Building a Pipe String for Use with GeoVISION™ Systems
The usual method of using a GeoVISION™ camera system is to suspend the camera and centralizer from the power cable with a safety clamp. This method allows the user to view straight down the borehole. If one wants to view to the side or up a borehole, a pipe string is recommended for depths less than 500 feet. At depths greater than 500 feet, the motorized pan tilt attachment is recommended for viewing up or to the side.
All GeoVISION™ systems except those with the motorized pan-tilt have a threaded pipefitting, ready for attaching a user supplied pipe string, and so that the camera can be pushed or pulled past obstructions. The camera can thus be pushed and pulled horizontally or overhead. When used in conjunction with the manual camera tilt assembly, pipe string also provides the user with the option of viewing to the side and up. Most users make their pipe strings out of ¾-inch CPVC pipe with a male fitting on one end and a female fitting on the other. To avoid high shipping expenses, it is more cost effective to have the users make their own pipe stings as opposed to shipping them from the factory.
Pipe strings are very helpful in allowing the user of a GeoVISION™ Camera system to tilt the camera head manually to view to the side or view back up the borehole. The normal position of the GeoVISION™ camera is viewing down. In many situations, viewing down the borehole with the GeoVISION™ camera will provide sufficient information.
In other situations, such as large boreholes greater in 12 inches in diameter, crevices, mines, and caves, a pipe string will allow the user to view much more detail to the side and back up. GeoVISION™ is the only borehole camera system with the capability to view up the borehole.
When a pipe string is attached to the GeoVISION™ camera system, the power cable is used to tilt the camera head to the side or up at any angle. The pipe may be turned by hand to aim the camera in the desired direction. The camera head is spring loaded so when the tension on the power cord is released, the camera returns to the down viewing position
Steps for making a pipe string
1. Gather lengths of temperature flexible CPVC pipe sufficient to make a length of pipe long enough to reach the depth needed. The most commonly used size of CPVC is ¾-inch diameter; however, other sizes will work. If the depth is greater than 300 feet, consider using 1-inch diameter CPVC and place a reducer on the centralizer’s ¾-inch adapter.
2. CPVC is often available in 20-foot lengths, so cutting these units in half makes convenient 10-foot lengths with which to work and provides sections with round numbers for ease of depth calculation. For the most accurate depth measurement, cut the pipe section so that after connecting the male and female adapters to the pipe section it is exactly 10 feet long after they are screwed together. Other lengths may be acceptable. If you use metric lengths cut the pipe to an even meter length that will make calculating the depth easy.
3. Gather sufficient numbers of threaded male and female adapters to make the proper length pipe string. If you are using 10-foot lengths, you will need 30 male and at least 29 female connectors to make a 300-foot pipe string.
4. Cut one length to about 91.5 inches. This will make the first pipe string unit, the equivalent of 10 feet including the camera and centralizer. This step is not necessary if measuring depth is not important.
5. Cement a male and female adapter to each end of each section of PVC.
6. Obtaining a locking clamp to hold the pipe in place is also helpful. This allows the pipe string to be assembled by one person and help provide protection from the falling into the borehole.
6. Velcro straps sufficient to wrap around the pipe once every 10 feet. These are used to keep the power cable attached to the pipe string.
Optional steps for measuring accuracy
For additional accuracy, you may wish to attach a tape measure to one or two pipe sections to use when you reach the working depth. This will allow you to have a very accurate depth measurement.
Placing marks on the pipe adapters will indication the rotational direction the camera is facing when it is tilted to the side.
Screw the pipe together, and then align your marks to the direction the camera is viewing when it is tilted. A soldering iron is one tool that will make a permanent mark on the adapters.
Refer to the GeoVISION™ website for a diagram of the pipe string. http://www.geovision.org.
Click on “Camera Operation, Advanced Techniques, Service, and Repair” in the index to expand the sub topics.
Click on “Down Hole Camera Techniques.”
In the forth box from the top click on “Making and using practical options.”
This will bring a pull down menu and the second item is “Making a pipe string.”
Click on it to get the pipe string diagram.
A pipe string locking clamp
Other side of a pipe string locking clamp