Baghouse Loading Up with Chips
Advice on getting chips to fall into the dust collector container instead of clogging the filter bag. February 12, 2010
Question
I have a Murphy Rodgers MRSE 14 20hp dust collector and I'm having problems with the filters in the baghouse loading up with chips rather than dropping into the container. I plane a lot of pine, so I have a light chip if that makes any difference. I have the electric shaker that comes on after I shut it down, yet over the course of a month or so I have to get up there and shake the bags loose myself. Does anyone have any suggestions for a cure?
Forum Responses
(Dust Collection and Safety Equipment Forum)
From contributor J:
We had a Murphy Rogers baghouse for years that worked well, and then experienced the same problem you’re having when we installed our S4S moulder. The problem is MR does not have enough cloth to air ratio in these units. We tried new bags and then a higher efficiency fan with no success. If you run the shaker too much it will fail and the replacement shaker motors have a defective mounting mechanism that MR will not stand behind. I was thinking a cyclone in combination with the baghouse might have worked but did not want to put any more money into it. We been using a Belfab baghouse with automatic dust transfer for 6 months now, it had a couple minor issues but overall works fine.
From the original questioner:
Thanks for your response. Another fellow contacted me off forum and mentioned putting a cyclone in front of the baghouse to catch the chips and just let the baghouse filter the fines. I don't seem to have as many problems with oak or maple, it's when I run pine or poplar through the moulder that it becomes overwhelmed. I too am not impressed with the shaker on the Murphy Rodgers either. I hope it holds out for me for a while. I run it at the beginning of my start cycle manually and also at the end it kicks in automatically. Would anyone know off the top of their heads how much a cyclone in front of a pull through baghouse add in static pressure to the system, or would I need to add an extra blower in the event I decide to go that route?
From contributor J:
Another thing you could try that would not cost much is to install a blast gate at the inlet side of the baghouse. You have more fan then cloth and this might slow down the air flow and let the chips drop.
From the original questioner:
I have a 10" drop to the moulder and I've always tried to maximize my air velocity so I leave a couple of extra gates open when I'm running it. I'll first try closing everything else down and see if this helps with decreased flow to the baghouse.
From contributor R:
When we added a cyclone in front of the baghouse we went from 15HP to 20HP. Whoever you buy from should be able to run static pressures and determine what you need.
From the original questioner:
Thanks for the response. I thought it would take an extra boost to account for the cyclone. As time permits I'm going to have to start looking into it.
From contributor R:
You might consider reworking the inlet to force the airflow down in to the hopper. This might decrease the chip loading on the bags. You could also review the cloth selection to improve the dust release.
From contributor C:
Read some literature from American Fabric Filter that mentions on the inside of their filter bags, they singe the fabric to get rid of the fabric hairs. This option would most likely help prevent the pine shavings from sticking to the inside of the bags.
From the original questioner:
I still haven't taken the time to climb up and measure the diameter of my bags, but from memory they are closer to 6" rather than 3". I installed a blast gate right before the baghouse and partially closed it to slow down the shavings coming in and it seems to help. What was happening was the shavings were going right up into the bags rather than dropping. After I would shut it down there might be another 20-30 gallons of shavings that would drop before the shaker would come on and then would be a whole lot more that would drop, maybe another 20-30. After a while I would lose suction and have to get up there and manually shake the bags to clear them. When it comes time to replace them I'll definitely take a look at the ones made by American Fabric and Filter.
From contributor F:
Keep an eye on your main ducts to make sure they do not fill up. Adding a blast gate can cause carrying velocity issues in the ductwork. The singe finish for filterbags generally is applied to needled felt bags. If you are using a woven filter, you might consider a shiny (slick) surface - a multifilament fabric or a texturized media. The seamless fabrics (non-Beane) are also quite good in this respect.
