C-15. Hydrostatic Test Data for Nominal 1.50-Inch (D;) -2.25-Inch (Dg) Flat Acrylic Windows, Test Specimens 71-75 (Sealed with grease; radial clearance 0.002 to 0.005 inch; nominal D,/D; ratio 1.5) Specimen Number Parameter Thickness (in.) D, (actual, in.) Temperature (CF) t/D; Ratio (actual) Pressurization Rate (psi/min) Pressure (psi) Axial Displacement of Center Point on Window's Low-Pressure Face (in. 1,000 0.000 0.000 0.001 2,000 0.006 0.001 0.002 3,000 0.010 0.002 0.004 4,000 0.015 0.002 0.015 5,000 0.019 0.003 0.015 0.002 6,000 0.023 0.008 0.025 0.003 7,000 0.027 0.015 0.025 0.010 8,000 0.031 0.015 0.025 0.012 9,000 0.035 0.016 0.034 0.016 10,000 0.038 0.021 0.034 0.021 11,000 0.042 0.026 0.034 0.026 12,000 0.046 0.033 0.045 0.030 13,000 0.050 0.034 0.045 0.035 14,000 0.055 0.041 0.046 0.039 15,000 0.060 0.045 0.058 0.044 16,000 0.066 0.051 0.058 0.049 17,000 0.071 0.060 0.069 0.054 18,000 0.075 0.066 0.070 0.060 19,000 0.083 0.073 0.082 0.067 20,000 0.088 0.080 0.082 0.076 21,000 0.095 0.089 0.094 0.084 22,000 0.103 0.113 0.102 0.093 23,000 0.112 0.118 0.112 0.104 24,000 0.132 0.125 0.116 0.114 25,000 0.138 0.173 0.128 0.129 26,000 0.150 0.237 0.148 0.148 27,000 ay ly, 0.180 0.173 28,000 0.210 0.230 29,000 Pressure at Failure (psi) 26,800 28,800 28,600 29,800 1) Time stopped to fix leak at 22,000 psi. 27 Abort due to pump failure at 26,350 psi. 63 Table C-16. Hydrostatic Test Data for Nominal 1.50-Inch (D;) -4.00-Inch (D,) Flat Acrylic Windows, Test Specimens 76 - 80 (Sealed with grease; radial clearance 0.020 to 0.030 inch; nominal D,/D; ratio 2.67) Specimen Number Parameter Thickness (in.) Do (actual) in.) Temperature (°F) t/D; Ratio (actual) Pressurization Rate (psi/min) Pressure (psi) Pressure at Failure (psi) 19,500 | 18,950 19,100 | 18,800 | 19,600 | 19,600 19,190 18,800 64 Table C-17. Hydrostatic Test Data for Nominal 1.50-Inch (D;) -4.00-Inch (Do) Flat Acrylic Windows, Test Specimens 81 - 85 (Sealed with O-ring; radial clearance 0.0005 to 0.001 inch; nominal D,/D; ratio 2.67) Specimen Number Value Parameter ras ce eee Thickness (in.) Dg (actual, in.) Temperature (°F) t/D; Ratio (actual) Pressurization Rate (psi/min) Pressure at Failure (psi) 19,150} 19,300 | 18,300 | 18,400 | 21,200 | 21,200} 19,270 | 18,300 65 Table C-18. Hydrostatic Test Data for Nominal 3.33-Inch (Dj) -5.00-Inch (Do) Flat Acrylic Windows, Test Specimens 86 - 90 (Sealed with grease; radial clearance 0.005 to 0.010 inch; nominal D,/D; ratio 1.5) Specimen Number Value Parameter eto fo[e[= [=| mm Thickness (in.) D 9 (actual, in.) Temperature (CF) t/D; Ratio (actual) Pressurization Rate (psi/min) Pressure (psi) Axial Displacement of Center Point on Window's Low-Pressure Face (in.) 50 OBIS2 {i 10N140) | 0-0N1500 1 O15 ai ON 0.171 0.150 | 0.132 100 0.176 | 0.194 | 0.203 | 0.209 | 0.224 | 0.224 | 0.201 0.176 Displacement at Failure (in.) | 0.197 | 0.194 | 0.240 | 0.216 0.194 | 0.218 66 Table C-19. Hydrostatic Test Data for Nominal 3.33-Inch (D;) -5.00-Inch (Do) Flat Acrylic Windows, Test Specimens 91-95 (Sealed with grease; radial clearance 0.002 to 0.005 inch; nominal D,/Dj ratio 1.50) Specimen Number Parameter Thickness (in.) Dg (actual, in.) Temperature (CF) t/D; Ratio (actual) Pressurization Rate (psi/min) Pressure (psi) 100 200 300 400 500 600 700 800 ilure ( eae OFS PON32 O07 Si OslOSi 20 m132 Pressure at Failure (psi) s00ly 590 1, Not included in averaged values. Displacement at Failure (in.) 67 Table C-20. Hydrostatic