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A O-A042 198 NAVAL TORPEDO STAYZON KEYPORY WASH F/S 13/10 ANAL YSIS OF ARRAY COMPONENTS RECOVERED At ST. CROIX , VI.(U) MAY 77 .1 N APO UNCLASSIFIED NAVTORPSTA—t33* ~~~~~~~~~~~ D A T E - FILMED 3 Report 1332 Cop~, r 9 ANA LYSIS OF A RRAY COM PONENTS RECO V ER ED A T ST. CROI X, VI Research & Engineedng Department M a y 1977 APPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED — 3 NAVAL TORPEDO $TATION~ K.yport, Washington 98345 DEPARTMENT OF THE NAVY NAVAL TORPEDO STATION KEYPORT , WASHINGTON 98345 JOHN G. FLETCHER R. 0. MELIM CAPT. USN CDR. USN COMMMWING OFFICER EXECUTIVE OFFICER E. H. LESINSKI TECHNICAL DIRECTOR ADMINISTRATIVE STATEMENT NAVTORPSTA Report 1332 , An a l~~sis o~ Arr a:~ Ccr7p cn ~~n;a Reco ’~~r ei at St. ‘ro ix, yr By J. M. Abo Prepared under internal range development funds Released by: ________________________________ R. L. MARIMON , Head -— Research & Engineering Department May 1977 SECURI TY C LASSI FICATION OF ‘THIS PAGE (WIi.n Dir. fnt.r.d) REPORT DOCUMENTATION PAGE BEFORE COMPLETIN G FORM I. REPORT NUMBER ~~~. ~2.~~QVT AC~ U1IQ1L~~ 3.~~~~~~lpLEu .T~$.4A S~ 06 NUMBER 1332 ( 1~~ ~~~~~~~~ r T ~~~~i~~~~~~~~ ” t -_ J ~~~~~~ ’ ~~~~~~ 4. TITLE (aid Subtitl•) — S. TYPE OF REPORT A PERIOD COVERED - )~NALYSIS OF ARRAY COMPONENTS ,~ ECOVERED / Analysis ~~~~~~~~~~~~~~~ VI _ —.-•-———‘ 5. PERFORMING ORG. REPORT NUMBER 1332 k 7. AUTHOR(.) 5. CONTRAC T OR GRANT NUMSER(i) 1’iT 7T~~T7~~~ _ _ _ _ _ _ _ _ _ 9- PERFORMING ORGANIZATION NAME AND ADDRESS 10 PROGRAM ELEMENT , PROJECT , TASK Tracking System s Branch (code 7032) A REA è WORK LINI PIL~~~~~~~~~~~~~ _ N T N U M U E R S Range SYstems Division / / ) i~f Research & Engineering Department /~~ _ II . CO N T R O L L I N G O F FICE N A M E A N D ADDRESS IA. REPORT DATE NAVSEASYSCOM ‘S. MWLR OF PAGES 14~ MON ITORING A G E N C Y N A M E A ADDRESS(II ditt.,.n I t?OOi Cone,ollln9 I 15. SECURITY CLASS. (at thu rI~ orl) UNCLASSIF I~~ ISa . OECLASSIFICA T IO N/000NGRADING • SCHEDULE NA 15. D,STRIBUT ION STATEMENT (ot ~~ Ripen ) Approved for public release; distribution unlimited I?. DISTRIBUTION STATEMENT (.1 A. .b.eract .,t .,.d Sn Stock 20. ii ditt. ,ait Ira., R.po,i) IS, SUPPLEMENTARY NOTES II. KEY WORDS (Continu. an ,.,.n.. aid. it n.e... ’p aid Sdaellt,. b~ block rn~~b.e) corrosion 3-D tracking array Morrison Seal 0—ring seal 20\~~~STRACT (Conftnu. an nov r~ •id IS n~c•~ I~~y aid Sdanulsp by block maib.r) ~~The pressure housings with electronic instrumentation from arrays re— covered at the Atlantic Fleet Weapons Test Facility (AFWTF ) in St. Croix , Virgin Islands were disassembled and inspected . A description of the arrays is given and photographs of the parts inspection are shown. Failures and their causes are described and discussed . ~ DO JAN 73 1473 EDITION OP I NOV 59 II OBSOLETE ~~~ ,5.2 ~~~~~~~~~~~ - S/N 0102•014 160 1 I SECURItY ~ %~A$~~~ ICATION OF ‘THIS PA St (*Siuø D.Ii 1’”IrSd) _ _ - - ~~~~~~--- ~~ - Report 1332 TABLE OF CONTENTS Page List of Figures ii 1. INTRODUCTION 1 Background 1 Description of Arrays 1 St. Croix Range Waters 1 Inspection Procedure 4 2. ARRAY 7 5 Recovery 5 Inspection 5 Array 7 Failures 12 3. ARRAY 1O 15 Recovery 15 Inspection 15 Array 10 Failures 23 4. CONCLUSIONS 25 Array 7 25 Array lo 25 5. RECOMMENDATIONS 27 Distribution 29 1~~ o. -; - k IJNI’ ~ . .. JM C ED 0 J~H~ CA tION i T ! ~~ IY*i1t~ IL~TY CODIS A ui a. •.~ ~ SIf C:&L Lfl~ Report 1332 LIST OF FIGURES Figur e Page 1. Rigid Array, St. Croix 2 2. Buoyant Array, St. Croix 3 3. Exterior Corrosion, Junc tion Box , Array 7 — — — 5 4. End Plate 0-Rings , Junction Box , Array 7 6 5. 0-Ring Surface , Main Cable Seal 7 6. Extruded Seal , Main Cable Seal 7 7. Morrison Seal Glands, Junction Box , Array 7 - — 8 8. Corrosion Between 0-Rings , X Preamplifier Cable Seal End Cap 9 9. 0—Ring Seal Surface , X Preamplifier Hydrophone End Cap 10 10. Void in Interconnect Cable Jacket 11 11. Open Contact in Qi Transistor 12 12. Corrosion Area, Seal 13 13. Tilt Housing , Array lO 15 14. Hold-Down Screw on Tilt Housing 15 15. Tilt Output Waveform Observed in Bench Test - - 16 16. Tilt Output Observed at St. Croix 16 17. Corrosion on End Plate, Main Junc tion Box - - - — 17 18. Corrosion in Housing , Main Junction Box 17 19. Corrosion on Circuit Board , Main Junction Box - — 18 20. Corrosion of 0-Ring Surfaces, Main Cable End Plate 18 21. Corrosion of 0—Ring Surface , C Preamplifier Cable Seal 18 22. Corrosion of 0-Ring Surface , X Preamplifier Cable Seal 19 23. Corrosion of 0-Ring Gland , C Preamplifier Housing 20 24. Ruptured Capacitor, C Preamplifier 20 25. Main Cable Seal, Array 10 21 26. Jacket Cracks, Interconnect Cable 22 27. XY Hydrophone , Boot Removed 23 28. Watermark on Lower Side of Sphere, C Hydrophone 23 Report 1332 1. INTRODUCT ION BACKGROUND The Nava l