WAVY PCE L_ Tech Va te N-1858 May 1993 NI = By H. Thomson Sponsored By Naval Facilities Technical Note Engineering Command TA Sa NZ Nis58 DIVER-OPERATED BURIED PIPE AND CHAIN LOCATOR ABSTRACT A prototype system has been developed for use by the Navy Underwater Construction Teams (UCTs) in locating submerged ferrous objects (such as pipelines and mooring chain). The system con- sists of a commercially available magnetometer modified to meet the UCT mission requirements. The magnetometer, a fluxgate sensor built for terrestrial use, is manufactured by Forster Instruments, Incorporated. The sensor was modified to be used underwater by divers, or dipped (slow towed) from a small inflatable boat. This report documents the develop- ment of this prototype tool, called the Diver-Operated Buried Pipe and Chain Locator. en en CIVIL ENGINEERING LABORATORY PORT HUENEME CALIFORNIA 93043-4328 Distribution limited to U.S. Government agencies and their contractors; Research and Development, May 1993. 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Send comments regarding this burden estimate or any other aspect of this collection information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302, and to the Office of Management and Budget, Paperwork Reduction Project (0704-0188), Washington, DC 20503. 1. AGENCY USE ONLY (Leave blank) 2, REPORT DATE 3. REPORT TYPE AND DATES COVERED May 1993 Final: FY83 through FY92 4. TITLE AND SUBTITLE 5. FUNDING NUMBERS DIVER-OPERATED BURIED PIPE AND CHAIN LOCATOR PR - Y1606-SL-01-001-A600 6 AUTHOR(S) WU - DN387346 H. Thomson 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESSE(S) 8. PERFORMING ORGANIZATION REPORT NUMBER Naval Civil Engineering Laboratory 560 Laboratory Drive TN - 1858 Port Hueneme, CA 93043-4328 9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESSE(S) 10, SPONSORING/MONITORING AGENCY REPORT NUMBER Naval Facilities Engineering Command Alexandria, VA 22332 11. SUPPLEMENTARY NOTES 12a. DISTRIBUTION/AVAILABILITY STATEMENT 12b. DISTRIBUTION CODE Distribution limited to U.S. Government agencies and their contractors; Research & Development, May 1993. Other requests for this document shall be referred to NCEL. 13. ABSTRACT (Maximum 200 words) A prototype system has been developed for use by the Navy Underwater Construction Teams (UCTs) in locating submerged ferrous objects (such as pipelines and mooring chain). The system consists of a commercially available magnetometer modified to meet the UCT mission requirements. The magnetometer, a fluxgate sensor built for terrestrial use, is manufactured by Forster Instruments, Incorporated. The sensor was modified to be used underwater by divers, or dipped (slow towed) from a small inflatable boat. This report documents the development of this prototype tool, called the Diver-Operated Buried Pipe and Chain Locator. wom 14. SUBJECT TERMS 15. NUMBER OF PAGES Magnetometer, fluxgate, pulse induced 60 16. PRICE CODE 17. SECURITY CLASSIFICATION 18. SECURITY CLASSIFICATION 19. SECURITY CLASSIFICATION 20. UMITATION OF ABSTRACT OF REPORT OF THIS PAGE OF ABSTRACT Unclassified Unclassified Unclassified UL NSN 7540-01-280-5500 Standard Form 298 (Rev. 2-89) Prescribed by ANSI Std. 239-18 298-102 - Ce OM RE eae Nadeeaniyrmeth annonce Weve’ eee ; AVON ov) GE na ANNAN: BL CN AERO T TARE aT nenhere AA NIOd Ga te nD peters went arnt extbant cot “d vee oi ait Penge “Kirtle ne = ony Dp aeage a oc ait eae ab ri = nem, iy Salers SO4FG Ns, nervy ants | Sev RgpomaH Ee, : ane me femmes RO et hi ; = ib wnt " Py. x - ‘ I iy Seaiesiceekdiineniinmeldametiniiedtatehiainn manana Retail rime yh din ORUFOOROT 2) “174 re he ee a Am | ita tis a a iad) bos asinaege jnonunrsveO 2. of heherll Ds aduaanin, THO 9EGEL CRM dearer yl 3 Crve! Bahay aly Cast st 3 ys #} eR gniigao! wi ( Rath le ensat juarieiedobae ‘Y sidsliave ylleenstimnas BAoxiieAOD Hee Ants 103 Sue tense oiKg aus Telstnobdg teiewiobnn Doel odo! i nee aie yourae oT. coil ,asglosrarsienl OHO" patent Ueto SHO. hi é Fa i af , 7 : a an eo paca cae Comets { fn i oe y 3 = fd a # rm, a ; if \) i v i ie ! A aeet tha G] Dal => a Ad sorry RM 2 t Pda Ae 60 ay eee mee jose wnt AT ma) sere i) Af YVR we ‘ ISABeA AO. , bailiegsionj oS owl) OS erat rene’ Seat) aol tree of Sete rant CONTENTS LINGER OD WGHONM acreage coves sins) cicetvanianeas agency seated suceihaerabet tus er AbcnuaWeN BACKGROUND? F20ssor ais OF Wit THAN ACHES ET RORE TLE COPS CONEY, ADVANCED DEVELOPMENT MODEL (ADM) SYSTEM .............. Equipment Descriptionie gamete Livre. vrcuicks suctans Fmt clio Maka ter lan seeetolee JEaloyey eke 7 ISHS 15.'o GB ANG Bais ek G00 bloc is duos Ob) (6. GuoccNOLbNoo10 Ould ol OD Oceanlestss, HM ARAN (RCT. MR SRE s,s ok sulle cas votieiiew eld aces, BBs Conclusions and Recommendations from the ADM Tests ............ ENGINEERING DEVELOPMENT MODEL (EDM) SYSTEM ............ SyStemPDESCHIPHOM ao ccsvehcrsiss enone ste eyes suelo au sine mana ianiomarml steawens cs RehiabilityTestsie SSRCoht Giese. WET ORR DVS IER RCaS. SANIT, diy, S08 SIDES @perationaldE flectivenessins ace 4 aueioney nea sc woke cies ats cece ore cater ats WSERGMES Siren c secce san tale Sint ewes eel ana aac y oie Gilera ab lor ateranres eat ala heyhey CONCLUSIONS Wr REF ON AECE, OR SURE NCEE MSE TTI OEE: TOES RECOMMENDATIONS ill cca tnasvehe suai av euet outers een anie ten at coments kel one aleey eels REDE RIENCES. haly ARE BME CORUTC EEOC, WO SUP OOR UND DMRS): CST APPENDIXES A - Component Description - Metal Detecting System Mission and Required Operational Characteristics ............. B - Comparison of Physical Characteristics .................... C - Detection Thresholds for Pulse-Induced Systems .............. D - Detection Thresholds for Forster Ferex ...............2.+e8. D-1 yen ert INTRODUCTION Under the sponsorship of the Naval Facilities Engineering Command (NAVFAC), the Naval Civil Engineering Laboratory (NCEL) has developed a metal detecting system. This system was developed for use by the Underwater Construction Teams (UCTS) to locate buried or submerged metallic pipe, chain, anchors, and miscellaneous ferrous objects. The tool is a marinized Forster Ferex magnetometer (Model 4.021) and is designed for use in either a dipping mode (from an inflatable boat) or a self-contained diver-operated mode. Attributes of the system include the following: 3 Zs Visual and audio output. Adjustable sensitivity. Adjustable standoff device between the magnetic sensor and the operator. Rechargeable battery-powered system (each set lasts up to 6 hours). Minimal maintenance at the UCT level (the unit is sealed and will not be broken down for repairs or overhaul except by the Depot maintenance activity Ocean Construction Equipment Inventory (OCEI) or manufacturer). This report documents the development of the Diver-Operated Buried Pipe and Chain Locator (BP&CL), and provides documentation to support the production milestone decision. BACKGROUND An efficient, safe, and reliable metal detecting system for UCT use is required to provide underwater detection and tracking of the following items: Ile De oe 4. Chain (1-1/2 inches or larger) buried up to 6 feet. Pipelines buried up to 2-1/2 feet. Anchors (6,000 pounds) buried up to 10 feet. Armored cable (SD List 5) buried up to 3 feet. In the past, several types of diver-operated systems have been investigated and developed for use by Naval Underwater Demolition Team (UDT) and Explosive Ordnance Disposal (EOD) divers. These include the MK-14 magnetometer, a cesium vapor magnetometer, and the MK-10 gradiometer. However, these developments were tailored to the special requirements of ordnance l work (i.e., low magnetic signatures and detection of nonferrous materials). In addition, these systems typically require specialized training and diving equipment that is not readily available to the UCTs. To provide a suitable system for UCT use, an investigation of specific UCT requirements and an evaluation of both military and commercially available systems were performed. Appendix A lists the Test and Evaluation Master Plan (TEMP) thresholds for the BP&CL. To identify candidate metal detecting systems and technologies suitable for UCT use, a literature survey of metal detecting systems was performed by NCEL. This survey, documented in Reference 1, encompassed both active and passive military and commercially available systems and identified several promising candidate systems that appeared to be suitable for UCT use. These systems were: @ Navy MK-10 @ Garrett XL500 @ Fisher Pulse 10 Fisher Pulse 8 @ White’s