Following proper start up and shut down procedures for your baghouse dust collectors is not only beneficial to the life of filter media in dust collector applications, but also to your baghouse system as a whole. Proper start up and shut down procedures are designed to prevent potentially harmful dew point excursions and help establish the formulation of dust cakes across the filter bags prior to full activation of the system.
Think of the dust cake as a protective layer surrounding the bag itself. Contrary to what many think, it is this layer that actually filters the air/dust stream while the bag simply supports the “dustcake.” By using a pre-coat to create this initial “dustcake,” a porous and efficient layer is created prior to the system starting up. This is due to the various sizes of particulates found within the pre-coat, as opposed to a more uniform particulate size often found in process applications. The porous cake allows air to make its way through the tiny crevices, but the dust particulate and sticky/tacky substances cannot.
Check to make sure the filter media (filter bags & cages or pleated filter elements) are installed properly.
Perform a leak test before start up of the baghouse dust collector. This will enable you to identify any filters that may have been installed incorrectly before the collector is brought back up on line.
Activate the dust removal system. This might include rotary airlocks, pneumatic conveying equipment or discharge devices. This will help ensure any residual dust is removed prior to full system activation.
Activate main fan.
If new filter media has been installed, introduce pre-coat powder to system.
Activate the bag house cleaning mechanism (make sure the cleaning system is set to pulse only when the operation/OEM recommends).
Begin dust collection / system process.
For applications dealing with extreme temperatures (above 250°F), and auxiliary heat sources and gases, preheating your baghouse to prevent moisture condensation is a crucial, yet overlooked step. This should be carried out once a measurement of the temperature within the baghouse states that it is appropriate to continue. This minimizes the potential of moisture condensation or passing through the dew point at start up where one could potentially activate chemically harmful particulates or cause dust agglomeration that could plug the filter media.
The fan should run for a short time span after the heat source and dust collection pick-up points are shut off, until the internal temperatures and conditions stabilize to the appropriate levels. This helps the “stagnant” gas stream to be expelled from the system as fast as possible, again minimizing dew point excursions. Below is a step-by-step process on how to properly shutdown your baghouse system.
Shut down the operation or process where dust is being collected.
Continue operation of dust-removal conveyor and cleaning of bags for 10 to 20 minutes to ensure good removal of collected dust.
Shut down the main system fan.
Shut down the bag house cleaning system.
Shut down the dust removal system that’s transferring particulates/powders into the hopper.