Attachment_2_-_LRI-II_Testing_Specification.pdf

Attachment 2 - LRI-II Testing Specification

1.1.1 Data Collection Planning

The Contractor shall prepare for data collection by familiarization with LRI-II platform and coordination with USCG personnel for asset availability and location. Familiarization shall include reviews of structural drawings, program documents, operation profile, and other information necessary to successfully collect data. Coordination with USCG personnel shall include requesting documents, attending meetings or teleconferences as necessary, alignment of asset schedule, and location for primary data collection effort.

1.1.2 Data Collection

1.1.2.1 General

1.1.2.2 Operating conditions. The Contractor shall record structureborne vibration measurements for the minimum positions specified in 1.1.3.1.1 and at the Contractor identified positions described in the response to this solicitation. Structureborne vibration data shall be collected at each of the three speeds that correspond to Idle, Cruise, and Wide Open Throttle RPM. Background measurements shall be taken in accordance with 1.1.3.2.1.

The Contractor shall record airborne sound measurements for the positions specified in Appendix (A) at each of the three speeds that correspond to Idle, Cruise, and Wide Open Throttle RPM. Background measurements shall be taken in accordance with 1.1.4.2.1.

RPM settings will be determined at the time of the testing or during the data collection planning phase.

1.1.2.3 Reporting standards. Reference quantity identification. The applicable reference quantity shall be indicated on every table, figure, and graph, and at least once in the text. The reference quantity may be introduced by "re" which indicates that the level is "with reference to". For example, the 100 Hz one-third octave band level re 10 um/s2 is 85 dB.

1.1.2.4 Measurement bands. The bandwidths of the measurement bands shall be reported together with the measured levels. Normal procedure for reporting measured levels shall include the bandwidth and the band-center frequency with the level. For example: one-third octave 100 Hz band level was 85 dB re 10 um/s2; the 10 Hz bandwidth 100 Hz band level was 85 dB; or, the 6 percent bandwidth 100 Hz band level was 85 dB re 10 um/s2.

1.1.2.5 Plotting format.All plots of data in which a level in dB is plotted against frequency on a logarithmic scale shall be made on graphs in which a factor of ten in frequency is equal in length to 25 dB (preferred) or 50 dB. Where the bandwidth of analysis is one-third octave or larger, one factor of ten in frequency shall be 50 ram (preferred) or 2 inches in length. The ordinate and abscissa of all graphs shall be labeled so that levels and frequencies can be readily understood without need to refer elsewhere in the report.

Narrowband data shall be plotted using a linear frequency scale and the vibration level in decibels

1.1.3 Data Collection - Limited Structure Borne Vibration Survey

1.1.3.1 Test Requirements

1.1.3.1.1 General. The Contractor shall conduct a limited structureborne vibration survey. At a minimum, the vibration levels shall be measured on the transom and engine foundations (above and below mounts).

The Contractor shall review the arrangement of the vessel and propose other measurement points of interest and accelerometer locations in the RFP response.

Measurements shall be made at all locations in three mutually perpendicular directions, one of which shall be vertical. Additionally, for equipment with horizontally oriented shaft, one other direction shall be perpendicular to the equipment shaft. For valves, measurements in two directions are required; perpendicular and parallel to the flow for outlet flanges or nozzles, and three mutually perpendicular directions for other structural connections, except the inlets.

1.1.3.2 Test Environment

1.1.3.2.1 Background Noise

When practical, background noise, shall be at least 10 dB below that of the equipment noise being measured.

1.1.3.3 Measurement procedures

1.1.3.3.1 Instrumentation.

Tri-axial accelerometers with a sensitivity of 100 mV/g with a frequency range of 3 hz to 10 khz shall be used to collect structureborne data.

1.1.3.3.2 One-third octave band measurement procedure.

One-third octave band La shall be measured for the ambient (non-operating) condition and for Idle, Cruise and Wide Open Throttle RPM using accelerometers, preamplifiers, meters, connecting cable, and actual or synthesized one-third octave band filters, a graphic level or X-Y recorder or digital printer, and connecting cables. The one-third octave band filters shall cover band-center frequencies over the range of 10-Hz band or the fundamental forcing frequency of the equipment, whichever is lower through the 10,000-Hz band and have rejection characteristics beyond the band-edges at least as good as those specified in ANSI Sl.ll, for class II filters. The complete system shall have a flat response within plus or minus 2 dB over the above specified frequency range. For every one-third octave band, the product of the analysis bandwidth in hertz times the sample time in seconds shall be at least 25. The complete frequency range of interest shall be analyzed and recorded. The correction factors required to convert recorded levels to actual La shall be indicated on the data.