Torpedo Station has been analyzing recovered 3-D tracking arrays as part of a continuing program to deter- mine the effects of long—term submergence on underwater equip- ment used on its ranges. The basic construction of arrays and sealing methods for pressure housings at St. Croix and NAVTORPSTA are similar since they have a common origin at the Applied Physics Laboratory of the University of Washington (APL/UW) . However , the arrays at St. Croix appear to have longer service life. The recovery of arrays at St. Croix offered an opportunity to study the e f f e c t s of the waters there. No direct comparison of the corrosion and its e f f e c t s was made between NAVTORPSTA and St. Croix arrays . This m a y be discussed in a future report. DESCRIPTIO N OF ARRAYS The electronics packages from two types of arrays were received for analysis. One set was from array 7, a ri gid type as shown in Figure 1; and the other from array 10 , a buoyant type as shown in Figure 2. The primary difference in the electronics is that the buoyant type array has a level or tilt sensing device which transmits array tilt information to the shore. The tracking electronics are essentially the same : the hydrophone signals are multiplexed at each individual pre- amplifier, then combined at the junction box and sent up the cable to the computer site . ST. CROIX RANGE WATERS The waters at St. Croix have a relatively high oxygen • con ten t, 4 mi/liter , indicating a high corrosion rate. However , • the waters at St. Croix are alkaline and the bottom sediment contains a large amount of calcium . This condition accelerates corrosion of zinc but is less corros ive to steel than normal seawater . In the balance , steel corrodes at a lower r ate at • St. Croix than in Pacific waters. Table 1 below shows water conditions at three tracking ranges. . 3 1 R~~ Report 1332 F Rc _•_ \ -- —~~ c — ~~~~~~~~~~~~~~~~~~~~~ ‘~~A F,I ~. ER - N - k~~I~1ATE - \~~ ~~~~~~~~~~~~~~~ 9 / ‘N S Rx.y QANSCSQ( E~~ • - N - - , - \ . . “ - ~~ ~~~~~~~~~~~~~~ ~ EF S - . - -~~~ 5, .. . .. . . . ~~•‘______S _ ~~~~~~~~ — ~~~~~~~~ ~~~ - - - — -~~ A_’ - ‘ ~ - ~-<~ _ / : ~-: ~~~~~~~~~~~~ ~~~~~ - ~~ C — ~ I -~ ~~~~~~~~~~~~ ~~~~~~~~~~~~ S - • F • ~. ~ __ K .-ç , —“ . ______ I ~. ~. . - , ~ ~~~~~~~~~~~~ . • - . . . I ELECTRICAL CA8LE~~~~~~~~ - . Figure 1. ~igid Array, St. Croix 4 2 — - ~~~~~~~- - - -- Report 1332 R i LIFT EYE R ,;\ 6 FT GSA . SPHERE I ~ ~I’i ~ I 5000 LB . BUOYA NCY \. ~~~~ R . ‘ ............ .. .. I \ ~~~ ‘ / y ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~;; ~~~~RS ~~~~~~~~~~ ‘ ~“ - r.~~’ ~~~~ \.-~ & P R E A M P L I F I E R S FIVE ON 3O FT CENTERS •‘~ ;~;~>~ ‘~7 TILT 4 1 ~~~~ U N I V E R S A L —~~ T RA NS0UCE RS~~~ ( ~ J O INT . — — ST RAIN RELIEF 77 F7• S E CTION , I S E P A R A T I O N . ~~~~ t\~~~ _ E L EC T R I C \J~ \ CABLE M~~0 I F I E 0 A R — A Y G E C . I E T R Y U N IV E R S A L ANCHOR — -. 9500 LB Figur. 2. Buoyant Array , St. Croix Report 1332 Table 1. Comparison of Range Characteristics Depth 02 Content Salinity Temperature Location (ft) (mi/i) (ppt ) (° C) Na noose 5 1,300 3.38 31.01 8.7 Dabobb 600 3.57 30.64 9.8 St. Croix~ 3, 300 4.00 35.00 5.6 ~Institute of Oceanography, University of British Columbia,1968 ~DeP~~ t1~~~t of Oceanography, University of Washington, 1966 Jim Jenkins , Civil Engineering Laboratory, Port Hueneme, California and Oceanographic Atlas of the North Atlantic Ocean , U.S. Naval Oceanographic Office , 1967 ECTION PROCEDURE The primary objectives of the inspection were to evaluate the effectiveness of the seals , appraise the performance of cable jacketing, determine causes of failure , and predict life of the parts . Individual seals were removed and inspected for signs of water intrusion. Cable jacketing was stripped to determine watertightness. Electrical resistance between con- ductors was measured , using a GR-1864 rnegohxnmeter and a Weston analyzer model 980 Volt-ohmmeter . It should be kept in mind that the observations of corrosion on the exteriors of the parts were made about 3 months a f t e r they had been brought to the surface. The character of the surface corrosion had undoubtedly changed considerably since the day of recovery. 4 Report 1332 2. ARRA Y 7 RECOVERY Array 7 was recovered in September 1976 because of faulty preamplifiers in the c and x hydrophones . The array had been planted in June 1970 at a depth of 3,283 feet. The array parts arrived at NAVTORPSTA in good condition with no apparent damage , al though the bottom of the outer shipping box was broken. The parts received were the junction box with the main cable seal , the c , x , y, and xy hydrophones , and the UQC hydrophones. The z hydrophone was missing. INSPECTION The array parts were generally free of marine growth . Photo- graphs taken at St. Croix at the time of recovery indicate that , except for some small hydroids , little growth was present . Junction Box. The junction box was heavily corroded on the exterior , with yellow powdery corrosion products accumulated around the Morrison seals of the hydrophone breakout end . See Figure 3. The end plate of the hydrophone side was removed ~~~~ a ‘ ~~~‘~‘~ S . . ,.