TV Antenna CollapseStaff posted on October 24, 2006 |
TV Antenna Collapse
Analysis of the Faulty Design
On November 18, 1982, Riggers called Antenna Engineering and asked if it was acceptable to remove the microwave baskets on the top 100-foot section of the tower so they could lift the antenna into position, and then reinstall the baskets after the section was in place. Antenna Engineering told Riggers that removing the baskets would void the warranty: at a previous job Antenna Engineering had allowed removal of the microwave baskets, and they were not reinstalled properly. Antenna Engineering was held responsible for correcting the problem, which cost them a great deal of money. The following telephone conversation took place between Randall Porter, Riggers' Vice President, and Harry Jordan, Antenna Engineering's Engineering Division head:
Porter: Harry, this is Randall Porter with Riggers, Inc. We've run into a problem on Tower 17.
Jordan: How so?
Porter: Well, thus far everything has been fine, but the top antenna section has the lifting ears in such a position that we can't cable them up to the crane without running into the microwave baskets.
Jordan: Well, we put them on as specified on the plans. Seems like they were right between two baskets, weren't they?
Porter: Yes, and that works great getting it off the truck, but when we try to get it on top of the previous antenna section, it has to be lifted vertically. The crane is barely able to get the antenna up high enough to bolt it to the preceding section as it is. No way can we lift it to the top horizontally.
Jordan: Well, what do you suggest? We pretty well signed off when you accepted the plans, and we don't have any connection with the construction of the antenna. We leave getting it up in the air pretty much to you guys. Not that we don't want to help in any way we can, but you and your people put these towers up every day of the year, and we really don't want to start getting into that area.
Porter: No, I understand that, but it's just that we really don't have an engineer on our staff who can redesign those little ears and put them in a location that will work. So what we would like to do is simply take off the baskets until we get the antenna in the air and bolted down on top. Our guys will then take the baskets up and bolt them on. Should be no problem, but we just wanted to check with you first.
Jordan: I don't know Randall. We took a beating on letting some other company remove those baskets last year. You wouldn't believe what a mess birds can cause when those microwave guides are left open. It took us 6 months and a small fortune to purge out nests, rats, sand — you name it. That's why you get the antenna section with the microwave baskets all bolted on and sealed, to prevent that.
Porter: We would take full responsibility for not letting that happen. You could make us some blanking plates to replace the baskets, and we would leave them on until we were ready to put them back on. Surely we can work something out, because that section is due to go up tomorrow, and we don't have a clue how we're going to do it.
Jordan: Well, let me talk to Bill about it, but I'll tell you now, he is absolutely rabid about removing the baskets once they are sealed. How's business down there?
Porter: We're always busy — got a job coming up in Louisiana next week so we're really pressing the completion of 17. Listen, be sure and call me on this, OK?
Jordan: I'll get right on it, Randall. See you.
Porter: Bye.
While Riggers requested the help of Antenna Engineering to determine how to lift the antenna without removing the microwave baskets, Antenna Engineering responded by stating that their job was to design and build the antenna, and Riggers was responsible for assembly. Following his conversation with Porter, Jordan drafted a memorandum to Antenna Engineering's president, William Harris:
Interoffice Memo, November 18
Bill Riggers, Inc., says they will be unable to use the designed lifting ears for little other than getting the upper section off the truck. The present position causes the lifting cables to strike the microwave baskets when the antenna is rotated vertically for bolting on to the previous section. They are asking that we let them take the baskets off until the section is in place. What do you think?
Harris' response is captured in a November 19 conversation with Jordan:
Harris: Morning Harry. I got your memo when I got back from Tampa last night. I'm really surprised that you didn't just tell them "no way" when they called.
Jordan: Yeah, I knew you weren't going to be happy with their request, but they do have a problem, and I thought it would be best for you to decide.
Harris: Listen pal, you and I just dropped a quarter million bucks letting some clown mess with the baskets on our last job. And for what? A dead rat and some bird droppings. I mean, that kind of trash really messes up wave guides, and these guys just cannot be trusted to do anything but make a mess of them. Now they know that the contract they signed said they would not touch those baskets during construction, and that the warranty was void the minute they did. And if you think they have a quarter million to fix the problems they might cause, you have another think coming. No way. We would be right back in court just like last time, and you know it.
Jordan: Well, what about redesigning the whole rig, so that they could grab onto something which extends outside the baskets?
Harris: How about letting them do that? I'll tell you Harry, I'm really not into getting into their business. They have put up over a hundred of these towers, they say they are the experts in this field, so let them put the danged thing up. That's what they're paid to do. Believe you me, if this antenna doesn't have the field of coverage we say it should, they sure as heck aren't going to help us take it down and redesign it. By the same token I really don't think you and I should get into their field of expertise and start telling them how to get it in the air. Do you want to take on that legal responsibility? Man, if that thing ever fell down, and we had so much as suggested their method of lifting it, or redesigned any part of it — even if it had nothing to do with our design — you can be sure we would be right in the middle of a court battle. No way. They are the experts in construction, let them construct.
Jordan: You're probably right. How did the Florida trip go?...
Thus, Riggers devised their own solution, without consulting an engineer, although they did request a review of their plans by Antenna Engineering. This request by Riggers for review was refused by Antenna Engineering due to their potential liability in the event of a mishap if they had commented on the plans. On November 20, the following conversation took place between Riggers' president, Frank Catch and his vice-president, Randall Porter:
Porter: Frank, Harry over at Antenna Engineering called about the lifting ears on the upper antenna, and they're just not willing to get into it at all. They're worried that if we take off the baskets some kind of junk may get in and ruin the whole thing. They say that the warranty is void if we so much as unbolt one of the baskets. They're really not being very helpful about redesigning the lifting lug either.
Catch: I was afraid that would be the case. Not that I can really blame them. They want to sit in their office and let us take all the chances out here in the field. But I guess that's what they pay us for. Anyway, what now?
Porter: Well, I guess we could stick a channel across two of the two legs, and bolt it to the antenna with some U-bolts. A channel would stick out far enough to let the cables clear the baskets. The section weighs about a thousand pounds, and each U-bolt is rated at twelve hundred, so if we use a couple of them that should be OK.
Catch: I would hope. Have you got everything you need?
Porter: Pretty much, but if not it won't be hard to get locally.
Catch: OK. Is everyone packed up and ready for the next job in Louisiana?
Porter: Pretty much ...