You can design for almost anything. With that in mind, what are the goals, advantages, and other factors which you wish to compare?

Cost, tightness of fit, reliability, auto-adjustment, and many other factors can influence your judgement. If you wish our support or recommendation of a particular species, then you must make very clear reasons for your preferences. ■

Roughly speaking, as usual, your 90m length is borderline in the eyes of most of the popular literature. 230 tph suggests a lightweight/low modulus belt will be the order of the day.

If that is the case you err on the side of stretch accommodation & provide a little GTU, it won't weigh much & masks the designer's face from airborne egg, or similar.

Like most old timers I detest employing elaborate mechanisms to compensate for system inadequacies: but the inextensible strings of the physics textbook have to be supplemented by belts more akin to knicker elastic.

A screw take up would be risky. Even if you start off with a belt strong enough it is possible that someday it will be replaced by a weaker belt. Also you will probably need an ARU which mitigates against screw take ups on safety grounds. ■

A screw take-up can be used and is best suited at the tail pulley.

You will have about a 25 kW drive, a EP 450 N/mm belt with a 1000mm take-up travel excluding splice and belt maintenance storage.

You can also use a gravity take-up. In either case, you will need to apply about 10 kN of belt tension at the tail TUP or more if at the head. Most of the travel ( 600mm) will be devoted to permanent elongation of the fabric.

Take care with belt tracking. Would be easier with gravity since the screws will need to be applied to both pillowblock bearings. So, how will you align the belt and apply the necessary force?

You chose. ■

Either manual or automatic take-ups are valid in this case or in any case for that matter. You must design according to your selection.

The belt tensions can be predicted in either case. At an automatic take-up the take-up tension is constant. At a manual take-up the strain energy is constant so the average tension around the conveyor loop is constant. Attention must be given to the loss of tension and frequent adjustments must be made especially during the early life of a new belt. Tension must be measured, by measuring the belt sag between return idlers according to the rope formula Tens=(Belt WtxSi**2)/(8xSag).

Another possibility is the Semi-Automatic Take-Up. DSI has used and produced such take-ups. These are screw-type take-up frames mounted on a slide frame that butts up against compression springs. Belt tenstion compresses the springs. The spring strength and constant-K are selected for the belt tension requirements. As a result:

1.) the belt tension is easily measured, by the spring deflection,

2.) time period between tension adjustments is greatly increased, and

3.) the system offers greater safety against belt overload due to trapped material entering between the return belt and the tail pulley.

Joe Dos Santos ■

As a thumb rule, approximate maximum elongation a belt of 90mtr long belt can have is 3.6mtr. In addition it can have a starting problem.

Looking at this two factors a HGT is a good option.

Regards, ■

Dear Sir,

In my opinion you should go for gravity type take-up instead.For a length of 90M & 230tph, one should select the same unless there is space problem.

Regards.

A.Banerjee ■

Dear Mr. Afsaneh,

Other respondents have already given useful information. I would like to mention as below.

The choice of take-up type is sometimes a compromise between following criteria :

1) Technically / performance wise best (this includes its design functional fulfillment as a component of conveyor, frequency of maintenance, ease of maintenance, reliability, reasonable frequency i.e. months / years to adjust belt length etc.)

2) Most economical or adjustment to suit layout construction.

3) Designer makes decision about the take-up type to be used in consideration to anywhere between the two aforesaid extremes, depending upon the situation and need.

If you wish to have the best of performance with utmost reliability then you can opt for take-up type accordingly.

If you wish to have economical type take-up then choose type accordingly.

If you wish to have economical gravity take-up then opt for take-up at tail pulley (this saves three pulleys), provided it suits the application.

If you wish to have only screw type take-up come what may, then people also create compact loop on return run and provide two sets of take-up (i.e. two take-up pulleys and two sets of screws). People have used this type of arrangement on bunker conveyors at great height, which is reversible and there is no scope for gravity take-up.

To make the matter clear, in a power station engineer would straight away ask for gravity take-up for the conveyor length you have mentioned where prime consideration is best of performance and reliability irrespective of the price.

Regards,

Ishwar G Mulani.

Author of Book : Engineering Science and Application Design for Belt Conveyors.

Author of Book : Belt Feeder Design and Hopper Bin Silo

Advisor / Consultant for Bulk Material Handling System & Issues.

Pune, India.

Tel.: 0091 (0)20 25871916 ■

Dear Dilip,

I note with interest your comment on applying a 4% take-up allowance. Where as such magnitude been referenced in the manufacuters' references. ■

Sir,

I had came across various belt manufactures and maximum elongation suggested by them is approximately 4%(in case of NN belt).

That is why I suggested to consider that elongation of belt and accordingly half of the same could be taken as take up stroke to be on safer side.

Regards,

Dilip ■

I have noticed your monicer "Urwithdilip". Error with Dilip? Why would anyone wish to error with you?

That asiide, the 4% number is not defensible with any large belt manufacturer. Normally, the elongation is suggested to be apprroximately 1.5 %. Even as such, there are ways to reduce this exaggerated dimension.

