how should a filter be tested

[edwardh1]

I got this from Purolater
PureOne filters meet the flow requirements of automotive applications. We
test our filters per SAE specification HS806 Chapter 1, and the standard
flow rate requirement that we follow states that the pressure differential
(between inlet and outlet) shall not exceed 3.0 psi at a flow rate of 3.0
gpm. On the PL30001 filters, flow restriction is 0.8 psi (avg) at 3.0 gpm.
#################
None of the tests done and reported here use these GPMs
- seems some testing should be done at 3 GPM if thats recognized as some sort of industry standard??
Pressure drop REALLY goes up as flow rate goes up -
testing say at 10 or 20 GPM would be meaningless in a system that runs at a lower rate

 

[labman]

In the equation for flow, pressure and volume are proportional. Double the volume, and you double the differential pressure. The 3 gallons a minute may be a realistic figure to test filters for the average engine. I would still like to see some data for used filters. Do they ever trap enough material to reduce flow before they are replaced? Are filters with more area better for your engine?

 

[edwardh1]

my thought was that all the oil filter tests / examinations I have seen tho well intentioned seem to skip over this SAe standard - seems we should be testing them to this first at least.
as an exageratiom if we tested filters at40 gpm, I think the results would be meaningless.
Maybe thats why sae wrote the standard

 

[XS650]

quote:

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Originally posted by edwardh1:

Pressure drop REALLY goes up as flow rate goes up -
testing say at 10 or 20 GPM would be meaningless in a system that runs at a lower rate

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IIRC, many engines actually do pump 10 gpm or more at high rpm. It would be nice to know how a filter pperforms at max rpm too.

 

[AV8R]

Labman, I agree with you that if you linearize the Navier-Stokes equations, you can get a term with linear dependence of deltaP on v, as I recall, the Hagen-Poiseville equation for fully-developed laminar flow. But in the measurements I have made, it didn't work that way. In the filter tests I have done, the pressure drop, across actual filters in actual engines with actual hot oil, was limited by the size of the filter outlet orifice, exhibiting a pressure drop proportional to the square of the velocity, as one would expect of flow through an orifice. (That is, flow proportional to sqrt(deltaP), non-laminar flow). The pressure drop across all of the filters we tested was fairly low, a couple of PSI max. Say in a 50 PSI system, this might reduce supply to the engine to 48 PSI. Taking the square root gives 0.98, or a 2% reduction in flow, which is insignificant, and already anticipated by the engine designer anyway. This is basically why I think that all of the concern on this board about "filter flow" is pretty meaningless: most filters, in actual use, will insignificantly reduce oil flow rate to the engine, which was designed to have more than enough in the first place. Manufacturers, though, are quick to use advertising to exploit imaginary advantages to appeal to consumers.