Telebelt Belt Tracking Troubles? Wearing out your rollers?

A few questions recently came in from a customer concerning belt tracking and wearing out of rollers on their TBS 130. These issues and resolutions apply to all ”active feeder” model Telebelts - TB 80, TB 110, TB 130, TB 600, TBS 130 and TBS 600. Let’s go over their issues, and how to fix them.

Issue 1: On the feeder belt, there are 2 gangs of 3 roller sets,  and for some reason, we are having to change out 2 of the three sets every 2 weeks (the belt is wearing on the shafts that the rollers are on). We checked our other two belts and they are not having this issue.

Resolution: The feeder triple rollers are directional.  Each side roller is set at a slightly different angle. Make sure the end with the widest (lowest) offset faces the hinge.  In other words, the wide offsets face each other (see left).  If mounted in reverse, only the narrow set contacts the belt, and I can see the possibility of the belt being pulled down to the shaft, especially with this thinner type of belt. The photo looks like the belt flattens out, going left to right. If that is the case, the triple roller is in  backwards.

 

Issue 2: On the main belt, when you have the boom extended, the belt tracks with no problems (stays centered on the roller). When you retract the boom, upon getting to the last two sections, the belt tracks to one side of the roller and rides there until you extend it back  out. We checked the belt tension and its sitting at 1,200 psi.

Resolution: Don’t over-tension the belt. The manual calls for 1,500 – 1,800 psi on the feeder. I instruct operators to go to the low end; 1,500 psi. Training (belt alignment) of the pulleys, with the boom extended, is very difficult. In this position, the head pulley of one section is very close to the tail pulley of the next. A centered belt can mean the pulleys are working against each other, or adjustment is correct – There is no way of telling.

DO NOT ATTEMPT ADJUSTING A BELT, OR CLEANING OF ROLLERS AND PULLEYS, WHILE THE BELT IS MOVING. Shut the belt off and push the E-Stop to make the adjustments or do the cleaning.

Never train pulleys unless the belt tension is first confirmed. A loose belt wanders on the pulleys, and attempts to train it will not succeed. Again, I suggest 1,000 psi, which is the low end of the 1,000 – 1,200 specification for the main belt (the slightly reduced tension yields longer splice life). Train the pulleys with the boom retracted as far as possible. Telebelts use crowned (tapered) pulleys. They are self-training, since each half of the belt is trying to run off the end of the pulley. This allows us to go without side idlers, which we have no room for . When the belt gets loose, the side that contacts harder pills the belt to that side.  Again, tension the belt first. This will take care of training problems.

A properly tensions and trained belt will not go out of alignment. Training is usually only required if a pulley is replaced. Grout buildup on the pulleys can also cause alignment problems, so keep them clean.

Issue 3: After adjusting the tension in all of our belt, the belt tracks fine when you extend the boom past the first section (it stays centered on the rollers without any problems), but if we have the belt rolling without extending anything, the belt seems to run on the one side of the pulley. Also, when you bring the boom back in and reach the second section, it moves over.

Resolution: When extending and retracting with the belt stopped, the belt can wander on the pulleys, When running, it should stay centered. Extend arm 2 partially and check the adjustment of the heel of arm 2 and the head of arm 1. If they are ok, extend arm 2  enough to gain access to the heel pulleys of 3, 4, and 5 since they are still bundled together. Check them and then check the remaining head pulleys.

DO NOT attempt to train the 12″ main drive pulley with the large adjustment bolts. This is a straight pulley, not crowned. Adjustment is made on the 5″  roller at the heel of arm 1. If the belt is centered on it it will be centered on the drive pulley.

 

Belt(s) won’t run? I’ll bet it’s not the pump.

Belt(s) won’t run?  I’ll bet it’s not the pump.

 1 of 3 – Mechanical

This is the first of three articles about Telebelt belt-related problems.

From time to time, I get calls involving a belt that won’t run, or runs very slowly.  The call I like the least is, “My feeder (or main) belt quit running.  I replaced the pump, but it still won’t run.”

With over 800 Telebelts in the field, we are looking at more than 2,100 piston pumps.  We don’t hear of pump failures very often.  Even if we go back to the Super Swinger 105s, of the early 90s, many are still running original pumps.

So, again, I’ll bet it’s not the pump.

Rule # 1 – Check to see if it will run with manual control.  If it will, the problem is probably electrical or in the radio.  If not, it’s mechanical or hydraulic.

Things that stop belts: 

  • Mechanical problems
  • Electrical problems
  • Hydraulic problems
  • Truck or engine failure.  This is beyond the scope of this series.

Let’s deal with mechanical problems, since they are the easiest to spot.

Are the PTO shafts turning? 

  • Actually look at them.  I once spent an hour on the phone with an operator who has just moved and set back up and his belts wouldn’t work.  I finally got him to look under the rig, where he found a pump drive shaft lying on the ground.
  • Is the PTO engaged?  Snow and ice can jam a PTO linkage.  Pins can fall out.  Air lines can leak.  PTO shaft gears can strip.

