Safety in the workplace
Dec 1, 2009 12:00 PM, By Kevin McNamara
Those of us who got into the broadcast business years ago had very little training about safety procedures and guidelines. Early in my career, I watched a more experienced colleague get thrown across a transmitter building from attempting to measure plate current from an operating transmitter. Fortunately he was thrown away from the transmitter before any fatal injury ensued, but it made me acutely aware of two lessons: 1. Always have someone else in the room when working on a transmitter and 2. don't stick your hands in an operating transmitter.
A typical broadcast facility contains an unusually large amount of potential hazards � electrical, climbing, RF exposure, etc. And reductions in personnel mean engineers are working alone.
Large group owners now provide routine safety awareness programs, which can be valuable assuming the company backs up the training with the proper tools, support systems and resources.
If you haven't had awareness training, or have been doing this for awhile and have it figured out, it is worth mentioning just a few of the hazards that lurk in your facility.
How many times does the transmitter decide to quit when you are awake and alert? My experience is that the call comes just after getting into a sound sleep. Let's not forget the majority of maintenance work also happens overnight.
We all know that shock occurs when one electrically places himself between a voltage source and a ground path. The rule of thumb has always been when working on electrical equipment, keep one hand in your pocket.
Figure 1 shows how humans experience the effects of electrical shock from as little as 1mA to 50mA when death can occur. Notice also that the trip current of the typical circuit breaker is about 15A. Ground fault breakers will trip under much lower current leakage conditions typically 5-500mA. You cannot depend on the circuit breaker to protect from lethal shock.
Table 1: Effects of Electrical Current in the Human Body
Below 1mAGenerally not perceptible. 1mAFaint tingle. 5mASlight shock felt; not painful or disturbing. Average individual can let go. Strong involuntary reactions can lead to other injuries. 6-25mA (women)
9-30mA (men)Painful shock, loss of muscular control. The freezing current or �let-go� range. Individual cannot let go, but can be thrown away from the circuit if extensor muscles are stimulated.* 50-150mAExtreme pain, respiratory arrest, severe muscle contractions. Death is possible. 1-4.3ARhythmic pumping action of the heart ceases. Muscular contraction and nerve damage occur. Death likely. 10ACardiac arrest and severe burns. Death is probable. 15ALowest overcurrent at which a typical fuse or circuit breaker opens a circuit. * If the extensor muscles are excited by the shock, the person may be thrown away from the power source.
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Safety in the workplace
Dec 1, 2009 12:00 PM, By Kevin McNamara
It is worth mentioning that dc power supplies can also be extremely deadly if precautions are not taken to remove the input power and completely discharge all capacitors. Older tube transmitter power supplies typically deliver dc outputs of several hundred volts at respectable amperage; it seems pretty obvious these will hurt. However, the power supplies in the newer solid state transmitters and dc UPS/battery backup systems might operate below 100V but would be capable of supplying several hundred amps of current. These low-voltage/high-current power systems are nearly perfect constant current sources.
OSHA specifies requirements to provide proper �Lockout/Tagout of electrical circuits where employees are exposed to electrical hazards while working on, or near, or with conductors or systems that use electric energy.� 29 CFR 1910.333 sets forth requirements to protect employees working on electric circuits and equipment. This section requires workers to use safe work practices, including lockout and tagging procedures.
Tower climbing is now considered the most dangerous job nationally. According to a 1998 study by NIOSH (National Institute for Occupational Safety and Health), 108 tower worker deaths were reported between 1992 and 1998. Of these, 93 were cause directly by falls from structures.
In 2008 alone, 12 deaths were associated with falls from tower structures in the Communication Construction Industry.
It goes without saying that any crew you permit to work on your tower needs to provide proof that it possesses the proper training equipment and training before being permitted to work on a tower, rooftop or other structure. You should always require qualified tower climbers produce a current certification card prior to start of work. Organizations such as the National Association of Tower Erectors (NATE) provide training and certification programs to qualified tower workers.
We became aware of the issues related to non-ionizing radiation back around 1996 when the FCC adopted guidelines to ensure the exposure of employees and the public to RF energy is below stated Maximum Permissible Exposure (MPE) limits. Since that time broadcasters have been required to take steps in preventing casual access and marking areas where levels are in excess of stated limits.
In the event you find yourself in an area rich in RF sources such as a rooftop, there are some signs to watch for to indicate RF exposure: Confusion, vertigo, headache, blurred vision, overall nauseous feeling, body heating, shocks and burns, and bad or metallic taste in the mouth.
It should become a requirement that any employee or subcontractor working in these areas carry some form of RF personal protection monitor with them at all times.
One last word. If it is necessary to work alone be sure to take a few minutes to assess the potential hazards that could cause injury. Categorize the potential hazard and create a control measure that would help address any risk. These control measures would include getting regular calls from someone at regular intervals, having surveillance monitoring of the area or periodic checks by someone nearby.
Summary of tower work incidents in 2008
3/12/08 Wake Forest, NC - A 34-year-old tower tech fell approximately 130' while transitioning on a monopole.
4/14/08 San Antonio - A 38-year-old tower tech fell 225' after leaning back while loosening bolts on a guyed tower.
4/14/08 Moorcroft, WY - A tower tech fell from an unknown height.
4/17/08 Frisco, NC - A 46-year-old tower tech fell from a 90' tower onto a fence and then the ground.
4/23/08 Natchez, MS - A tower tech fell approximately 100'.
5/16/08 Haubstadt, IN - Reportedly under contract to General Dynamics, a 25-year-old fell approximately 140' while rappelling down a 200' load line at a monopole site.
5/22/08 Miami - Age unknown worker performing maintenance on the Channel 7 WSVN tower fell at approximately 12 p.m. from an unknown height.
7/18/08 Vineland, NJ - A 55-year-old tower tech fell about 60' at approximately 10:50 am from a Crown Castle tower.
7/20/08 Petersburg, ND - A 38-year-old broadcast engineer fell an estimated 100' while painting a tower.
9/12/08 Port Angeles, WA - A 33-year-old tower tech fell 32' along exterior of elevator shaft; incident occurred around midnight.
10/24/08 Ellensburg, WA - A 24-year-old Internet cable tech fell through a skylight 35' at a Ford dealership.
11/18/08 Pima Co., AZ - A 22-year-old tower tech fell from approximately 65' from a self-supporting tower.
McNamara is president of Applied Wireless, Cape Coral, FL.