Tower Dun Fell Over - weld it back up!

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10/31/2011, lost link across a radio shot. Got the call on the way in. Spent an hour stuck in traffic because some knucklehead got creamed. Made it to the office at 0620 or so, diagnosticated the link, looks like the problem is at the top of the hill. This is good - the hill in question is road accessible, which is not always the case here in Alaska.At the site, I find... Well that's not good. The tilted mast is carrying my shot back to the home base, and the big dishes on the far side run down the Kenai peninsula..  fairly important. Get some tower climbers in. One of them puts an allen wrench on one of the 1/8th bolts holding the feed line to the antenna. This happensOh Boy!Crane, plow, gravel, welders, and a couple helpers later, we get the mast down, and find this.Look at that sexy weld! I've never seen..   well, much of anything. I'm new. But that's crap. So my welders get started, and they replace the rubber end cap which was the root cause of the problem with this.And the flange gets welded.And gusseted Which makes me a lot happier. Weld shop is putting together a plate for the top of the tower that will serve as a catwalk, and the game plan is to harness a welder up, run him up the tower on the ladder, stick him on the catwalk and weld gussets to the remaining masts, in place. OK, except..  I can't shut this site down. We've got live circuits running through here that I cannot shut off unless absolutely neccesary. So I'm coming to you guys - what do you think about welding stick on an active microwave tower? The tower is grounded, the dishes are bonded to the tower, which means the radios are as well. full disconnection is to be avoided. Any suggestions? Comments? Album is here. http://imgur.com/a/19YYL
Reply:looks good - cant see the close up of the gussets, but did yall grind down ur welds?it might just be me, but where i was taught you never grind down the weld...
Reply:not 100% certain whether they ground the weld down on the gussets or not. I know they did not on the flange. I'm just worried about the followup, welding on a live tower..  I REALLY can't afford to zorch my radios.
Reply:Tell'em it's absolutetly neccessary to shut it down, to be able to fix it Faster, Safer, Better and Cheaper than if it remains online. Do the work with less danger to your guys, then power it back up. If they INSIST it stay powered up while you work on it, charge them accordingly(hazardous duty pay).
Reply:I have no experience with this, so weigh my words accordingly.SafetyI think the weldor will be OK doing this - as long as the ground clamp is in the immediate vicinity of the weld(s) to be made and the weldor is never positioned between the electrode and the ground clamp.  It would be a good idea for the welder to wear rubber soled shoes and to wear rubber gloves inside normal leather welding gloves.Radio DamageElectrically the chance of radio damage can be minimized by keeping the electrode to ground-clamp distance very short; this reduces electrical currents outside the immediate vicinity of the weld.  Electromagnetic InterferenceYou will have to weigh the relative merits of taking a light-weight inverter welder up the tower powered by a long extension cord operating at low current and 230 volts... as opposed to leaving a big welder at the bottom hauling up long ground/whip cables operating at say 25 - 30 volts but kicking out significant magnetic fields as 100 - 150 amps surges to and fro through the cables.Rick V 1 Airco Heliwelder 3A/DDR3 CTC 70/90 amp Stick/Tig Inverters in Parallel1 Lincoln MIG PAK 151 Oxy-Acet
Reply:Eh, to clarify, I'm not the welder here. This is production/liability stuff, so instead of the jackoff with the wirefeed in his garage (that's me), we're using our certified guys who weld for a living. Regardless of what happens with the radios, the welders will be as safe as kittens, that I'm certain of.The worry is the radios. The guys will 100% be fine - we're putting up a grated 'lid' on the plane they'll be working on, and they will be harnessed and supported by rescue trained climbers, top and bottom firewatch, and any other precautions I can think of. The worry is the radios hooked to the dishes bolted to the masts they'll be welding on..Edit: Rick V,  your reply showed up between my starting typing and hitting 'go'!Safety is 0% worry. My welders are sharp, they're comfortable company men as opposed to pipe chasing mustangs - they're more concerned about going home intact than they are about making a buck (especially since they're hourly  ). I'm just hoping someone has some experience welding on a tower with a live microwave.Last edited by Wiregeek; 11-02-2011 at 05:50 PM.
