Originally Posted By: DuckRyder
Originally Posted By: CR94
Originally Posted By: DuckRyder
What does “straight” pleats do for us?
Tells us the media bundle wasn't buckled by excessive compressive stress, and didn't warp due to moisture.
On the buckling by excessive compressive force: I’ve seen this brought up a couple of times - Doesn’t the center tube support the compression? It doesn’t seem that the media should be under any compressive stress. Is there something I am missing?
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Fair question. I'd suspect whether the axial (spring+hydraulic) force is carried mainly by the media or by a center tube (or shared) probably varies widely, depending on the filter design and manufacturing details. On most modern cartridge filters I've seen, and maybe some spin-ons (e.g., end-capless Densos? early e-cores?) there's effectively no center tube* lending support against that force. Whether the funky crooked pleats we see in photos on bitog are due to compressive buckling failure or to other causes, I can't tell. Both cartridge filters I've removed so far from my present car came out undistorted, with the pleats still straight.
*Cartridges do have what amounts to center tubes as part of the cap, to support the media against inward (radial) collapse, at least in theory. (But in SOME brands of filters, the inside of the media bundle is so far outside the center tube that it could partially collapse to a considerable extent before touching the center tube.)