To start, let's describe the purpose and design of a housing wiper unit. These tools were originally conceived to act in the same manner as the windshield wipers on a car. They are to keep rain and dirt off the front window of the housing, allowing for a constant, clear view in various types of foul weather. However, design and reality are two different beasts. Overall, housing wipers are great on paper but fairly ineffective in actual use. In fact they quite often cost the system and the owner of the CCTV system far more than they are worth. The major problems with wipers are maintenance orientated.
First is the dust factor. A certain amount of extremely fine dust and dirt films will always adhere to the housing window. Under normal circumstances, this film will not be noticeable in the video picture unless it becomes severe. The next thing that you know, a guard will turn on the wiper assembly. With or without rain or moisture on the window, this dust film acts with the blade to grind or etch the window in the shape of the wiper path. Over a relativity short period of time, you will have crescent moon etchings in the center of your pictures. This will cause you minor to extreme image clarity problems, focus problems, and/or in general lousy pictures.
To combat dry wiping, many designers add the all important, solvent reservoir with a sprayer attachment. Unfortunately with the addition of this unit, the cost of the initial CCTV housing goes up in direct proportion with the cost of maintaining the overall hardware of the system. First, solvent assemblies are basically ineffective. The guard must remember to spray the solvent and allow it to soak into the dust film for a few seconds prior to turning on the wiper blades to be effective. Unfortunately, the most common reaction is to first turn on the blades and then squirt the solvent. Scratching or etching of the glass is still very prevalent. You also have the fact that reaction time to viewing a scene does not generally allow for a few seconds of soaking time. Secondly, you now have a constant maintenance unit in your video system. How many times have you gone to use the solvent in your car and found it to be empty or dry. If your cameras are mounted in the air, above reach, you will have a person that will have to; drag out heavy ladders; climb towers; power up man-hoists; go onto rooftops; etcetera; to check and fill these units daily (or at least weekly) for solvent. Thirdly, you have added a very expensive and irresistible toy for the guards on the second or third shifts to play with. I know these are security professionals that you are going to hire. It doesn't matter. When things get boring and the day or night stretches on, the guards will play with the solvent sprayers and the wipers. I can't explain it, I can only tell you (from personal experience) that it happens. Ignorance is a strong factor here. Ignorance is a lack of information and/or understanding of the situation unlike stupidity, which is the inability to admit or acknowledge ignorance.
Another maintenance problem is the blades themselves. The blades are designed to stop at the end of their cycle. The majority of the time, the blade remains in the picture. This can cost the loss of valuable information by blocking part of a scene. These blades also dry out and crack. Ultimately, when a dry or cracked blade is made active, the image is more blurred than if the blade had been left inactive. You will find that the blades need to be replaced on an average of once a year (dependant upon the environment). Once again adding to the cost of system maintenance. In the fall and spring, the blades will freeze to the housing window. This will cause them to tear when made active in a slush or wet snow situation. You will also burn out motors and break gear systems from the excessive force needed to push them across the window.
Wiper assemblies are to keep the rain off the housing window allowing the viewer to work in all forms of foul weather. If you are truly concerned about the view through your housings, I suggest that you invest in "Glass Wax" and "Rain X". These two products work very well to keep dust, water, and other things from settling and/or beading up on your housing windows. The nice thing about using these products is that your technicians should be cleaning the glass during quarterly inspections anyway. This is a perfect time to apply an updated dose on the housing window. Washing the housing windows should be done during inspections anyway as part of simple maintenance. You will save money on the up-front installation and on the long term maintenance of you CCTV system. Overall, your system will produce excellent, etch free pictures for many years to come, in most situations.
In the past twenty years of consulting, designing, installing, servicing, reviewing, and operating hundreds of CCTV systems, around the world, I have found only a small handful of circumstances where I would or have recommended wiper blades. I have found even fewer circumstances where the wiper blades have been effective to their design. One such system was inside the tunnel of a car wash where the moisture content was such that the window was consistently wet. Even here, "Glass Wax" worked best. The problem was that the solvents in the soap that traveled on the water spray dissolved the wax too quickly, causing a different type of maintenance problem. A second system was literally mounted under water at a submarine base. Even in this submerged environment, the housing glass and wiper blades had to be replaced fairly often. This was due to etching of the glass and deterioration of the blades caused by the salt water.
My final word is that I highly recommend that you avoid CCTV housing wiper assemblies when ever and wherever you can. The problems and costs that they create, both short term and long term, far outweigh their effectiveness. Good luck to you. I hope that I have been of some help in this dilemma and invite you to email or write again at any time.
Sincerely, Charlie Pierce President LRC ELECTRONICS COMPANY LTC TRAINING CENTER
