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I
M
NSTRUCTION
ANUAL
VIBRATING WIRE PIEZOMETER
Model PW
Roctest Limited, 2014, 2024. All rights reserved.
This product should be installed and operated only by qualified personnel. Its misuse is potentially dangerous. The Company makes no warranty as to the information furnished
in this manual and assumes no liability for damages resulting from the installation or use of this product. The information herein is subject to change without notification.
Tel.: 1.450.465.1113 • 1.877.ROCTEST (Canada, USA) • 33.1.64.06.40.80 (France) • 41.91.610.1800 (Switzerland)
www.roctest-group.com
E1100D-20240408
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Related Manuals for ROCTEST PW Series
Summary of Contents for ROCTEST PW Series
- Page 1 The information herein is subject to change without notification. Tel.: 1.450.465.1113 • 1.877.ROCTEST (Canada, USA) • 33.1.64.06.40.80 (France) • 41.91.610.1800 (Switzerland) www.roctest-group.com...
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Page 2: Table Of Contents
TABLE OF CONTENTS APPLICATIONS ...................... 1 PRODUCT ....................... 1 General description ................... 1 Description details and specific uses ..............1 2.2.1 ModelS PWS and PWC................1 2.2.2 Model PWF ....................2 2.2.3 Model PWP ....................2 2.2.4 Model PWL ....................3 2.2.5 Multi-level piezometer ................ - Page 3 Taking measurements ..................19 Quick verification of measurements..............20 CONVERSION OF READINGS ................20 Pressure value ....................20 Temperature value ..................22 Temperature and barometric corrections ............22 TROUBLESHOOTING ................... 23 Unstable reading ..................... 23 No reading ...................... 24 Temperature troubles ..................24 Other troubles ....................
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Page 4: Applications
E1100D-20240408 1 APPLICATIONS The PW series vibrating wire piezometer is designed to measure pore water or other fluid pressures. It is used to monitor engineering works such as hydraulic structures (dams, embankments, landfill dikes), foundations, retaining walls, excavations, tunnels, etc. -
Page 5: Model Pwf
E1100D-20240408 A filter can be set in the front end of the housing and sealed with an o-ring. With the filter in place, the diaphragm is protected from solid particles, and senses only the fluid pressure to be measured. The filter housing is easily removable for calibration and saturation. -
Page 6: Model Pwl
E1100D-20240408 Figure 2A: Model PWP piezometer with drive train retrieval option 2.2.4 MODEL PWL The PWL piezometer is a low pressure sensor. Similar to the PWS model, a pipe-threaded adapter or a filter can be set in the front end of its housing. 2.2.5 MULTI-LEVEL PIEZOMETER The multi-level piezometer provides significant advantages in terms of time, resources and cost reduction related to installation, while providing quick and reliable reading at... -
Page 7: Filter Types
E1100D-20240408 2.2.6 FILTER TYPES Two types of filters are available: high air entry ceramic or low air entry sintered stainless steel filters. The table below summarizes the main differences between the two filter models. Stainless steel filter Ceramic filter low air pressure entry high air pressure entry pore diameter: ~50 µm pore diameter: ~1 µm... -
Page 8: Calibration
A portable unit as the MB-3TL (or MB-6T(L)) can be used to read vibrating wire sensors. It proceeds to all necessary operations: wire excitation, signal conditioning and reading display. Please contact the Roctest Group for further information. 2.4 CALIBRATION A calibration sheet is supplied with each sensor. It enables conversion of gross readings into pressure values and temperature correction. -
Page 9: Filter Installation
E1100D-20240408 Take a reading of the temperature gauge as well, to make sure the thermistor is working properly. For details about how to take readings or how to convert frequency into linear units, please refer to section 4 (Reading Procedure). 3.2 FILTER INSTALLATION 3.2.1 LOW AIR ENTRY SINTERED STAINLESS STEEL FILTER The filter is shipped already mounted on the piezometer body. -
Page 10: Initial Readings
E1100D-20240408 Keep the piezometer underwater for at least 24 hours before proceeding with field installation. This will allow the pressure induced by the filter installation to decrease. When ready to be installed, the piezometer reading should be close to the one of acceptance test with the filter removed (see details in section 3.3). -
Page 11: On-Site Calibration Check (Optional)
E1100D-20240408 Figure 3: Summary of the different readings Note: It is not necessary to apply corrections to pressure calculation at that moment, but it is important to record both temperature and barometric pressure. 3.4 ON-SITE CALIBRATION CHECK (OPTIONAL) The best method for an on-site calibration check consists in proceeding as follow: 1. -
Page 12: Sensor Installation
E1100D-20240408 3.5 SENSOR INSTALLATION Vibrating wire piezometers are installed in various ways to suit each individual application. Specific guidelines for the piezometer installation have been set by various agencies and specialists. Standard methods are explained below. 3.5.1 INSTALLATION IN FILL 3.5.1.1 COMPACTED CLAY Excavate a trench or recess about 30 cm deep. -
Page 13: Installation In Borehole
E1100D-20240408 Make sure the cable does not cross over itself or other cables in the same area. Keep the cables apart. Backfill the recess with screened clay containing no particles larger than 2.5 mm of diameter. The backfill should have a water content and density as the surrounding material. - Page 14 E1100D-20240408 5. Wait for the bentonite to set up. Two hours are generally enough. Refer to supplier’s instructions for exact time. Keep the borehole filled with water. This will prevent the bentonite of drawing water from surrounding soil during its setting.
