Dear Sir

I have extensive experience but to answer all your points would require a book!! ■

Have you asked the manufacturers why the belt corksrews? I doubt most can provide the answer. Be pleasantly supprised if one gives you the correct answer.

Yes, the reason you do not get support from the constructors is because they do not know.

When one claims, in public, then the competition all answer in unison that they also know. So, why should those that know divulge to those that do not, but compete for the same business?

We know, because we took the time and cost to investigate and confirm the physics. We filed patents on the new design, made the necessary tests on the full scale belt construction and on a well known competitor belt that do not possess the necessary construction. We have installed the new design and can demonstrate the new construction verses a competitor belt on the same property.

I have stated in the forum hints on the corkscrew that should be sufficient, to any good engineer, to identify the cause.

I also note the sarcasm of some forum members regarding the claim. Their loss.

All clients are welcome. We can demonstrate how and where so they may enjoy the benefits of controlled rotation whether empty, or full, or for all loading cases in between. No more spillage. Don't need to make the belt construction ultra-stiff and a power hog. As stated on another thread, the return belt seam will also run up. Therefore, the return strand will not leak material as is the normal case. ■

I also note with some curiosity that you do not reference the leading supplier of pipe conveyors - Bridgestone. Many of Krupp and Bateman installations are of the Bridgestone design.

Others include all Japanese you ignore: Yokohama, Bando, ...

Zigong, CHEC, CCCC and other Chinese designers and turnkey suppliers are well known. Zigong advertised on this forum with an 8 km overland pipe. CHEC and CCCC have longer ones in the pipe line.

Sandvik does. Metso? FLS, which were until Koch was purchased, were done by Phil Staples under the CKIT name. ■

On large engineering projects any supplier who claims that information is an unsubstantiated trade secret will get binned straight off. Either the information required is in the public domain and ready for scrutiny or the buyer is considering tremendous risk. If a supplier cannot demonstrate compliance with existing Codes, Standards or recognised published work then he is asking the Owner to buy a cat in a bag'.

As Larry Nordell says such oversight is one of the aspects of our business that keeps these forums busy.

I've lost count of the number of times I heard it said " It works well on wheat so I can't see any problem with it handling cement clinker/sponge iron/quartzite."

As our young Silesian colleague requests: "Publish and be dammed" (The Duke of Wellington circa 1840) ■

Originally Posted by louispanjang

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I've lost count of the number of times I heard it said " It works well on wheat so I can't see any problem with it handling cement clinker/sponge iron/quartzite."

Actually the quote from a short lived Sales Director regarding a new lightweight machine specifically designed for grain was "We should try it with other materials, like cement clinker"

As I said, short lived, yet another ship that passed in the night !

But if we make our living in this business we do amass knowledge and the understanding of knowledge. But we need to keep some to ourselves to give us an 'edge' when competing for orders otherwise we'll be gone and our understanding of the knowledge gone with us. ■

Louis,

We wonder are there any techniques or tricks-of-the-trade you wish to hold close?

We will doubt your answer if you say none.

All who contribute to this forum share many details, but certainly not all. Especially, as Designer says, the tricks that cost a lot to develop and give the edge in competition.

We employ 15 people whos daily task is to engineer on the cutting edge. Without the edge, they would not have a job in this business. It takes about 3 years to adequately train an employee. Why should this become common knowledge? ■

Dear Pawel

There is very good example project in Poland of which i was personally responsible Project Manager.

It is 800m long with complex curves and when commissioned was set up without tracking problems.

However corkscrewing can occur:-

1. at initial startup it can happen before adjustments due to misaligned steel etc.

2. it can happen during operation if system is overloaded or large foreign body is entered into pipe.

Either way protection device can be installed and adjustments made. ■

Originally Posted by nordell

We employ 15 people whos daily task is to engineer on the cutting edge. Without the edge, they would not have a job in this business. It takes about 3 years to adequately train an employee. Why should this become common knowledge?

NOBODY should expect this. ■

Originally Posted by nordell

Have you asked the manufacturers why the belt corksrews? I doubt most can provide the answer. Be pleasantly supprised if one gives you the correct answer.

Yes, the reason you do not get support from the constructors is because they do not know.

When one claims, in public, then the competition all answer in unison that they also know. So, why should those that know divulge to those that do not, but compete for the same business?

.......

Simply because, in this age of litigation, if a purchaser engages someone to provide equipment or services then that purchaser is not excercising due diligence if he fails to ascertain the full implications of the purchase. If no one is prepared to divulge the necessary information then the diligent purchaser will look for alternative equipment.

