Geosense VWNPC-3000 Instruction Manual
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Geosense VWNPC-3000 Instruction Manual

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V1.4 March 15
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NATM STRESS CELLS
VWNPC-3000

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Summary of Contents for Geosense VWNPC-3000

  • Page 1 NATM STRESS CELLS V1.4 March 15 VWNPC-3000...

  • Page 2: Table Of Contents

    2.0 CONFORMITY 3.0 MARKINGS 4.0 DELIVERY Packaging Handling Inspection Functionality test & zero readings Storage 5.0 INSTALLATION Cell installation 5.1.2. Tangential cell VWNPC-3000 5.1.3 Radial cell VWNPC-3010 5.1.4 Initial readings Re-pressurising the cell Cable 5.3.1 Cable installation 5.3.2 Cable marking Tools 6.0 DATA HANDLING...

  • Page 3: Introduction

    V1.4 March 15 1.0 INTRODUCTION ® This manual is intended for all users of Geosense NPC-3000 NATM Cells and provides information on their installation, operation and maintenance. It is VITAL that personnel responsible for the installation and use of the NATM Cells READ and UNDERSTAND the manual, prior to working with the equipment.

  • Page 4: How It Works

    V1.4 March 15 1.2 How it works 1 - Sensor cable 2 - VW sensor (no elasticity) 3 - Stress cell body - comprises of two stainless steel rectangular plates welded together around their periphery, leaving a thin space between the plates which is then filled with an relatively incompressible de-aired fluid.

  • Page 5: Application

    V1.4 March 15 1.3 Application The "New Austrian Tunnelling Method", or NATM, calls for the support of a tunnel by the rapid application of shotcrete to the freshly exposed ground. The theory behind this method of support, particularly useful in weaker ground, is that if the inherent strength of the ground can be preserved, it will be almost self-supporting and will require much less artificial support in the form of concrete or steel.

  • Page 6: Conformity

    Tel: +44 (0)1359 270457 Fax: +44 (0)1359 272860 Email: info@geosense.co.uk, Web: www.geosense.co.uk Declaration of Conformity We Geosense Ltd at above address declare under our sole responsibility that the Geosense products detailed below to which this declaration relates complies with protection requirements of the following harmonized EU Directives,...

  • Page 7: Markings

    V1.4 March 15 3.0 MARKINGS ® Geosense NPC-3000 NATM Cells are labelled with the following information:- Manufacturers website & telephone number Product type Pressure range Model Serial number Cable length CE mark Maximum pressure...

  • Page 8: Delivery

    Inappropriate handling techniques may cause damage to the packaging and the enclosed equipment. The packaging should be carefully inspected upon delivery and ® any damage MUST be reported to both the transportation company Geosense 4.2 Handling ® Whilst they are a robust devices, Geosense NPC-3000 NATM Cells are precision measuring instruments.

  • Page 9: Functionality Test & Zero Readings

    If these ‘out of the box’ CHECK readings show significant differences ( +/- 40 digits ) to the zero pressure values on the calibration sheets, contact Geosense for assistance. ( It should be noted that the ‘CHECK Readings WILL be affected by the atmospheric pressure &...

  • Page 10: Storage

    V1.4 March 15 4.4 Storage ® Whilst Geosense NPC-3000 NATM Cells are relatively robust they are a precision instrument and if they need to be stored care should be taken to protect them against any impact or weight. Ideally they should be stored in their original packaging but if not do not stack units on top of each other or any other item that could damage the sensor or connecting pipework from the cell body.

  • Page 11: Installation

    V1.4 March 15 5.0 INSTALLATION ® This section of the manual is intended for all users of Geosense NPC-3000 NATM Cells and is intended to provide guidance with respect to their installation. It must be remembered that no two installations will be the same and it is inevitable that some ‘fine tuning’...
  • Page 12 V1.4 March 15 5.1.2 Tangential cell (VWNPC-3000) contd.. STEP 4 - fix the cable firmly to other pieces of rebar or to the reinforcing mesh (if one is used) and feed out to the readout location which typically is a junction box.

  • Page 13: Radial Cell Vwnpc-3010

    V1.4 March 15 5.1.3 Radial cell (VWNPC-3010) STEP 5 - Install re-bar sections or nails adjacent to the cell location so that the radial cell can be attached to them. STEP 6 - make a pad of quick setting mortar onto the surface of the tunnel wall.

