borehole video camera system
Borehole Camera System Design Factors
Elegance, Fact, and Fallacies
www.acisa.biz
If you are considering the purchase of a borehole video camera system, a review of these twelve design factors may be the best investment of your time you can make. With years of experience focused on video camera systems for boreholes and water wells, GeoVISION™ has effectively resolved the important design issues necessary to provide convenient, cost effective video camera systems for boreholes 600 meters (2000 feet) deep or less.
Professional Quality Standards for Borehole and Water Well Video Systems
This list explains the balance between costs and professional quality standards in determining ideal borehole and water well design configurations. There are other ways to achieve a professional grade camera system. GeoVISION™ achieves this standard at the most economical level.
1. Borehole Depth Design Challenge
Design a borehole camera system to go into most water wells and still be portable and inexpensive.
A design alternative and resulting problem
Generally, the deeper a camera can go, the better; however, as depth capability increases, so does
1. The wire size and signal strength needed to carry a clear signal over a greater distance
2. The expense, weight, and complexity of the power supply and related electronics become greater as cable length is extended.
3. The cable or wire strength in order to support the additional downhole weight.
Borehole camera systems designed for greater water pressure require greater case strength, which adds to the weight and cost. Some systems can withstand extreme pressure at great depth. These systems are often used in the gas and oil industry but are usually not cost effective for well drillers, borehole inspectors, and many geology consultants.
GeoVISION™ Solution - Depths to 2000 feet
The GeoVISION™ Deluxe systems are designed for maximum depths of 2000 feet with their longest cable. These depths are adequate for the vast majority of borehole applications. The cost is reasonable and GeoVISION™ systems are light enough for one person to carry. One or two people can carry the Deluxe system. All GeoVISION™ systems will fit into almost any vehicle, including automobiles.
2. Camera Housing Design Challenge
Design a durable camera housing that can withstand the pressure of a deep water well and yet be small enough to fit into a small borehole and be repaired if necessary.
A design alternative and resulting problem
Manufactures of underwater cameras solve this problem by making the housing strong enough to withstand high pressure. One way to strengthen the housing is to support it by filling all the voids in the camera with a potting compound so there is no air left inside (the optical path and lens cannot be filled with potting compound. This makes that area still subject to leaks). The potting compound provides support for the housing and might even allow for a thinner housing; however, if epoxy or an equivalent substance is used, the camera cannot be repaired. With hundreds of electronic parts, it only takes one to go bad for the entire camera to be worthless. While disposable products are appropriate for some uses, throwing away a borehole camera is an expensive proposition. Filling all the voids in an underwater camera with a potting compound may tempt a designer to save costs by using a flexible rubber like tube as a housing. This housing will require clamps at the ends effectively increasing the diameter of the camera and if the clamp becomes loose water can enter the optical path and cause failure of the camera. They may also attach the cable directly to the housing without a connector. If the camera or the cable fails, both will have to be replaced.
GeoVISION™ Solution – Stainless steel and High Temperature Plastic Housing
A strong, well-designed repairable housing is better for borehole cameras. Protrusion on the housing can be minimal and only the head tilting bracket option adds to the diameter of the case. GeoVISION™ uses a housing sealed at the factory. This housing can be opened at the factory for repair if necessary or upgrades to the circuitry can be made. All GeoVISION™ cameras can be repaired at the factory for much less than the price of a new one. GeoVISION™ cables can be repaired or replaced without the need to replace the camera.
3. Lens Window Design Challenge
Design a strong, durable, scratch resistant lens window.
A Design alternative and resulting problem
A designer might use plastic for a lens window, thinking that it is less likely to break. While this is a questionable advantage, plastic has one serious disadvantage. It scratches much more easily than glass and when it is scratched can degrade the image quality.
Solving one design problem may create a very different problem - The air bubble problem.
One camera manufacturer protects the lens window by placing a cup-like extension in front of it. If the lens window were plastic, one would be especially tempted to use a protective cup. This is a good idea when the camera is not used in water. The camera points down and the protective cup captures an air bubble and dirt particles, making the underwater downhole image very distorted until the air bubble is removed.
Cascading problems
An open water camera designer might place LEDs in a clear plastic housing/lens window. While this may work well under normal light conditions, in low light situations the refraction and reflections from the clear plastic will be visible and degrade the image as the camera electronic shutter attempts to compensate for the low light conditions. Some designs place the lights and lens behind a single lens/light window. This design is also subject to the refraction and reflections problem.