PI-1000 @ Forster Ferex 4.021 Figure 1 shows the family of metal detecting systems. The MK-10 is a portable diver-held fluxgate magnetometer designed as an ordnance locator. It has been in service since the early 1960s. However, the Navy EOD community has experienced extreme difficulties in keeping sufficient units operating (Ref 2) and is in the process of phasing this system out. The Garrett, Fisher, and White’s units are commercially available pulse-induced systems. With the exception of the Fisher Pulse 10, these systems were developed primarily for the treasure or sport diver. The Pulse 10 is a boat-towed system. The Forster Ferex 4.021 is a magnetometer designed for terrestrial use. UCT-ONE has used this system with some limited success to locate a 12,000-pound anchor at the Naval Weapons Station, Earle, New Jersey. It was reported (Ref 3) that one of three buried anchors was located using this system. However, only the probe can be submerged. The power and control modules are not submersible. To determine the suitability of these systems for UCT use, tests and evaluations of these systems were performed at NCEL. The results of this evaluation are provided in the next section of this report, Advanced Development Model (ADM) System. Based on the results of the ADM testing, the Forster Ferex magnetometer was modified to provide enhanced performance for UCT use. This development is documented in the Engineering Development Model (EDM) System section of this report. “stun g[qepreae - sulayshs SuNjeOO] [RII [ inst “1X4. NI SHASWNN NOILOAS OL H343H SHABWNN, 2 "ew J8usi4 Gps | wey Jeusi4 bb's €eS-VD ipalsuoyys H'l'S Xa]aW 13}S1904 E'S O02-AVD IPsISUOYIS E'S KO8ZI YOIeaseaY JE YSI4 Z' b's X9194 19}SIB04 OIG i! SGOd t'9°S 6 MW I'S Gc MW LS OLMWE LS O00S1X Heed p'Ss 998-5 D894 eS OOO! Id S8NUM E°S'S 18D GOW S84 ECS Ol esind JaYsIy oG'S | UOJOJd JBUSIA CCS 8 Sind JaYsi4 1°S'S viLHN cos paonpu| $J0]e907] JOyOes | pedwnd UOISS899Jq WALD asind Y/L a1ge0 Ajeondo U0}OJd areBxn|4 JB}AWOA ceyv Lop ez b 22'b Lop BOK] aAHOY BAY @AISSed aAissed aAISSed | | apow (s10}9818q |e18W\) S10}B90 7} JayawoIpely jenuajod HYVNOS onauBbew;-01199|9 joyawoyeubey snoauejuods vy ev rAn yl SSeID SWAILSAS DNILV9OT 1O3raoO OMVLaW aal"uns ADVANCED DEVELOPMENT MODEL (ADM) SYSTEM To evaluate the most promising candidates identified in the state-of-the-art survey (Ref 1), the following units were purchased for test and evaluation: li. Garrett XL500 De Fisher Pulse 10 35 Fisher Pulse 8 4, White’s PI-1000 ah Forster Ferex 4.021 The Navy MK-10 system was not available for evaluation. A request to the Navy EOD community for loan of an MK-10 indicated that there were relatively few of these units operating. The following is a description of the systems purchased for evaluation. Equipment Description Pulse-Induced Systems (Garrett XL500, Fisher Pulse 8, and White’s PI-1000). Pulse- induced systems operate by intermittently pulsing an electric current into a coil, creating a high- energy magnetic field. When a transmitted pulse encounters a metallic object, eddy currents begin to flow in the metal, which in turn generates a second magnetic field. This field is sensed by the coil, amplified, and then either displayed by a meter or heard in an earphone. Figure 2 shows the Garrett XL500. It is supplied with either a 10-inch or a 13-inch coil. The electronics package is detachable so that it can be worn on a belt. Control features include the following: Ie Detection Depth Setting - A three-position rotary switch for maximum, normal, or minimum output. 2: Audio volume. 3: Trash Eliminator - A rotary switch for adjusting the discrimination level. The Garrett has both audio and visual output. Headphones are provided for the audio output. A meter located on the electronics package provides visual indication of the signal strength. Figure 3 shows the Fisher Pulse 8. It comes with a 10-inch-diameter coil. Detection is indicated to the diver by both a meter and tone (via an earphone). The electronics package can be removed from its holder for servicing or replacement. Control features include the following: Ihe Detection Depth Setting - A three-position rotary switch for selecting high, medium, or low output. A U/W Earphone Handle Extensions Caseholder Figure 2 Garrett XL500. Figure 3 Fisher Pulse 8. Manufacturer: Garrett Metal Detectors, Tx. Model: XL500 Class: Metal Detector Sizes: 8 inch coil standard 13 inch coil optional Power Supply: Rechargeable Batteries Description: Totally Submersible, Diver Held Manufacturer: J. W. Fisher Manu- facturing Co, Ma. Model: Pulse 8 Class: Size: Charger Power Supply: Rechargeable Bat- terles Description: Totally Submersible, Diver held Metal Detector 10 inch dia. coil De Zero Adjustment - A rotary switch for adjusting the discrimination level. 3F Battery check. Figure 4 shows the White’s PI-1000. It comes with a 10-inch-diameter coil. Detection is indicated to the diver by an audible clicking and by light-emitting diode (LED) display. It can be powered by six "AA" alkaline or rechargeable batteries. Controls feature a rotary switch for on/off operation, battery check, and tuning/zeroing. Magnetometer (Forster Ferex 4.021). A fluxgate magnetometer is made up of a coil of wire wound around a highly permeable core. The core is driven in and out of saturation by a low-frequency electrical signal. This saturation, which is affected by changes in the total ambient magnetic field, is sensed by a separate winding and amplified to provide a signal to the operator. Manufacturer: _ White's Or. Model: PI 1000 - Class: Pulse Induced Sizes: 10 inches dia. coil Power Supply: Batteries Description: Totally Submersible, Diver Held Figure 4 White’s PI-1000: The Forster Ferex 4.021 consists of two fluxgate magnetometers mounted in the opposite ends of a probing bar. This unit is available in both land and underwater versions. The underwater version, shown in Figure 5, is designed for use in bore-hole applications. The system consists of a 24-inch-long submersible probe, extension cable, power supply, and a control/signal strength indicator unit. The power and control units are not waterproof. Control features include the following: 1. Sensitivity Dial - The sensitivity of the unit is adjustable between 3 gammas and 10,000 gammas. 2 Operating Mode Switch - The operating mode switch provides selection of one of the following: a. Normal searching. b. Normal searching with some small ferrous metals damped out. (Bs Special searching for searching next to large ferrous metal objects such as pipes. d. Compass to find north, south, east, and west. de Sensitivity Test Switch - A momentary contact switch for checking proper operation. 4, Battery Check - Located at the first position of the sensitivity dial. Do Volume Control - Two momentary contact switches (up and down) for adjusting the audio output of the probe. Laboratory Tests The objective of the laboratory tests was to provide initial performance data on the candidate metal detecting systems. Three sets of laboratory tests were performed: (1) comparison of physical characteristics, (2) sphere of detection tests, and (3) electronic characteristics analysis. The results of these tests are summarized below. Comparison of Physical Characteristics. The physical characteristics of each unit were examined for general construction, human factors engineering, and maintenance. Table 1 lists test results of the items measured or evaluated. Appendix B contains a discussion of qualitative results. Manufacturer: Institute Dr. Forster, West Germany Side view —————— =775 ————_} L* "Bee Sag Hal - ; : 3