Test Data for Nominal 3.33-Inch (Dj) -5.00-Inch (Dg) Flat Acrylic Windows, Test Specimens 96 - 100 (Sealed with grease; radial clearance 0.002 to 0.005 inch; nominal Do /D; ratio 1.50) Specimen Number Parameter ee eed Thickness (in.) Do (actual, in.) Temperature (CF) t/D; Ratio (actual) Pressurization Rate (psi/min) Displacement at Failure (in.) } 0.109 | 0.100 | 0.081 0.076 | 0.138 | 0.100 | 0.076 Pressure at Failure (psi) } 1,910, 27300)4|) 2,100 2/025 | 1,960 | 2,300 |} 2,060 ier 68 Table C-21. Hydrostatic Test Data for Nominal 3.33-Inch (D;) -5.00-Inch (Dg) Flat Acrylic Windows, Test Specimens 101 - 105 (Sealed with grease; radial clearance 0.002 to 0.005 inch; nominal D,/D; ratio 1.5) Specimen Number Parameter Thickness (in.) Dg (actual, in.) Temperature (CF) t/D; Ratio (actual) Pressurization Rate (psi/min) Pressure (psi) Displacement at Failure (in.) | 0.124 Phe beat 0.138 ONSSMNORTS? |) 02084 Pressure at Failure (psi) 4,750 | 3,550 | 3,400 | 3,600 | 4,000 | 4,750 | 3,860 | 3,400 _1y Preloaded pressure unknown, plugged gage line. 69 Table C-22. Hydrostatic Test Data for Nominal 3.33-Inch (D;) -5.00-Inch (DQ) Flat Acrylic Windows, Test Specimens 106 - 110 (Sealed with grease; radial clearance 0.005 to 0.010 inch; nominal D,/D; ratio 1.5) Specimen Number Value ee [oor [oe [io [ae | om [ne [oe Thickness (in.) D, (actual, in.) Temperature (°F) t/D; Ratio (actual) Pressurization Rate (psi/min) Pressure (psi) Axial Displacement of Center Point on Window's Low-Pressure Face (in.) Displacement at Failure (in.) | 0.782 | 0.610 | 0.456 | 0.536 ew 0.782 | 0.596 | 0.456 Pressure at Failure (psi) 8,300 | 7,825 | 8,025 | 7,650 | 8,450 | 8,450 | 8,050 | 7,650 J/ Deflection wire disengaged suddenly. Note: Cracking at about 5,000 psi and 7,000 psi. 70 Table C-23. Hydrostatic Test Data for Nominal 3.33-Inch (D;) -5.00-Inch (Dg) Flat Acrylic Windows, Test Specimens 111-115 (Sealed with grease; radial clearance 0.005 to 0.010 inch; nominal Dg /D; ratio 1.5) Specimen Number Parameter Thickness (in.) D, (actual, in.) Temperature (CF) t/D: Ratio (actual) Pressurization Rate (psi/min) Pressure (psi) Axial Displacement of Center Point on Window's Low-Pressure Face (in.) Displacement at Failure (in.) | 0.428 | 0.424 0.4641/| 0.454 | 0.486 | 0.486 | 0.451 0.424 Pressure at Failure (psi) 15,750 | 15,300 | 15,200 | 15,475 | 15,400 | 15,750 | 15,425 | 15,200 Vy Held 2 minutes at 500 psi to fix leak. Notes: 1. 500-psi preload. 2. Audible cracks at about 9,000 psi and 11,000 psi. 7\ Table C-24. Hydrostatic Test Data for Nominal 3.33-Inch (D;) -5.00-Inch (D,) Flat Acrylic Windows, Test Specimens 116 - 120 (Sealed with grease; radial clearance 0.005 to 0.010 inch; nominal D,/D; ratio 1.5) Specimen Number 0.001 0.001 0.012 0.019 0.026 0.033 0.041 0.048 0.056 0.064 0.073 0.083 0.091 0.101 0.115 0.128 0.140 0.156 0.171 0.191 0.208 0.251 0.294 0.001 0.011 0.018 0.026 0.033 0.041 0.048 0.056 0.064 0.072 0.080 0.090 0.098 0.109 0.119 0.135 0.148 0.161 0.181 0.198 0.220 0.253 0.301 Parameter Thickness (in.) Dg (actual, in.) Temperature (CF) t/D; Ratio (actual) Pressurization Rate (psi/min) Pressure (psi) 1,000 2,000 3,000 0.021 0.010 0.022 4,000 0.025 0.018 0.030 5,000 0.033 0.026 0.037 6,000 0.040 0.033 0.044 7,000 0.046 0.040 0.052 8,000 0.052 0.050 0.059 9,000 0.067 0.057 0.066 10,000 0.073 0.066 0.074 11,000 0.083 0.075 0.083 12,000 0.091 0.083 0.092 13,000 0.101 0.092 0.101 14,000 0.114 0.103 0.111 15,000 0.127 0.114 0.122 16,000 O37; 0.125 0.132 17,000 aly, 0.137 0.146 18,000 0.152 0.160 19,000 0.170 0.177 20,000 0.197 0.192 21,000 0.221 0.223 22,000 0.248 0.252 23,000 0.288 0.292 24,000 Displacement at Failure (in.) 0.359 Extrusion Set (in.) 0.010 0.0682/ Pressure at Failure (psi) 23,900 1) Abort at 16,250 psi due to pump failure. 