SAAV can be installed in 27 mm ID conduit similar to previous model ShapeArrays. When installing SAAV in this manner, the borehole should be pre-cased with the 27 mm conduit. This installation method is susceptible to buoyancy effects and care must be taken to avoid sinuating the PVC prior to installing the ShapeArray.
The following short video provides a great overview of the installation process. Each step in the installation process is described in more detail following the video.
Step 1 - Choose the Right Conduit
Figure 1: 27 mm ID electrical conduit, end cap, and coupler appropriate for ShapeArray installation
Step 2 - Choose the Right Adhesive
PVC couplings are attached with PVC solvent cement. In cold temperatures, it is imperative to use an appropriately rated cement. Do not use too much cement, as it can squeeze into the inner part of the conduit. Debur, clean, and use a solvent cleaner on the conduit before applying cement. Most manufacturers specify applying glue to only one surface of the joint.
Figure 2: An example of PVC solvent cement
Step 3 - Prepare the Conduit
All PVC conduit ends should be kept clean from dust, oil, and snow. Look inside the PVC pipes to ensure that no foreign objects are inside the PVC pipe. The edges of conduit over which the ShapeArray is being installed should be smoothed using a deburring tool to prevent abrasion.
Figure 3: Preparing conduit - (a) examples of deburring tools, (b) cleaning and deburring the conduit
Step 4 - Assemble the Conduit
It is easier to assemble the PVC conduit as it is lowered into the borehole. Start by gluing and taping the end cap onto the bottom most piece of PVC before inserting it into the borehole. Lower the first piece of PVC conduit then glue the next piece on and tape the joint. Due to buoyancy effects, an assistant will be needed to hold the pieces in place while working. Keep adding more conduit, gluing and taping each joint, until the required length of conduit has been assembled. Glue the bottom part of the top stack included in the SAA Install Kit to the top of the PVC conduit at this time.
Figure 4: Assembling the conduit as it is lowered into the borehole - (a) Assistant holding it in place, (b) next piece glued and taped at the joint
Step 5 - Avoid Buoyancy During Grouting
A factor which must be considered during installation is the buoyancy of the PVC conduit. Typical grout used for back-filling the PVC conduit has a density ranging between 1,200 kg/m^3 and 1,450 kg/m^3. The grout mix recommended in the Backfilling Recommendations section of the ShapeArray Installation manual has a low density similar to the density of the PVC filled with chain.
It is important to weight the PVC down rather than allowing it to float up against a hard stop at the top. When the conduit is held from the top, buoyancy causes the conduit to bend and form S-curves making it difficult to insert the ShapeArray. It is recommended that the ShapeArray conduit be weighted down using chain to minimize buoyancy effects.
WARNING: Do not use water to weigh down the conduit. The water will make it difficult or impossible to insert the ShapeArray into the PVC due to hydraulic forces. If water egress is impeded, the attempt to insert the ShapeArray could lead to hydraulic pressure beyond the pressure ratings of the ShapeArray protective coverings.
Figure 5: Inserting chain to weigh down the PVC until the grout has cured
Allow the grout the set for 24 hours prior to installing the ShapeArray.
Step 6 - Place the Reel Stand
Figure 6: Place the reel and reel stand approximately 1 m - 1.5 m from the borehole such that the ShapeArray comes off the top of the reel
Step 7 - Lower the ShapeArray Into the Casing
Step 8 - Pump the SAAV to Settle it into the Casing
Once the SAAV is resting on the bottom of the casing, mark the position of the SAAV inside the casing on the PEX. Raise the SAAV between 0.5 m and 1 m, then lower it into the casing again using a pumping action similar to churning butter. This will cause the SAAV to settle further into the casing. Continue to pump the SAAV up and down until you notice that the mark made on the PEX is no longer settling down inside the casing.
Figure 7: Pump the SAAV 5 to 7 times to settle it into the casing
Figure 8: An example of an SAAV in 27 mm conduit being pumped
Use the SAAV Installation Verification tool from the Diagnostics menu in SAARecorder to confirm that the SAAV is properly settled. More information on using this tool is available in the Verifying your SAAV Installation guide.
Figure 9: The SAAV Installation Verification tool in SAARecorder
Step 9 - Find the Azimuth Offset from the X-Mark
Place the square protractor around the PEX at the top of the ShapeArray. Rotate the square protractor until the arrows are pointed to one of the following:
- The expected direction of movement
- Other desired heading of the ShapeArray
- Other job site datum
Figure 10: The square protractor placed around the PEX at the top of the ShapeArray
If the protractor needs to be placed over the PVC casing rather than the PEX, the required hole size is marked so it can be cut to fit.
Place the clear disk marker with the X-Line around the PEX on top of the square protractor. Rotate the clear disk around the ShapeArray until the X-Line on the disk and the X-Line on the PEX are aligned.
Figure 11: The clear disk aligned with the X-Lines on the ShapeArray and the square protractor
Make note of the azimuth offset angle at the X-Line. This will be directly used in the software to rotate the X-mark axis of the ShapeArray towards a known azimuth.
Step 10 - Use the Install Kit to Finish the Installation
Once the SAAV has been properly pumped and settled into the casing, the Install Kit should be used to complete the installation.
Apply downward force of no more than 20 kg (approximately 50 lbs) on the PEX and turn the set screws on the top stack to maintain compression and orientation of the ShapeArray within the PVC.
NOTE: If the ShapeArray is installed in an area with heavy vibration or blasting, it is possible that the set screws will loosen with time. You should take steps to ensure that the set screws remain tight.
WARNING: Be careful. Over-tightening the set screws will strip the threads in the PVC.
Cut away any excess PEX tubing.
Figure 12: Cutting away excess PEX tubing
Thread the top portion of the pre-assembled Install Kit over the cable and screw it into the bottom portion. Tighten the gland at the top of the top stack until the rubber gasket seals the cable. Make sure to remove the hanging fixture once the grout has set. Leaving it in place may lead to rotation.
Figure 13: The top portion of the pre-assembled Install Kit threaded over the cable and screwed it into the bottom portion
Step 11 - Run the Cable to a Data Acquisition System
Run cable to the data acquisition system. Use conduit to protect the cable and to ease cable replacement if required, as shown in Figure 13.A below. Since the PVC conduit containing the ShapeArray has been sealed, it is not necessary for the flexible conduit to cover the entire cable. If the top of the ShapeArray is protected using a well head covering or some other buried structure, it is possible to use zip ties provided in the kit to hold the conduit in place under the protective conduit. It is also possible to do cable splices or attach items such as the SAASPD surge protection device at this point, as shown in Figure 13.B below.
Figure 14: Running cable to a data acquisition system - (A) conduit to protect and ease cable placement, (B) SAASPD spliced onto the cable