Mr. Hassan:

The number of plies required for a given application will depend on the total strength required and the strength of the indivual ply. In addition to belt strength requirements, you should be looking at minimum pulley diameter requirements for each belt under consideration.

Since the ply strength can vary greatly with fabric style and manufacturer, generalized tables will not cover all possibilities. However, most trade organizations and reference books can provide you these tables.

Regardless of what general tables tell you, refer to the belt manufacturer's information on the requirements for their belt. As an end-user, you may choose to have a single ply belt or a four ply belt for a given tensile requirement -- there will be valid reasons for either choice.

Regards, ■

Mr. Hassan,

The answer you seek is more complex than can be covered in this forum. Many issues need to be setforth to make a prudent selection. From the list below, you can get a start.

You can visit the online websites of various mfgrs. Goodyear provides online selection service for fabric/textile belt and ply number criteria:

Goodyear is most helpful here with min. and max. ply criteria:

http://www.goodyearcvb.com/conveyorb...plylonplus.pdf

Georgia Duck gives some insight in their catalog - part of Fenner:

http://www.gd-enerka.com/gaduck/gadu...56A1D004EDEC0/$File/BeltConst.pdf

Fenner Group website to view:

http://www.fennerdunlop.com/WebSites.../pages/fdhome/

You can obtain brochures or catalogs from other reputable mfgrs that dont give on-line service:

1. Bridgestone

2. Contitech

3. Phoenix

4. Yokahama

Lawrence Nordell

Conveyor Dynamics, Inc.

web: www.conveyor-dynamics.com ■

Mr. Hassan,

Carcass selection is not based solely on the tensile factor. When selecting a carcass, the choice should be based on the following:

* tension requirements

* impact resistance

* load support

* empty belt troughing

* pulley flexing

* splice strength capabilities

* cost

There are a number of sources available for general consideration of this isssue -- CEMA, NIBA, RMA, and indivual reference books (see posts in this forum and the e-library). However, I still believe that the best source is the belt manufacturer of your choice.

Mr. Nordell has provided a few web addresses and the names of the major belt producers. You can obtain charts and base information direct from them.

Regards, ■

THE NUMBER OF PLIES SHOULD NOT BE YOUR CRITERIA FOR CHOOSING A PARTICULAR BELT FOR AN APPLICATION. THERE ARE BELTS OUT THERE THAT HAVE ONE OR TWO PLIES, SUCH AS USFLEX BY SCANDURA THAT ARE AS STRONG AS A 4PLY FROM OTHER MANUFACTURERS. GOOD YEAR HAVE FOR EXAMPLE: A 3/600 PIW BELT AND THEY ALSO HAVE A 3/375 PIW BELT. ALTHOUGH THEY ARE BOTH 3PLY BELTS, EACH BELT OFFERS VERY DIFFERENT RESULTS ON A DRIVE.

TONS/HOUR, BELT SPEED, PULLEY SIZE, TAKE UP ARRANGENT, BELT WIDTH ETC. ALL PLAY AN IMPORTANT ROLE IN HOW YOU CHOOSE A BELT.

REGARDS,

R. BABIN ■

Dear Mr. Ehab A. Hassan

The basic technical considerations for selection of number of plies are as below :

1) The belt carcass (i.e. fabric together with ply quantity) should be adequately stiff to support load, on spaced idlers. This implies required minimum stiffness of carcass. The belt manufacturers published data provides allowable minimum carcass to support load of particular bulk density. The carcass always means ply strength x number of plies. The number of plies can never be decided in isolation of ply rating (characteristics)

2) The belt carcass should not be very stiff so that it does trough properly. This implies maximum permissible stiffness in particular case. The belt manufacturers published data provides this information as allowable minimum belt width for particular carcass

3) Carcass should have adequate resilience to absorb lump impact energy. Some manufacturers published data provides this information. The calculation of this lump impact energy needs certain engineering judgement & solution

4) Belt carcass should have certain minimum tensile strength to withstand tension in belt, by certain safety factors, momentarily and continuously (i.e. starting, braking & continuous running)

The chapter 4 of my book describes this selection method, calculation, belt technical data etc. The chapter is made up of 49 pages. In addition certain portion of chapter 13 is also related to this issue. In view of the aforesaid magnitude of this issue, it is not possible to describe direct solution on this forum.

While solving the problem; one will find that there are several options. Then it is very important that one has to opt for the technical option, which provides most economical solution (i.e. total cost of belt, pulleys, output coupling and gear box needs to be minimum). The problem is further compounded by standardisation of belts in the plant and consequent assessment.

Generally, one will find that the technical acceptable belt options, with matching strength; but one having least number of plies is economical.

Regards,

I G Mulani

Author - Book - Engineering Science and Application Design for Belt Conveyors.

Email : parimul@pn2.vsnl.net.in ■

Dear Ehab - My Second Comment,

Many have offered assistance to aid in the criteria for ply selection. They are all right (pun). Unfortunately, the scope of the criteria has a much bigger net than given thus far. The following comments are not conclusive but add to the prior list.

1. Construction of the belt ply : nylon-nylon, nylon-polyester, polyester-polyester, kevlar, etc. will inflluence all noted conditions in different ways

2. Fabric weave and denier construction - stiff or compliant weaves - a single ply may work as well as many plies for the same strength for certain conditions

3. Balancing cost of increasing idler spacing with necessary minumum load support (more plies) and fabric stiffness for troughing (less plies) - as Mr. Mulani suggests

4. Pulley diameters (minimizing) and their influence on belt cleaning, belt splice strength, belt turnovers, idler transition, head room clearance, ........

5. Belt country of origin limiting available construction techniques and materials

6. Special treatment or lack of, on fabric, to control stretch and interply splice adhesion

7. Ability of field craftsmen to execute the necessary splice joint construction for maximum fatigue strength and thus the influence on the manufacturer and product

8. Vertical curve geometries and their commercial influence on structural steel works and or civil cut and fill requirements that are controlled by the ply construction, weave, et al.

I could go on. My point is that you must involve the support of the various manufacturers and their references that can meet you overall commercial need. Then the technical alternatives can be explored. There is no one answer if you want to investigate the best solution for the job.

Lawrence Nordell

Conveyor Dynamics, Inc.

www.conveyor-dynamics.com ■

Dear Ehab,

If you seek that which you do not know, there is good reason to follow the pursuit of knowledge that will give you strength.

It can take a long time, reading the knowledge of others, whereas, letting others read to you, in their experience and understanding, is much quicker. Let the teachers teach.

You do not have to be so accurate. However, what is it that you seek? It takes time, experience, ability, desire, and dedication to amass the tools where there are no more questions. Take them when you can if they possess value.

If you know your quest is superficial, then look to your own knowlege.

Go with your wisdom,

Lawrence Nordell

Conveyor Dynamcis, Inc. ■