Even occasional readers of this column know by now that the author is highly in favor of regular preventative maintenance. Although modern equipment is far more reliable than older systems, simple housekeeping and checks of operating parameters will lower downtime even further and improve overall physical plant reliability. That, in turn, decreases the shouting at the station, improves employee evaluations and generally makes for a smoother running operation.
A few recent events observed by the author have reminded all involved that careful checking of everything will pay off in the long run. In the first of those events, an FM antenna failed on the first really cold night of the season. It was found that a bolt holding an inner connector together had backed all the way out of the threads, causing the connection to be completed only by being held together by previously applied pressure. The first time that the line cooled enough to cause the inner conductor to contract slightly, the connection was broken and the system failed.
In this instance, the bolt had been installed initially but had not been sufficiently tightened. The tower was observed to have a significant amount of high-frequency vibration. No dampers were installed. The vibration simply caused the bolt to slowly back out until it fell free into the center conductor. It should be pointed out that this was not an economy model antenna but from one of the major manufacturers. The entire problem could have been avoided if all bolts were carefully checked for tightness before the system was installed on the tower. The moral of this story is that it pays to carefully check every piece of equipment before it is installed. Even the best of companies sometimes leave a bolt loose, a cable not supported or a bracket not secured.
In the second event, an old bugaboo reared its ugly head again. An FM antenna system failed. Upon inspection, the problem was water in the antenna due to a failure of the pressurization system. That is the type of problem that consultants love. The failure is massive and total, the problem is easy to find and the repair is quick. That all makes for an easy fee that would have been avoided by some simple checks.
Pressurization systems are often neglected as they don't make any obvious calls for attention unless pressure warnings are installed. Even then, faults can go undetected. In one instance, the author was advised by the station that the transmission line had been continuously under pressure and didn't leak at all. In fact, the same bottle of nitrogen had been in use for more than five years and the pressure was constant at five pounds. When the gas line was broken at the transmission line, the reassuring hiss of escaping nitrogen was noticeably absent. The problem was found to be a blocked filter in the output of the regulator. The five pounds of pressure existed only in the regulator itself. The removal of about a pint of water from the transmission line at the drip loop returned the system to normal. It is highly recommended that a pressure gauge be installed using a tee fitting right at the connection to the line. That ensures a more accurate measurement of the pressure in the line even if someone has placed a corner of the transmitter on the pressure hose.
There are a number of causes for the water-in-the-line problem. Older dehydrators have a tendency to continue to maintain airflow even when they have long since ceased to remove the moisture from the air. In other words, they very efficiently, albeit slowly, pump water into the transmission line. As a simple check of the air quality, an additional desiccant cylinder can be purchased and placed in the line at the output of the dehydrator. That makes for a simple way to ensure that the moisture is removed from the system. If air is moving and the color doesn't change, all is well. It helps if the staff isn't color-blind and actually looks at the cylinder now and then.
The problem can also be eliminated by using a nitrogen generator. Such units are now available at a reasonable price for large systems. They don't make much sense financially for a little single-line system but are very good when several lines or when large lines are involved. These systems were originally designed to maintain a positive nitrogen gas pressure in the fuel tanks of helicopters in combat situations. As fuel was consumed, nitrogen filled the empty space instead of fuel vapors. If a bullet penetrated the fuel tank, there was no atmosphere inside the tank that would cause an explosion. After lengthy testing on transmission lines at a television station near their plant, the manufacturer decided to enter the broadcast market to broaden their sales possibilities. These systems do a good job, as do the current crop of air dehydrator systems from the major manufacturers. The point here is that it is still necessary to check the system regularly, whether it is a dehydrator, a nitrogen system or a simple nitrogen tank and regulator.
The third event that caused widespread headaches concerned a bolt falling from a tall tower. According to standard practice, structural bolts on towers are normally equipped with components that will prevent them from coming loose. One problem is that occasionally they still get loose. More prevalent is the problem that items attached to the tower often don't have similar precautions taken and are more likely to shed parts of various size. Bolts are commonly installed with the head down so that they will fall free if the nut comes off — making them easy to spot during a tower inspection. The bad part here is that they will fall regardless of what or who may be in the vicinity of the tower itself. In this instance, a station staff member had the bad luck to be walking near the tower and was struck by the falling bolt. Now, let the trumpets sound to announce the entry of the parade of personal injury lawyers, OSHA officials and inspectors, local building inspectors and authorities. Those in the northern parts of the country know not to park near the tower during icing conditions. They also know not to go outside anywhere near the tower when it is shedding ice. However, most people don't think about the shedding of mechanical pieces.
Here, about the only thing a station staff member can do is to have annual inspections of the tower by a competent tower crew. While that helps, the occasional failure of a tower or tower attachment component is going to occur.
To that end, a number of steps need to be taken. First, make sure that your insurance policy covers damage or injury due to falling objects from the tower.
Second, bring the station fully into compliance with the requirements of OSHA for maintaining a safe work area. At the least, a Hazard Assessment should be prepared and posted prominently for the station staff. Everyone at the station should be required to read the document and sign it to acknowledge its contents.
It is highly recommended that you contact the area OSHA office and ask them to visit the site to advise you of any further steps that you must take to comply with their regulations. If you contact OSHA and ask for their help before any problem actually occurs, the atmosphere will be much more pleasant than when the ER personnel are removing an FM bay from a passerby. OSHA is a little different in this regard. In this case, they are from the government and they really are here to help you. On the other hand, if they advise you of necessary steps to be taken and risks to be avoided, it is highly recommended that you comply. If you don't and an accident occurs, you are now playing in the area of willfully allowing something to happen that you could have avoided. Get the checkbook ready.
Don Markley is president of D.L. Markley and Associates, Peoria, IL.
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