Small shop dust collection
As some of you know, I have a small basement shop. For dust collection I have a Ridgid WD1450 shop vac with a CleamStream filter. I run that through a cyclone dust separator.
When I last cleaned the filter, per instructions, by tapping out the dust and rinsing the outside of the filter under running water, I noticed that the filter media has gotten noticeably darker. I really haven't a noticed a significant difference in suction but, if it has gradually decreased over the couple of years that I've had this filter I may not have noticed it. So, I wrote to the the manufacturer asking how I would know when it was time to replace the filter. I received a prompt and very informative response and I'd like to share it for any of you that use that filter and have a similar setup.
"Discoloration after use and cleaning (rinsing with water) is not necessarily a sign the filter needs to be replaced. Some dust can actually stick to the membrane and not be easily removed. In the case of wood dust, some dust may have same or sticky tar like substance that can be difficult to remove even from our ePTFE membrane.
That being said, the two drivers that determine when it's time to replace are as follows:
1. If you notice the reduced suction or lack of recovery of suction after cleaning (either tapping or rinsing), then it may be time to replace your filter.
2. If you notice small fibers or strings at the pleat tips or in areas where these is dark discoloration, this can be a sign of membrane abrasion and is an indicator of the filter needs to be replaced.
In regards to your specific application you describe below, I want to highlight the fact that by using a cyclone separator, you are sending only the fine particulate to the filter itself. Dust that is mixed with larger particles and debris can have a loosely packed dust cake and thus still allow the filter to pull air even though there may be significant dust within the pleated material. The loose dust cake still has a permeability that allows the flow of air. If you are only sending the fine dust to the filter, this will have a more densely packed dust cake and thus the suction will be reduced more quickly and the pressure drop will increase faster. These smaller dust particles are also typically more difficult to remove from any filter (even our membrane filters) as they can be more agglomerative (sticks to itself) and also more abrasive in nature. If you think of this finer dust as being similar to "sand blasting", it can effectively reduce filter life over time.
I under(stand) the reasoning for using a cyclone separator and how it separates the dust from the larger chips etc, but in most testing we have done, this can reduce the filter life over time because our filter is only seeing the more difficult, abrasive type of fine dust versus a broad distribution of particle sizes.
We guarantee our filters for 1 year. In most applications, the non-everyday user can see several years of filter life before needing to change. Another question to ask is, when you first turn on your vacuum, do you see any puff of dust emissions from the vacuum motor? If you see any dust coming through the vacuum, that could be a final indicator that it is time to replace your filter.
Hope this information is helpful."