File under some new everyday. Yesterday, there was an area wide power outage in Woodstock, NY. The backup generator failed to start, however, WDST remained on the air until the UPS batteries ran out several hours later. Then my cellphone rang. Alas, yet another Sunday on the job.
Upon arrival, I found the power had just come back on, so the DJ (yes, there was a live person in the studio, on Sunday) was restarting the NextGen system and getting the station back on the air. I restarted the rest of the servers, streaming computers and what not. While I was there, I figured I might as well see why the generator didn’t run.
Pressing the start switch led to the “click, click, click, click…” which normally indicates the battery is dead. Deciding that I should dig a little deeper, I got the volt meter out. Battery voltage, no load 13.8 volts. A normal reading. Flick the starter switch and measure the battery voltage again, under load 13.7 volts. Hmmmm, now that is not what I suspected. If the battery were bad, the voltage should drop down under load.
I grabbed the negative cable and it came off in my hand. Another one of those “ah ha!” moments. Upon closer examination, the terminal connector is cracked in half.
I went to the local Ford dealership and bought a heavy duty truck battery cable. Since the battery itself is six years old, I decided to bring it and have it checked, and sure enough, the battery was going bad too. Rather than suffer through another power outage without generator, I went ahead and replaced the battery.
Why the terminal cracked in half in the first place, I don’t know. Perhaps it was over tightened, or some type of manufacturing defect.
Broadcasters historically have tried to remain on the air during emergency events like major storms, earthquakes and other forces of nature. Often times, commercial power is interrupted, and thus, the backup power generator is installed. Propane powered generators for medium duty (powers up to 45 KW) are popular because of the decreased environmental hazards, availability and expense of fuel, ease of maintenance and repair. This sized generator can run the critical loads of a studio facility or a transmitter site with TPO’s between 5 and 10 KW.
Most propane generators use a gasoline engine modified to use propane. These generators can also use natural gas, however, because natural gas has slightly less energy, the generator’s service rating is reduced by about 10 percent.
The biggest error I consistently see with propane generators is improper fuel tank sizing. It might seem just fine to plop a 500 gallon tank down next to a 45 KW generator and expect everything to be just fine. 500 Gallons may sound like a lot of fuel, but the more important consideration is tank vaporization, that is to say, how fast can the liquid propane can be removed from the tank for use. Propane fuel companies should be able to sizing these things correctly, most of them have books and charts that tell what capacities and sizes are needed. However, as a general trouble shoot guide, the following information is provided:
Generator manufactures will specify how many BTU per hour a generator will require under full load. If not, these are some conservative rules of thumb:
For every 1 KW of electrical generation, 2 horsepower of engine is needed*
Under full load, each horsepower will consume 10,000 BTU per hour*
Propane has 92,000 BTU per gallon
Propane weighs 4.2 pounds per gallon
*Note: These are not the figures you will find in your engineering handbooks, they are adjusted for generator winding and engine efficiency.
Propane Tank Vaporization Rates (Continuous BTU/hr vs volume at tank temperature):
Size propane in a tank (assumes 1/3 full)
Maximum continuous BTU/hr at degrees F
Note: Tank vaporization depends on fuel level, tank temperature and withdrawal rate. The above chart is a conservative generalization and represents a safe median value.
If a propane tank cannot vaporize fuel fast enough, the generator will begin to run lean, eventually overheat and shutdown. The vaporization rate depends on the tank temperature, which drops as fuel is withdrawn. For the above cited 45 KW generator called to duty after a sever winter storm, the tank would need to vaporize: 45KW x 2 HP = 90 HP. 90 HP x 10,000 BTU/hr = 900,000 btu/hr. A 500 gallon tank is too small for that size generator.
As the tank temperature drops a propane tank can develop frost on the outside of the tank, even on a hot summer day, which compounds the problem.
The correct size tank for a 45 KW generator is a 1000 gallons. This can also be two five hundred gallon tanks connected in parallel via a high pressure line.
Also note, the generator’s radiator is facing the tanks so that when the unit is running, hot air is blowing on the tanks, warming them up. This particular generator is about 25 years old, which is why it looks a little worn. It still carries the load and mechanically is in sound condition.
Most propane fuel systems have two regulators; one high pressure regulator on the tank, which takes the variable tank pressure and steps it down to about 10 PSI, and the vaporizor which steps the pressure down to a few ounces per square inch (or inches water column) and adds air creating propane gas for the generator to burn.
It is important that the vaporizer be mounted above the snow line and that there is a little screen on the air intake, otherwise mud wasps will build a nest in the air intake and the next time the generator is required to run, it won’t start.
Fuel piping is also a concern, if the low pressure lines are not large enough to handle the required BTU, the generator will run lean, creating the same problems of an improperly sized tank. Different piping has different capacities, see the following charts:
Assumes pressure less than 1.5 PSI, one MBTU is equal to 1,000 BTU per hour.
Once the generator is installed, maintenance is required. As a minimum:
Exercise engine bi weekly for 15 minutes. Propane generators do not need to run under load.
Check fuel, oil, and antifreeze levels monthly, more often if heavy use.
