Dear Andrew,

The steel cord will expand as other steel members. The only question is whether to include the helical spin path to the length.

In english units:

expansion = 0.0000065 inches/inch/ one degree F rise in temp. x length (units of choice).

The helix path is not normally considered. There are a number of issues involved which I will not elaborate on.

You are now doing design work? The 20C change is small for the higher elevations of Chile.

Beware of fixed take-up analysis. This more tricky than the gravity TUP. You also need to consider the sag between idlers verses the tension profile, if the conveyor has any length of consequence.

The engineers, on a number of Chile's overlands, have not made the necessary comprehensive analysis, by my opinion, and the resulting conveyors' performance. Can have dramatic effect on the belt's safety factor and component stresses. ■

Andrew,

Welding the take-up carriage is a very unprofessional idea. It sounds like the shaft weldment, fatal flaw that Chuquicamata ‘s maintenance staff did that cost them approximately $50 million production losses and corrected repair when the shaft failed at the weldment. The nines’ are putting their operating crew at risk of life and limb.

The temperature variation +/- 20C will cause a -/+ 76 kN change in belt tension.. If the belt is rated St-2900 N/mm with a 1600 mm belt, and you have an expectant belt Safety Factor (SF) = 3.8:1, then the SF may drop to 3.58:1 or about 6%.

The temperatures can easily vary by more than 20 C in an 24 hour day or between setting it (welding?) and the alternative extreme. I do not believe you will weld and unweld with swings in temperature that exceed 20C. You can get more than 40C as we have seen on El Abra and Collahuasi.

The calculation is not straight forward in the real sense. I used BELTSTAT to vary the temperature +/- 20C about a mean of 20C. I changed the apparent fixed take-up position to accommodate the thermal elongation. Belt sag is compensated for.

I can say the belt construction has a higher than normal cord diameter for the given ST rating. This is a strange construction from the manufacturer . This belt will cost more to build. Also the 77 cables represent a lack of knowledge on modern day splice designs.

Wish you success. ■

Dear Nordell,

I am working now in the cement factory & in this factory, they have Steel cord belt conveyor 900m long, Phoenix, ST1000, belt with 1200mm, 96 cord 3.5mm. Conveyor is straight for 700m, take up angle 15degree last 200m. Gravity take-up (weight around 4ton). FAM design.

This conveyor has 4 joints and all of them have problem, 3 have been teared, other is going soon,

My question is the joints are out because lack of experience when the do vulcanized or may be other problem? Note that the belt was design for 600t/h and it's only running about 200t/h.

Sorry for my English and thanks a lot if you can give me the guide soon,

PS, you can see in the att. for belt cal. from supplier,

Hungnq,

Attachments

steel cord conveyor (PDF)

■

As I often say, engineers should not work for free. It is impolite to ask for more than advice. We are free to say or not say.

When you respect this, we understand you are willing to be fair.

Having made these comments, I will share some small details of your design.

1. Your general comments does not agree with the German analysis.

2. Our analysis of the German analysis is in reasonable agreement except.

a) gravity takeup force - where is takeup? have place @ head

b) acceleration rate of 150% could produce drive slip

c) acceleration peak tension is higher 216 kN vs 211 kN

d) running safety factor 7.77:1

e) starting safety factor 5.03:1

There may be a little problem with the start. If the drive slips, then you can have a large momentary impact force on splices.

I recommend you look to the design/geometry arrangement that may be placing added edge cable stress on outer steel cords at the trough transitions and at the convex vertical curves.

Good Luck ■

A second thought:

The belt design is in the acceptable range. The motor and belt ratings are OK. Therefore, I would look to such things as bad local geometry or bad practice in splicing.

Bad splicing practice, with high humidity, body sweat, cable contamination on handling or allowing to fall into dust or mud, bad splice kits that have been warmed by sun for a day or more all can lead to bad result. There are many other details that also can result in bad form. Make a video of the splice construction and submit to experts then you will get better result. Usually, some ambient temp and humidity data is also good.

You can have bad vulcanizer, equipment out of calibration, and so on. The method of placing cables can be flawed. The list is too long to elaborate on. ■

Dear Nordell,

Thanks for your 2nd advise, I always think of bad practice in splicing as you said.

This was made by local supplier in Vietnam, now we are in contact with specialist team in Malaysia, they will come with they know-how, I hope will better.

I am a new member of this forum, so, I don't know most about it. Next time, I will be more careful before asking something,

Sorry & Thanks again,

Hungnq, ■

vulcanizer ■

vulcanizer ■