2, Extrusion and bending caused seal to fail, release of pressure. Note: 1,000-psi preload; smooth deflections. 72 0.048 0.056 0.064 0.073 0.083 0.091 0.103 0.114 0.125 0.137 0.152 0.170 0.191 0.208 0.288 0.326 23,450 Table C-25. Hydrostatic Test Data for Nominal 4.00-Inch (D;) -6.00-Inch (Do) Flat Acrylic Windows, Test Specimens 121 - 125 (Sealed with grease; radial clearance 0.005 to 0.010 inch; nominal D,/D; ratio 1.5) Specimen Number Value Parameter Thickness (in.) dD, (actual, in.) Temperature (°F) t/D. Ratio (actual) Pressurization Rate (psi/min) Axial Displacement of Center Point on Window's Low-Pressure Face (in. Displacement at Failure (in. Pressure at Failure (psi) aes Notes: =| [foo ae 1. Pressurization rate hard to hold due to pumping gage lag and gir in line. 2. Reading difficult to make at close intervals. 73 Table C-26. Hydrostatic Test Data for Nominal 4.00-Inch (D;) -6.00-Inch (Do) Flat Acrylic Windows, Test Specimens 126 - 130 (Sealed with grease; radial clearance 0.005 to 0.010 inch; nominal D,/D; ratio 1.5) Specimen Number Parameter Thickness (in.) D, (actual, in.) Temperature (F) t/D; Ratio (actual) Pressurization Rate (psi/min) Pressure (psi) Displacement at Failure (in.) dc Dee Pressure at Failure (psi) | 10 | 1,030 1,170 | 700 | 1,170 700 Note: 50-psi preload. 0.157 | 0.090 74 Table C-27. Hydrostatic Test Data for Nominal 4.00-Inch (D;) -6.00-Inch (Dg) Flat Acrylic Windows, Test Specimens 131 - 135 (Sealed with grease; radial clearance 0.005 to 0.010 inch; nominal D,/Dj ratio 1.5) Specimen Number Parameter Thickness (in.) D, (actual, in.) Temperature (@F) 1/D; Ratio (actual) Pressurization Rate (psi/min) Pressure (psi) Displacement at Failure ( Pressure at Failure (psi) 3,550) || -2;900) ||=3, 100) |) 37800) 37500)" || 37800))|) 373709 || 2-900 Notes: 1. 50-psi preload. 2. Audible cracking at about 2,500 psi. 75 Table C-28. Hydrostatic Test Data for Nominal 4.00-Inch (D;) -6.00-Inch (D,) Flat Acrylic Windows, Test Specimens 136 - 140 (Sealed with grease; radial clearance 0.005 to 0.010 inch; nominal D,/D; ratio 1.5) Specimen Number Value Parameter 196 i ee ee ee Thickness (in.) D, (actual, in.) 5.9851/| 5.984 Temperature (°F) t/D. Ratio (actual) 0.5361) 0.498 Pressurization Rate (psi/min) Axial Displacement of Center Point on Window's Low-Pressure Face (in.) Pressure (psi) 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000 11,000 12,000 13,000 14,000 15,000 16,000 17,000 18,000 Displacement at Failure (in.) Pressure at Failure (psi) 18,240 | 17,800 1/ Not averaged because of thickness variation. 2/ Deflection post popped off suddenly. Note: Audible cracking at about 13,000 and 15,000 psi. 76 REFERENCES 1. U.S. Naval Civil Engineering Laboratory. Technical Report R-512: Windows for external or internal hydrostatic pressure vessels: Part |. Conical acrylic windows under short-term pressure application, by J. D. Stachiw and K. O. Gray. Port Hueneme, Calif., Jan. 1967. 2. C. E. Bodey. Private communication concerning pressure effects on Plexiglas circular discs. Autonetics Division, North American Aviation, Anaheim, Calif., Apr. 22, 1965. 