1.1.3.3.2.1 Scanning rate. Continuous scan measurements that do not provide a time bandwidth product of 25 or greater are not permitted for one-third octave band measurements. If analyzer with automatic step advance is used, manual control of step rate for several of the lower frequency third-octave bands may be required to obtain a time bandwidth product of 25 or greater.

1.1.3.3.2.2 Amplitude adjustment. Instrumentation shall be adjusted so that the readout shows all levels within the frequency range of interest.

Do not allow lower amplitudes to drop off the bottom of the data sheet.

1.1.3.3.3 Narrowband measurement procedure.

Narrowband La measurements shall be made when specified by the contracting activity (see 6.3). The system used shall include the basic instruments of :accelerometers, preamplifiers, meters, and connecting cables with a narrowband analyzer (may be synthesized by FFT), in lieu of the one-third octave band analyzer, digital printer, a graphic level or X-Y recorder and connecting cables. The recorder shall provide a permanent reproducible copy.

1.1.3.3.3.1 Frequency response. Unless otherwise specified, the complete system shall have a flat response within plus or minus 2 dB over the frequency range from 9 Hz or the fundamental forcing frequency of the equipment, whichever is lower, through 11,225 Hz.

1.1.3.3.3.2 Time bandwidth product. The product of the analysis bandwidth in hertz times the total sample time in seconds shall be at least 25 at all frequencies. The complete frequency range of interest shall be analyzed and recorded. The correction factor required to convert recorded levels to actual La shall be indicated on the data. The bandwidth used for the analysis shall also be indicated.

NOTE: As an exception, if swept analysis is used, a constant sweep giving a time bandwidth product of at least 25 at 40 Hz and above is acceptable.

1.1.1.1 Measurement locations.

Measurement locations shall be in accordance with 5.2.4.1.1. Proposed measurement locations will be considered in minimum required locations as on site evaluation may require additional locations of interest. Should additional locations of interest be identified during testing their additional measurement locations shall be documented and shall be presented in the final report.

1.1.1.2 Accelerometer attachment.

Accelerometer attachment and attachment mounting method to aluminum structural components.

1.1.1.3 External influences.

Measured levels of equipment vibration shall not be adjusted to compensate for the effects of ambient magnetic, electrical, and acoustical fields. Ambient effects shall be at least 10 dB below the levels specified for the equipment. Corrective measures shall be taken to reduce the effects of external sources on the equipment's measured vibration level.

1.1.1.4 Calibration of instrumentation.

Instrumentation used shall have been calibrated and have been found to meet the requirements specified herein.

1.1.1.4.1 Laboratory calibration. A laboratory calibration shall be made of all vibration measuring instrument components within 12 months prior to each use, or after exposure to mechanical shock or other unusual disturbance, or upon request by the Government inspector. All calibration instrumentation, including the accelerometer calibrator used for field calibration, shall have been calibrated within 6 months prior to each use traceable to the National Bureau of Standards. The laboratory calibration of the components shall be accurate within the instrument manufacturer's specifications or plus or minus 1 dB, whichever is more stringent.

1.1.1.4.2 Transducer calibration. Calibration of field transducers shall be performed by one of the methods specified in ANSI S2.2 within 12 months prior to each use. It is recommended that transducers intended for use with voltage amplifiers be calibrated with the particular cable and amplifier to be used in making the field measurement. When secondary transducers are used, they shall be kept under controlled conditions in the manufacturer's laboratory and used only for calibrating the transducers used for equipment measurements.

1.1.1.4.3 Field calibration. For each work shift, prior to making measurements, an electrical calibration check shall be made of the vibration measuring system exclusive of the accelerometer by introducing a known calibration signal in place of the accelerometer signal and recording the level at the following frequencies (for field calibration, the accelerometer may be disconnected from the system):

(a) For analyzers with fixed filter sets, at 32, 125, 500, 2000,and 8000 Hz.

(b) For analyzers with tunable filter sets, at representative frequencies within each range of frequencies scanned.

