Just out of curiosity -- if the old bags ran at 2-3" wg WHY did you replace them with a more expensive bag?

Operationally, the PTFE will allow better cleaning efficiency of the material and is usually used when the product tends to blind the filtration media and higher differential pressures are experienced.

Regards ■

Sounds like you may have a larger volume - process related application. If the filters are working harder to capture more (finer) particulate with the same gas volume then a higher pressure drop may not be unreasonable result because you are building more of a filter cake and passing less material through bags then you had in before.

I have been involved in changing out old bags with PTFE and have not experienced that magnitude of an increase on pneumatic conveying applicatipns of filter receivers and silo bin vents

Regards. ■

PTFE and (Goretex) coated filter bags will always show a higher d.p. than standard materials. Your filter bag supplier should have told you this. PTFE is an expensive solution, basically the last resort.

2" to 3" doesn't sound too high a d.p. so it sounds as if your filtration velocity (air-to-cloth ratio) is O.K.

If your standard bags are passing too much dust, then there are many styles of cloth which could be tried before going to the extreme of PTFE. You need to talk to a competent filter bag supplier.

Over-cleaning of the standard bags is another trap. Too frequent pulsing can cause sifting of dust through the medium. You also need to allow the filter cake to develop on new bags before turning the cleaning system on. A artificial filter cake of hydrated lime is often used to "season" new filter bags if the application is sensitive.

What is the application, the airflow and the cloth area?

Michael Reid. ■

Originally Posted by TedHNewEngland

We have recently installed PTFE coated filter bags in several of our dust collectors, replacing standard polyester bags.

I realize that these are more efficient than the standard bags, but the differential pressures are running at about 7", the old ones ran at ~2-3".

Does anyone have any experience with these? Is this normal?

Thanks

Ted

Hello Ted,

Ptfe coating treatment makes material with lower air permeability and higher efficiency. It is normal that the pressure will be higher.

We are nonwoven needle felt and filter bags maker, our ptfe foaming coating is an advanced technology in the world. It has better air permeability.

Any interest,pls contact me.

Best regards,

Sophie

Shanghai BG Industrial Fabric Co.,LTD.

Tel:+86 21 54893777 Ext. 255

Fax:+86 21 54893772

Mobile: +86-13601851502

Email:ycxsophie@hotmail.com,sophie@bgfiltech.com

www.bgfiltech.com

1106,No 9, Lane 300, East Nandan Rd, Shanghai, 200030, China. ■

As for the Polyester needle felt with PTFE membrane finished, the air permeability will down too much when compared with the normal one, for example, as usual, the normal felt the air permeability is about 14CBM/m2.min@200Pa, but if with membrane finished, they will just about 4~6.

So, the membrane will increase the filter effeciency, that no doubt about it, but will lower the filter speed of course.

For elongate the bags life, just down the air flow is not the best chooice I am afraid, that's to say the speed will lower much, on the contrary, high air flow means the bigger pressure on the bags, so the bags may damaged soon.

so I personally believe that the best choice is to increase the filter area.

Thanks.

Welcome to communicate with me for dust collector matters.

website: http://www.filtercloth.whipie.com

mail: filtercloth@126.com ■