As I understand the nature of your description, the belt predominantly off-tracks when tension is applied between two joints or one section of the belt.

1. what is the belt construction?

2. describe the width and other belt features

3. describe the product loading

4. mark the splice ends and note what happens to the shift with respect to the splice ends - i.e. how much of the section of belt is on the incline whens the shift occurs and how much of the belt disappears over the head end when the belt shifts back?

First observation note: to have just one section off-track when tension is applied, tends to indicate the construction has a fault. When tension is applied, the center of tension shifts to one side, like the weave or tensile member alignment configures the internal relationship of tensile members to pull off-center. Does this happen as the misaligned section of the splice approaches the head pulley? Where is the drive station located? ■

So I am clear on what I am reading. The belt runs to one side after the first splice, then to the other side after the second splice? IF this is the case, it sounds to me that the belt was made as a full width slab and slit to two separate rolls at teh factory and shipped without having the "Factory edges" matched. This is not a splice issue, but a missed detail at the factory that would require that one of the rolls be cut out, rewound, reinstalled & re-spliced. Alot of work. ■

I believe we now understand the "bow" effect. The belt appears to have a major construction defect. Under lower tension, the belt responds to the construction defect with a sideways motion as tension is applied. When the tension terminates across a fixed object, like the drive pulley, the application of a fixed point tends to arrest the defect behavior. Nonetheless, the belt appears to be defective. It may, in time, realign its center to some extent. What change in tensile capacity will result, and so on?

How to determine the extent of the defect? Request the manufacturer to explain the behavior. Maybe, a sample can be taken for examination.

Some manufacturers lie, some avoid a response, some blame others, and some are truthful and try to find a solution to fit the client's needs. Hopefully, you find the later, and try to assist them. Honest manufacturers should be cultivated for willingness to support the client's needs, they are hard to find.

There can be many reasons for the transverse motion behavior from: fabric curing, fabric construction defects, misalignment of the fabric in the plant vulcanizing stage, press tension anomalies, thickness variation of the raw goods, et al. ■

On the factory slitting and bowing: effect would be seen on all such slit and bowed belt. Slitting can produce a bow due to a multitude of press effects. When you slit and then see a bow, you usually will also see the bow in the opposite slit belt i.e. each section of slit and bowed belt will have a twin. ■

Originally Posted by WilsonBW

So I am clear on what I am reading. The belt runs to one side after the first splice, then to the other side after the second splice? IF this is the case, it sounds to me that the belt was made as a full width slab and slit to two separate rolls at teh factory and shipped without having the "Factory edges" matched. This is not a splice issue, but a missed detail at the factory that would require that one of the rolls be cut out, rewound, reinstalled & re-spliced. Alot of work.

I heard of this situation once before, in Germany of all places, and had forgotten it until now. Thanks for reminding me. Belting identification embossing is done by the manufacturer: so if the installation has the markings reading in the same direction then the belt supplier is liable for the rectification costs: according to the specification which I am just preparing. Thank you very much. ■

As listed above, mowst reputable manufacturers brand their belting with with the manufacturers name, belt stecification &/or roll number. The roll number is located on the belt edges (Fenner Dunlop).

I would suggest, in order to prevent issues where factory edges are not matched, request that the belt is marked at the factory by spray paint so it is very clear once it arrives on site. Again, most reputable manufacturers do this. ■

We may not have touched on the exact reason for the bad behavior. Without witnessing the action, we should not guess wrong and feel sorry later.

Common sense tells you something is not right. A number of participants have offered observations from experience on some ills.

You cannot ask a question of certainty, when safety can be seen to be uncertain.

Someone must do a little common sense engineering to set the operating conditions with safety in mind. The system should approach (stretch) to a more normal condition after loading for a few days. If not, then consider it permanently flawed.

Some thoughts:

1. What belt safety factor are you operating in?

2. On point 1: Motor power will give you the best guess on peak tension

3. How badly misaligned is the belt when it crosses the head pulley?

4. You say the offset can be about 31% of the belt width as tension is applied and belt moves up the hill. How far does it maintain this offset? Where does the offset start, when does it become maximum, and return to what offset across the head pulley? By applying the estimated axial forces and noting the offset and its location, you or a competent engineer should be able to compute the lateral force at work

5. Apply some side guide rolls and try forcing the belt toward the center. Run the belt for awhile and see if the belt relaxes back toward the center with a day or two running and after a low level capacity see if it moves of the side guide rolls.

6. Apply 30% load and see if this brings the belt toward the center on the incline, and if so apply 60% load and see if it returns further toward the center. These recommendations only apply if you have greater than 10:1 safety factor from points 1 & 2. If the belt does not track near its center after running for a week with partial load, then you should think about safety before proceeding to run at design. Since the belt has a flaw, and the splice will still likely be the weak link, set an inspection program to inspect the splice on a weekly basis for the first six months.

7. DO NOT buy from this belt supplier again.

Use common sense. ■

Originally Posted by nordell

DO NOT buy from this belt supplier again.

Even if he is cheap ......... ■

Due diligence should be practiced, when the risk to benefit ratio are distorted in direction of costly risk taking.

Unfortunately, too many decision makers error on price over performance. We are continuously penalized by poor thinking judgment when good designs are discarded in favor on a false bottom line economic decision. Then you sit back, watch the prediction come true, and still see the scenario repeat again and again.

For this thread, the only sage advice is: evaluate the present based on good and acceptable performance of the past. Let the supplier risk their reputation on someone else, if they do not have a track record or investment method to show due diligence.

How does a good supply record become established? Measure the suppliers who stand by the product, when the product does not perform, or does perform with knowledge of a background on why, based on significant investment to uncover hidden pitfalls. No one has all the answers, but, the art of diligence is to know what you do not know, and are committed to discovery that protects the client.

All too often, clients seek low price, or better lowest price, and wish to remain ignorant on what it takes to be diligent and what it takes to warrant performance.

Diligence takes work, time, and money. That is why the sign says "Buyer Beware". ■

Assuming an installation is properly aligned, its the splice or a "banana belt"

The trouble is that all to often the erector installs the idlers at the end of their upstream end of the slots in the frames. They then start the conveyor and "train the belt" by bashing the hell out of the frames with a 4 pound hammer.

This is not good as you then don't know if yoy have a bad splice a banana belt or wonky idlers.

Anyway, I had a conveyor that was nicely aligned, but did what yours is doing.

The manufacturer had to replace one roll of belting (banana) and then all was OK.

(Deja vu)

Cheers

LSL Tekpro ■

Graham,

I now believe we are all speaking with one tongue. ■