3. Rohm and Haas Company. Plexiglas handbook for aircraft engineers, 2nd ed. Philadelphia, Pa., 1952. 4, U.S. Naval Civil Engineering Laboratory. Technical Note N-755: The conversion of 16-inch projectiles to pressure vessels, by K. O. Gray and J. D. Stachiw. Port Hueneme, Calif., June 1965. V7 ie: Cree Poste a ~ us {ie ‘saaiBap (06 UDYy 19610) 10 ‘oy jpnbe ajBup papnjou! Yy4!M SMOPUIM [DD!UOD 4O 4DY4 OF a}qoDd =Wod aq of punos usaq spy ainsseid 91404s01pAY UUa4-J10Ys 4apuN sMop 4D]j JO BoUDWIOJJed OYy sainssaid o14p4soipAy 04 pasodxa any MOPUIM a4} 4O JaJ@WDIP ||DJ9AO S! °q pup ainssaid o1s94dsowyo jUaiquin oJ pasodxs MOpUIM au 4O JayaWDIP aA149a}j9 B44 B1dya1ayy puDd eBuD|y ayy U! 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Unclassified Security Classification DOCUMENT CONTROL DATA-R&D (Security classification of title, body of abstract and indexing annotation must be entered when the overall report is classified) ORIGINATING ACTIVITY (Corporate author) 2a, REPORT SECURITY CLASSIFICATION Naval Civil Engineering Laboratory Unclassified ii ee ps5. ae REPORT TITLE WINDOWS FOR EXTERNAL OR INTERNAL HYDROSTATIC PRESSURE VESSELS — PART II. Flat Acrylic Windows Under Short-Term Pressure Application DESCRIPTIVE NOTES (Type of report and inclusive dates) Not final; January 1, 1966 to June 30, 1966 AUTHOR(S) (First name, middle initial, last name) Stachiw, J. D. Dunn, G. M. Gray, K. O. 6. REPORT DATE » TOTAL NO. OF PAGES 7b. NO. OF REFS f May 1967 77 4 6a. CONTRACT OR GRANT NO » ORIGINATOR'S REPORT NUMBER(S) . PRosectNno. Y-F015-01-07-001 TR-527 - OTHER REPORT NO(S) (Any other numbers that may be assigned this report) DISTRIBUTION STATEMENT Distribution of this report is unlimited. Copies available at the Clearinghouse for Federal Scientific & Technical Information (CFSTI), Sills Building, 5285 Port Royal Road, Springfield, Va. 22151 — Price $3.00 - SUPPLEMENTARY NOTES 12. SPONSORING MILITARY ACTIVITY Naval Facilities Engineering Command . ABSTRACT Flat, disk-shaped acrylic windows of different thickness-to-diameter ratios have been tested to destruction under short-term hydrostatic loading at room temperatures, where short-term loading is defined as pressurizing the window hydrostatically on its high-pressure face at a 650-psi/minute rate till failure of the window takes place. Critical pressures and displacements of windows with thickness to effective diameter ratios less than 1.0 have been recorded and plotted. The critical pressures derived from testing flat windows in flanges with 1.5-inch, 3.3-inch, and 4.0-inch openings have been found applicable also to flanges with larger openings, so long as the larger windows are of the same t/D; and D /D; ratios, where t is thickness of the window, D; is the clear opening in the flange and therefore the effective diameter of the window exposed to ambient atmospheric pressure and D, is overall diameter of the window face exposed to hydrostatic pressure The performance of flat windows under short-term hydrostatic pressure has been found to be com- parable to that of conical windows with included angle equal to, or larger than 90 degrees. DD eta GAGE a) Unclassified S/N 0101- 807-6801 Security Classification Unclassified Security Classification KEY WOROS Undersea structures Flat acrylic windows Hydrostatic pressure Short-term loading DD newer © Wy A (BACK ) Unclassified (PAGE 2) Security Classification Pay ONE . Wee AG tLe 1 im Hits i” ay aL m4 1 i Vie TAU (US ciankY ati \ Alics pas ie ra tee yu pay Oe iY