Includes only the probe with 2 pounds ballast weight. Detection Threshold. The objective of this test was to obtain baseline detection threshold data on each unit in air. Figure 6 shows the test setup for the pulse-induced systems. As a standard, twin 72 SCUBA tanks were used as the detection target by moving them toward the detector from various angles. Upon initial detection of the tanks, the angle and distance of detection were noted. Figure 7 shows the test setup for the Forster Ferex magnetometer. Since proper operation requires that the probe be oriented with its major axis perpendicular to the earth’s surface, these tests were conducted by lowering the probe toward the tanks until a half- scale reading was obtained. Appendix C contains detection thresholds of the pulse-induced systems plotted for coil angles of 0 degrees, 45 degrees, and 90 degrees at the various power settings of each unit. Appendix D shows detection thresholds of the Forster Ferex plotted for sensitivities of 100 and 300 gammas. The results of these tests showed the following maximum ranges for each of the units in air: i Forster Ferex - 7.0 feet (sensitivity switch set at 100 gammas) De Fisher Pulse 8 - 5.7 feet 3 Garrett XL500 (with 13-inch coil) - 5.1 feet 4, Garrett XL500 (with 7-inch coil) - 2.7 feet os White’s PI-1000 - 3.3 feet ANGLE DETECTION METAL DETECTOR GROUND Figure 6 Setup for testing the range of pulse-induced systems. From the results of these tests, it is clear (in air at least) that larger detection distances can be expected with the Forster Ferex unit. Electronic Characteristics Analysis. The electronic characteristics of the pulse-induced systems were analyzed in order to obtain a baseline comparison of common features. Several of the characteristics examined include pulse width, response time, energy per pulse, and battery life. Figure 8 shows a general block diagram for pulse-induced metal detecting systems. Table 2 summarizes the test results. In comparing these results with the results of the detection threshold tests, the units with the larger signal output have the greater detection range. They also have the shortest battery life. Also, the response time of the different units should be noted. In comparison to the other units, the Fisher Pulse 8 has a very long response time. The long response time is undesirable since the unit can easily miss a target unless the coil is moved very slowly. Ocean Tests In January and February 1986, ocean tests of the four candidate metal detection systems were conducted offshore of the West Jetty at the Naval Construction Battalion Center, Port Hueneme, California. These tests were conducted to determine the detection capability of each unit for buried chain (1-1/2 inch) and buried armored cable (3-1/2-inch diameter). No tests were planned at this time for detection of an anchor (6,000 pounds) buried to 10 feet and armored pipeline (5-inch diameter) buried to 2-1/2 feet. 10 u Ferex we Measured i Control Instrumentation | ~ Distance and. Power Supply “ddd Figure 7 Setup for testing the range of the Forster Ferex. TIMING TRANSMIT CIRCUIT DRIVER SAMPLE/ HOLD BATTERY/ POWER RECEIVER/ SUPPLY AMPLIFIER EARPHONES Figure 8 Pulse-induction metal detector block diagram. Table 2. Electronic Characteristics Analysis Garrett XL500 White’s PI-1000 _ Sas Pulse 8 Output Pulse Width Output Pulse 9.5 milliseconds 300 milliseconds 11.5 milliseconds Repetition Rate Energy Per Pulse 4.6 millijoules 25 millijoules 13.8 millijoules BOWE USURRIY. 9.6 volts DC 9.0 volts DC 8.2 volts DC Voltage Power Supply 110 to 125 ee 310 to 325 approximately 100 approximately 500 approximately 200 Receiver | Receiver Sensitivity _| | unable to measure _| to measure 12 to 15 hours on six nonrechargeable "AA" batteries 9 hours on fully charged batteries 4 hours on fully charged batteries Battery Life 12 In preparation for these tests, an underwater search range consisting of 1-1/2-inch chain, 3-1/2-inch armored cable, and twin 90 steel tanks was prepared in about 35 feet of water. These targets were buried in sand approximately 30 feet apart from each other with floats attached for identification. The targets were buried by fluidizing the soil around the target with a jetting nozzle. Burial depths were estimated by measuring between the surface of the sand and reference marks on the float line. The test procedure consisted of swimming the range with the metal detecting device and searching each target location. At sites where a target was located, the maximum detection distance was estimated by raising the sensor above the target until its detection threshold was reached. The detection depth was estimated by adding the distance between the sensor and the seafloor to the burial depth of the target (estimated from the tape marks on the float line). In addition to these tests, the Forster Ferex was used in the dipping mode to assess this operating scenario. During these tests, the Ferex was used from an inflatable boat with the probe submerged to within about 10 feet of the bottom. The distance off the seafloor was estimated by periodically lowering the probe until slack appeared in the cable. Results of the detection tests are shown in Table 3. Detection thresholds from the TEMP are also listed for comparison. These tests show the following: ile The detection ranges of commercially available pulse-induced systems cannot meet the detection thresholds of the TEMP. In addition, several serious deficiencies were noted for each system. These are as follows: a. Garrett XL500 - Although this unit out-performed the other pulse-induced systems, it did not have the ruggedness required for UCT operations. During these tests the arm rest bracket broke off. In addition, the meter display was small and difficult to view. The headphones were awkward to wear and had a tendency to slip off the head. The sound was also muffled significantly when the headphones were worn over a diving hood. b. Fisher Pulse 8 - This unit was difficult to zero (adjust to background interference) because of the 2-second response time of the electronics. Proper adjustment of the zero is important for optimum performance. If the zero is overadjusted, then the unit becomes too sensitive and is susceptible to the detection of small, insignficant items. If the zero is underadjusted, then the sensitivity of the unit is decreased, thereby decreasing the detection distance. Once properly adjusted, the slow response time requires that the unit be moved very slowly to avoid missing a target. In addition to the zeroing problem, the unit was awkward to handle because the front end "planes" from side to side. This is because the front-end housing of the sensing coil is shaped in a solid disk and therefore presents resistance to forward motion. This motion further compounds the problem related to the slow response time of the electronics. Cc. White’s PI-1000 - This unit could not be zeroed during these tests. Subsequent inspection of this unit indicated that the detent mechanism on the main switch was either broken or worn at the position for tuning/zeroing the unit. No further tests were conducted with this unit since it generally lacks the integrity and ruggedness required for UCT use. 13 Table 3. Metal Detecting Systems Testing Summary Tank (Twin 72) Armored pice Armored Laboratory Cable (3- Pipeline Tests 1/2-Inch (6000 Diam) Pounds) Roc Dn The Forster Ferex unit has the greatest detection range among the systems tested. As shown in Table 3, the Ferex unit met the TEMP threshold for detection of armored cable and was within | foot of meeting the TEMP threshold for detection of chain. These tests were con- ducted with the unit set at a sensitivity of 300 gamma. While the unit does have a greater sensitivity (and presumably a greater detection distance), it was difficult to use at a higher sensitivity for the following reasons: a. The diver’s gear became a significant magnetic target. To reduce this effect will require either nonmagnetic equipment for the diver or a standoff device (about 5 to 7 feet) between the probe and the diver. b. Periodic adjustment (zeroing) is required and the diver does not have direct access to the control instrumentation with the present configuration of the unit. Since the control instrumentation is not waterproof, all tuning adjustments (such as selecting the operating mode (mode 1, 2, or 3) and the sensitivity, as well as periodic compensation for background noise) must be done at the surface by a remote operator rather than at the dive site by the diver. This operating scenario can easily result in confusion (particularily at the higher sensitivity levels) unless the diver and top-side operator know exactly what the other person is doing. © Use of an earphone as the sole means to provide detection signals to the diver is inadequate. Although the diver earphone provides a good general indication of target strength, it does not adequately provide specific location information. This is because the tone 14 level does not change significantly when the unit is moving over a target (unless the probe is moved very slowly over the exact magnetic center). By comparison, the meter located on the control instrumentation swings from one extreme to the other (i.e., positive to negative) when the sensor is moved over a target. This provides clear indication of the target location. Results of the dipping test indicated that the Ferex used