This is the maintenance manual for the EM 122 Multibeam echo sounder system. The manual contains detailed descriptions of each of the units in the system. Each circuit board and mechanical assembly is described. The manual also describes the troubleshooting process based on the Built-In Self test (BIST) software, and it includes procedures for disassembly and reassembly of the replaceable items. This manual does not describe the maintenance of the Operator Station and the peripheral devices (printers, plotters and sensors). For information about these items,
refer to the applicable manufacturer’s documentation. 1.2 Maintenance philosophy Kongsberg Maritime defines three levels for maintenance. 1 Organizational: You will only perform limited preventive and corrective maintenance on the system. There is no need for technical education or training, and no need for any instruments. Typical tasks are exterior cleaning, or changing fuses. 2 Intermediate: You will perform overall preventive and corrective maintenance on the system. It is recommended that you are an educated engineer with experience from computer, mechanical or survey systems. It is further expected that you can use standard electronic instruments, such as an oscilloscope. You should be trained by Kongsberg Maritime to perform maintenance on the system. Typical tasks may include troubleshooting, testing and circuit board replacement. 3 Depot: You will perform detailed maintenance on the system and on the circuit boards and modules. You must be an educated engineer with experience from computer, mechanical or survey systems. It is further expected that you can use standard electronic instruments, such as an oscilloscope. You should be trained by Kongsberg Maritime to perform maintenance on the system. Typical tasks are circuit board repair The EM 122 is designed to perform seabed mapping to full ocean depth with an unsurpassed resolution, coverage and accuracy. The system is cost effective, reliable, and easily operated. Compared with the EM 120 the EM 122 has up to four times the resolution in terms of sounding density through inclusion of multiping capability and more than twice the number of detections per swath.
High density signal processing is a major improvement, to keep the acoustic footprint size small even for the outer beams in the swath. In typical ocean depths a sounding spacing of about 50 m across and along is achievable The achievable swath width of the EM 122 is in the order of 30,000 m. This is obtained by using long FM chirps which improves the signal to noise ratio compared to CW pulses. The sectors are frequency coded or have FM chirps, and they are transmitted sequentially at each ping. The sector steering is fully taken into account when the position and depth of each sounding is calculated, as is the refraction due to the sound speed profile, vessel attitude and installation angles. The pulse length and range sampling rate are variable with depth (auto or manual) for best resolution. In shallow waters due care is taken to the near field effects through nearfield focusing individually applied in the different sectors. The EM 122 applies different focus ranges for each of the transmit sectors which are used. Dynamic beam focusing is used for the reception beams. The EM 122 operates at sonar frequencies around 12 kHz for high resolution. The ping rate is mainly limited by the round trip travel time in the water up to a ping rate of 5 Hz. Number of beams and soundings for each ping: • 4 degrees receiver: – 144 beams giving 216 soundings in High Density mode • 1 or 2 degrees receivers: – 288 beams or 576 beams in dual swath mode giving 432/864 soundings in High Density mode Functionality to limit Mammal Harassment The maximum sound intensity generated by the EM 122 is about 210 dB re 1 mPa. Maximum intensity is encountered in a thin wedge extending below the ship with an angular coverage of about 150 degrees. The intensity level may be lowered by 10 or 20 dB by the operator, at the lowest level the intensity will be less than 180 dB re 1 mPa for ranges larger than 30 m from the transmit transducer. The EM 122 may be set in a mode to begin pinging with a flexible soft-start as a possible means of inducing marine mammals to leave the area of high intensity sound. Transducer arrays The EM 122 transducers are linear arrays in a Mills cross configuration with separate units for transmit and receive. The arrays are divided into modules. For both arrays 1 and 2 degrees beamwidths are standard options, and 4 degrees beamwidth is available for the receive array. The resulting array lengths are between 2 and 8 m. Optionally the EM 122 transmit array can be delivered with a beamwidth of 0.5 degrees.
The system can also be delivered with a non-standard number of modules to optimize beamwidth in accordance with the vessel hull shape and size. Optional sub-bottom profiling The receive transducer is wideband. In conjunction with a separate low frequency transmit transducer, the EM 122 may optionally be able to deliver sub-bottom profiling capabilities with a very narrow beamwidth. This system is known as the SBP 120 Sub-Bottom Profiler. Acoustical seabed imaging Integrated seabed acoustical imaging capability is included as standard. Software to use this data for automatic seabed classification is available. Water column backscatter A real time display window for water column backscatter is available. Logging of water column data and of raw stave data (before beamforming) is a system option. Choice of operator softwares The EM 122 is delivered as a complete stand-alone seabed mapping system. The Operator Station, a high-performance PC workstation, includes the necessary operator controls for setting up and running the system, data logging and system testing. The Seafloor Information System (SIS) by Kongsberg Maritime also includes an extensive set of graphical displays for data quality control, as well as system calibration and other tools which are required. SIS supports on-line real-time data cleaning to improve the overall survey efficiencyOPERATOR STATION The HWS Hydrographic Work Station is the operator station normally used with the EM 122 Multibeam echo sounder. This is a basically a PC work station, but it has been specially designed for rugged maritime use, and it is prepared for mounting in a standard 19” rack. In the rack it will require four rack height units. The HWS is by default supplied with at 19” industrial LCD monitor, a keyboard and an optical mouse. The display monitor can be mounted in a 19” rack, however a bracket for table, bulkhead or roof mounting is provided.All components making up the HWS Hydrographic Work Station are standard commercial computer parts. 4.1 HWS overview The primary task of the HWS Hydrographic Work Station is to safeguard the collected data and to visualize it for quality control. The computer is equipped to handle the heavy processing requirements and the high speed, large volume data storage demands of hydrographic systems. It has been specifically designed as the optimal platform for running the Seafloor Information System (SIS) real-time operating software used on the Kongsberg Maritime EM multibeam echo sounders. The special features of SIS include real-time: • Gridding of sounding data • Filtering of sounding data • 3-D visualization of sounding data • Storage and visualization of high resolution backscatter data from the seabed and the water column
Reviews
There are no reviews yet.