(not verified)

Re: Elimintating Angel Hair From Pe Conveying

Posted on 17. Jan. 2003 - 12:52

Please use shot peening pipes instead of smooth conveying pipe!

shot-peening pipes can decrease heat generation.

Dense phase pneumatic conveying process can effecrtively decrease angel hair too. Because it adopt lower velocity relative to dilute phase process.

Re: Elimintating Angel Hair From Pe Conveying

Posted on 19. Jan. 2003 - 04:13


Thanks for the info. But can you let me know the details of shot peenings. I have visited your URL but could not find the details.

Re: Elimintating Angel Hair From Pe Conveying

Posted on 19. Jan. 2003 - 06:39

the shot peening is done by specialized custom built equipment that shoots a stream of steel shot(or equivalent) through a special nozzle at a specific angle to pit the internal surface of the pipes and bends. The equipment provides for the nozzle to travel inside the pipe along its length at a specified speed.

The effect is that the surface gets roughened and the pellets bounce off the peaks of these roughenings being unable to slide on a smooth surface eliminating the tendency for a part of the pellet to heat/melt/solidify and form the angel hair.

We have this equipment and can shot peen any quantity and size of pipes and bends.

Best regards


Dennis Hauch - Freeport, TX, USA
(not verified)

Angel Hair & Shot Peening

Posted on 19. Jan. 2003 - 03:51

Certain types of plastic materials when pneumatically conveyed in smooth pipe tend to deposit material on the inside wall of the pipe. These mini-depositions tend to meld together and are randomly released into the conveying stream. The nature of the released material varies between short threads and long streamers. QC issues occur when downstream gravity flow paths are blocked by agglomerated threads / streamers.

It is well known that treating (roughening) of the pipe wall is effective in reducing streamer generation. There are numerous treatment methods available but the most cost-effective solution has proven to be directional shot peening.

Shot peening is a cold working process in which the inside surface of the pipe is bombarded with a spherical media called shot. For conveying pipe applications a special nozzle using high pressure air is forwarded through each section of pipe. A dimpled surface is created that changes the pellet-to-wall impingement mechanism from sliding to impingement. In this way streamers can be effectively eliminated but be aware that the level of fines will likely increase.


Dennis Hauch

Re: Elimintating Angel Hair From Pe Conveying

Posted on 21. Jan. 2003 - 01:36

Thank you for your replies.

Well dense phase conveying is not possible coz of the high speed.

Can you let me know what are the other possible methods of removing the angel hairs, if any.

Re: Elimintating Angel Hair From Pe Conveying

Posted on 21. Jan. 2003 - 02:52


You could possible use an elutriator at the discharge end of the conveying pipe. This is a countercurrent air washer with its own fan and will lift out the fines and remove them from an outlet nozzle on top while the pellets will fall down into your silo through the bottom opening. A wash air fan does the lifting off of the fines.

If you send us your complete address and the specifications of the conveying system we can send you a proposal for this equipment.

Best regards


Mike Cannon - Belsco Services, USA
(not verified)

Re: Elimintating Angel Hair From Pe Conveying

Posted on 27. Jan. 2003 - 04:50

Treated pipe and elutration are acceptable starts. I would suggest that you also look at blower speed, air volume and line size. If you do not have a cooler and you are running at high velocitys, you will continue to have fines and streamer problems even after you treat the pipe.

If the product is virgin, treating the pipe will help. If the product has additives that will destroy the treatment. Some compounded Polymers will not cause streamers because they are self cleaning the line. If you are conveying with 50c-65c air (120f to 200f) you will possibly coat even treated pipe. Also look at velocity and try to stay below 6000 fpm terminal. It migh help to step the pipe at the end.

There are other variables based on copolymer and homopolymer materials.

You should have a study done to identfy all the problems so when you do spend capitol, you do so wisely.

Belsco Services, Inc.


Re: Elimintating Angel Hair From Pe Conveying

Posted on 6. Feb. 2003 - 06:34

My experience is that about 1/2 of the streamers are formed in long radius bends. You should be able to reduce your problem if you changed the bends from long radius to short radius or to pocket tees.

Roughening the internal surface of the pipe by shot peening, sand blasting, or using a spiral grooved pipe will reduce streamers provided the grade of PE that you are using is not very soft (high melt index and low denisty).

If you can accept emission of streamers to the atmosphere, you can install a receiver at the end of the conveying line with a large vent so that the streamers flow out of the receiver and the pellets flow down due to their differential densities.


Amrit Agarwal

Pneumatic Conveying Consultants

(not verified)

Re: Elimintating Angel Hair From Pe Conveying

Posted on 12. Feb. 2003 - 09:58

Dear kalpesh,

Since some years we are using a typical kind of pneumatical transport at low air velocity. If you are investigating a new installation this application might be of your interrest.

At this low air velocity the behavior is a bit different from high velocity transports. Because of air viscosity a laminar air sheet is formated and almost no contact between the material and pipes will occur. The velocity of the material is the same velocity as the air velocity and thermic influences are almost 0. We even use this method to transport milk powders with increased amount of fat which is extremely sensitive to temperature influences.

Technical specs:

Starting velocity of the system is about 2-3 m/s at 2-2,5 bars overpressure, end velocity is about 6-9 m/s at 0 bars overpressure. Loading degree is about 100-300 kg material / kg air. The amount of air needed can be produced by a normal 6 bar compressor and pipe dimensions are less then traditional transport systems, 2 bars effective air consumption or . Maintenance costs are in your case about 25-50% related to traditional systems. Obstructions in the pipes, caused for example by power drops, are automatically pulled back to the sending vessel, prohibiyting the necessity to take apart the piping.

If this is of your interest, please contact me.