HOLLOW SHAFT AND BLOWER WHEEL REPAIR

[mrhvacmechanic]

I have done alot of bearing jobs over the years. I will be repairing a TRANE air handling unit with a hollow shaft.

I have replaced bearings and drives on a shaft like this before but never a blower wheel. Parts being shipped over weekend to do repair.

My question: Since its a hollow shaft, is there a torque value for the tightining of the blower wheel bands that secure the wheel to the shaft. I know this sounds silly but if their tightened to much will the shaft crush?

Any info or tecnique would be appreciated.:couchhide:

[Dallas Duster]

If you can crush a hollow shaft with the fan bands you are a bad MOFO.

[StayinCool]

After all is replaced, be sure to have it balanced!! No more than 3 Mils displacement at line frequency. And yea, if you can crush that shaft you are a bad MOFO.

[ovruss]

You are correct in thinking that there is a proper torqe for those bands what it is I couldnt tell you . I usually go by the rule tight is tight and too tight is broken and do not have any fear of distorting the hollow shaft its not going to happen.GOOD LUCK!!

[Octopus]

There is a torque value I forget what it is like the others said, heres another bit of advise replace both of the bearings don't be lazy and before you put those set screws on the shaft drill a countersink into the shaft so they don't slip and use locktight. Use trane bearings some of those cheap Chinese bearings use crappy metal and have bad tolerances. and twist lock em on if they are twist locks. If your only replacing the bearing make sure the surface of the shaft is not worn.

[apycf29]

There is a torque value I forget what it is like the others said, heres another bit of advise replace both of the bearings don't be lazy and before you put those set screws on the shaft drill a countersink into the shaft so they don't slip and use locktight. Use trane bearings some of those cheap Chinese bearings use crappy metal and have bad tolerances. and twist lock em on if they are twist locks. If your only replacing the bearing make sure the surface of the shaft is not worn.

Totally agree with this quote and the other one about having the wheel balanced, its going to blow the quote out of the water but its better than blowing out bearings in a week or month. I have replaced many blower wheels and always had them balanced, you would be surprised how bad they are.

[mrhvacmechanic]

Thank you all.
Everything is comming from TRANE. Air handler had no name plate, removed along time ago. I took all measurement of all parts. Some how they came up with all the replacements. I start the job Monday.

I'll have office put a call to tech service on the torque values. It's good to know the shaft is that strong. I just wasn't shure about damaging it. I won't worry about it now.

Chris, you say make a counter sink for no slipage? Does this normally happen on the bearings? I belive the bearing are oval in shape.

[jayguy]

2 clamp units are different than 3 clamp units. there is a very specific procedure. check your email...have fun.

[mrhvacmechanic]

Jay,
Thank you much!!
The info you sent will be a great help. Appreciate it.
Mr HVAC:angel:

[ovruss]

As others have mentioned it is always a good practice to have a new blower wheel balanced.It is more critical on larger diameter and multiple blower systems.The reasoning for a hollow shaft is to prevent a whipping affect on longer shafts which will cause premature bearing failure if wheels are not balanced.If it wasn't allowed for in your price just qualify it after start up its a fraction of total job. An educated customer will appeciate the many trouble free years operation and your company will appeciate it made warranty!!As others said always try to stay with OEM bearings !!Because these bearings have an actual air handler rating and are different than a standard industrial type bearing.GOOD LUCK!!

[WhoIsThat?]

Lok-Tite makes up for many sins.

If it's a setscrew there are tables for max. torque values.

If it's bands the uniform circumferential force is directed toward the center of the hollow shaft and it should not be possible to crush the shaft.

[mrhvacmechanic]

Thank you all!:ghug:

[BillLohr]

I've done a few hollow shafts don't remember the torque, but those I did were Trane and the shaft is very slightly tappered. The wheel goes on only one end and only go to where it should sit no further.

[mrhvacmechanic]

Started repair today but all parts didn't arrive! What else is new?LOL!

Bearings have no set screws, compression type with torx screws. I did put some locktite on threads.

Clamp torque on this fan is 25 ft pounds. New housing didn't have fan cut off plate. being overnighted. I reccommended to my office a balancing as all have told me.

So I have wheel, housing, shaft, and bearings installed. I'm waiting on a new 10HP motor and drives. The existing motor bearings were screetching. The MER entrance is from a lirbrary in a college. I try to figure out how to post a picture.

[mrhvacmechanic]

A few photos:

[tipsrfine]

We replaced a hollow shaft with a solid shaft about 4 years ago. The new shaft was so heavy. The senior tech said he's done it before, but I always wondered what negative results would happen by doing it. Memory says it was 5'x1". It's still working.

[hvacker]

Had a hollow shaft fail some years ago. Trane was going to take a long time to diliver. There was a GE maintenance facility next door. They made the shaft and balanced the install for 1/3 what Trane wanted. They were good.
I always like to find a work around with manufactures.

[mrhvacmechanic]

Finished job yesterday. However fan moving litte amount of air. Next week we are going to pull steam coil from rear of unit to check chill water coil. Unit moves plenty of air when we remove access panel to fan section.

When panel is on, fan sucks in all panels after coil? CW ciol is about 14" thick. It looks like hw coil sits on a track thats bolted to rear of air handler. Hopefully old valves will hold and unions open easily.

[marvin]

might want to check for tripped dampers before pulling coils.

[mrhvacmechanic]

Marvin,
All fire dampers are open. Unit is very old. Steam coil never pulled. If you saw the filters we found laying around the MER it would make your stomach sick. Fans been off two years!

[mrhvacmechanic]

Here's an update and a couple of pictures.

I returned to job after conviencing office steam coil needed to be removed to check chill water coil. Here's what we found!

[Jettinvr6sc]

thats one fine looking coil:eek2:

[Freezeking2000]

I am sure that will convince the office it needed to be cleaned.

[targetman]

Pulling those coils can be a real pain in the ass.

[mrhvacmechanic]

Well, job is complete coil cleaned an back on line. Plenty of air flow!