>~~~~ .. Figure 3. ~~terior Corrosion , Junction Box , Array 7 (Approx. life size) 5 Report 1332 first. Very little corrosion was evident at the sealing sur- face to the first 0-ring . The 0—rings had a moderate amount of grease on them , as ca~ be seen in Figure 4. The inside surface of the end plate had a dull green coating which , a uiscussion with APL personnel indicated , was a proprietary dichromate sealing finish used on zinc—plated surfaces. ~~t~ t ‘A • . J • .. / : ~ ~; - •I ~~~~~~~ *~~i~ ~~~~~~~~~ A • 1 L ~ Figure 4. End Plate 0—rings, Junction Box , Array 7 (Enlarged) The 0—ring surface of the mating housing surface was lightly corroded in spots up to the first 0—ring . No corrosion was found on the interior side of the first 0-ring , indicating that no water got beyond that seal. The end plate at the main cable end of the junction box was removed . Again corrosion had reached only to the first 0—ring of the double 0-ring seal. The 0-rings were lubr icated with a moderate amount of grease.6 Report 1332 Morrison Seals The Morn- son seal of the main cable was ins~ e~ ted . The 0—ring seal of the Morrison seal body was cor- - roded to a max imum depth of 1.241 inches at one point , which is beyond the second 0-ring ; how— - ever , rio water was found in the seal area (see Figure 5) . The - 0—rin~ s were fairly heavily oreaseci . The grease on the outer 0-ring had become a chalky white due to exposure to seawater . • •~~•~~~~ ‘ T’iis condition has also been ob— ~ served on components recovered .~~1\ - .. - at NAVTORPSTA ranges. The 0- ring squeeze was found to be - •, - abou t 12 to 13 per cent , which was about one-half tha t of the ; - squeeze at the preamplifier - seals. The observed dimensions Figure 5. 0-ring Surface , were found to be in accordance Main Cable Seal with a detailed drawing of the (Approx. life size) part. The back-up washer at the face of the first Morrison seal was slightly off center , causing the seal to extrude slightly ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ at one side. (See Figure 6) Water which apparently en- tered along the gland wall , was found under the third main seal. Corrosion depth in the Morrison seal gland - ~ •/ ~za~ 1.724 inches from the top of the gland . The corro- sion line reached to the ~~. middle of the third seal. - Water was also found at the • solder cup, where the cable — I . ~~~~~~~~~ . shield is attached to a - ~~~~ . feed—through pin. . ‘ Personnel present durino the recovery operation ~x- plained that the method for transport of recovered arrays was to cut the cable at the a r r a y , re—submerge the array below a tow ship, proceed to- ward shore until the array Figure 6. Extruded Seal, Main Cable Seal , hit bottom and at that point (Approx. life size) “store” the array until it • could be raised again for 7 dismantling . Report 1332 The water found in the solder cup evidently entered the severed end of the cable during re-submergence . Supporting this observation , water was found along the complete length of the cable stub attached to the seal. - The interconnect cable Morrison seals at the junction box were disassembled and inspected . Of primary interest was the depth of the corrosion in the glands. The depth of a complete seal is 2.450 inches. The average corrosion depth as measured in six glands was 1.278 inches. The deepest corrosion was 1.683 inches to a point on the gland wall beyond the third seal. It is interesting to note that the spare hole , sealed with 0- rings on a metal plug , was corroded only to the chamfer at the hole entrance. The spare hole is at the 2 o ’clock position in Figure 7. __________ • ~~~~~~~~~~ q.~~. ~~~ -—/ ~~~~ ~~~~~ . ~ ~~~~~~~~~~~~~~~~~~~~ ~~~~~ ~~~~ ~ a~~~7 • . ~~ ,4 ~ ;. ~ ~~ - . ~‘ .b. • .‘, ~~~~~~~~~~~~~ 4 _v~ ( ~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ , ~~ F , Figure 7. Morrison Seal Glands, Junction Box, Array 7 (Approx . life size) The average corrosion depth in the five Morrison seals at the preamplifiers was 1.787 inches , the deepest being 2.095 inches. This is about 1/2-inch deeper than the corrosion of the glands at the junction box . The outer diameters of the8 Report 1332 seals and inner diameter of the respective glands were com- pared . The differences in diametric seal interference did not directly correlate with the differences in depth of corro- sion in the gland . ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ • • Preamplifiers. No water -~~ _ _ _ _ [d.