Keith - Belle lagging refered to in the previous message is an Australian creation. Diamond pattern, plain rubber, ceramic and weld-on ceramic are available from Belle Banne Flexco (2-9680-3322) in Baulkham Hills B. C., near Sydney. ■

Dear Keith and Bigdave:

Keep an open mind to respondents. Some give info which may have considerable background.

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Bigdave:

I can vouch for Mr. Beckley not being in the employ of Belle Bane or any other manufacturer. He is quite autonomous. He is also one Australia's most respected belt conveyor consultants with over 30 years experience.

Holtz slide lagging does have its adherents. You appear to be one. As a historical note to preamble my comment: a) I worked as an employee for R J Dick , b) consulted to and with pulley manufacturers Dodge, Precision, and RASP in North American for many years, c) consulted with Prok and others in Australia d) consulted to many large consulting companies world wide. I own an engineering company in the USA which practices - apply the best and most suited technology and products.

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Keith:

Holtz does (did) have problem(s) as David noted with shell failure and corrosion. He and many are aware of another serious failing of Holtz slide lagging - designing and maintaining the metal clamp so that it does not either corrode in place or the lagging does not slide within is holding metal strip. When the later happens in wears the metal-to-metal grove to the point of failure. As the groove wears the lagging can be heard to slap in its socket and become misaligned. Often maintenance will weld it in place. Is this its intended use?

Applying Holts lagging introduces another potential for diameter irregularity or error. Applying Holtz to dual drives is more iffy with the need to keep drives balanced and free from oscillation.

These problems have been more prominent with higher power, higher strength, and wider belts. I say "have been" because I have not heard of their advancements in recent years. These criticisms.

All producers of lagging have their horror stories be it the wrong application of their product, bad fab quality control, or bad a installation procedure. Some defamation is deserved and some is not. I would bet a good lunch that there is a significantly larger successful installation base of both hot and cold vulcanized lagging in existence that Holtz and its derivatives. I do believe, as many do, that Holtz lagging does have a deserved niche in our industry.

It can also be said that the lagging geometry configuration is not as well understood by the industry as it should be such as: herring-bone, diamond, diamond w/ axial grooves, Holtz, Lori-align, ceramics of many varieties.

In conclusion, what rubber, geometric, and bonding properties should a lagging have to guaranty success for a specific or all installations? What features are ambiguous, better for one over another, or are redundant? Can this be fairly tabulated outside the manufacturers' sales force? ■

Dear Bigdave,

I appreciate your candid response. I acknowledge that your success with Holtz lagging and agree you should promoted it. In doing so, as you now have, please give reasonable details for others to know, by field trials, the minimal boundaries of success.

I have had the good fortune to talk to many users of belt conveyor related equipment throughout the world, on all continents, over the last ~ 40 years. I am an advocate, in the extreme, of the forum's function to inform interested parties, to share ideas and experiences. THis forum represents an opportunity that few would be able to experience before the internet and Dr. Wolhbier's vision.

On the point of shell failures, I find it hard to crically blame the pulley manufacturer or design engineer of their product. When you get down to the design details, good pulley designers will tell you not to weld in any critical stress area without compensations. So if you tack weld across the pulley face with a stitch weld or even full penetration weld, you will likely reduce the shells bending and hoop stress allowances by ~ 50 % of the the non welded form. The shell does have a seam weld that fully penetrates the shell connection and is performed in a controlled manner. It is often check and ground if the weld has undercut or other weld concerns. The Holtz lagging may be applied by a field journeyman or at the factory by a manual non-jigged method. Without elaborating on these details, the pulley load or stress capacity may be compromised.

Factory and field application of cold bond and hot vulcanized rubber can be tainted by bad actors, over zealous production supers, environmental influences et al. This is the well we first go to when a complaint arises.

There is an abundant history of successes to maintain the advocates of the status quo.

Good Luck and continue your invovlement. ■

I would like to add a welding procedure that has performed well in this application (and others as well). The slides should be welded in a procedure called back welding. If you are facing the pulley, start at the left side aproximately 1 1/2" from the end, welding right to left. Then move across the pulley to the right, start welding again from the right to the left back towards the weld previuosly completed. The lagging does not have to be welded solid but in a stitch method. Continue skipping and welding from right to left back towards the previous weld.

By using this method of welding the stresses on the pulley and lagging are minimized. ■

Dear sir

I donot understand why to weld pulley on alredy machined pulley just for fixing particular type of lagging and take risk of pulley deformation increasing stessess etc.

I have seen good hot vulcanised rubber lagging working for last 10-12 years without any problem .