in this mode of operation provides a system for general location of targets. This feature is clearly beneficial since it can minimize diver time in the water. For use in this mode, the Ferex must be used at high sensi- tivity levels since it is towed with the probe approximately 10 feet off the bottom. This requires that a maximum distance be maintained between the probe and the boat since the boat can be a significant magnetic target at high sensitivity levels. It was also noted that there is a tendency for excess cable in the boat to become tangled and knotted. Snarling and entanglement of cable in a small boat is a nuisance and a safety hazard, and can also result in damage to the electrical conductors in the cable. As shown in Table 3, the TEMP thresholds for detection of an anchor (6,000 pounds) buried to 10 feet and armored pipeline (5-inch diameter) buried to 2-1/2 feet were not tested with these systems. Based on the results of the laboratory and ocean tests, it appeared unlikely that the pulse-induced systems in their current off-the-shelf form would meet these requirements. However, the Forster Ferex appeared to have the capability for detecting these items. Table 4 shows the magnetic signature of SD cable (list 5), armored pipe (5-inch diameter), and a 6,000- pound anchor at 5 feet, 4-1/2 feet, and 12 feet, respectively (Ref 1). Based on this information and the results of the ocean tests, it appeared highly likely that the Forster Ferex could meet these TEMP thresholds. Table 4. Magnetic Signatures of SD Cable, 5-Inch Pipe, and 6,000-Pound Anchors Burial Depth (ft) | Sensor Distance (ft) pee tae SD List 5 S-Inch Pipe 2-12 6,000-Pound Anchor 3,055 Conclusions and Recommendations from the ADM Tests 1 Commercially available pulse-induced systems cannot satisfy the performance requirements of the TEMP. Increasing the detection thresholds may be possible by modifying these systems to incorporate a more powerful system with a larger sensing coil. ae The Forster Ferex magnetometer had the greatest detection distance among the units tested. Modification of this unit holds the most promise for providing a metal detecting system suitable for UCT use. 15 Based on these results, the following recommendations were made for the Engineering Development Model system: le The Forster Ferex magnetometer should be modified for use in both dipping mode (from an inflatable) and self-contained diver-operated mode. This system should also be designed for quick and easy conversion between these two operating modes. 2 The dipping mode should incorporate a spring wound reel for paying-out and handling the cable between the probe and the electronics module. 3) The self-contained diver-operated mode should incorporate ready access to all control adjustments and a standoff mechanism between the sensors and the diver. No electronic modifications are anticipated. ENGINEERING DEVELOPMENT MODEL (EDM) SYSTEM From May through August 1987, laboratory and ocean tests of the engineering development model BP&CL were conducted to verify reliability and performance thresholds (as specified in the Test and Evaluation Master Plan, TEMP) and identify any safety or human factors deficiencies. System Description The EDM system consisted of a commercially available Forster Ferex (Model 4.021) system modified for use by the UCTs. Modifications to the magnetometer consisted of new waterproof housings and accessories for use in two different operational modes: (1) as a dipping mode from an inflatable boat, and (2) as a self-contained, hand-held diver tool. Figure 9 illustrates the two operational modes. The stock Forster Ferex 4.021 magnetometer is designed to sense anomalies in the earth’s magnetic field resulting from the presence of a ferrous object. To sense the anomaly, the magnetometer uses two fluxgate sensors located a fixed distance from each other inside a cylindrical probe. The output from the fluxgate sensors are processed and converted to provide the operator with both audible and visual signals. As the magnetic field disturbance increases, the intensity of the signal output increases. The visual output is a meter with an indicator needle that shows increasing signal strength by moving off-center to the nght or left depending on the polarity of the section that the probe is approaching. As the probe is passed over the object, the needle swings across the meter to indicate signal strength in the opposite polarity. The earphone indicates increasing signal strength by increasing the frequency of the audio output. Standard control features of the Forster Ferex 4.021 magnetometer include the following: It Mode Selector Switch - Any one of four different search functions can be selected with this switch. Mode 1 is for normal searching of all ferrous metals. Mode 2 is also for normal searching but eliminates disturbances from small ferrous objects. Mode 3 is used when searching next to a large ferrous object (such as a pipeline). Mode 4 allows the tool to be used as a magnetic compass. 16 Figure 9 Two operational modes for the buried pipe and chain locator. 3 Compensation Switch - The compensation switch is used to "zero" the instrument in operating modes | and 2. This feature compensates for magnetic noise at a search site by resetting the output to read zero. 3s Test Switch - The test switch is used to check for proper operation of the system. 4, Sensitivity Selector Switch - The sensitivity switch is used to select one of eight sensitivity levels between 0.3 to 1,000 gammas. Do Volume Switch - The volume control switch regulates the output level of the audible signal. Modifications to the existing system consisted of reconfiguring the tool for use in both the dipped mode (from an inflatable boat) and a diver-held mode. The modifications included new, waterproof housings for the control electronics and batteries, a telescoping standoff device (to maintain distance between the diver’s gear and the sensing probe), and a cable reel for using the probe in the dipped mode. Figure 10 shows the EDM BP&CL. Reliability Tests Reliability is expressed as the probability that the BP&CL will perform its functions without failure within performance characteristics for a-4-hour mission. The threshold reliability specified for this tool by the TEMP is 90 percent. The mean time between failure (MTBF) is an estimate of the true system reliability based on the mission time and threshold reliability. To assure that the test duration will verify the system reliability, a confidence level multiplier is applied to the MTBF estimate. Table 5 summarizes the required test durations for confidence levels of 60, 80, and 90 percent. The number of failures recorded within the test period determines the confidence level achieved at 90 percent reliability. Based on this information, a 98-hour test period with no failures is required to demonstrate a 90 percent reliability with 90 percent confidence for a MTBF of 42 hours. Table 5. Reliability Test Time Required MTBF (hours) Confidence Test Time (hours) re 42.4 60 130 42.4 A as 180 42.4 97 160 220 18 A1SW3assv MYOS "11¥dd [oepow jusuidojaasp suusoursua ay) Jo Ajquiase pue sjuguodwog OL ans ywovd ANOHdYva AUSLLVE SdWV19 ONILNNOW | yuvay 2 LNOU D Cy Le ‘LS - — LANYDO07 3JIGNVH ; 5 ONISNOH AYSLLVE 1071S 3718v9 a31av9 uaMOd 4HOLOANNOD ONISNOH sa SINOHL9373 ae ane ONILNNOW a1avo 380Ud \ 3gGOud S38nL NOISN3LX3 19 Table 6 shows the results of the reliability tests. No failures in over 107 hours of operation were observed, demonstrating a reliability greater than 90 percent with 90 percent confidence for a MTBF of 42 hours. The test was interrupted only once a day for replacement of batteries. Two items requiring minor modification were identified during these tests: the sensitivity switch and the low battery indicator system. The sensitivity switch is a "break before make" type that sometimes tums the output volume off when changing sensitivity levels. Since this does not affect completion of the mission (the operator simply readjusts the volume), this item was not categorized as a failure. However, a more suitable switch will be used on the preproduction models. The low battery indicator system monitors the battery voltage and provides early warning to the operator when the battery is getting low. During the initial part of these tests, the indicator system was only providing about 2 to 3 minutes warning before the system would quit working. Table 6. Reliability Summary : Test Hours ae Completed Volume level sometimes affected by changing sensitivity levels. 