Why do problems occur?

Posted in: , on 27. Jan. 2003 - 17:46

It is not rare for plant productivity to be adversely affected by discharge problems associated with silos. Accepting that there can be several causes for vessels to perform erratically, a core element is often the use of inappropriate feeders, geometry, wall finishes or outlet sizes for the material(s) being handled. Product quality issues that can often be attributed to the operational characteristics of vessels, include inconsistent discharge rates, variable bulk density, exaggerated segregation effects or caking as a result of regions of non flowing product.

What is the general opinion as to why these problems are still present in industry, even though approaches to avoid these pit falls have been in the public domain for at least four decades?

Where does the responsibility lie for achieving an uptake of the existing knowledge? – end users?, equipment manufacturers?, academia?, research institutes?, government departments?

Lets have your opinions!


Richard Farnish

Peter Brown
(not verified)

Re: Why Do Problems Occur?

Posted on 27. Jan. 2003 - 05:38

Well for staters how about :-

1) buying on price

2) materials handling being regarded as a 'low technology' area of engineering leading to anyone who can fabricate offering to supply the equipment (follows from 1)

3) lack of knowledge by those seeking new plant to adequately specify the material to be stored, but still requiring (demanding?) a quotation

4) lack of knowledge of the properties of the material to be stored due to it being a new product or a representative sample not being available (but you still have to supply a quotation!)

5) Academic research not always being presented in a user-friendly form

There are undoubtedly more!

Re: Why Do Problems Occur?

Posted on 14. Feb. 2003 - 10:15

Dear All,

I dont know whether this thread is still "live" but here is my view as a plant engineer in the food industry.

I have always relied upon the knowledge of the equipment suppliers to provide kit to meet my process requirements. If I go looking for a car I don't expect to have to know all the details about how the engine is designed - similarly if I need process equipment I rely on the suppliers to have the expertise! The knowledge for reliable equipment operation (i.e silos, etc) should reside with the equipment manufacturers / suppliers.

Quite how they obtain their knowledge (whether through trial and error or from technical papers) is their responsibility.


E. Quill

Earnie Quill Plant Engineer

Feedback On Comments

Posted on 19. Feb. 2003 - 10:32

It appears from the two responses to this question that equipment manufacturers feel that they are not given adequate understanding or information relating to the application for which they are supplying, and that end users expect manufactuers/suppliers to have inherent knowledge of their requirements.

This probably reflects quite well the "no mans land" into which particulate storage/handling equipment design falls.

Other than taking advantage of the limited number of industrial courses offered by various institutions it is hard to percieve how information can be brought into the industrial sectors that need it. Clearly, end users need to know how to draw up specifications that consider the requirements of the material being handled (as opposed to considering only capacities and through puts) and equipment suppliers/manufacturers need to know how best to provide an effective and reliable engineered solutiuon. Without sufficient knowledge by which to assess requirements in terms of operational efficiency and reliability, tenders will invariably be judged on price rather than "suitability for duty".

Perhaps a certificate of competence in bulk solids handling would be of use to all parties? Work undertaken (specifying or designing) by non qualified personnel being frowned upon by the insurance companies?

As always, your comment are welcomed!


Richard Farnish

The Wolfson Centre for Bulk Solids Handling Technology, Univ. Greenwich, London

Peter Brown
(not verified)

Re: Why Do Problems Occur?

Posted on 19. Feb. 2003 - 01:35

Equipment suppliers do have knowledge to a greater or lesser extent and will consider all parameters when offering solutions. However their knowledge can only be applied against information about the material to be handled/stored. This resides, one way or another, with the customer/end user as they are living with the material day in, day out. Both supplier and customer/end user must bring their knowledge together to end up with an effective solution.

To take the example of the car, it's no good complaining to the garage that the car is no good as it's got a petrol engine and won't run on diesel if you didn't tell the garage you had a supply of diesel that the car had to run on.

Why Problems Occur

Posted on 24. Feb. 2003 - 11:45

Many problems arise with solids handling plant for the reasons given by Peter Brown. Earnie Quill puts forward the reasonable case, which I agree with, that the supplier should be relied on to provide the specialised knowledge. However, the problems posed by Peter indicate the gulf that often exists between user and supplier on the degree and quality of information that is required to prepare a fair and equitable contract for a given duty. Efforts made to bridge this gap include the I.Mech.E ‘guide to the Specification of Bulk Solids for Storage and Handling Equipment’, The British Materials Handling Board ‘Guidelines for Specifying Weighfeeder Systems’ and the SHAPA publication, ‘The Surface Finish of Stainless Steel’.

There is a need to establish technical rapport between the end user and the supplier of solids handling equipment. This can be impeded by main contractors, sub-contracting situations, and sometimes by intransigent buyers concerned only with price, particularly if other suppliers adopt a more cavalier attitude to guarantees. ‘Caveat Emptor’ not only applies to suspicions of a suppliers motives but, in these cases, pertains to the fact that it is virtually impossible to insulate the user from serious liabilities should to performance of the equipment go catastrophically wrong.

A responsible supplier should ferret into any information gap, even against resistance, because it is to the mutual interest of both parties to ensure reliable performance. If data is not available for any reason, then this should be brought out and the implications allowed for by agreement prior to order placement.

It is also the responsibility of industry to interpret scientific research and present this in the form of developments and innovative equipment to users. For examples of this and attempts to present technical information to users, see the Ajax web site – www.ajax.co.uk.

It is often difficult to convince users to spend money on powder testing for apparently simple and relatively low capital cost items, such as chutes, transfer points and small hoppers. The importance of such items for reliable performance has no relation to their cost. Attention can only be drawn to the effects of difficulties and consequences of their failure. As for buying at the cheapest price, our advice to Un-enlightened Buyers of Solids Handling Equipment is given in the following extract from our series of ‘Ten Key Steps for Good Performance in Solids Handling Plant’

1. Do not give the supplier any information about the bulk material. Show him a sample that you have obtained from the floor or nearest rejection bin. This will test his ability to find out what the material is really like in practice, and he should be a clairvoyant anyway. The real benefit though, is that you cannot be held responsible when the plant doesn't work.

2 NEVER call in a consultant. People might come to think that you do not know your job. He will cost you hard cash now. Any lost production and increased manufacturing costs will fall some time in the future, and can be blamed on others, if your still around.

3Do not compromise the bin holding capacity with minor details, such as steep wall angles for slip or large outlet size for reliable flow. Any fool knows that most materials will slide down a 45 degree inclined surface and the hole must be bigger than the largest lump. And after all, it is the operator’s job to get the material out, so why should you worry?

4Buy the cheapest kit. That's the way to save money on capital goods. Higher revenue costs come from another pocket and will always be accepted as an inevitable ongoing expense.

5 Do not read technical literature about the state of the art. It's specialised and not all that simple. Your concern is what the plant has to do, not how it is done. It's not your job to design kit. Let someone else worry about that, and take the responsibility.

6Make sure that you have a good lawyer. He will not make your plant work, but you may have the satisfaction that the equipment supplier will get a good pasting, if your guy is able to make some stiff penalty clauses stick.

7Specify thick plates on the bin, and weld some heavy steel sections near the outlet, so that it can be hammered without causing too much damage. Buy ear plugs for operators.

8 Collect leaflets for vibrators, air cannons, sledgehammers and other flow-promoting devices. You'll need them, or note Ajax's fax, phone and Email address for retrofits.

9Get well equipped with overalls, dust masks, goggles, long boots, gloves, a big shovel and a long pole. Revise your production schedule to be more 'elastic', and cancel your holidays.

10 Study acting, your day job does not look all that secure.

Lyn Bates