~~~~~~~~~~~~~~ *~~ ~~~ leaked beyond the second 0— • • _____ ~. 4 ring of any of the preainp— T lifiers. However , some S 4. moisture had leaked past the • first 0—ring of the cable - • ~ . seal end caps. This was - ~~~~~• ~- . . evidenced by slight corro- r . ‘ . ‘ ~~~~~. sion of the surface between ‘ • ~~ , the two 0—rings of the cable _ _ _ _ ~ ‘ . _ _ _ _ seal end caps of the c , x , ____ . I xy, and EJQC preamplifiers. _ _ _ _ . ~ • - Fi gure 8, a photogra ph of _ _ _ ...“ the x preamplifier cable _ _ _ _ _ _ seal end cap shows this con - _ __ __ _ dition . The hydrcphone end • _____________ of the preamp is capped by _ ___ a similar double 0-ring seal. These showed no leak- age past the first 0—ring in any of the preamplifiers. _ _ _ _ Figure 9 is a photograph of the x preamplifier hydro - _ _ _ _ phone end cap seal. The scratches on the land s were ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ I’j’I made during disassembly. It _ _ _ _ _ _ _ _ _ _ _ _ _ FT IN. was noted that the 0-ring surf aces of the end caps Figure 8. Corrosion Between 0-rings, had two types of finishes: X Preamplifler Cable Seal End Cap some the dull green type (Enlarg ed 2X approx.) mentioned earlier , and the others a bright gold type . The bright gold—colored surface is a sodium dichromate seal f i n i s h used on zinc plate. There appeared to be no difference in corrosion protection between the two types of finish. The 0—ring squeeze of the preamplifier seals was determined - - by measuring the outboard groove/gland dimensions and the corres- ponding 0-ring dimensions. The average squeeze was about 23 per Cent on the cable seal end and 24 per cent on the hydrophone end. The lubrication , or amount of grease , on the 0-rings on both ends appeared to be about equal. All 0-rings had back-up rings. Report 1332 S - _ _ ~~~~~~ i! ~ !1 ~ i-~4! • , ~: 1 ~~~~ ~~~~~~ ~~~~~~ . • .5 : ~~‘ •~~ ‘ : , .~~~~ lit . . ~~~~~~~ • • —. • ~~~~~~~~~~~‘ i ’ • . . - 4~~~~~~~~~~~~~~~~~~ , .-~~~~~ . • . . • - 4 Figure ~~. 0-rinq Seal Surface, X Preamplifier Hydrophone End Cap ~En1arged 2X approx.) Interconnect Cables. The interconnect cables were a co- axial type similar to RG-58 . The jacket was a black high- density polyethylene about 0.075—inch thick. The shield was tinned copper laid over a teflon inner die~itetric . The center conductor was a silver—coated , stranded copper wire. The cables were cut open to determine the condition of ti d con- duc tors. Table 2 below shows the results of the inGpection . The corrosion of the shield did not result from jacket leaks. The leaks occurred at the seals primarily at the preamplifier end. Voids in the jacket were also seen at the interface of the shield and jacket. Figure 10 is a photomicrograph of a cross section of a void in the jacket. These apparently did no harm as no leaks could be attribu ted to them . A red fluid was also found in various sections of the inner conductor , but did not appear to be detrimental to the cable function . No attempt was made to determine its composition . 10 Report 1332 Table 2. cable Condition Preamp Cable End Remarks x preaiup Shield corroded along 118-inch section starting at seal. Center conductor okay. x j—box Shield and center conductor uncorroded . y preainp Shield corroded along 6-inch section from seal. Center conductor uncorroded but contained a red fluid under the insulation. y i—box Shield and center conductor uncorroded . xy preainp Shield corroded a distance of about 10 inches from seal. No corrosion in center conductor. xy j—box Shield and center conductor uncorroded . z preamp Shield corroded a distance of 33 inches from seal end. z j—box Shield and center conductor uncorroded . c both ends Shield and center conductor uncorroded . UQC preamp Shield corroded and wet. Center conductor con- tained red fluid . UQC j-box Shield dull and center conductor contained red fluid. Figure 10. Void in Tnte rconn ect Cabl e Jacket (Enla rged 9X approx.) --— — - 1 ~ _ _ _ _ Report 1332 ARRAY 7 FAILURES The array was recovered because of malfunctioning of the c and x preamplifiers. Bench tests of the c preamplifier indicated its failure was due to an open in the base of the f i r s t input transistor, Qi , a 2N2484. The transistor can was cut open and it was found that the lead to the base junction of the transistor had melted , thus creating an open to the base. See Figure 11. The failure of the x hydrophone was not _ - _ Figure 11. Open Contact in Qi Transistor (Enlarged 19X ap1~ro~c.) so clear cut. The preamplifier was tested on a bench but no malfunction was apparent. However, the interconnect cable had a resistance of 29k ohms between shield and center conductor prior to disassembly of the housing . With the ohmmeter polarity reversed , the resistance was 52k ohms. This difference ind i- cates a small battery action which occurs with seawater leakage . This resistance was taken after the cable and seals had been out of the water for 3 months ; the resistance when the array was in the sea is not known . Corrosion in the seal gland at the preamplifier indicated that moisture had reached the point where the center conductor and shield are separated just ahead of the last seal. Thi s is shown as A in Figure 12. Moisture at that point resulted in a conductive path between the two con- ductors. The e’ffect could range from no signal to a very noisy signal from the preamplifier depending upon the resistance of the path . - 12 V/Al - — - ~2~4~\ \ A~~~77~~ ~~ / ft~~ . \T~~~~2~~\ ~~~~~~~~~~~ . ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~ N~~~~~~ _ _ \ —--c ~~~ ~T7~77? ~~~~ • Figure 12. Cor rosion Area , Morrison Seal 13/14 Report 1332 3. ARRAY 10 RECOVERY .~~ • Array 10 was recovered on k . ~~ -.~~ * . September 1976 because of . faulty tilt and tracking sig— nals . The array was originally _ _ _ _ _ . planted in January 1967. The ~~~~~~~~~~~~~~~ ~~~~~~~ array parts , con sisting of a - ‘-~~~ ,., junc tion box , tilt housing , and . -~~~ - f ive preamplifiers were uncra ted in good condition. The tilt, • - z preamplifier and explosive - ~~~~~~~~~~~ link cables had been cut off. . However , the other four pre— . ‘- ‘ ~ amplifier cables were intact. ~, INS P ECTIO N - The exteriors of the hous— . ______________ ings were heavily corroded . . - There was no evidence of marine _ _ _ _ _ _ growth on the components as re- ceived at NAVTORPSTA . However , . ‘d a close—up photograph taken at _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ the recovery site shows several - • hydroids growing on the level - _ _ _ _ _ _ _ ing shackle loca ted at the base _ _ _ _ _ “ - of the flotation sphere. _ _ _ _ ~~. ft Figure 13. Tilt HousIng , Array 10 • . . Tilt Housing. The ex- ten or of the housing was heavily corroded with red- brown to yellow—brown layers. . See Figure 13. However , the - • 3/8—16” stainless—steel hold— down screws were uncorroded ; Figure 14. Hold-Down Screw see Figure 14. On removal czai°~~~~~ ’~°~~’~~ox. of the housing cover , about 15 Report 1332 3 to 4 ounces of oil spilled out. The oil had come from the two pendulum housings (behind the circuit boards). The oil acts as a damping fluid for the tilt pendulums . The tilt housing had been shipped in an inverted position and the oil leaked through the synchro transmitters which are mounted on the housing above the normal oil level. A visual inspection of the tilt circuit board revealed no defects. The circuit was powered up on the bench and the output signa l observed on a Tektronix 545 os— - _ __ __ __ cilloscope . The output at the cable terminals — with the pendulums in a level attitude was ~~~~~~~~~~~~~~~~~~~~ a 20—kHz sine wave on _ _ _ _ a pulsed frequency of _ _ _ _ _______ ~~~~ __________ _ _ _ _ _ _ _ ~~~~ volts dc power . See —, Figure 15. The lower _ _ _ _ _I sawtooth wave is the -~~~~~~~~~ output of the unmodu- — lated synchro trans- mitter. Operation of - ~~~~~~~ — the t i l t circuit appeared normal. As a comparison Figure 16 shows the out— Figure 15. Tilt Output Waveform ut a wa Observed in Bench Test p - en a e computer site at St. __________________________________ Cro ix when the array ~~~~~ was still on the range - Main Junction Box. - - • . The main junc tion box exterior was heavily 4~ ! ~~~ - • corroded with red rust /t ~ : ~~~ and a yellow powdery ( \!“~ / ‘ - ~ residue around the inter- - - IA. ‘ ~~ connect cable seals. The I.. .~ ~~~~ j-box housing was oil \-; V;- ~;. - filled , which is unusual. - ~~~~ - Some corrosion was noted - in the in terior at the interconnect cable end plate and on the housing [ • wall, which had two dime- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ size spots. These cor- rosion areas appeared to Figure 16. Tilt Outp~it be isolated and not a re- Observed at St. Croix suit of a seawater leak. 16 I Report 1332 _ _ _ _ (See Figures 17 and __________________ 18.) A corrosion - • spot was also seen on the printed cir- ,r cuit board which was 5 ’ mounted on standoffs ~i i________ - •J. ’ •~~ on the end plate. (See Figure 19.) This - - - - indicates that some _____________ - I moistur e may have • been in the oil at the time of installation. • , ~~~~~, ~ The double 0-ring - , seals of the end plates - - , ,ffl ~ - •~~ were heavily greased . - ‘ ~~~ • ‘-i Some corrosion was -~~~ ~ • evident in the 0—ring Figure 17. corrosion on End Plate, grooves but was irreg— Main Junction Box (Enlarged) ular ; see Figure 20. Seawater Corrosion of _ _ _ _ _ _ _ _ 0—ring surfaces ordi- _ _ _ _ nar ily advances along • - a line roughly parallel - to the grooves , as in -, _____________ Figure 21. - _____________ - ~~ - Pream~lifiers. The ‘ ‘ • 5 - preamplifier housings - -~~~~~~ • . -... - were encrusted with - , - - fairly uniform layers - •1 of red rust. Some cre— _ _ _ _ vices and corners con— • - - ~ tam ed a yellow pow— • dery corrosion product. _ _ _ _ _ _ - ‘ The housing interiors _________ had no evidence of - - ~~ seawater leakage. Cor- ________________________ rosion at the seals -. progressed up to the ~l:~L 5 ~~~~~~~~~~~~~~~~~~~~~~~~ _ _ _ first 0—ring in all . ~~~~~~~~ •-.