- Page 15 Soil Hardness Material Ratio by Soil Hardness weight weight Portland Cement Hard to Medium Portland Cement Soft Bentonite Hard to Medium Bentonite Soft Water Hard to Medium Water Soft For more information about this method, please contact Roctest. Page 12...
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Page 16: Piezometers Driven In Soft Ground
E1100D-20240408 3.5.3 PIEZOMETERS DRIVEN IN SOFT GROUND The PWP model is designed to be pushed into place from the surface in soft materials. For deeper installations where driving from the surface is impossible, the piezometer may be pushed into place from the bottom of a pre-drilled borehole. The PWP model piezometer comes fitted with a male EW rod thread that screws directly onto EW rod. -
Page 17: Installation Of A Multi-Level Piezometer
E1100D-20240408 3.5.4 INSTALLATION OF A MULTI-LEVEL PIEZOMETER The installation of a multi-level piezometer is quick and reliable since multiple piezometers are connected to a single communication cable, which is in turn connected to the data acquisition system (SENSLOG) or readout (MB-3TL or MB-6T(L)). A typical installation of the multi-level piezometer uses a direct grouting installation so that only the multi-level piezometer string and a grout injection tube are required to complete the installation. -
Page 18: Horizontal Cable Runs
E1100D-20240408 hand-placed concrete is sometimes used, depending on site conditions. During cable routing, read the instruments at regular intervals to ensure a continued proper functioning. Make sure the cable does not cross over itself or other cables in the same area. Record the cable routing with care and transfer this routing to the drawings. -
Page 19: Vertical Cable Runs
E1100D-20240408 Figure 6: General view of horizontal cable routing 3.7.4 VERTICAL CABLE RUNS The procedure shown below is an efficient and safe way to route cables from the sensor to the top of the embankment or of the dam. Figure 7: Procedure to route cables vertically Page 16... -
Page 20: Splices
E1100D-20240408 Figure 7: Procedure to route cables vertically (continued) 3.8 SPLICES Generally, cable splices are to be avoided. If necessary, use only the manufacturer’s approved standard or high-pressure splice kit. Splicing instructions are included with the splice kit. Should the cable be cut, we recommend the use of our high pressure cable splice kits, especially if the splice is located underwater. -
Page 21: Cable Wiring
Actually, individual sensor cables can be merged into a multi-conductor cable using a splice or junction box. Figure 8: Example of junction box use Please contact the Roctest Group for additional information about junction boxes and splice kits. 3.9 CABLE WIRING Before cutting a cable, make sure of its identification. -
Page 22: Reading Procedure
E1100D-20240408 electromagnetic pulses. All junction boxes and data logging systems furnished by Roctest Group are available with lightning protection. 4 READING PROCEDURE 4.1 GENERALITIES Readings can be taken manually with a portable readout unit model MB-3TL (or MB- 6T(L)), or automatically when connected to a SENSLOG data acquisition system. -
Page 23: Quick Verification Of Measurements
E1100D-20240408 Record LINEAR units and temperature readings as they appear on the display. Physically, the NORMAL reading is the vibration period in μs of the wire (called ) and the LINEAR reading is proportional to the wire strain (called LU or The jumper cables should never be short-circuited when they are connected to the readout unit front panel. - Page 24 E1100D-20240408 Polynomial equation: where = pressure in kilopascal = current reading in linear units (LU) or in Hz, if applicable = calibration factors (see calibration sheet) = constant calculated during installation (in kilopascal) Examples: The calibration sheet gives the following values: = -3.8444E-01 kPa/LU = -4.0179E-06 kPa/LU = -3.6641E-01 kPa/LU...
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Page 25: Temperature Value
E1100D-20240408 If the frequency is measured, convert it into linear units using the following equation: where = reading in linear units = gage constant for piezometer = 1.0156 = frequency in Hz Example: With = 1 625 Hz, We get: 2 681.8 LU 5.2 TEMPERATURE VALUE Although the MB-3TL (or MB-6T(L)) readout box gives directly the temperature in °C and... -
Page 26: Troubleshooting
E1100D-20240408 Use the following relation to apply corrections: where = corrected pressure in kilopascal = pressure previously calculated in kilopascal = thermal coefficient (see calibration sheet), in kPa/°C = current temperature reading in degrees Celsius = initial temperature reading in degrees Celsius = current barometric pressure reading in kilopascal = initial barometric pressure reading in kilopascal Example:... -
Page 27: No Reading
- Cuts or shorts are located, the cable may be spliced in accordance with procedures recommended by Roctest Group. - The sensor may have been damaged by shocks or water may have penetrated inside its body. -
Page 28: Other Troubles
E1100D-20240408 6.4 OTHER TROUBLES If pressure variations are suspicious, check if those variations are correlated to recorded temperature and/or barometric pressure. Check if corrections to raw pressure are applied correctly. 7 MISCELLANEOUS 7.1 ENVIRONMENTAL FACTORS Since the purpose of piezometer installation is to monitor site conditions, factors which may affect these conditions should always be observed and recorded. - Page 29 E1100D-20240408 APPENDIX 1 Example of Calibration Certificate Page 26...
- Page 30 2004/108/EC Electromagnetic Compatibility directive, as amended by EN61326-1, ed3 RocTest Limited hereby declares under its sole responsibility that the products identified above comply with the protection requirements of the EMC directive. The manufacturer has applied the following standards: Harmonized Standards: EN 61326-1:2006 Lab Equipment, EMC...
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