2 20.6 Battery voltage low. Low battery indicator not yet lit. Battery test functioning and shows a low battery condition. New batteries installed. Battery voltage low. Low battery indicator not yet lit. 5 64.5 New batteries installed. Battery life was 43.9 hours. Note: No audio output was generated during this period of battery use. meee | 105.1 Battery voltage low. 7 107.5 New batteries installed. Battery life was 43.0 hours. Note: No . audio output was generated during this period of battery use. Pe 107.5 Reliability testing completed. This problem was corrected during the testing by changing a resistor value in the low battery circuit. About 30 minutes of operation is available after the low battery indicator light comes on. Operational Effectiveness To determine the operational effectiveness of the BP&CL, both laboratory and ocean tests were conducted. The objective of the laboratory tests was to establish detection thresholds for the BP&CL. The effects of sand on the detection distance of buried objects were also 20 investigated. The ocean tests were performed to verify performance under operational conditions and to identify any safety or human factor deficiencies. Laboratory Tests. The objective of the laboratory tests was to verify the detection thresholds specified in the TEMP. Table 7 lists the TEMP detection thresholds for SD List 5 cable, armored Simplex Pipe, 1.5-inch chain, and a 6,000-pound anchor. Table 7. Vertical Detection Distances TEMP Hee Ge ty an (ft) Detection ensitivity Level (gamma) Threshold Sah an ea Dae ioae Pipe (5-inch) Simplex with Armor inch) CHO Set OO | Oe) SO a SHG Pounds) gro] [Leos [| fe In theory, the sand or water covering a buried ferromagnetic object should not greatly affect the detection distance (provided this covering has a relatively undetectable magnetic signature of its own). To verify this, the detection thresholds for an SD List 5 cable section (about 7 feet long) and 3/4-inch chain were measured while they were buried in sand and lying on the beach surface. The results of this test confirmed that the individual detection distances of the SD List 5 cable and the 3/4-inch chain were the same whether the objects were buried or lying on the sand. The detection threshold for both the buried and unburied cable was 36 inches with the tool set for a sensitivity of 100 gammas. The detection threshold for both the buried and unburied chain was 20 inches with the tool set for a sensitivity of 100 gammas. Based on the above results, the detection thresholds for the buried objects listed in the TEMP were determined in the laboratory by measuring the vertical distance between the probe and the object with the object lying on a bed of sand. These tests were performed by lowering the probe directly over the target for each sensitivity level until a half-scale deflection of the meter was observed. The vertical distance between the probe and the target was then recorded for each sensitivity setting. 21 The results of these tests and TEMP threshold values are shown in Table 7. These results show that the BP&CL met or exceeded all of the detection distance thresholds specified in the TEMP. During these tests, it was observed that a slight swinging of the probe produced detection ranges that were greater than those possible with the probe hanging still over the target. With the probe hanging still over the target, increasing signal strength is indicated by an increase in the deflection of the indicator needle. As the probe is moved over the object, the indicator needle swings from one polarity to the other. The motion of the indicator needle swinging from one polarity to the other provides a better indication of the presence of the object than a slowly increasing needle deflection. In performing these tests, the accuracy of locating the position of the target was also evaluated. The TEMP specifies an accuracy of 1 foot or the depth of burial, whichever is greater. Because the indicator needle swings from one polarity to the other as the midpoint of the object is crossed, the accuracy of locating the target is very good. Based on these tests, the accuracy of locating the target is estimated to be within the TEMP specifications. Ocean Tests. The objectives of the ocean tests were to verify the operational performance of the system and to identify any safety or human factor deficiencies. These tests were conducted offshore Port Hueneme, California, with dive support provided by the NCEL dive locker. To verify the operational performance of the system, both the dipping mode and diver- held mode of operation were tested from an inflatable boat. Prior to beginning the test, a 7-foot length of SD List 5 cable and a 6-foot length of 3/4-inch chain were positioned on the ocean floor in approximately 35 feet of water. The chain was stretched out in a line to produce a line source target (as opposed to a point source for a pile of chain). The relative positions of the tar- gets were recorded using visual sightings. To verify the operational performance of the system in the dipping mode, the system was assembled for operation in the inflatable boat (at the test site) and suspended in the water column while the boat performed a slow speed grid pattern search. The probe was positioned about 3 feet off the seafloor during this search by periodically lowering it to get slack and then reeling in 3 feet of cable. To aid in towing the probe, a 2-pound brass weight was attached to the end of the probe. While executing this search pattern, both the cable and the chain were located with a sensitivity setting of 10 gammas. In both cases, the meter polarity was observed to change as the probe passed over the target. To verify the location of the target, the system was converted on site (in the inflatable) to the diver operation mode and used by the divers to pinpoint and provide positive identification of the target. To locate objects on the seafloor, the divers were given about 1/2 hour of instruction prior to the operation. Locating objects in the diver operation mode requires the diver to conduct an iterative procedure of rotating 360 degrees (with the probe extended outward), observing the direction of the largest magnetic signature, and following the direction of the largest magnetic signature until he finds the object or travels 20 to 30 feet. Using this technique, both divers were readily able to find both targets in water with visibility of about 5 feet. In one case, the diver reported that he walked right by the target without seeing it but observed that he passed it by the change in the meter polarity. After completing the above tests, the operators were asked to complete a human factors evaluation form on the system. In general, the tool qualities were judged to be suitable for use 22 by the UCTs. One of the divers felt the probe end of the telescoping rod was slightly heavy and could use a small amount of buoyancy (less than 2 pounds). This addition would make the tool almost neutrally buoyant in the water and easier to handle and operate. Two of the divers commented on the need for diver training in the operation of the tool. Neither felt the amount of training required would be excessive, perhaps an hour or so of instruction in its use, restrictions, operating procedure, and search techniques. In addition, many of the operators commented that the audio output turned off at least once when they switched sensitivity settings. Controls were judged easy to operate and located properly for a hand-held tool. In the 2- to 3-foot visibility, the display could be seen and the individual LEDs were distinguishable. One diver commented that the green color of the display LEDs might be more difficult to see under certain limited visibility conditions than a red display. None of the divers felt the need to increase the length of the standoff because of interference from ferromagnetic items of their scuba gear. One diver commented that he was able to swim with the tool as he operated it. High/Low Temperature Testing. To verify the operation and performance of the BP&CL at extreme operating and storage temperatures, both high and low temperature tests were performed. Table 8 shows the TEMP thresholds for temperature. Temperature thresholds as listed in the manufacturer’s literature on the commercial Ferex are also listed for comparison. Since the modifications to the commercial unit were limited to the housing and the LED operator display, the