GeoVISION™ Solution - Glass or Sapphire Lens Covers
GeoVISION uses a sapphire lens cover on all its stainless steel cameras.
Some design concepts are not always intuitive. A layperson might think of glass as brittle or easily cracked. In actual use, properly designed glass lens window is difficult to break. It would take a deliberate act for a glass lens window to be broken in a camera. GeoVISION™ cameras use glass in its Jr plastic cameras and sapphire in its stainless steel cameras. They have a flat surface so that air bubbles cannot be easily trapped in front of the lens. GeoVISION Jr. camera use opaque plastic to mount the LED lights to avoid the refraction and reflections problem.
4. Lighting Design Challenge
Provide an unbreakable light source sufficient to illuminate most boreholes
A design alternative and resulting problem
Manual dimmers are used with the old style incandescent lights with some success. However, when using LEDS as the primary light source and with the cameras automatic electronic shutter controls, manual brightness controls are not necessary. Any increase in a manual brightness control causes the electronic shutter to decrease exposure, and any decrease in a manual control causes the automatic electronic shutter in increase exposure. Manual override controls just increase the complexity of the system, and provide additional parts that can break. The only time a manual light brightness control can be used effectively, is when the camera can have its auto exposure control turned off. This also adds more complexity and the operator must constantly control the light brightness.
GeoVISION™ Solution - Automatic Electronic Shutter
When simple is better, keep it simple for the operator. There are no manual dimmers in GeoVISION™ camera systems; the automatic electronic shutter does it all. LED lights provide the best all-round light source for borehole applications due to the advent of low light video cameras. LEDs produce the most light for the energy consumed and are almost indestructible. GeoVISION Jr™ uses LEDs with all systems and has optional means for attaching other light sources for large boreholes.
The best solution is to set the LED light output to maximum value and allows the automatic electronic exposure control to adjust the exposure level down as necessary. In large boreholes, a supplemental dive light is available or you the ultra low light camera option is available.
5. Stabilize and Centralize Design Challenge
Provide a stable view from the middle of the borehole while moving the camera up or down.
.
A design alternative and resulting problem
Sewer cameras rest on skids and open water camera systems have plenty of room to operate. The designers of these types of cameras do not use centralizers. Without centralizers, a camera in a borehole will slide against a side of the casing or borehole when it is lowered downhole. The one side of the picture will be very bright and mostly out of focus and the other side will be very dark. A sewer or open water camera designer who never used a camera in a borehole might not realize that a camera on a cable will not stay in the center of the borehole. A camera without centralizers will not work well in a borehole.
GeoVISION™ Solution - Adjustable Centralizers
All GeoVISION™ camera systems have adjustable centralizers.
6. Quality Image Design Challenge
Provide a good resolution image sufficient to analyze boreholes problems.
A design alternative and resulting problem
Designers operate under economic constraints. Sometimes they settle for marginal optics.
GeoVISION™ Solution - Wide-angle Coated Glass Lenses with Large Depths of Field
All GeoVISION™ cameras are supplied with wide-angle fully coated glass lenses with large depths of field.
Picture quality GeoVISION™ customers say GeoVISION has the best picture. A good high-resolution image is obtained from all GeoVISION™ systems. The standard focus range of GeoVISION™ cameras is 2 inches to 3 feet and the camera is in usable focus from 1 inch to infinity. A 5 inch to infinity focus range is available for mining and related uses as an alternative and can be adjusted at the factory.
7. Getting Past a Protrusion Design Challenge
Provide a means to push or pull the camera past a protrusion.
Provide a means of firm control of the camera in unstable or damaged boreholes.
A design alternative and resulting problem
Most borehole camera systems can be supported by a cable only. This causes the operator to have very little control over pushing the camera past objects and no control over where they can have the camera look.
GeoVISION™ Solution A – Pipe-string Ready
All GeoVISION™ systems have a threaded pipefitting, ready for attaching a user supplied pipe string, and so 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 to view to the side and up. Most users make their pipe strings out of ¾” 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.
GeoVISION™ Solution B - The nano Camera
The nano camera is only ¾ in diameter and can usually get past a pump and other protrusions.
8. View in All Directions Design Challenge
Provide a system to allow the camera to view to the side in any direction and up.