Just try selling a catalyst regenerator to a refinery operator with the line "It's proprietary information" We want the i's dotted & the t's crossed.

I've had the 'trade secrets' story from a particular manufaturer on 2 power station projects. I never approved his drawings; the vessels & HP heat exchangers failed hydrotest with monotony; I insisted on complete remanufacture; the Client took the reworked vessels at his own risk; the vessels then wouldn't site commission; I risked a grin at the expense of the Authorised Inspector.

While there is no obligation to put all our cards on the table, we are obliged to provide the information which the purchares requests.

I personally detest that sentence in the enquiry which goes "If the Bidder knows of any...anything else." just as much as any Supplier would.

In some pre-contract meetings I have led preferred bidders with questions about the reasons for, their opinion about, known problems with the type of equipment. If I get a satisfactory answer they stay at the front of the running.

Now what about these bleeding pipe conveyors then?■

Some talk about corkscrew motion but do not offer insight to its mechanisms. Some claim they have never experience corkscrew action. Some claim the action is produced by unusual operating conditions. I offer a brief note on what causes this phenomenon.

Corkscrewing is produced by the imbalance of forces acting on the tensile members (fabric and steel cords) with respect to earth. If you turn the belt around a right hand turn ( looking from tail to head) the belt crossection will try to rotate in a clockwise direction. If you turn to the left, the belt will rotate in counter-clockwise direction.

Corkscrew motion is just a matter of degree. Rotation is produced by the imbalance when the seam overlap overpowers the opposite section of belt that does not have this overlap. Empty belts are more prone to rotation, just observe the return strand where the seams seeks the bottom position.

When the belt fills the center of gravity shifts and the rotation force imbalance is significantly reduced. However, tight horiz. curves, vert. curves, and high tensions can still induce rotation. There are mfgr's. published adds, by leading suppliers of pipe conveyors, where photos of the seam is rotated to the 3'oclock position, the seam is dialated outward and opened upwards so that rain water enters the pipe. This is an example of corkscrewing.

Once the belt seam moves off 12 oclock, the added weight ,applied to one side, will exacerbate the rotation action.

Continued vertical and horizontal curve routing can induce further rotation until the belt has turned 360 degrees or more. ■

Dear Sirs

Although some of the theory explained by Mr Nordel is true i can explain in practice what happens.

When a pipe conveyor is set up initially it is obviously desirable to have the seam at the top and with some complex routes this can be difficult all the way.

When empty there is a tendency for the seam to move to the bottom but thats normally where it stays as it corrects at the delivery and also this can be tracked out.

Normally when the material comes along the seam corrects to the top due to weight of material.

On ocasions when the belt moves more than 180 deg there is some additionally inducement and must be checked and corrected. ■

Paul,

I find your response lacking. First, you comment that "some" of the theory is true. Then you go on to say nothing about what I have said is not true, and then say nothing about why the corkscrew occurs or any substantial technical details about empty or full behavior.

Why does the belt rotate when empty?

Why does the belt rotate when full?

You seem to acknowledge that it can rotate more than 180 degrees and then needs inducement. What are you talking about?

Give the forum technical understanding and counterpoint on the implications of your wording: "some of the Nordell theory is not true". What is not true? We are all eager to learn what we do not know. ■

Dear Larry & Forum

I have been responsible for the design and installation of more than 30 pipe conveyors and all these characteristics I have seen and experienced to varying degress depend on the system complexity and sometimes they can happen for no clear reason however:-

On long conveyors an empty belt can rotate because with the overlap there is more weight in this area and gravity wants to send it to the bottom i.e. 180 deg also depending on tension and curves this can have influence but generally in this case the overlap will stay at the bottom, if it continues there is excessive inducement so must be corrected. This can be seen on the return belt as the overlap almost always stays at the bottom. Either way it can be tracked to a better position.

Generally with material in the pipe it is more stable due the the weight however particular with light materials there can be structure induced rotation which should be tracked out.

The belt should be tracked both empty and loaded but even so overfilling or other elements can change this alignment.

I did not suggest that the previous theory was not incorrect only to say that in practice other elements come into play and only after experiencing and solving can they be understood. ■

Dear Paul,

I ask a favor. Could you reword the tautology, of the last sentence for my simple ability. ■

Dear Larry

I was trying to explain the different characteristics that effevt this system and although there is a theory which you point out it is not easy to calculate only with practice can you confirm and understand fully.

In all the PC systems I have been involved with they have all been different depending on the route, pipe diameter, belt strenght, belt rigidity etc (as I am sure is true of you).

Some systems have started imediately without problem or adjustment and some systems have been problematic until the correct adjustments are made.

As guess with all things its the experience that counts. ■