Do the hoses jerk, like there is pressure?  Does the belt move a little?  Put a pressure gauge on the test port.  If there is 280 bar, and nothing is moving, look for:

  • A seized 5” pulley
  • A seized feeder drive pulley
  • Over-tensioned scraper – Yes, that can stall a belt.  It can also stall a belt that is heavily loaded.
  • Rocks packed at tail pulley (feeder) or drive pulley (main).
  • Rocks packed at the heel of the arm back from the tip section (arm 3 on a TB-105 or 110, arm 4 on a TB-130).  There is supposed to be a v-scraper there to guard the close clearance between the heel pulley and the steel end frame.
  • Feeder motor hoses kinked.  Active (hydraulic lift) feeder machines (TB130, 80 & 110) can do this if the feeder is slewed more than one time around.  On 105’s, feeder lines can get pinched in the transfer.  Also check 105 feeder line quick connects to make sure they have not backed out.
  • Is more torque required?  This is as much a hydraulic issue as mechanical.  Most Telebelt feeders operate just fine with 130cc motors.  Belts that are heavily loaded, paving for example, might require 160cc motor.

Do you think oil is flowing but there is not much pressure? 

  • Feeder – check for stripped drive pulley collet or broken motor shaft.
  • The Main has 2 motors that plug into splined adapters welded into the ends of the pulley shaft.  If the welds on an adaptor break, that motor will be free to spin.  You will hear oil going through the motor.  Operators have finished pours by capping the lines to the “bad” side motor, thus forcing the other motor to drive the pulley.
  • Check main motors for broken shafts.

Are the belts tight enough? 

  • Feeder belt pulleys are more likely to slip, especially if they are the old-style steel-lagged pulleys.  Maintain feeder tension at 1,500 to 1,800 PSI.
  • Once in a while, you will find a ready-mix driver that will wash what he spills.  If he gets the back side of a loose feeder belt wet, the drive pulley might slip. 
  • Main conveyor pulleys are less likely to slip, even if the belts are real loose.  Worn or missing drive pulley rubber lagging leaves a steel surface that will slip.  Maintain main belt tension at 1,000 to 1,200 PSI.
  • Keep lagging grooves, on main and feeder drives, free of grout buildup.

 

 

Q&A Session- Question 1: Why are there 16″ scraper blades on an 18″ belt?

ANSWER:

Telebelts are equipped with “crowned” pulleys. Slightly tapered pulleys allow for easier adjustment when training or tracking of the belt. This is especially true on faster moving belts such as those used to place concrete. This feature is even more important for the purposes of belt training when the conveyor is telescopic, multi-section as is the Telebelt. Trust me, flat pulleys were tried in the very early design and training the belt throughout the telescope range was impossible! Even when only half the pulleys were flat it was still an impossible task to track the belt.

When a tensioned belt wraps around a tapered pulley it leaves that pulley with its edges opposite the pulley taper. That is to say the belt comes off the pulley in a crescent shape, with edges of the belt somewhat lower than the center (see diagram 1, left). For this reason, using a scraper as wide as the belt wears out the edges of the belt pre-maturely.

Getting proper surface tension between the blade and the belt also becomes more difficult because the force being used to pull the scraper against the belt has to deflect the edge of the belt that much more before adding any appreciable force in the middle or center (once again see diagram 1). This problem becomes worse the further behind the pulley the scraper is mounted. This is because you now have to deflect the tensioned belt in both directions, width and length, before significantly effecting the tension of the blade against the surface of the belt (see diagram 2, below, – upper right-hand corner).

You may have read in some of our past literature words like belt “flutter” and scraper “bounce”. These are also symptoms of the scraper being too far behind the pulley. A mistimed or an unlucky scraper bounce can catch a rock and render the scraper useless, or worse wreck a belt! A “fluttering” belt will not run clean. In all cases, an 18” blade on an 18” belt makes every condition or symptom worse!

When you hear customers saying things like; “I just can’t get that thing to run clean no matter how much I tension the scraper!” or “My scraper springs are stretching and I have run out of adjustment on the scraper chains or T-handles!”, the main two causes are scraper blades that are too wide and scrapers that are too far behind the pulley.

Besides these problems, you have to ask why do you want to clean the belt out that wide anyway? The tunnels, even on a machine set up for high volume placing, will only expose a max of 12” or 14” of belt, and most are set up with only about 9” to 11” of belt exposed. The material leaves these transfer skirts on a “V” shaped belt and the material profile on the belt doesn’t reach to those outside edges of the belt. If the concrete is so liquid that the material profile within that the normal “V” shape or in the discharge transition area reaches the edges of the belt, more than likely the belt is running too slow or there is too much belt exposed between the skirts or both. The bottom-line is that on a machine that is properly set up and run, there is nothing out on the last inch of belt on both sides to clean!

The only historical leg to stand on in defense of same width blades and belts is that the earliest Telebelt model I mentioned earlier ran 16” blades with a 16” belt. There are couple reasons for this. Firstly, that machine ran 4” pulleys and they just were not as aggressively tapered, lessening the severity of the systems described above. Second, and the most reality based reason, is that the manufacture just never got around to making a 14” scraper blade (assigning a whole new part number, etc). Every other concrete conveyor built used the ‘2” narrower than belt width scraper blade’, up to and past 48” belts. So, the only machine that ever used same width scrapers did so because the manufacture just never got around to making a 14” blade with some of its components allowing it to get away with that oversight. That doesn’t make it correct!