‘ cases as shown in Fig- ure 21. This was ex— ~~~~~~~~~~~~~~~~~~~~~~~ pected since water is _ _ _ _- ~— ~~;-- ~~~~~~~ - normally present up to that point. In cases - - - - -~~~~ ii where the 0-ring is ‘ •~~ r . - ~~~~~~~~~~~~~~~~~~~~ heavily greased the ~~~~~~~ • between the plug and gland to Figure 18. Corrosion in Housing, prevent intrusion of Main Junction Box (Enlarged) water for some time. This delays corrosion 17 of the 0—ring surface. Report 1332 43 - • ~~~~~~~ ~~~~~ • ~ _ - ~~ . - - _ i ‘5 :‘ . ‘ Figure 19. Corrosion on Circuit Board , Main Ju nction Box (Enlarged) ‘ ~~~~~~~~~~~~~~~~~~~~~~! I __ _ - • - • ,. •,5• - - & ~~~~~~~~~~~~~~~~~~ -•- • ~~~~ - _ _ _ _ _ _ _ ____ ~~~~~~~~~~~~~~ _ -. _ _ _ _ ___ j ~~~~~~~~~ _ ~~~~~ ,- ~ -‘ _ ~~~~~~~~~ — _ _ _ _ _ _ _ _ _ _ _______ Figu re 20. Corrosion of 0-rin g Surfaces , Main Cable End Plate (Enlarged) _ _ _ _ Figure 21. Corrosion of 0—ring Surface, C Pr.a~aplLfier Cable Seal (Enlarged 1.5X) - - - • - 18 - - - - Report 1332 In the case of the x pre- amplifier cable seal end cap, _ _ _ _ -~~ ~~~~~~~ _ _ _ _ corrosion reached the seccrid -, .~~~~~~~ - •. _ _ _ _ _ 0—ring (see Figure 22). The _ _ _ _ 0-ring glands of the housings _ _ _ _ _ _ ~~- ~~ - were corroded to the depths _ _ _ _ • 1. corresponding to the corro— ~~ ~~- $ 5. __________ sion on the plugs , as shown in Figure 23 for the C pre— * - ~ _ _ _ _ amplifier . The c preampli- ~~~~~ - ___ fier had a ruptured capaci- ~~‘ . 1 tor (Figure 24) in the tun- ~~~~~. - ~. ing circuit. This was a a _ _ _ _ 0.l-microfarad capacitor _ _ _ rated at 200 Vdc . It pro- vided ac ground to seawater • _ _ _ _ _ _ _ on the secondary side of the hydrophone tuning cir - _ _ _ _ _ cuit to prevent oscillation - ~ _ _ _ _ _____________ in the preamplifier circuit. ~~~ -. The failure is believed to _ _ _ _ _ _ have been caused by the high voltage surge of a lightning strike . Strikes had occurred _ _ _ _ _ in 1968 and 1973. The resis - _ _ _ _ _ _ _ tance across the damaged capacitor was 1 megohm. This ~~~‘ - would not have materially - I - - l ‘ affected functioning of the - I & ti~ preamplifier. - - _______ 1 eiIE~ Morrison Seals. A total TTIhTj”f i I I ! Ii of 13 Morrison seals were _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ - inspected including one on - the main cable; seven on the Figure 22. CorrosIon of 0-ring Surface , interconnect cables at the ~ n1arged 2X) junction box , and one on each of five preamplifiers. The corrosion in the gland of the main cable seal had pro- gressed 1.238 inches into the seal to the point at which the shield is soldered to a feed-through pin. Figure 25 is a photograph of the seal, whose overall length was 2.4 inches. Water was found at the shield termination but little corro- sion had occurred there. Since the main cable had been cut and the array subsequently re-submerged for towing to shore , the water probably entered along the shield from the cut. However , the corrosion path along the gland wall indica tes that some water entered at the wall. The copper foil of the shi eld on the main ca ble was corroded along its full length, about 10 feet, indicating the presence of water. No evidence of water leakage was seen beyond the second seal. The assembly of the seal differed from current 19 Report 1332 -J - -~~~~~~~~~~~~~~ _ _ _ _ - - - _ _ _ _ -~~~ • ,, ~~ -1 _ _ _ • _ _ _ _ _ _ Figure 23. Corrosion of 0—ring d ana, C Preamplifier Housing (Enlarged) _ _ - figure 24. Ruptured Capacitor , C Preamplifier (Enlarg ed) 20 Report 1332 ~~~~~~~~~~~~ ~~~~~~~~~~ ~~~~~~~~~~~~~~~~~ 4/ — / •,// - - ~~ - •-- - ~~~~~ - ~ -~~~- ___ / - ~~~~ - ~~~ --- ~~~~~~~~~~~ , ~~~~~~~~ ~~~~~~~~1 ~~~~~~~~~~~~~~~ ~ - ~~~~~~~~~~ ~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~- -~ -‘~!~ ~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~ ~1 Ji ~ ~~~~~~~~~~~~~~~~~~ ~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ _ _ kr~ r~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ p -4t _ _ _ _ __ __ __ ~~~ - - : . ~~ - ~~~ - - - 5 - - ‘- • - ~i* • - ~ •• ~~~ I ~ • ~ • 1~ 5• - .5 ~ • - • _____________ _________ ~ ____________ • - ~~—~~~~~~~~- p - - ~~~~ - - ,.,. — - • • **5*.