  • Page 14: Initial Readings

    V1.4 March 15 5.1.4 Initial readings BEFORE SHOTCRETING TAKE INITIAL PRESSURE & TEMPERATURE READINGS 5.2 Re-Pressurising the Cell During concrete curing, temperatures very often rise and will cause the cell to expand in the still green concrete. On cooling, the cell contracts leaving a space between it and the surrounding concrete which, if allowed to remain, would prevent the transmission of pressures from the concrete to the cell.
  • Page 15 V1.4 March 15 5.2 Re-Pressurising the Cell contd... It is recommended that results are graphed so that site characterisation can be obtained. STOP CRIMPING Crimp number GRAPH 1 - a gradual increase in pressure occurs showing that there is initially little contact between the cell and the concrete.

  • Page 16: Cable

    5.4Tools. 5.4.1 Tools list Obtain any tools necessary to carry out the installation. The following is a brief list of ® tools typically used during the installation of Geosense NPC-3000 NATM Cells:- NATM Crimper - to re-pressurise the cell. •...

  • Page 17: Data Handling

    6.1 Monitoring the NATM cell readings ® Geosense NPC-3000 NATM Cells include both pressure and temperature sensors. NATM cells are installed in a zone where the temperature is likely to fluctuate significantly and therefore records of both pressure and temperature data should be recorded.

  • Page 18: Data Reduction

    For most Vibrating Wire sensors, these factors are unique and are detailed on the sensor ® calibration sheet. A unique calibration sheet is supplied with all Geosense NPC- 3000 NATM Cells (see page 21).
  • Page 19 V1.4 March 15 (Continued from page 18) 7664.8 Readout Display 3612 –7 Linear Digits (Hz /1000) ( 1 / 3612 x 10 / 1000 7664.8 If the readout displays ‘Frequency’ values, ( e.g. 2768.5 Hz ) only a simple calculation is required to convert the readings to Linear Digits.
  • Page 20 An instrument calibration sheet similar to the example on page 21 includes the following information: ® Model This refers to the Geosense model number. Serial Number This is a unique sensor identification number that can be found on the cable just behind the NATM cell body and, for long cables, at the end of the cable.

  • Page 21: Calibration Certificate

    V1.4 March 15 6.3 Calibration certificate...

  • Page 22: Pressure Calculation

    V1.4 March 15 6.3 Pressure calculation ® Readings from Geosense vibrating wire sensors can be in various different formats depending on what readout is used. Typical examples are:- Readout Format RST VW2106 Digits Campbell data logger Frequency Calculation of the pressure is as follows:- STEP 1 - Confirm what format the data is in i.e.

  • Page 23: Temperature Compensation

    ® Geosense NPC-3000 NATM Cells are fitted with internal thermistors which allow temperature to be monitored.
  • Page 24 V1.4 March 15 6.3 Temperature compensation USING STEINHART & HART LOG Thermistor Type. YSI 44005, Dale 1C 3001 B3, Alpha 13A3001-B3 Resistance/ temperature equation:- T= (1 / (A + B (LnR) + C(LnR) )) –273.2 Where:- T = Temperature in degrees Centigrade LnR= Natural log of Thermistor resistance.

  • Page 25: Maintenance

    V1.4 March 15 MAINTENANCE ® Geosense NPC-3000 NATM Cells are a maintenance free device for most applications. This is because it is intended for sub-surface installation and would normally be irretrievably sealed into concrete. Maintenance of wiring connections between the NATM cell and any terminal panels / or loggers should involve occasional tightening of any screw terminals to prevent loose connections or cleaning to prevent the build up of corrosion.

  • Page 26: Specification

    Civil engineering sites are hazardous environments and instrument cables can be easily damaged if they are not adequately protected. Geosense can therefore provide the following parts that may be required to effect repairs to instrument cables: PU coated 4 Core cable with foil shield and copper drain.

  • Page 27: Return Of Goods

    11.2 Packaging and Carriage All used goods shipped to the factory must be sealed inside a clean plastic bag and packed in a suitable carton. If the original packaging is not available, Geosense should be ® contacted for advice. Geosense will not be responsible for damage resulting from inadequate returns packaging or contamination under any circumstances.

  • Page 28: Limited Warranty

    Unauthorised alteration and/or repair by anyone which, causes failure of the unit or associated components will void this LIMITED WARRANTY in its entirety. ® The Purchaser warrants through the purchase of the Geosense NPC-3000 NATM Cell that he is familiar with the equipment and its proper use. In no event shall the...
  • Page 29 V1.4 March 15 NOTES:...
  • Page 30 V1.4 March 15...

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