A design alternative and resulting problem
All serious designers of borehole camera systems provide one of a couple alternatives for a camera to view to the side. Designers provide a camera head tilting mechanism or supply two cameras with their system to allow viewing down or to the side. Either of these methods works well; however, the duel camera approach increases the initial cost of the system significantly. Neglecting both of these alternative methods places severe limits on the usefulness of the system.
GeoVISION™ Solution A – Manual pan and tilt
By using a pipe string and the GeoVISION™ supplied manual head tilting assembly the operator can view in any direction including upward.
GeoVISION™ Solution B - Side-looking Mirror
An optional side-looking mirror is available to allow side viewing in small diameter bore (2” & 3”). A motorized side looking mirror is available for the micro and nano cameras.
GeoVISION™ Solution C - Motorized Pan and Tilt
The optional motorized pan and tilt option allows the operator to view in any direction including up by controlling a single joy stick on the control panel. The best view of detail in a borehole can be obtained from viewing an object from several diffident angles. The tilting ability of the pan and tilt camera allows the camera to go below the object and look at it at an infinite number of angles and to do the same from above. The dual cameras can only view straight to the side or straight down.
9. Many Different Uses Design Challenge
Provide customers with different camera options to meet special viewing and light conditions
A design alternative and resulting problem
Product managers prefer to make only one type of product, since it is easier to produce. That is good if the camera does what you want it to do, not so good if it does not.
GeoVISION™ Solution A – Many Systems and Options
GeoVISION™ has three winch systems and seven camera options available in both color and black and white. Black and white ultra low light cameras for large boreholes and voids are available. GeoVISION™, it has 20 other options and upgrades. The micro and nano are high quality cameras and are often used to record images in the smallest boreholes, since they are the smallest diameter borehole camera available anywhere.
The standard LED lighting systems used in GeoVISION™ cameras provide the appropriate amount of light for boreholes less than 12 inches in diameter. Supplemental lights provide adequate light sufficient for larger boreholes. Mine inspection and viewing other voids requires either much more light or a much lower lux. For regular use in large voids, using an ultra low light camera is the most economical and convenient means of providing a sharp image with limited light.
10. Upgrade Design Challenge
Allow borehole camera users to modify and upgrade after the original purchase.
A design alternative and resulting problem
Some manufactures prefer to make their product only one way and not allow subsequent additions.
GeoVISION™ Solution
Should your needs and/or resources change, you can add optional features. Modular GeoVISION Jr™ systems starting in 2003 are completely upgradeable. You may buy just the features you want. If you need something else later, you may buy it later.
The GeoVISION Jr™ Deluxe systems are now designed in a modular configuration that allows owners to upgrade to any GeoVISION™ option.
11. Replace or Upgrade Cable Design Challenge
Design a strong cable that can be replaced or repaired.
A design alternative and resulting problem
A designer of borehole cameras might be concerned that the cable should be attached very well to the camera so that the camera can be retrieved under adverse conditions. Such a designer might jump to the conclusion that the cable should be permanently attached inside the camera. If a cable is permanently attached inside the camera and if the camera cannot be opened for repair then such a system is worthless if the cable is damaged. This combination of cable and cable attachment makes such a system camera impossible to repair and more likely to be disposed at an early age.
GeoVISION™ Solution
The GeoVISION Jr™ configuration uses 3-conductor polyethylene sheath cables that can be spliced and repaired or replaced. The cable connects outside the camera. The cable is connected to the camera head tilting mechanism and centralizer when it is used. These attachments hold the camera.
12. Cable Storage Design Challenge
Design a convenient way to store and inspect the cable.
A design alternative and resulting problem
A marketing person might want to have an enclosed reel for the cable so that the system would always have a neat appearance. Such a design gives the impression that if the cable is out of sight it is free from maintenance. The enclosed reel design sometimes contributes to the cable tangles, as the operator may not see how the cable is feeding onto the reel.
GeoVISION™ Solution – Open winch
All GeoVISION™ systems have an open reel or winch that allows the cable to be fed neatly onto the winch as it is cleaned and rewound. This process prevents tangles. The open winch design allows easier inspection to insure proper cable cleaning before use in the next well.
13. Durability and Convenience Design Challenge
Most GeoVISION™ systems sold are still in use by the original owner, even those manufactured in 1989 when the first GeoVISION™ borehole system was produced. Resale value of GeoVISION™ systems remains high after many years. All GeoVISION™ systems are repairable.