Change the oil, oil filter, air filter, check antifreeze freeze point, battery electrolyte specific gravity yearly
Change out belts and hoses as needed, pay close attention to the block heater hose, this is where leaks often develop
The tower climbing video that has gone near viral pointed out a few things. Climbing towers is dangerous business, best left to those who are trained for it and have the insurance.
It is true that tower climbing contractors have the responsibility to protect their own workers while working on a clients tower. That does not completely absolve the tower owner from liability. The it is incumbent on the tower owner to provide a safe structure to climb. This can mean the mechanical integrity of the tower, reduction of transmitter power while workers are in high RF energy fields, and providing the proper permanently attached safety equipment on the tower itself; Climbing ladders, ladder safety cages, rungs, elevators, and fall arresting gear.
In that tower video post, I mentioned something called a safety climb. That is a cable, usually 3/8 inch stainless steel aircraft cable, attached, about eight inches from the climbing surface like this:
The tower itself was built in 1959 and did not have this equipment when new. This was a retro fit kit, installed in 2003, I believe.
The tower climber wears a harness with a special karabiner attached to the front and waist level. When climbing this ladder, the karabiner slides up the cable. If he were to fall, the karabiner has an auto locking or braking mechanism that would stop his fall.
Many tower climbers, especially those that have been in the business for a while, do not like these things. When climbing, especially if one has long legs, the tendency is to bump your knees on the bottom of the next ladder rung. This is because the belt holds the climber’s waist in making it difficult to get the rear end out, away from the ladder the way most people like to climb. The alternative is to climb with the knees spread apart, like a frog, which is hard on the hamstrings and quite literally, a pain in the ass. However, if a tower is so equipped, it must be used.
I have, wherever possible, retro fitted towers with these devices. Of course, all new towers come equipped with them. In some situations, it is not possible to retro fit towers with safety climbs, either because there is no attachment point at the top of the tower that meets the OHSA spec, there is not a climbing ladder, or it would affect the tower tuning, as in an AM tower or near a TV or FM antenna.
Hundreds of gallons of ink have been spilled by Los Federals in OHSA regulations 29 CFR 1926 and 29 CFR 1910.268(g) regarding fall protection and fall protection equipment for telecommunications workers. In this litigious world we live in, tower owners and or their on site representatives should know these rules and make sure they are followed.
It they don’t care all that much about traditional phone service anymore. Through attrition, they have reduced their tech work force to about half what it was 15 years ago. All of the infrastructure; over head cables, buried cables, office frames, switching equipment, is getting old. Some of the cabling around here, both buried and overhead, is the original stuff, installed 100 years ago. Because it is expensive to replace, they don’t want to change it out, opting to simply limp along, swapping out pairs when a line or circuit goes dead.
I will be surprised if the traditional wired telephone network still exists in ten years. Think about it, ten years ago were were just heaving a collective sign of relief that Y2K turned out to be nothing, remember that?
For the local phone giant, offering 3 in one (telephone service, internet service and cable TV) is more appealing than servicing their existing accounts, including HICAP (high capacity) data circuits like T-1, BRI&PRI ISDN, etc. Much less so for a POTS line, which, good luck if you really need it fixed right away, we’ll be over when we get to it, just keep your paints on mister.
I’ve written about this before. A particular station for my former employer uses a T-1 circuit to relay the program from the studio to the transmitter site. This is fairly common in larger metropolitan areas where 950 Mhz STL frequencies are not available, nor is line of site between the studio and transmitter site obtainable.
Back in 2002, when the company was in the process of aquiring said station, I recommended a 950 Mhz STL. There was an existing STL license, fully coordinated, that came with the main station license. Only the equipment was needed. No, I was told by the CFO, we will do a T-1, thank you very much. I argued my point, saying that putting our radio station exclusively in the hands of the phone company was a bad idea. We would have problems with outages and service. No, said the CFO, this is New York, all the radio stations do that. Not exactly, New York is about 15 miles SOUTH of here, this is Westchester, the cables are old, a lot of them are overhead, which exposes them to lightning, vehicle damage, water, etc. There will be service issues if we rely solely on a T-1.
No, he said, “We are using a T-1 and that is final.” I hate to say I told you so, but… Let us examine the history between then and now:
Date of outage
Date of restoration
April 5, 2004
April 9, 2004
September 8, 2006
September 10, 2006
May 2, 2007
May 5, 2007
August 27, 2009
September 4, 2009
September 5, 2010
September 15, 2010
Fortunately, I wrote all this down in the transmitter site log. I was able to check it yesterday, when I went to restore the station to normal operation after the latest T-1 failure.
During those periods, we have used BRI-ISDN, which is okay but it was carried the same phone cable. It is likely to go down if there is a major cable interruption. We have installed a second T-1 circuit, which fails when the other T-1 circuit fails. We have used 3G wireless sprint card and streamed audio from the internet. That didn’t sound great, but we did clear inventory. We have moved one of the AudioVault servers to the transmitter site, and updated it once a day via shoe leather network, that sounded great, but it was difficult to do. We have borrowed an ethernet connection from another tower site tenant onsite and streamed internet audio via wired connection, which sounds pretty good.
Still, the best thing to do would be to establish our own STL path to the transmitter and get rid of the T-1 lines.
The Problem with the Phone Company is they are not all that interested in simple copper circuits anymore. Now, there is something called FiOS, which, it would appear is a much better profit center than ordinary copper circuits.