In case of initial lagging wear off cold vulcanising can be done at site which also have about 50 percent life compared to hot vulcanising

A R SINGH ■

Gentlemen,

As a leading supplier of conveyor pulleys in particular to Australia, but also world wide, I read with interest your comments on slide lagging. I agree whole heartedly with the comments that welding on the pulley shell surface will lead to some reduction in the life of the pulley shell. It does not matter what techniques you use pre and post welding there will be reductions in fatigue life due to the installation of the slide lagging rails. We (Sandvik Materials Handling – ex-Prok) have in the past supplied pulleys with slide lagging on a number of occasions in the early 90’s. I do recall one client coming back to us a while later and request we remove the slide lagging and re-lagg with hot vulcanised lagging. The client reported issues such as belt flap and inability to be able to remove the slide lagging due to rust and build up of particles in the slide rails.

Paul Attiwell ■

Dear sir

whether some body tried slide lagging rails fixed by countersunk bolts istead of welding

A R SINGH ■

Hi Keith

Number 1 is Hot vulcanized lagging.

a/ Has to be done in a workshop.

b/ It stays on but is hard to remove/replace when worn.

Number 2 is Cold vulcanized lagging.

a/ Can be done in situ.

b/ Subject to skills of the applicator.

c/ Easier to replace when worn.

and if you can't do the above you could try as a last resort the weld on type. ■

The Flexco(R) brand of ceramic weld-on lagging is not of a retainer design. The Flexco weld-on is an interlocking design that eliminates the vibration of belt cleaners. This vibration is common when a retainer style of lagging is used without the retainers. It is common, at least in the US, to find that many of the operators do not bother installing the retainers. The retainer style of lagging is installed directly onto the surface of the pulley. The Flexco weld-on lagging is designed so that the pieces fit together nicely around the pulley diameter but adjustments can be made using the interlocking feature. ■

I don't want to butt in but this discussion gives the appearance of some unethical approach from the manufacturers of pulleys or the lack of requirements by the conveyor designers.

When one designs a pulley, wouldn't make sense to design it already incorporating the lagging features? Or at least have the design features for incorporation of the lagging system.

In my view, the issue is related to the surface characteristics of the pulley. With today's JIT one should be able to order the correct pulley for the application.

With respect to retrofits, I never had the opportunity to do retrofit work in a 500 HP conveyor other than idler work and basic maintenance.

In smaller conveyors 12" Dia. pulleys, I had the opportunity to install lagging by screwing it to the pulley with 1/4-20 flat head screws and they performed.

Welding on a pulley does not appear to be a good idea.

My two cents

Antonio Reis

President

Vitrom Mfg Consultants, Inc

Your Process and Manufacturing Solutions

Phone: 209.834.1900

Fax: 209.834.1039

www.vitrom.com ■

"Unethical" is a strong statement, Why not become informed by asking the question before rushing to judgment.

Most pulleys are factory lagged with hot vulcanized rubber.

Some lagging is replaced due to severe duty and poor plant hygiene. These continued replacements become tiresome for plant personnel. In steps a salesman for Holtz lagging, with the panacea for the operator’s problems.

Then sometimes the pulley shell fails because the salesman and operator, not being engineers, are unaware of the added stress level applied to the pulley shell.

Had they consulted a qualified pulley manufacturer or design engineer they would become informed of the limitations of the about-to-fail pulley. Pulleys can be designed to take the Holtz or other bolt-on, weld-on, glue-on .... types once the operating and design features are known.

Its bad form to accuse the uniformed. Save it for the informed. ■

I don't know why you rush to the conclusion that I'm uninformed.

Go to any catalog of pulleys either motorized or otherwise up to 48" in diameter and 50 HP.

In the other available features you can read statements such as:

cold bonded lagging is available.

Larger size pulleys have segmented lagging.

Vulcanized rough top.

Bolt on rough top.

Vulcanized rubber lagging and grooving.

Than you have the entire array of "self cleaning", "easy cleaning" "wing tip" type idlers that in my opinion require some type of lagging in the tips of the blades and in those the lagging is also in the other available features.

To me, it is like selling the mercedes benz with wood tires and the radials are on the other available features category.

The pulley manufactures should strive to provide an optimized pulley taking in consideration the belt type, the load and the application. Such job should not be delegated to consultants or to maintenance departments.

This is my opinion.

Antonio Reis ■

Antonio Reis' comments have great merit. Punters pay loads of money for a machine which is essentially a big rubber band going round a few drums. For over half a century there has been much learned discussion about belt slip, diaphragm failure etc. If a manufacturer factory vulcanises the drum & also provides a safety factor which provides for later attaching replacement lagging then something is wrong.

Why not fit replaceable lagging in the first place????

Is/was the life expectancy of the factory lagging (etcetera) adequate?

More insight could be gained from the tender stage if customers insisted that bidders included drums in their list of recommended spares. Then we could compare extra downtime while fitting lagging against the cost of a fresh & balanced drum. ■

MFG don't install replacable slide-on lagging because much of the world does not see the need in price premium and the noted negative attributes.

If the manufacturer knows that welded or bolted slide-on lagging will be used, then they may increase the shell thickness to compensate for the decreased stress allowance.

MFG dont make slide-lagging but do offer it as a VAR product dependent on a client's wish. ■