At 90 meters and 1.5% suggests 1.35 meters and at 4% the value would be 3.6 meters. Any number greater that 1.4 mters is a safe number. If you wish to allow 3.6 meter no big deal. The belt will not reach this extension for years, if ever.

This is not a technical argument. It is not a political arguement, It is not an old verses new or yesterday verses tomorrow preference. So, what is the point?

Afsaneh asked a question. Manual or screw? We can only imagine the scream eminating from the ancients do it or else (we will comeback to the living and reek a massacre.

A lot of wishey washey and detailed suggestions on the need to identify how to make the selection. Its now up to Afsaneh!

Let it happen, enough said. He cannot go wrong. ■

Dear experts,

I believe the conveyor's counterweight need to be optimum designed. Because more counterweight ( tension on the conveyor) may lead to less life of bearings, rollers, vulcansied joints, bealt wearing out. Less weight will lead to slippage.

So I was deliberately going through our forum to know more about sag and came across the formula as Mr.Joseph A. Dos Santos has given in this same thread a few posts back.

"Tension must be measured, by measuring the belt sag between return idlers according to the rope formula Tens=(Belt WtxSi**2)/(8xSag)."

I am a maintenance engineer. Kindly help me to understand the terms he has mentioned.

What is Tens? Belt weight is the endless length belt weight or the weight of the belt between the two suceesive return roller?

What is the unit ? Is it Kg or tonnes ?

What is Si ?

The sag of the unit? Is it in mm?

I am attaching a pdf file, which shows the exercise I have carried out in few conveyors. Please let me know, whether the method is correct? What should be the range of sag? Is it between 1% to 2%? Is it applicable to any type of fabric or steel cord conveyors?

Waiting for your valuable comments and also clarification for the above formula qouted by Mr. Joe.

Many thanks in advance.

Regards,

S.Ganesh

Attachments

belt sag between return idlers (PDF)

■

Mr. S.Ganesh,

Keeping consistent units, the variables are as follows:

Tens: is the belt tension measured in kgs.

Belt Wt: is the unit weight (mass) of the belt measured in kgs/meter

Si: is idler spacing between the two flat return idlers, measured in meters, where you are calculating the belt tension.

Sag: is the maximum sag (drop) of the belt, at mid-span between the flat return idlers, measured in meters (small fraction of a meter). The sag is measured by stringing a tight piano wire from over the two return idlers and measuring from the strung wire down to the sagging belt.

I hope this is now clear.

Joe Dos Santos ■

Thank you Mr.Joe!

By transferring the above value in my 1.33 conveyor,( as given in attachment in my yestreday's post )

Belt unit weight is 12.3 kg/mtr

Return idler spacing is 3 metres

Sag is 30 mm .ie., 0.03 metre

So belt tense is = 12.3 x 2 x 3 / ( 8 x .03 )

= 307.5 kg

Since we are measuring in return side , can we say that T2 is 307.5 kg ?

If we apply this same formula in carrying side , can we get T1?

Please advise from here ,how to go ahead to improve the belt's performance? ■

Can we have a manual take-up?

YES...WE...CAN!

(Apologies to Borak Obama).. but I inherited a 1.2km overland conveyor with a fabric belt and a manual take-up. We simply stretched the belt to be nice and tight, and left the take-up there. It worked.

A lot of long underground conveyors work like this too, with manual winches.

Cheers

LSL Tekpro ■

Take up system of a conveyor belt should be able to take up slack caused by elongation of belt. The tension on the belt has to to be kept within permissible limits to prevent slippage of belt.

Belts with increase in length during use. Elongation will depend on type of material used in construction of belt. Conveyor belt suppliers supply the data about elongation. Screw take can only take care of length by which tail pulley is allowed to move.

In small capacity conveyors in emerging economies, where labour costs are not high, I have come across decisions to use screw take-up and re-splicing the belt after shortening it. ■

I give up.. ■

Dear Mr.Spriggs,

Part 1:

It is quite interesting to know that 1.2 km conveyor was provided with screw take up. So endless conveyor length is minimum 2.4 km. What was the specification of the belt? What is the chain block capacity you used for tightening., i.e, the pulling force? What was the belt's elongation % under it's test certificate? Usually how long will the belt take for attaining it's full elongation? What are the weather (climate) factors affecting its elongation?

Part2 :

Also request you to give you opinion about my calculation and queries submitted in my last post in this same thread.

Thanks a lot. ■

Mr. S.Ganesh,

Checking your calculation, you have mistaken 3**2 which is 3 squared, for 3x2. So when you correct this, the calculated tension is actually 461 kgs. This is the tension of the (non-running) belt between the idlers where you are measuring and this says nothing about tensions elsewhere. If your measurement is near the take-up then this is approximately your take-up tension. running tensions with various loadings can be calculated by knowing that, for a manual take-up, the strain is constant thus the average tension around the endless belt remains constant.

Joe Dos Santos ■

Decent manufacturers aloow a 1.5% take-up travel for an EP belt.

Here 1.4m take up travel.

I strongly advise to use a Sempertrans Multitrans belt which is pre-stretched and superior to any belt available on the market worldwide. ■