Angel hair formation has been discussed here a number

of times.If you search this forum you will get loads of

information. ■

Dear Mr tolar,

The formation of angel hair and streamers is induced by friction forces and velocity,generated by the pneumatic conveying process

(N*m/sec # Watt)

At a rate in kg/sec, this means (Nm/sec)/(kg/sec) = Nm/kg = J/kg # energy/kg)

In general, forces are proportional to velocity^2.

This means that the available energy for the formation of angel hair and streamers

is proportional to the velocity^3 at a certain friction factor.

This energy is released in heat and forces, which is partly dissipated into the pellets.

(Ideal combination for deforming the polypropylene)

By using stainless steel pipes, you are aiming at friction reduction, which is OK.

In addition to this, it is important to convey at the lowest possible velocity.

From your description it is not possible to judge whether this is the case.

Required information is:

pelletize, material density, air volume, design vacuum, operational vacuum range,

ambient temperature, conveying rate, etc.

As you have a working installation available, you must be able to test and valuate

the pneumatic conveying process of those pellets according to calculations that predict the

results of parameter changes.

Also take the opportunity, suggested by Mr Mantoo and search this forum on the subject.

The search-function will be usefull.

Success

Teus ■

Your options basically come down to the following;

Reduce your conveying velocity to the lowest possible value you can and still move your material -- blower speed change is most likely the easiest way to do that -- either a sheave change or presumably, your blower motor isn't very large and todays VFD's are reasonably priced in the smaller sizes and give you a wide range of adjustability

Another option is to consider using internally treated pipe -- there are several designs all with decent results and one really isn't significantly better than the others as each supplier will give you data to support his own product. Internal sprial grooving, internal shot peening and internal sand blasting are all commercially available techniques to consider.

Using short radius elbows or tee bends have shown the ability to reduce the formation of debris at the elbows as there is less turbulence and "collisions" with the pipe wall

Be sure your pipe couplings are correctly aligned and pipe joints do not have gaps as that will encourage turbulence which in turn creates more debris

There isn't any single quick fix to make your problem go away -- small incremental improvements in your conveying system will yield incremental improvements in the quality of your product.

Good Luck ■

Fines and streamers can be eliminated downstream the pneumatic conveying.

see the site www.valitec.eu ■

We are glad to inform you that we undertake the process of internally roughening of the Pipe & Bends through process of Shot Peening, which reduces the Angel Hair or Streamers formed while transporting plastic pellets through Pneumatic Conveying System.

Our plant is equipped with automatically controlled shot peening machines for wide range of components of job diameter upto 1 metre with consistent and unerring results. We can deliver Stainless Steel Pipe & Elbows as per the required Grades & Drawing having roughness value as per your Specifications required at affordable prices and short delivery periods.

Please do read the attachment for further details.

Thus, we request you to give us an opportunity to serve you and we assure you our best service.

Warm Regards,

V.C. Chandan

VIKAS METALS

4-4-168, Mahakali Street,

Ranigunj,

Secunderabad-500003.A.P.(India)

E-Mail: vikasmetals@yahoo.co.in

Ph: +91-40-27712995/66385055/9885977337

Attachments

shot peening-solution for angel hair formation (PDF)

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