SERVICE TIP

Troubleshooting Bell Problems

One of the greatest concerns of a packerhead pipe producer is the quality of the bells. Most of the problems encountered here can be avoided by following proper bell-making techniques.  

The following list of problems and possible causes, while not complete, should give you a good starting point toward solving your bell area concerns. Beneath each problem heading are listed possible causes, and items in parentheses indicate suggestions to try, or comments.

What to Check First When Bell Problems Develop:

1. Make sure that the bell down unit is lifting the curing pallet to the proper height.
2. Check that the top of the longbottom is 1/4" (6 mm) above the top of the pallet when the bell down unit is raised.
3. Check the timer for proper vibrating and turning time.
4. Make certain that the proper amount of water is sprayed onto the concrete during the bell cycle, if applicable.
5. Check that the pallets have been properly cleaned and oiled.
6. Check to see that the shock absorber pads have a minimum of 1/8" (3 mm) clearance (applies only to older machines).

Problem Cage Lift

Causes:

1. Too much concrete on the rollerhead while making bell (over-packing).

Problem Cracks in Top of Bell

Causes:

1. Bell down unit is lifting pallet too high. 
2. Pallet is not properly seated in mold for turning and vibration.
3. Improper stripping of mold (mold not level).
4. Pipe sticking to mold (material too wet).

Problem Exposed Wire or Wire Shadow in Bells

Causes:

1. Cages are going off-center (try using cage stirrups).
2. Cages are out-of-round.
3. Cage diameter is incorrect.
4. Bells were not properly expanded (bells should be expanded to center on pallet flange).

Problem Rocky Exterior Bells

Causes:

1. Bell material too dry.
2. Not enough bell water added.
3. Not enough material in bell (add concrete until cage stops turning).
4. Over or under vibration during bell cycle.
5. Vibrator weights incorrectly set.
6. Adjustment to shock absorber pads incorrect.
7. Bell down unit not lifting pallet.
8. The top of the longbottom should be 1/4" (6 mm) above the top of the pallet when the bell down unit is raised.
9. Check mix design (may have too much rock).
10. Check bell reinforcing for size and location. 

Problem Rough Interior Bells

Causes:

1. Bell material too dry.
2. Not enough bell water added.
3. Not enough material in bell (add concrete until cage stops turning).
4. Over or under vibration during bell cycle.
5. Vibrator weights incorrectly set.
6. Adjustment to shock absorber pads incorrect.
7. Bell down unit not lifting pallet.
8. The top of the longbottom should be 1/4" (6 mm) above the top of the pallet when the bell down unit is raised.
9. Dirty pallets.
10. No release agent being used.
11. Release agent not properly applied.
12. Wrong type of release agent used.
13. Check mix design (may have too much rock).

Problem Picking Off of the Bells on the Transition

Causes:

1. Concrete is too wet.
2. Cage lift.
3. Over or under vibration during bell cycle.
4. Vibrator weights incorrectly set.
5. Adjustment to shock absorber pads incorrect.
6. Bell down unit not lifting pallet.
7. The top of the longbottom should be 1/4" (6 mm) above the top of the pallet when the bell down unit is raised.
8. (Try using an admix to reduce concrete bond to mold.)

Problem Swedging

Causes:

1. Concrete is too wet.
2. Too much concrete on the rollerhead during the first pass while making the bell (over-packing).
3. Too much concrete on the rollerhead during the second pass.
4. Cage lift (pipe settles after stripping).

If you have additional questions, or feel you require service assistance, contact Besser International Pipe Machinery by phone (800) 621-7768, fax (712) 277-1222, or via e-mail at sales@besser.com.

Posted 30 October 2000