When it comes time to perform your dam lift operation, the inclinometer casing and the SAAV Extend can be resized to accommodate the lift in the field. Much like when determining the appropriate SAAV Extend base array length for the preliminary installation, you must also have a few key pieces of information to successfully lengthen the SAAV Extend and casing prior to performing the dam lift. The details required are described below and illustrated in the following figure.
- Fiberglass Cut Length (FCL) - the length of fiberglass extension tube used in the existing base installation (minimum 150mm)
- Lift Extension Length (LEL) - the length of the SAAV extension to be added
- Repair Coupler Length (RCL) - the length of the casing repair coupler used for extending the casing (standard repair couplers for RST Instruments inclinometer casings are 152 mm or 6")
- Casing Cut Length (CCL) - the length of casing to be removed from the base casing to access the connector for a lift
- CCL = FCL + 750 mm (29.5")
- Casing Extension Length (CEL) - the length of casing required to complete a lift
- CEL = LEL + CCL - RCL
Figure 1: SAAV Extend Diagram, showing casing lengths
WARNING: Care should be taken throughout the lift process to avoid disturbing the SAAV Extend base array already installed in the casing as much as possible. While it will not be completely possible to avoid moving the already installed array, preventing large disturbances will improve the results of the monitoring after each lift.
Once you have the measurement details described above, the SAAV Extend and the casing can be extended by executing the following steps.
Step 1: Remove Casing Cap
Remove the casing cap lid, then loosen the cable gland. Release the compression bolt and remove the casing cap screws. Lift off the casing cap and put it aside. Observe and record the Fiberglass Cut Length (FCL) using the scale marked on the fiberglass tube.
Figure 2: Removal of the Casing Cap
Step 2: Calculate Casing Cut Length (CCL) and Remove
Calculate the Casing Cut Length (CCL = FCL + 750 mm) and measure the CCL from top lip of the casing downward, marking the cut location. Cut, using a cutting wheel type pipe cutter. Lift off cut casing to expose the connection between the top assembly and the base array (or top of last lift assembly). Avoid pulling or twisting on the installed segments or electrical cable.
NOTE: If FCL is greater than 150 mm there is opportunity to shorten it to reduce the final stickup.
Figure 3: Calculating and Cutting the CCL
Step 3: Disconnect Top Assembly
Have an assistant support the top assembly. Disconnect the top assembly by holding the lower connector steady, preventing twisting of the installed segments, and unscrew the brass nut. Place caps on lower section connector and top assembly connector to protect from debris.
Figure 4: Disconnecting the Top Assembly
Step 4: Install Casing Repair Kit
Install a Casing Repair kit using the Casing Alignment Tool to ensure the orientation grooves are aligned. Allow the cement to cure and remove the alignment tool.
Figure 5: Installation of Casing Repair Kit
Step 5: Measure and Cut Casing Extension Length (CEL)
Prepare a length of casing to add on. Cut a length of casing to the Casing Extension Length (CEL), which is calculated using the following formula:
CEL = CCL (from Step 2) - 152 mm (length of the repair kit) + lift extension length
Measure and cut casing to the CEL, excluding the reduced diameter portion on the lower end of the casing in the measurement.
Step 6: Connect Lift and Top Assemblies
Add a fresh fiberglass extension tube onto the Top Assembly.
Connect the Lift Assembly to the Top Assembly and feed into the top of the casing extension, exposing the connector through the bottom end.
Figure 6: Connection of Lift and Top Assembly
Remove the connector caps, align the X-Markings and connect the extended top section to the installed section, taking care not to disturb the installed section. Hold the lower connector steady and screw on the brass nut.
Figure 7: Connection of Top Extend Section to Installed Section
Step 7: Install the Extend Casing and Complete Extension
Install the extend casing into the pre-installed Casing Repair kit.
Figure 8: Installing Casing Extension
Carefully complete the dam lift/backfill. Once the dam lift operation at the casing is complete, reinstall the casing cap (inspect bronze compression screw and replace it if worn).
Follow the normal casing cap procedure but do not perform the pumping operation. If an azimuth offset was previously measured, check the azimuth offset using the X-mart protractor and compare the value to the last installation. If necessary, make small azimuth adjustment to prevent the azimuth drifting over the life of the dam.
Figure 9: Replacing the Casing Cap
Step 8: Generate A New Calibration File and Site File
Once a physical extensions has been added to the base array, a new calibration file and site file that defines the newly combined array must be created. This is done by connecting to the SAAV Extend with a computer running SAARecorder as described in Generating New Calibration Files for SAAV Extend.