In addition to system electrical field calibrations, the total vibration measuring system, including the accelerometer, shall be checked for at least one frequency using an accelerometer calibrator. This total system calibration using an accelerometer calibrator shall be conducted at the beginning of each day, and at the end of the equipment measurements. If measurements commence with one day on another unit, the final system calibration for the previous unit may serve as the initial calibration for the next unit. Also, whenever any component of the measuring system is changed, a field calibration shall be made with the new component in the system. Field calibration shall be accurate within plus or minus 2 dB.

1.1.4 Data Collection - Airborne Noise Survey

1.1.4.1 Test requirements

1.1.4.1.1 General.

The Contractor shall conduct an airborne noise survey of the following positions in accordance with Appendix (A): Row 1, Row 2, Row 3, Row 4, Row 5, Row 6.

The data recorded and reported shall include A-weighted, C-weighted, and octave-band sound pressure levels, and speech interference levels.

1.1.4.2 Test Environment

1.1.4.2.1 Background Noise

When practical, background noise, including wind noise, shall be at least 10 dB below that of the equipment noise being measured. A windscreen shall be used at wind velocities of 10 km/h or more.

1.1.4.2.2 Personnel limits and locations during tests.

Operator(s). During testing, the operator(s) shall not occupy that location where the noise is being measured unless required to operate the equipment.

No operator present. When no operator is present, the measurement shall be made at the center of the operator's probable head location. For standing locations the microphone shall be 1.60 m above the floor, for sitting locations it shall be 0.80 m above the seat which, if adjustable, shall be positioned at the center of its vertical adjustment range.

Operator present. When the operator must be present, the measurement shall be made at ear level, 15 cm from the right ear. If a wall or other reflective surface is closer than 3 cm from the operator's right ear, the microphone shall be positioned equidistant from the right ear and that surface.

Test personnel. Noise measurements shall be made with the minimum number of people in the area, including test personnel. When noise is being measured in personnel-occupied enclosures, no test personnel or observers shall be present within the Appendix (A) unless required to operate or adjust the test equipment, or to record data.

1.1.4.3 Measurement Procedures. Data collection shall include on-site, unweighted octave-band and A-, and C-weighted measurements. Slow meter damping shall be used. Measurements shall be made with an integrating sound level meter or other recording instruments that measure time weighted average level (Lavg) as defined in MIL-HDBK-1908. Lavg shall be measured using the time-sound level exchange rate appropriate for USCG COMDTINST M5100.47 Safety and Environmental Health Manual.

1.1.4.3.1 Instrumentation Specifications. Sound level meters shall conform to requirements for Type 1, as specified by ANSI S1.4. The instrument shall have data logging capabilities. Band filter sets shall conform to requirements as specified by ANSI S1.11. Other noise recording instrumentation or combinations of instrumentation shall conform to SAE J184 and applicable provisions of ANSI Sl.4.

1.1.4.3.2 Microphones. Pressure microphones having an essentially flat response at grazing incidence (90 degrees) should be used, but free field microphones having an essentially flat response at normal incidence (0 degrees) may be used with the addition of a random incidence corrector. The microphone shall ordinarily be placed vertically at the measurement location with the sensitive element up. However, for exterior measurements of stationary test items (at distances greater than three times the major dimension of the test item), a normal incidence microphone without a random incidence corrector may be used if it is pointed at the item.

1.1.4.3.3 Windscreen performance. When a windscreen is used in accordance with 5.3, and when specified in the contract or order, data shall be prepared (see 6.4) which demonstrates that the windscreen does not change the frequency response characteristics of the microphone by more than 1 dB in any octave bands specified for measurement (see 5.2.3.2). A correction factor which accounts for the change in frequency response may be applied to the measured levels.

1.1.4.3.4 Instrumentation and obstructions. Measurements shall be made using a microphone connected to a sound level meter. No obstruction, including the instrument operator, shall be between the equipment being measured and the microphone.

1.1.4.4 Measurement location. Noise measurements shall be made at:

a. each operator or crew position.

b. representative positions where one or more individuals (e.g., passengers) will be located.

Expected measurement locations are shown in Appendix (A).

The Contractor shall measure and record insertion loss at the engine intakes.

The Contractor shall measure and record additional data as necessary if other sources of vibration and airborne noise transmission paths are identified to address all requirements for the report.

Calibration. Acoustical calibration procedures shall be accomplished in accordance with the sound level meter manufacturer's instructions (see also ANSI S1.10). Calibrators shall conform to ANSI S1.40 Calibration shall address the influence of microphones, cables, amplifiers and recorders. Calibration shall be performed any time instrumentation is changed, before and after each test sequence, but not less than at the start and end of each day.