manufacturer’s temperature values apply only to the sensing probe and the processing electronics. Table 8. TEMP and Manufacturer Thresholds for Temperature TEMP Thresholds Operational Water Temperature 28 to 85 °F -22 to 130 °F Nonoperational (storage) ‘ ; To verify the cold operating and cold storage temperature thresholds in the TEMP (28°F and -20°F, respectively), the BP&CL was tested in the NCEL Polar Laboratory Facility. These tests were performed in air and in a tank filled with fresh water. The temperature in the fresh water tank was regulated by adjustment of the air temperature in the cold chamber. A thermocouple with digital readout was used to monitor the temperature of the water. Air temperature was monitored using the temperature gages provided in the cold chamber. To begin the cold tests, the air temperature in the cold chamber was lowered to about -17°F. The BP&CL was then placed in the chamber (going from a temperature of about 63°F to -17°F) over night while the cold air cooled the water in the tank. In the morning, new batteries were placed in the BP&CL and the tool was turned on and used (in air) to find rebar placed in the cold chamber. The BP&CL was then placed in the tank while the water 23 temperature was being lowered. After about 4 hours, the BP&CL was pulled from the tank and operated in air to find the rebars. The water temperature was about 34°F with ice beginning to form at the surface. No operational problems were encountered during these tests. To verify the high temperature operating and storage thresholds in the TEMP (85°F and 140°F, respectively), tests of the BP&CL were performed with the tool submerged in a tub of warm water after sitting outside (in direct sunlight) while packaged inside its storage container. To monitor the temperature inside the container, both a thermometer and a thermocouple (with digital readout) were placed inside the contain. With the ambient air temperature (in the shade) at approximately 82°F, the temperature inside the box eventually reached 125°F. The BP&CL was then taken from its storage container and placed in a tub of warm water (approximately 90°F) for about 20 minutes. The BP&CL was then turned on inside the tub of water and then pulled out and used in air to locate rebar laid on the ground. No operational problems were encountered during these tests. USER TESTS To verify the suitability of the tool for UCT use, user tests of the modified Forster Ferex system were performed offshore Anacapa Island by the NCEL dive locker. Although these tests were originally scheduled with UCT-TWO (and NCTC Delta Company as a backup), fleet scheduling conflicts required using the NCEL dive locker to avoid further schedule delays and additional project costs. Reference 4 authorized NCEL to conduct the user tests with in-house personnel previously stationed with either UCT-ONE or UCT-TWO. These tests were performed in March 1988. The test consisted of divers using the BP&CL (in the diver-held mode) to find a 10-foot section of 1.5-inch chain placed on the seafloor. The chain was placed about 100 feet away from the dive station (LCM-8 boat) in about 45 feet of water. The sea conditions were considered good, with 10 feet of visibility, no current, and a water temperature of 65 degrees. Prior to beginning the dive, the operators received a 15-minute instruction on how to use the BP&CL (both divers were unfamiliar with its use). Upon reaching the bottom, the divers determined which course to take by using the audio and visual output of the BP&CL while making a 360-degree turn. This procedure was repeated after traveling a short distance (about 30 to 40 feet) until the chain was found. The total time on the bottom actually searching for the chain was about 5 minutes. Comments from the divers indicated that the BP&CL meets the operational effectiveness and operational suitability thresholds stated in the TEMP. One problem mentioned was the loss of the audio output signal while adjusting the frequency control. This problem will be solved by substituting the switch with a "make before break" type. CONCLUSIONS The EDM test results show that the BP&CL has met or exceeded the TEMP thresholds. Table 9 shows TEMP thresholds and summarizes test results. The reliability thresholds were met with a confidence factor of 90 percent. There were only two minor incidents observed during this portion of the test and neither would prevent the unit from performing its mission. The test battery life of 43 hours was judged to be in excess 24 of actual operating battery life since the unit was not generating any audio output during the tests. It is estimated that actual battery life will consist of at least 25 hours of operation. The detection thresholds were met for all items listed in the TEMP. This includes a detection range of: (1) 2-1/2 feet for 5-inch-diameter Simplex pipeline (with a layer of armor), (2) 3 feet for SD list 5 armored cable, (3) 6 feet for 1-1/2-inch chain, and (4) 10 feet for a 6,000-pound anchor. The weight and balance of the tool in the diver-operated mode was judged acceptable by the divers. However, making the probe end of the standoff device neutrally buoyant would add to the tool’s effectiveness. In the dipping mode of operation it was noted that the unit can be used effectively from an inflatable boat. The speed of the boat must be kept slow enough to permit the probe to remain perpendicular to the seabed. RECOMMENDATIONS Based on the results of the development effort, it is recommended that: 1. The Buried Pipe and Chain Locator be approved for limited production of three systems. 2. The performance of the three systems should be monitored by NCEL during a UCT operation to insure a smooth transition into fleet use. 3. The User Data Package prepared during the EDM effort should be updated with as-built drawings after fabrication of the three production systems. 4. The Buried Pipe and Chain Locator should be included in the NCTC school as part of the training curriculum. REFERENCES 1. Naval Civil Engineering Laboratory. Memorandum to files on the survey of diver-operated metal detecting systems, by Eastport International, Inc. Port Hueneme, CA, Jul 1985. 2. Naval Explosive Ordnance Disposal Technology Center ltr Ser FL/165 of 19 Sep 1985. Subj: Use of MK-10 magnetometer. 3. M. Oliver, CEC (DV). Personal communication, Naval Civil Engineering Laboratory, Ocean Operations Division, Port Hueneme, CA, Jan 1986. 4. H. Herrman. Telephone conversation, NAVFAC and H. Thomson and S. Black, NCEL, Mar 1988. 25 Table 9. TEMP Thresholds and Test Results Characteristics TEMP Threshold EES ® Test Results Specification 1. Operational Effectiveness Self-contained, rechargeable, or replacable 6 to 12 volt (6 mono- cells each 1.5V) Power Supply 6 replacable alkaline D cells Operational life cycle 6 hours Detection Distance 6 feet 6.1 feet Buried chain, 1.5 in. or larger 2.5 feet Buried pipeline (S-in.-diam Simplex 4.0 feet w/armor Anchors (6,000 Ib) 10 feet 10 feet Armored cable (SD List 5) 3 feet 6 feet Location on seafloor will <1 foot be 1 foot or the depth of burial, whichever is greater Accuracy of Detection Location on Seafloor Weight (system) In air 35 pounds 21 pounds (excluding 20.8 pounds = case) In water 3 pounds +/- | pound N/A 3 pounds On the beach to 190 feet of water Demonstrated 0 to 55 feet Operational Range 0 to 300 feet (probe) Handling Diver-held mode Carried by one free swimming diver (requires only one hand to carry underwater, but may require two hands to operate) One hand to carry, two hands to operate Boat-towed mode The sensing probe can be towed at slow speed from an inflatable boat Demonstrated towing from inflatable boat 28 to 85°F 5 to 149°F Demonstrated 34 to 90°F Operational Water Temperature Demonstrated -20 to 125°F Nonoperating Temperature -58 to 176°F (with lithium batteries) Operating Turbidity N/A Demonstrated 3- to 10- foot visibility Clear water to zero visibility 26 Table 9. Continued Characteristics TEMP Threshold A Enea Test Results Specification 2. Operational Suitability Life Mean Cycles Between Failure >20 based on MTBF of 42 hours Reliability of a Single Unit >90% at 90% confidence level Preventative Maintenance Times Daily (excluding recharging power <1 hour (limited to source) wash-off and O-ring lubrication) End of Project 1.5 hours <1 hour (limited to wash-off, O-ring lubrication, and systems check) <3 hours (recalibration at Depot level) 1 hour <1 hour (limited to O- ring replacement) Skill Level 75% of all divers can 4 