In just a few minutes, I have to go help align a "long spacer coupling" on a cooling tower (did I say that right, Sam?) which I've not done before. Intuitively, I'm thinking the easiest way to do this is to just put the laser receiver on the motor shaft, and then mount the transducer an equal distance from the motor end coupling, but on the spacer shaft. Assuming the spacer shaft is straight, if I align the motor shaft to the spacer shaft, it's going to be pretty close, right? Then I could move the transducer to the gearbox shaft and check it. This would seem to be easier than doing a 'long range' alignment (and quicker than using dial indicators).

Does anyone else do it this way, or have any ideas?

Indicators by far are easier and faster. What type couplings do they employ: Thomas?

Check your normal E-mail.

Rusty,
If you have the visable beam just mount the laser on the shaft of the machine that has been replaced, tape a piece of cardboard or paper on the front of the reciever on the other machine. Sweep from the 3 o'clock position to the 9:00 position. Note the location at both positions, then move the machine with the laser so the difference is split. Do the same at 12:00 and 6:00, if you can't get the 6:00 and have got the horizontal ok just shim the laser machine so the dot doesn't move much. This should let the beam stay in the target so you can do a partial sweep and proceed with the regular alignment. We use a dual beam laser and just aligned a cooling tower last week that had both motor and gearbox replaced in 2 1/2 hours. Our laser faces has a grid to center the beam and after we did this rough alignment we had minimal corrections to finish up.

Generally with dial indicators you can one-shot it everytime. There's an outfit that uses my procedures (the procedure really doesn't belong to me; many were doing it this way before I came along) for installing cooling towers around the world. When they get a client that wants laser, they align using dial indicators then get a final with the laser as they said it is far easier and faster this way.

So many cooling towers have the torque tube going through a hole in the shroud anyway.

I hope I never do another one of these again.... the alignment wasn't too bad, but working off a 22" wide plank (11" at the motor end), with the wind whipping like it does that high up, is not for this fella!

I did it like I said above, and it went fine. The hardest part was moving the gearbox (with no jacking bolts of any kind). Wouldn't have been any problem if I'd been standing on terra firma.....

Not for the faint of heart.... Sam, can you briefly outline your technique? I'd like to give it a try next time.

Thanks for the replies.

Congratulations Rusty!

I assume you ducked your head as the fan blade came by. I've done a few of these jobs, and it is a tough work environment. I use a laser and measure across each coupling. The gearbox coupling results usually dictates whether the gearbox needs to be moved. The final trim moves can usually be done at the motor where it is easier to work.

Walt

I saw a guy demo the full-body harness at a safety meeting once, but I still wonder if it would work if I ever fell. I did remember to bring the lanyards over my shoulder before tying off. When I get my hoist wired up in the shop, I think I'll hoist myself up and see how comfortable it is..... don't think I want to actually try a "drop test" (would probably ruin the lanyards)

Rusty,
I agree that the indicator method is far easier. I just use face-face method and start at the gearbox end. Top to bottom first to get the shims right. A heavy hammer will nudge the gearbox for yaw. I did and 8 cell tower once and built a simple jig that allowed me to use a porta-power jack to move the gearbox/fan (28 ft) around. That tower had no walkways at all (money issue I assume) so multiple scafolding boards with lots of rope were used. Torquing the 2" bolts to 700 ft lbs was interesting. By the way, if you have recurring alignment problems at the gearbox, try putting tappered pins at an angle throught the gearbox foot and mechanical support so the pins would have to shear for the gearbox to move (drill and taper after alignment of course) when startup torque is trying to rotate the gearbox.

Good Vger,

The GB should be a fixed unit and only motor movement is required hopefully.

You can acquire data Face (Rim & Face) method or Rim method. The rim value is twice actual value while the face value is actual. Always use actual values for calculations.

Some cooling tower couplings will have a hole plugged with a set screw (couple); remove them and insert a bushing that accomodates the dial indicator and gather face data from each coupling (it's really easy). Generally 100% of the time it's a one-shot alignment as the tolerance is ~1.5 minutes on some and 1 minute on most. So if there is not a bold-bound situation expect one-shot alignment.

Rusty,
Concerning Safety harnesses and will they work. YES. I was an ironworker for 15 yrs, yes one of those "nuts" that climbed all over a steel structure like a squirrel. I had the "pleasure?" of taking a fall twice. The first one was off a scaffold 32 ft in the air. Unfortunately I was not tied off, matter of fact not even wearing a harness. The only thing that probably saved my life or kept me from being paralyzed after landing on my head and neck in hard clay was the fact that I hit the scaffold 3 times on the way down. Blacked both my eyes, sprained my neck and hurt my pride, but I did get up and walk away after I came to. It just wasn't my time. The second fall was connecting iron on an overhead crane housing at a carbon bake plant 75 ft in the air. I tied off (cooned) the iron to unhook the headache ball from the rigging on a beam we had just hung, stood up, forgot that I was tied off and tried to walk to my next destination (ooops). My laynard pulled me off the iron, nothing but 75 ft of air between me and the concrete. I dangled there for about 3 mins. (seemed like forever) with my butt puckered shut so hard you couldn't have squeezed a bb in it. Thankfully I was tied off because I don't think I'd have walked away from that one. All I ended up with were bruised ribs and ego. The bruised ribs were from the jerk when the lanyard grabbed (didn't have "shock absorbers" back then). Fortunately I have found that I no longer have the nerve for that type of work anymore.

For those having to do this: use a bungie cord on the lanyard. It will keep some tension on a short rope and as soon as you go past the premission ground the bungie will give a slight tug and you know something pulling on you. In addition, it keeps the lanyard out of your way.