Reply:No safety issues as far as EMR exposure to personnel with the systems left operating?What is the specific FCC or OSHA or other reference so you are covered? Aircraft radar requires a cordon around it during ground operation, and if you point a radar antenna at a (turned off) light cart which is facing you the reflected RF will light the incandescent bulbs quite nicely even 70 yards out! Been there, done that.As an aircraft mechanic I wouldn't be getting next to an operating emitter even from the rear. I'd just walk away. Beats getting cataracts etc you can't prove came from previous overexposure. Safety isn't just avoiding the stuff that kills or injures on the spot!Since owners may not care about personnel safety, I'd insist using the "risk to equipment" argument. Possible voltage spikes from the welding machines, etc.
Reply:You mean your welders haven't already? if they are company men, you would think they'd have already done it a time or two. or maybe the only one who has was the guy who retired last spring?There are no problems. There are only solutions. It's your duty to determine the right one.Hobart Handler 210Airco 225 Amp MSM Stinger
Reply:Are the other antennas still live? I have worked around towers that are live.  The safest one you had to stay 10' from the live antenna. The other extreme, grounded wire mesh suits had to be worn.  The danger is standing Radio Frequency.  The least thing you had to worry about, was cooking the sperm banks.  Went downhill from there.  Eyes, brain and so on.    Still a cold job.  Makes a simple job hard.  Any pre heat needed for the welds?  Spent 5 1/2 years there.  I was out in -40. Not something you do for long.   It got colder but did not go out in it.
Reply:dont do it!!!! turn that baby off!
Reply:"No safety issues as far as EMR exposure to personnel with the systems left operating?"Nope. Regulated RF exposure levels start several thousand times higher than anything on this tower, or, for that matter, everything on this tower, twice. This isn't multiple kilowatt radar sweeps, this is sub-watt microwave (one one-watt spread-spectrum 902-928)edit:I have worked around towers that are live. The safest one you had to stay 10' from the live antenna. The other extreme, grounded wire mesh suits had to be worn.I dun goofed The tower isn't live. This is a microwave site, not an FM broadcast site. The facility is 'live', in that there are transmitters running, but the tower structure itself is grounded, and non-transmitting. Though I have to admit, I'd love to drive a few thousand KW of 6hz or so through the structure and light the next-door-neighbor's house on fire.. You mean your welders haven't already?Nope, this is the first time in institutional memory that we've had in-house welding done on a tower. This whole site is an aberration.Last edited by Wiregeek; 11-02-2011 at 07:03 PM.
Reply:Originally Posted by QuickStill a cold job.  Makes a simple job hard.  Any pre heat needed for the welds?  Spent 5 1/2 years there.  I was out in -40. Not something you do for long.   It got colder but did not go out in it.
Reply:All your coaxs'/heliaxs'/wave guides are or should be bonded to the tower either individually or on a buss near the building entrance. I'd think about flooating that from the general tower connection with its own temporary lead to the ground field grounding electrodes for the welding period. If nothing else verify that the ground buss has it's own quality path to the ground field, which it really should have anyway but not all do. Some are merely relying on the bolting to the tower for the path to ground.  May want to give the whole grounding issue a quick once over.Last edited by Sandy; 11-02-2011 at 09:10 PM."The things that will destroy America are prosperity at any price, peace at any price, safety first instead of duty first, the love of soft living and the get rich quick theory of life." -Theodore Roosevelt
Reply:That's not "fell over".  Last spring we had a chunk of tower bigger than that whole structure snap off from the top of a 100+' tower.  It was swinging by the cables.__David Hillman
Reply:I'm with Rick V on two accounts.1) No personal experience welding on microwave towers.2) Keep the work clamp close to the weld point (I'd clamp it to the gussets).I have welded on computer equipped vehicles with them connected but know enough not to connect the work clamp to the front bumper and then go weld on the rear one.As for ill effects on transmission lines from the currrent flowing thru the welding cables, the best thing to do is keep them as far away from close proximity to transmission lines as possible and/or if it can't be avoided, make sure they run perpendicular to them same as woudl be the case with high current circuits (300A alternator output cables) and radio antenna cables in emergency vehicle applications.The suggestion to use an inverter machine might be worthy of consideration but you'd still want to take the necessary precautions with the welding leads.If it's safe for your guys work on live towers as you've indicated, then it appears there's no danger of them coming away with fried mountain oysters from the experience.Again, as with Rick V - take any of what I say for what it's worth.MM200 w/Spoolmatic 1Syncrowave 180SDBobcat 225G Plus - LP/NGMUTT Suitcase WirefeederWC-1S/Spoolmatic 1HF-251D-1PakMaster 100XL '68 Red Face Code #6633 projectStar Jet 21-110Save Second Base!