out of 4 divers can operate with | hour of operate with | hour of instruction on beach instruction on the beach 27 - soe je TMA baad Oe i 1 eek Mh ya one ae hai lial 4 =. By. ean \ ‘ Pisce eeaspart {eae ST, ahs | a i ki | rem a ghar hy resets > oto / yo de Tie omg 5 deg nihge noiaaementt AoW IKs SUA Oe faerie i Chmnectivehe anele Laeeeaierme. Winns Teugeprtivire 2 Meare seedy dypeweet 7D titans Aris mgnnarcateny et tin mime Mira ate Nalin: ahd na OR a arin ipo nt mog wont ee Pe ee oe Ton ro reser ae con i | | a eee i Ww 1 sabe Sioa Da eae 1 bei at dae ae NA Se Aneaediag iver, (peiquclaneil, | HAAY anes Decent) (ah gure ree, a ah Pegs Wwe ands ber ; RCA j asntied ity od t Wyk saiplany occ Mpa an ti ede np A, ferris a8 hee sorted Row | fe 4} hoe \otanshely heeh’: eva Ae ig PS mies Fo neon eS me Ye Wn laassunt Ee pai Appendix A COMPONENT DESCRIPTION - METAL DETECTING SYSTEM MISSION AND REQUIRED OPERATIONAL CHARACTERISTICS MISSION: To locate and track underwater metal pipelines, armored cable, and chain. Characteristic Threshold A. Operational Effectiveness @ Power Supply Self-contained, rechargeable or replaceable - Operational life cycle 6 hours @ Detection Distance - Buried chain (1-1/2 inches 6 feet or larger) - Buried pipeline (5-inch 2-1/2 feet diameter Simplex with layer of armor) - Anchors (6,000 Ib) 10 feet - Armored cable (SD List 5) Sifeet ®@ Accuracy of Detection <1 foot or depth of burial @ Weight - In air <35 Ib - In water 3) oe Mt Me) ®@ Operational Range On the beach to 190 feet of water Characteristic Threshold @ Handling - Diver-held mode Carried by one free swimming diver (requires only one hand to carry underwater, but may require two hands to operate) - Boat-towed mode* The sensing probe can be towed from an inflatable boat @ Operational Water Temperature 28 to 85°F @ Operational Turbidity Clear water to zero visi- bility B. Operational Suitability @ Life (sensor system or >7 years component which will likely contact seafloor regularly during operation shall be abrasion resistant (on sand or gravel) or inexpensive and easy to operate) @ Mean Cycles Between Failure >20 ®@ Reliability of Single Unit >90% @ Redundant Supply or Two or More Units is Acceptable @ Reliability of Two Units >99% @ Preventative Maintenance Times - Daily (excluding recharging 1.0 hour power source) Characteristic - End of project - Annual @ MTTR/On-Site Maintainability (limited to replacing O-rings and power pack - all other repairs at depot level) @ Production Cost (assume order of 5, FY85 dollars) @ Skill level *Revised content. Threshold 1.5 hour 3.0 hours 1.0 hour $20,000/unit 75% of all divers can operate with 1 hour of instruction on the beach » Vantin 0 MONEE Mia besos Lo erg soe 0.1 fi \O00 OSE Heatownnd) “ingde” fey aot the Yo aET to wow | Rew stew Seaidiaiiibneihibiaiiaal @ Dennen Tiartidiey B, Capevaticoaad, Sciiatylliny ® Lith (sensor svokim ir component welrich will likely contact pratoor rexgularty: during operation «ial. an sherman. fasistant (oe. sail ‘or Braves) of inenpensive oe Rey 1h Operate ® Meng Cycits Between Failure Reltabitity of Single ( fot * —oeys ub Supe ply iar Two or More Jit la Agesptabie * Ratiability of Teo Unit | * Proventalive Mainienante Termin "1 Dally (excludi ig there prone wutgn) Hime : Appendix B COMPARISON OF PHYSICAL CHARACTERISTICS VISUAL OUTPUT Garrett XL500 POOR. The indication meter is located on the top of the electronics housing, which is either worn around the waist or attached to the top of the sensing wand. Target strength is indicated by an analog meter with scale readings between low and high. In either position, the meter is poorly positioned for viewing. With the housing attached to the sensing wand, the operator must lean forward over the wand and electronics housing to view the meter. With the housing attached to the belt, the operator must twist and bend over at the waist to view the meter. In addition, the meter is not back-lit for viewing in dark or low visibility areas. White’s PI-1000 POOR. There are two light-emitting diodes that are located inside the electronics housing. One diode provides a battery check indicator. The other diode indicates the presence of metallic objects by blinking (the higher the frequency of blinking, the greater the target strength). Although these diodes are positioned well for viewing, this form of indication is somewhat ambiguous since the output is qualitative in nature. Fisher Pulse 8 FAIR. The target indication meter is located on the sensing wand and is an integral part of the handle. The meter is adequately sized and positioned well for viewing. However, the meter is not back-lit for viewing in dark or low visibility areas. Forster Ferex GOOD. Signal strength, battery status, and check indicator for proper operation are all displayed on an analog meter. Although the meter is not submersible, it provides a good indication of target strength and location. This is because the sensitivity of the unit can be adjusted to obtain quantitative readings and the meter swings from one extreme to the other (i.e., positive to negative) when moving over a target. B-1 AUDIO OUTPUT Garrett XL500 FAIR. The audible output from this unit is an oscillating tone that increases in volume as an object is detected. This method of detection is adequate and allows for a reasonable reaction time. However, the headphones are cumbersome and the sound may become muffled if the headphones are worn over a hood. White’s PI-1000 FAIR. This unit has a clicking indicator that changes clicking speed as an object is detected. Discernment of the change in clicking rate is fair. However, the headset has only one transducer and is not well balanced. Because of this, the headset is very difficult to keep from sliding off the user’s head. The sound may also become muffled if the headset is worn over a hood. Fisher Pulse 8 GOOD. This unit comes with a diver earphone that may be used inside a diver’s hood. The earphone indicates the presence of a target by a change in its output tone (higher frequencies indicate increased target strength). Forster Ferex FAIR. This unit has a clicking indicator that changes clicking speed as an object is detected. Discernment of the change in clicking rate is rated as fair. GENERAL HANDLING Garrett XL500 FAIR. The handle design and weight distribution is good for supporting this unit. However, the wand length is adjusted by adding either one or two extension rods that are connected together by nuts and bolts. This type of fastening arrangement is not well suited for quick adjustment to wand lengths, particularly in a small boat or by divers in the water. The parts of the fasteners are also likely to become lost. White’s PI-1000 GOOD. The handle design and weight distribution is good for use in handling this unit. In addition, the length of the wand is easily adjusted by means of a telescoping mechanism on the wand. The rod uses compressive pins that lock into holes on the outer tube. Since no tools are required for adjustment, varying the length can be done easily on land, boat, or in the water. Fisher Pulse 8 POOR. The handle design and weight distribution is poor due to inadequate balancing (the front end is heavy) and lack of a forearm rest. As a result, short duration, limited handling of this unit is likely to fatigue the arm. The mechanism for adjusting the wand length is also rated as poor. Adjusting the wand length is done by unscrewing threaded pieces of PVC pipe and removing or adding sections. The extra sections would have to be taken with the diver for adjustment to be made underwater. Forster Ferex NOT APPLICABLE. This system was not designed as a diver tool. RUGGEDNESS Garrett XL500 FAIR. The ruggedness of this unit is rated as only fair. Although the electronic housing appears very rugged, the arm rest and sensing coil attachments appear weak and prone to damage. All plastic portions of the wand should be replaced with aluminum tubing. White’s PI-1000 FAIR. The wand and the attachment points for the handle, arm rest, and coil appear to be fairly rugged. However, the overall rating is only fair because the electronics housing appears prone to damage. The housing is a thin-walled plastic enclosure that is positioned on the top of the wand grip. In this position, the housing extends outside the body of the unit and is susceptible to impact or snagging. Fisher Pulse 8 POOR. This unit is poorly constructed. The wand, fabricated from PVC pipe, is weak and inadequately designed for supporting the components of the