~~ - _ _ _ _ _ _ - _*y - ~ ~~~~~~ -t~~~ ~~~~~~~ ;• ~~~~~~~~~~~ _ _ _ _ _ • -~~~~~~~“ - ~~~~ - ~~ ~- *~~~ ~~~~~~~~~ Figure 25. Main Cable Seal , Array 10 (Approx . life size) practice in that the cable armor wires were terminated about 10 feet short of the junction box in a lead—filled steel collar. The conductors then continued to the junction box seal through a protective rubber hose. The Morrison seals of the interconnect cables at the junc- tion box were inspected . The average corrosion depth along the gland walls on seven seals was 0.839 inches. The depth of a complete seal is 2 3/8 inches. The deepest penetration was 1.075 inches (in the c preamplifier seal), reaching the area of the shield breakout point where the shield is soldered to a feed—through pin. Seawater at this point would create an elec- trical path between shield and ground . The lowest resistance measured was 59k ohms between shield and case at the x preamp- lifier . This resistance is not low enough to cause a signal or circuit failure ; however , it could cause a very small amount of electrolysis. The average corrosion depth in the Morrison seals at the five preamplifiers was 0.904 inches; the deepest at 1.005 inches. This is about the same depth as the corrosion in the junction box seals. Interconnect Cable. The interconnect cable was a coaxial type similar to RG—58. The jacket material was polyurethane • 21 Report 1332 and the underlying shield a braided , tinned copper wire. The dielectric was polyurethane extruded over a stranded center conductor. Close examination revealed transverse cracks in the jackets of all the interconnect cables. The cracks became evident on the outside radius as the cable was formed into a small—radius loop (see Figure 26). In most cases the cracks did not completely penetrate the jacket; however , in the cases where the cracks did penetrate it was not obvious that water had entered to the shield . The shield was not badly corroded as would have been the case if the jacket had leaked . This indicates that the cracks appeared during or after recovery and were caused by flexing of the cabling . It appears that the plasticizer in the polyurethane leached out, leaving the material brittle in spots. The cracks did not appear to be localized to any particular area of the cables and apparently were not re- lated to cable placement on the array. Hydrophone Seals and Transducer. The rubber boots sealing the transducer mounted atop the preamplifiers were inspected . All five hydrophones evidenced water leakage to the 0-ring from the wire—wrapped seal at the base of the boot. Figure 27 is a photograph of the xy hydrophone without the boot , which fits over the 0-ring and the rounded flange at the base of the - - ~~~~ ~~~~~~~~~~~~~~~~~~~~~ -. • - -. . . . ,‘. %,• .5 — -‘U ’. - * Figure 26. Jacket Cracks , Interconnect Cable (En larged BX approx.) 22 Report 1332 transducer. The boot is secured — _ _ _ _ below the round ed flange with a _ _ _ _ _ double wrap of stainless steel _ _ _ _ wire. The wire in no case showed • ____ _ evidence of deterioration. Evi— - dence of water leakage past the _ _ _ _ S 0—ring was present on the c , y, .. - . and z hydrophones , although no • . ;‘ . 5 moisture was visible. The c _____ - • - . hydrophone had the “highest” __________________ watermark and is shown in Fig- _ _ _ _ _ _ - ure 28. Elec trical resistance between the hydrophone and case ‘ ~~~~ ~~~~~~~ - . _ _ _ was about 1 megohm , which again _ _ _ _ _ _ _ • would probably not affect opera- - _ _ _ _ _ _ _ _ _ _ _ _ _ _ tion of the hydrophone. It was - • ~~~~~~~~~~ - _ _ __ _ __ _ __ _ _ noted that the surfaces of the ~~~~~~ - ~~~~~. ~~~~ - transducers were dry upon re- ~~~~ ‘ . ~~~‘ ~~~~‘ .:!:j . ;. . ~~~.. - . moval of the boot. The practice - S~ -::~. - . . , at NAVTORPSTA is to use trans- - ~~~~~~~~~~~~~~~~~~~ ••~~~ ducer oil in the boot to facili— - - tate assembly and to preclude - ~~ •* -• air under the boot. The oil Fiqure 27. XY Hydrophone , Boot Removed - - (Enlarged l.4X at~ rox.) also helps prevent intrusion of - water . ARRAY ‘10 FAILURES _ _ _ _ - _ _ _ _ The faulty tilt signa l origi- ~~~~~~~~~~~~~~~~~~~~ nally noted was not evident in ‘s” P a bench test. However , infor- - - mation from recovery personnel _ _ _ _ - • indicates that the main cable _ _ _ _ _ / • • • leading to the array was defec— _ _ _ _ _ ‘ - • tive .- The section between the • - in—line amplifier and the array _ _ _ _ _ _ - • - . : was replaced when the new array _ _ _ _ was planted . Poor signal con- _ _ _ _ _ _ ditions are a typical result of _.. ~~~~ low resistances between conduc- • I tors in the main cable. The sig— - nal waveform observed at St. Croix , (Figure 16), may be the - tracking signal super imposed on _ _ _ _ _ _ _ _ _ a full—wave rectified 60-Hz line ripple. The frequency of the • -, ‘ - : ~~~ ,~~ ,. . larger amplitude signal is about -. -~~ . . • ~~~~~ , 120 Hz and the frequency of the 5 .j ~~~~~ ~~~~~~~~~~~~~~~ -. ~~~~~~~~~~~~~~~~~ smaller wave about 20 kHz. The F igure 28. Watermar)c clipped appearance of the 20 kHz , on Lower Side of Sphere, which contains tilt information , C Hydrophone (Enlarged l.4X approx .) may be caused by a power-starved amplifier , which cou ld r esul t from a bad cable. 