Hi kirubasankar,

This type of question is best answered by the Vendor's technical department. It depends on the diameter of the tube. I would think you would need about 100 diameters at least.

Regards - Sgt John.rz

www.latviantourists.com.au ■

Dear Kirubasankar,

As per JPC the minimum radius will 300 times the pipe diameter for NN belt & 700 times the pipe diameter for steel cord belt.

Regards.

A.Banerjee ■

Dear sir

As explained by Mr Banarjee above thumb rule may be suitable for most of normal pipe conveyor applications . However radius depends upon tension in the belt at curve location.

For long distance pipe conveyors where tension ratings are large belt construction should be checked for suitably of belt at desired radius and tension .

You must consult your Belt manufacturer for minimum recommended radius for your application.

Radius less than above thumb rule are working satisfactorily

A R SINGH ■

Included in the above limiting radii selection, you should note comments for both veritical and horizontal curvatures, belt cover thickness and internal carcass construction, belt orthotropic bending modulii as they are affected by the local belt tension and filling factor. ■

Hi gurus,

This topic has been viewed by 1,000 hits. Can we not guide people to a more definite answer?

The original question related to a tube, or pipe conveyor with 4 rollers, and a wrap around belt. The answer was "anything from 8 meters to 700 diameters. Can we do better than that for out 1,000 hits?

Please advise - Sgt John.Rz

www.latviantourists.com.au ■

Beyond rules-of-thumb, the analytic procedure differs with technique that becomes the domain of intellectual property.

By example, CDI has developed a pipe conveyor composite finite element analysis techniques that does demonstrate many difficult criteria. These cannot be put into simple words and formulations.

Among the difficulties is how much power and differential belt tension ocurrs within any geometric configuration. As the forum shows there are significant differences in the approach and accuracy. To obtain true power and tensions you need to evaluate viscoelastic/rheological losses. The technique is written in the general and not the specific. Again, IP.

We design pipe conveyor systems. Interested parties are encouraged to contact CDI per the below details. ■

The minimum radius of curvature of pipe belt installations has been guessed at 300 x pipe diameter for Fabric and 600 x pipe diameter for steel core belts.

I use the word guess as this is what we tend to do. We do not base this on any other factor like for example cross ply rigidity belt tension and idler spacing.

If applying rule of thumb principals then one should obviously apply the principle of installing the largest radius one can in the area available to operate the system.

As you may be aware we are trying to push the envelope of bigger, longer and more complex profiles and as noted in a previous thread we have developed a test rig to confirm the parameters of cross ply rigidity for a given idler spacing, radius and belt tension.

This test rig is far from a complete solution because it is static and as anyone who has built a pipe conveyor knows that the initial profile within the idler configuration and the profile after say 1 year is totally different.

Today we are building a complex pipe conveyor where we initially applied the results of the test rig to the development of the belt. We now intend undertaking the same tests under operating conditions on the working conveyor over a period of 1 year.

This will then give us an improved understanding of the real world and we will eventually be able to provide more accurate guidelines to the selection of belt radius.

To answer john. rz. The real solution as a standard is not definable for all applications so many respondents tend to baffle us with dialogue, so to conclude I advise that if you wish to push the envelope by developing a profile which has no previous reference then please start with the biggest radius possible and arrange to undertake the tests I have defined previously.

Regards

Phil Staples

Phil@ckit.co.za ■

Thanks Phil,

I guess we all know now when we are guessing.

It seems the time has come to ask - What are the failure modes we anticipate in stipulating the sweep bends

1 - Rubber fatigue - it seems the rubber has a non-elastic non reverseable creep issue. It wears in from new - like a pair of good shoes

2 - Over-stressing of the fabric

3 - Kinking collapse of the envelope at some parts of the belt

4 - Increase in friction

Looks like ZA is leading the world again.

Well done - John.Rz

Bionicresearch Institute ■

Dear Mr. Jhon RZ,

Your replies are not very clear. I donot understsnd what you want to say!

Regards.

A.Banerjee ■

Conveyor Dynamics, Inc. (CDI) has made a number of studies on allowable pipe conveyor curvatures. The allowable curvature is a very complex problem and cannot be easily distilled into a 300 or 700 or other fixed formulae multipliers.

Our analysis shows other factors at work that would put the novice designer at great risk of losing their nouveau reputation:

1. Highly axial tension dependent - crushing force on pipe diameter

2. Very belt cover thickness dependent - transverse stiffness of top cover (non-linear compression) and bottom cover ( almost linear tension) on carry side and reverse on many return sides

3. Highly elastic modulus dependent which in turn is steel cord strength dependent - higher axial and transverse modulii will cause higher forming and bending resistances along with higher than expected power consumption

4. Direction of curvature with respect to orientation of seam - is the seam overlap pointed away from the center of curvature or toward to curve locus

5. Reinforcement method, placement, and materials

6. Absolute diameter of pipe and its bending stiffness properties including steel cord construction and cable diameter wrt the other noted properties

7. Age and strain-flexural history of rubber and polymer fabrics - more flex equals more supple belt in transverse pipe forming stiffness

8. Rubber cover's viscoelastic hysteresis properties with respect to temperature, strain, strain-rate, that vary dramatically between manufacturers - incoming hype to follow

9. There are other factors as well – keeping it simple.

A Fools Paradise:

I am not surprised to see so many failures to control the pipe system, even among the more advanced and experienced pipe conveyor designers. Many of the noted 7 points are ignored or are not analytically evaluated in a proper fashion. Just ask the designer for evidence of such a comprehensive analysis of the 8 or more points. Few designers admit to lack of sufficient knowledge.

-- In paradise, a wise sage once said --

“If I tell you what I know, knowing more than you, you will think me highly skilled if not a genius. If I tell you what I do not know, on this subject, you will think me a fool to attempt to better you.” ■