Reply:I read most of the thread.  I welded on cell towers.  Never shut em down.   I don't know about microwaves.    Zero problems, did not expect any either.  Those things are grounded Everywhere and  more.  Ground on the tower, don't let your electrode touch the fence.....  EVERYthing is grounded.In many or all there is a ground bus in the ports.   A whole bunch of grounds meet there.  Not all by a long shot.  They were held to the tower on plastic standoffs.  Go figure.I do have my ground cable attached to a pair of C vice grips for a good solid connection, but that st for my benefit, not the tower.Real world weldin.  When I grow up I want to be a tig weldor.
Reply:Originally Posted by David R......In many or all there is a ground bus in the ports.   A whole bunch of grounds meet there.  Not all by a long shot.  They were held to the tower on plastic standoffs.  Go figure.
Reply:Originally Posted by smokin_dodgelooks good - cant see the close up of the gussets, but did yall grind down ur welds?it might just be me, but where i was taught you never grind down the weld...
Reply:That's barely a tower!HH 187Miller Bluestar1EAHP AlphaTig 200X
Reply:cute little thing, isn't it? The site is about 2000' ASL, and in a nice wind concentrator. Lot of it is old school versus new school. Then there are the non believers out there that flat won't go with the single point theory. If it is done 100% one way or the other it's easier to deal with. When it's a hodge podge then you have to really look things over and think about it. This is the vast majority of my sites. I've got hodgepodge and 'temporary' sets that are ten plus years in service. The vast majority of my feedlines across all systems are ungrounded, believe it or not. Some of them are even ungroundable, per the radio manufacturer (I still don't have my head quite wrapped around some of this split architecture stuff).I'm meeting with my safety guy here in about 20 minutes, I'm going to turn him loose to run the numbers on the RF exposure vs. the FCC. I'm confident as can be that we're going to be far away from exposure limits, but I would love some paper.Working with a local tower/telecom company, we've managed to plan around 2/3 of the remaining masts - with a little foresight they can be removed from the tower and welded on the ground without interrupting service. Looking at drilling a weep hole in the remaining mast and putting some propane heat on it to melt it clean.
Reply:Its not the wattage that can harm you, its the frequency.  Certain frequencies affect different parts of the body differently.Have a look over at this: FCC Maximum Permissible ExposureI come from amateur radio and we're taught to be weary of RF radiation.
Reply:Originally Posted by Donald BranscomNever grind a structural weld.
Reply:Originally Posted by WiregeekThe tower isn't live. This is a microwave site, not an FM broadcast site. The facility is 'live', in that there are transmitters running, but the tower structure itself is grounded, and non-transmitting.
Reply:Late arrival to this thread...  No experience with broadcast systems, little knowledge of such.  But my offering is from a eye exam for a laser certification class 25 years ago...Lasers can burn the retina, the eye exam was to map my retnias for previous damage to protect my employer from future liability.   On to the microwave --- Another  student in the class had 10 years microwave expereince in the military.  His retinas had no damage, but the corneas of both his eyes had tiny bubbles in them.  This was damage caused by close exposure to microwave energy from working around live antennas.- MondoMember, AWSLincoln ProMIG 140Lincoln AC TombstoneCraftsman Lathe 12 x 24 c1935Atlas MFC Horizontal MillCraftsman Commercial Lathe 12 x 36 c1970- - - I'll just keep on keepin' on.