23/24 Report 1332 4 . CONCLUSIONS ARRAY 7 The malfunction of the c preamplifier was due to an open in the base junction contact of the Ql input transistor. The x preamplifier failure most probably was due to a low-resistance path between the shield and center conductor . Crevice corro- sion at the seal gland progressed past three ru bber seals in- to an area where seawater created a conductive path between the conductors. The 0—ring seals held up well except for the seal at the main cable entry in the junction box . Corrosion was found beyond the second 0-ring in that seal, whereas little to no corrosion was seen beyond the first 0—ring in the other seals. The main cable seal had a 12 per cent squeeze versus a 23 per cent squeeze on the 0-rings at the preamplifiers. The leak past the second 0—ring is attributed to the lower squeeze. Corrosion in the Morrison seal glands had reached an average of 1/2 to 3/4 of the total length of the seal at the junction box and preamplifiers respectively. Differences in seal interference fit did not account for the difference in corro- sion depth. The polyethylene—jacketed interconnect cable held up well. The shield showed slight corrosion in some cases at the termi- nations where some moisture got through the seals. The life of array 7 apparently was approaching its limit as indicated by corrosion in the seal glands. The failure of the x preamplifier appears to have been caused by seawater intrusion into the cable seal. This type of failure is ex- hibited by a gradual degradation of the tracking signal and a decreasing electrical resistance between shield and seawater ground . Arrays of similar design and age should be showing these indications now and if not will do so within two to three years. ARRAY 10 The cause of the tilt circuit failure could not be deter- mined . In a bench test at NAVTORPSTA the circuit functioned normally. However , during array replacement at St. Croix , a portion of the main cable indicated low resistance readings and was replaced . This section of cable could have been the cause of the bad tilt and tracking signals received at the computer site . 25 Report 1332 Lightning damage was apparent in the c preamplifier , which sustained a burned grounding capacitor at the secondary of the hydrophone tuning transformer . The Morr ison seal glands of the in ter connect ca bles showed water intrusion to an average of about one-third the length of the seal. The Morrison seal of the main cable had water leakage to its midpoint . The 0—ring seals in the worst case showed slight corrosion between the redundant 0-rings. In most cases corrosion did not extend beyond the first 0-ring . The polyurethane jacket of the coaxial interconnect cable cracked when a small loop was formed , indicating lOSS of plasticizer in the jacket material. The cracks apparently were not present when the array was on range , since the shield was not corroded in areas where the cracks penetrated the jacket completely. Three of the five hydrophones showed evidence of water leakage at the boot. Watermarks were visible on the trans— ducer elements above the mounting pedestal. It is estimated that the additional life of this type of array will be about 3 years. The crevice corrosion in the Morrison seal glands went deeper on array 7 than in array 10 although array 10 had been in service 117 months compared with 76 months for array 7. Some difference in construction of the seals was noted . The older array 10 seal used hard rubber back—up washers behind each seal , whereas the array 7 seals used nylon back-up washers. Also the rubber seals were slightly harder in array 10, which had a shore A of 43. The array 7 seals had a shore A of 35. No analysis of the metal in the seal glands was done . The reason for the difference in corrosion rates was not determined. 26 Report 1332 5. RECOMMENDATIONS 1. The only leak past a double 0—ring occurred where the 0—ring squeeze was 12 per cent versus 23 per cent at other 0—ring seals. It is recommended that the higher squeeze be • used to achieve a longer service life. 2. The type of polyurethane—jacketed coaxial cable used on array 10 should not be used for long—term submergence applications. - ~~ Report 1332 DIST RIBUTIOfl Copy AFWTF , St. Croix , VI Commanding Officer AFWTF , St. Croix , VI St. Croix Range Officer 2 RCA — Ron Kirkpatrick 3 RCA - John Williams 4 NAVFACENGCOM , Chesapeake Division , Wash. Navy Yard FPO 1 5 FPO lE9 (Bill Gardner ) 6 APL/UW Pence 7 Sandwith 8 DDC (TIMA) 9,10 NAVTORPSTA Code 70 11 7002 12 702 13 7032 14 ,15 704 16 7041 17 80 18 ~üi 19 8012 2fl 0115 - ?1 throu&t ) I~ t 29/30