CDI has built the necessary tools to quantify the problem and have means to correct its effect. ■

Designer,

I read the posted thread from eng-tips. His query is clear. However, eng-tips do not allow contact with participants.

I stated we know what causes the pipe conveyor corkscrewing and how to stop it. I have given the concept in earlier postings.

We have built codes to evaluate the corkscrew forces that lead to a number of solutions. We do not practice the Man Takraf method of keeping the seam up. There is a better and more positive method.

The method will not be disclosed in a public forum. ■

Dear Sirs

Rotation, corkscrewing in a pipe conveyor is the same as belt mistracking in a convetional conveyor sometimes it is within controlled limits and sometimes it needs attention to resolve.

At commissioning time we have experienced this but it can be solved, there can be several practical reasons.

A pipe belt is more unstable when empty but can run without problem (empty) with the seam at the bottom, this is where it wants to be due to gravity, with material it is usually stable, either way adjustments can be made.

I have experience long pipe conveyors where the seam is at the top all the time and shorter conveyors where it twists 180 deg (to the bottom) the most important is not to twist more than 180 deg.

Paul Holt

AMCO Construction Ltd (Dosco Overseas Eng Ltd. ■

Dear Paul,

I beg to differ.

Belt corkscrewing in a pipe conveyor is NOT the same, and does not occur for the same reason, as the maltracking of a conventional conveyor and takes different action to correct it.

We have made systematic analysis of field measured the collapsing pipe top-to-bottom, side-to-side, with rotating belt seam clockwise and counter-clockwise along one common belt tail to head during a fully loaded operation.

Measurements include the separation of pipe wall contact with the idlers depending on the direction of curvature and magnitude of curvature with fabric and steel cord construction.

In addition to the walls collapsing the inner section of the pipe separates from the outer section leaving an opening for product to be exposed to the ambient conditions, potential for wind errosion, and fugitive dust escaping.

The condition is not that uncommon, just not well published.

In order to see many of these conditions, the pipe belt design needs to be configured to impose the physics. Small repeated horizontal and vertical curves will produce these events. Radii in the neighborhood of 300 time the pipe crossection can produce the conditions at low, mid and high tension zones. ■

"We have made systematic analysis of field measured the collapsing pipe top-to-bottom...." should have read:

"We have made systematic analysis of field measurements of the collapsing pipe top-to-bottom..." ■

Dear Larry

Full corksrewing is different to mistracking but can be caused by the same elements but more agressively.

I don't believe it is possible to calculate this as there are many factors.

I have been involved in the design of 35 pipe conveyor and only once had serious corkscrew, 8 times clockwise and 8 times anticlockwise. This was due to a large foreign body going down the tube and disrupting a long of mounting brackets and it was possible to put right and re track.

With the correct belt and perameters complex curves can be accomodated and tracked so that the joint is correct.

Please see attached photograph thisis 800m long and as you see complex and we have tracked it with the joint on top all the way.

It is attention to the detail.

Paul Holt

Attachments

imgp2306 (JPG)

■

GAME, SET & MATCH! ■

Congratulations Paul.

These are facts.

Thanks.

Darrell ■