system. The attachment points for the coil, handle, and electronics housing are welded PVC and also appear fragile. The electronics housing appears to be the only ruggedly constructed component of this system. Forster Ferex GOOD. The components of this system appear very rugged and well constructed. However, only the probe is submersible. The electronics housing and power supply would require redesign to make these components waterproof. MAINTENANCE Garrett XL500 GOOD. Maintenance is rated as good since this is limited to recharging the batteries (required after 9 hours of operation), periodic lubrication of O-rings, inspecting for signs of wear or damage, and rinsing the unit with fresh water after use. The batteries are charged by plugging a 12-volt transformer (supplied with the unit) into the earphone connector. All O-rings on the connectors and the electronic housing cover are accessible and easily replaced. White’s PI-1000 GOOD. Maintenance on this item is rated as good since it is limited to replacing the batteries every 12 hours, lubricating O-rings on the cover to the electronics housing, inspecting the unit for wear or damage, and rinsing the unit with fresh water after use. Although the batteries are nonrechargeable (six "AA" batteries) they should be readily available in most locations. Fisher Pulse 8 FAIR. Maintenance on this unit is minimal (limited to charging the batteries, inspecting the unit for wear or damage, and rinsing the unit with fresh water after use) but is rated as only fair since the batteries require recharging after 4 hours of operation. Forster Ferex GOOD. Maintenance on this unit is limited to replacing the batteries, inspecting the unit for wear or damage, and rinsing the probe with fresh water after use. REPAIR Repair of all four systems is rated as fair. Repair of these units in the field is limited to replacement of O-rings. All other repairs such as replacement of faulty electrical components or repair of mechanical items (i.e., broken handles, stripped threads, or damaged electrical housing) must be conducted at the Depot level. MATERIALS OF CONSTRUCTION Garrett XL500 SENSING WAND: aluminum tube and plastic COIL COATING: plastic ELECTRONIC HOUSING: plastic OUTPUT TRANSDUCER: plastic earphones B-4 White’s PI-1000 SENSING WAND: COIL COATING: ELECTRONIC HOUSING: OUTPUT TRANSDUCER: Fisher Pulse 8 SENSING WAND: COIL COATING: ELECTRONIC HOUSING: OUTPUT TRANSDUCER: Forster Ferex SENSING PROBE: ELECTRONIC HOUSING: POWER SUPPLY HOUSING: aluminum plastic plastic plastic coated PVC pipe plastic and potting compound plastic plastic coated aluminum aluminum aluminum clear with yellow stickers orange with clear cover COLOR Garrett XL500 WAND: white and silver COIL: white ELECTRONIC HOUSING: White’s PI-1000 WAND: black COIL: black ELECTRONIC HOUSING: Fisher Pulse 8 WAND: gray COIL: black ELECTRONIC HOUSING: Forster Ferex PROBE: ELECTRONIC HOUSING: POWER SUPPLY HOUSING: yellow with clear cover gray gray gray B-5 aE TAY. ohaens Eamets sie iyi ss ie, Ost NE ing ye aint wists 6 cl. Hic rel Aan peri war cage itae: ovith Fees unit) baler the con ions a ERS sein PES Re Cover ire: Pre ae bait uty Bae” Meee Lapananl bas pee wiv me sinele, MIRON NOR: CAig.. *aioranmn ov, phy enn is Balpn.aga IEA Val Ava hu wnneny T 2 Tenaga, Ly Cat DR Coschiegs, cats int Ayia With, chuotrnties nou ee ae, A Rea te dastigs, wus ere? ABV RT ‘wad, foes. water alter. dem. adnate: ae cn aN sAnaiteca ae Lene) ey shoud pa. haga’ : dl ee py a: pote, a Pieter Ptr’: . | eeeneenies a, Aeleaibeatatenanits aa ie aS ee iia HO: veene os ido: cath foe rome ver dace, Gd rinsing the cab, wiih) fiegh water after“aue) Wut likey ties the, bea sovton fe’ wi renhangine weft 4 hours of sail 2 ne om T eens VD, NenaeeHgbel by aay is oath vite a renny OW Samoan, ad = RANE OR ShPAse Rayalr uf all (our yystenns is tated as (Wir, Regasr ary hy rephicementat Outings, Another aayetsl aired RETR alt oe Weir of cnharical lems (1.4) broken. aren spo trea, ha heater). Wee: le comeiyictany eM the Depot siti VAT aa ») yes LAT CHtALS OF OO aie ro a rng Garvert ALA HATO AERTS SENTING WAITS shat tube and pe CONE COATING: pilastie. bc TRE BO Po pbaatie. hia. MSTREY PRs ANH ry lassi: ree Appendix C DETECTION THRESHOLDS FOR PULSE-INDUCED SYSTEMS NS as St. a be o> 60° \\ fo) 6' = as ; 90 Ss “a oa [ERE Ws) SEY high settings, O° coil angle. COILANGLE: 45° VES Ror TG RATT NZ, Appendix D DETECTION THRESHOLDS FOR FORSTER FEREX | Deaton arene (i ihe | a panes Probe Position Relative to Tartet at Half Scale Reading Height Above Target (Feet) 100 Gammas 7 ———= 5 300 Gammas Horizontal Distance From Target (Feet) D-3 er tbean efeok (Yost) dupe) onpdd tipieh | ‘ee oul feck DISTRIBUTION LIST AF / ROBERTS, PARTICK AFB, FL ARMY CEWES / (TW RICHARDSON), VICKSBURG, MS ARMY EWES / PERRY, VICKSBURG, MS; WESCD-P (MELBY), VICKSBURG, MS; WESCV-Z (WHALIN), VICKSBURG, MS BUREAU OF RECLAMATION / D-1512 (GS DEPUY), DENVER, CO; SMOAK, DENVER, CO CAL STATE UNIV / C.V. CHELAPATI, LONG BEACH, CA CHESNAVFACENGCOM / CODE FPO-1C, WASHINGTON, DC; YACHNIS, WASHINGTON, DC CITY OF MONTEREY / CONST MGR (REICHMUTH), MONTEREY, CA COLORADO SCHOOL OF MINES / DEPT OF ENGRG (CHUNG), GOLDEN, CO COMNAVACT / PWO, LONDON, UK, FPO AE COMNAVAIRSYSCOM / CODE 422, WASHINGTON, DC COMNAVSURF / CODE N42A, NORFOLK, VA; LANT, CO, NORFOLK, VA; PAC, CODE N-4, SAN DIEGO, CA COMSUBDEVGRU ONE / OPS OFFR, SAN DIEGO, CA COMSUBPAC / CODE 541, SCE, PEARL HARBOR, HI CORNELL UNIV / CIVIL & ENVIRON ENGRG, ITHACA, NY DCD, USAES / ATSE-CDM-S (SFC FARBER), FT LEONARD WOOD, MO DEPT OF BOATING / ARMSTRONG, SACRAMENTO, CA DFSC-F / ALEXANDRIA, VA DTRC / CODE 2724, BLOOMQUIST, ANNAPOLIS, MD EODMU / THREE, POINT MUGU, CA EXXON PRODUCTION RSCH CO / OFFSHORE OP DIV, HOUSTON, TX GEI CONSULTANTS, INC. / T.C. DUNN, WINCHESTER, MA IOWA STATE UNIV / CE DEPT, AMES, IA LONG BEACH PORT / ENGRG DIR (ALLEN), LONG BEACH, CA; ENGRG DIR (LUZZI), LONG BEACH, CA MBARI / SHANE, MOSS LANDING, CA MCAS / 16, MAG, TUSTIN, CA; PWO, KANEOHE BAY, HI MCRD / PWO, SAN DIEGO, CA MICHIGAN TECH UNIV / CO DEPT (HAAS), HOUGHTON, MI NAVCOASTSYSCEN / PWO (CODE 740), PANAMA CITY, FL NAVDIVESALVTRACEN / CO, PANAMA CITY, FL NAVFACENGCOM / CODE 04A3, ALEXANDRIA, VA; CODE 04A3C (HUBLER), ALEXANDRIA, VA; CODE 07M (BENDER), ALEXANDRIA, VA NAVOCEANO / CODE 6200 (M PAIGE), NSTL, MS NAVSHIPYD / CARR INLET ACOUSTIC RANGE, BREMERTON, WA NAVSPNSTA / PWO, CHARLESTON, SC NAVSTA / ENGR DIV, PWD, FPO AA; PWO, ROTA, SPAIN, FPO AE NAVSTA PUGET SOUND / CODE 922, EVERETT, WA NAVSUPACT / CODE 430, NEW ORLEANS, LA NAVSUPPFAC / CONTRACT ASSISTANT, FPO AP NCTC / PLATT, PORT HUENEME, CA NOAA / JOSEPH VADUS, ROCKVILLE, MD NORDA / CODE 500, NSTL, MS NRAD / CODE 944 (H.C. WHEELER), SAN DIEGO, CA; CODE 944 (ROBERT WERNLI), SAN DIEGO, CA NUSC / CODE 0031 DIVING OFFR, NEWPORT, RI NUSC DET / NEWPORT, RI; CODE 2143 (VARLEY), NEW LONDON, CT; CODE TA131, NEW LONDON, CT; DOC LIB, NEW LONDON, CT OCNR / CODE 1121 (EA SILVA), ARLINGTON, VA OREGON STATE UNIV / CE DEPT (BELL), CORVALLIS, OR; OCEANOGRAPHY SCOL, CORVALLIS, OR PACNAVFACENGCOM / CODE 102, PEARL HARBOR, HI PMTC / CODE P4234 (G. NUSSEAR), POINT MUGU, CA PURDUE UNIV / CE SCOL (ALTSCHAEFFL), WEST LAFAYETTE, IN; CE SCOL (LEONARDS), WEST LAFAYETTE, IN; ENGRG LIB, WEST LAFAYETTE, IN PWC / CODE 4004.3, FPO AP; CODE 421 (KAYA), PEARL HARBOR, HI; CODE 421 (QUIN), SAN DIEGO, CA SAN DIEGO STATE UNIV / CE DEPT (NOORANY), SAN DIEGO, CA SEAL TEAM / 6, NORFOLK, VA SEATTLE UNIV / CE DEPT (SCHWAEGLER), SEATTLE, WA TEXAS A&M UNIV / CE DEPT (HERBICH), COLLEGE STATION, TX; OCEAN ENGR PROJ, COLLEGE STATION, TX UNIV OF CALIFORNIA / CE DEPT (MITCHELL), BERKELEY, CA; NAVAL ARCHT DEPT, BERKELEY, CA UNIV OF HAWAII / LOOK LAB, OCEAN ENGRG, HONOLULU, HI; MANOA, LIB, HONOLULU, HI UNIV OF MICHIGAN / CE DEPT (RICHART), ANN ARBOR, MI UNIV OF NEW HAMPSHIRE / LAVOIE, DURHAM, NH UNIV OF RHODE ISLAND / PELL MARINE SCI LIB, NARRAGANSETT, RI UNIV OF TEXAS / CONSTRUCTION INDUSTRY INST, AUSTIN, TX UNIV OF WISCONSIN / GREAT LAKES STUDIES CEN, MILWAUKEE, WI USA EWES / WESCR-P (HALES), VICKSBURG, MS USACOE / CESPD-CO-EQ, SAN FRANCISCO, CA — USAE / CEWES-IM-MI-R, VICKSBURG, MS USDA / FOR SVC, EQUIP DEV CEN, SAN DIMAS, CA USN / CAPT COLIN M JONES, HONOLULU, HI USNA / OCEAN ENGRG DEPT, ANNAPOLIS, MD WESTNAVFACENGCOM / CODE 407, SAN BRUNO, CA; ROICC, SILVERDALE, WA WOODS HOLE OCEANOGRAPHIC INST / DOC LIB, WOODS HOLE, MA su DISTRIBUTION QUESTIONNAIRE The Naval Civil Engineering Laboratory is revising its primary distribution lists. 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