On Sun, 07 Dec 2003 06:24:24 GMT, Rich Hampel
wrote:

Nope.... I suggest a test for you
Take 25-50 grams of the finest dust/crud you can find. Dump it in
upstream of a TP filter and see what happens ..... it will immediately
plug - or will hardly capture anything.

OK; as far as I can tell, particulate fines *will* pass a depth filter
on the first pass. This makes your proposition completely true for one
clause of the either/or proposition.


Change to a high surface area pleated filter dump in 25-50 grams of
crud, another 25-50 grams of crud, another 25-50 grams, then another
25-50 grams, then another .... then it will plug.

OK: as far as I can tell, particulate fines will mostly pass a surface
filter rated for considerably larger particles, and block, for a
filter rated at considerably smaller particles. In the intermediate
range, as is well known, the retained particulate film provides
increasing resistance, and retention of decreasing particle sizes.

Take out the
filter, examine .... you will find a small layer of crud on the
surface. That layer is called a "filter cake". That layer of debris
because the velocity throuth the 'cake' is so much smaller (than the
velocity through a TP etc. roll

This was the only piece that left me uncomfortable. Supposing that
surface filters use lower velocity flow than depth filters in the
fuel polishing role is presuming a design choice that "don't
necessarily happen." Filter cakes are an artifact of surface
filters.

....that it does in fact flow and until the
cake reaches a 'terminal' differential pressure will be the principal
means of particle captu dirt filtering out other dirt.
This cannot happen in a depth filter....because there is *no room for
the 'cake' to form* (inside the filter).

For a true depth filter, you add a filter aid (Diotomaceous earth,
perlite, etc.) on a continual basis so that the deposition is
controlled, the debris is contained in the cake of DE + crud.

I am pleased that you are now referring to industrial uses of depth
filters: - like the one that brings you your tap-water, for instance,
or the depth filter that brings you your room-air.
But pre-loading a filter is not the fuel-polishing approach, so I
don't find it specially relevant,

The
surface of the depth filter holds the cake. If the particles get
inside the depth filter it PLUGS. You can design a 'profiled' depth
filter that has a graded pore density.... bigger pores on the upstream
side, smaller pores on the downstream side ....and that costs about 20
times the price of a toilet paper roll ..... and also is a resin bonded
cellulose matrix. Resin bonded so that the cellulose matrix desnt
collapse upon itself during increasing differential pressure, doesnt
fall apart if it gets wet with water, etc.

You again mention non resin cellulose filters falling apart when wet.
The home test I mentioned recently (I thought) would convince you
that these filter materials *don't get wet* in the intended
application?

Brian W




In article , Brian Whatcott
wrote:

On Fri, 05 Dec 2003 20:02:22 GMT, Rich Hampel
wrote:

Please appreciate that I dont want to appear to be an arrogant
know-it-all after being in on and around critical filtration/separation
most of my working life ...

Sounds good to me...

/// Whats wrong with TP, etc. is that the material used to filter
is not bonded, can digest (make more particles) in the presence of
water --- thus to do the exact opposite of what you are trying to do.

Perhaps a test at home would be helpful.

Take a kitchen collender, A seive or funnel would also work well.
Place a sheet of kitchen roll in the aperture, pleated once to fit.
Spray the surface with Pam, olive oil, or soybean oil or any other oil
Momma has on hand. Make sure the paper is saturated.

Now pour water onto the surface.
Let me know how many particles break loose.
We'll compare notes if you like...
///
My objection to TP - very poor efficiency, migrates particles, migrates
fibers
\////
You either believe the folks who say that depth filters have saved
their fine surface filters from blocking, or you don't.
If you do believe that they are reporting honestly, then I imagine
you would say that at the operational level, that's the kind of
efficiency they prefer?

The home test may (or may not) demonstrate that an oil-soaked paper
tissue does not migrate particles or fibers.
I expect you will let us know if this is misconceived...

DO NOT depend on filters to remove the crud in your system.
////

Or in the version I prefer, referring only to the surface filters that
you use and prefer:
DO NOT depend on fine surface filters to remove crud in your system -
they will certainly block: fast.

Respectfully,

Brian Whatcott

We're starting to flog a dead horse here .... so my very last comment
on all this is:
.... take a toilet paper roll, get a container, immerse it in any oil
that you want and let it soak, then add 1" of water to settle at the
bottom of the container with the TP .... to the bottom of whatever you
contain the toilet paper, let sit a week or more, remove and examine
that the TP has fallen apart where the water has come in contact with
the TP. Now consider that the TP in poorly designed boat system is
held in place by a knife edge seal biteing into the end of the TP
roll........ What happens later on when there is differential pressure
across 'mush' (papier mache) being held by a knife edge seal and has a
differential pressure across it.

Water in fuel oil is common, as an emulsion from the refinery (errors
in handling, etc.) and as the product of condensation on the tank farm
walls with water entering the tankage through the tank vent, etc.

I've herein posted what is the normal industry methods,
'state-of-the-art' ..... and what is 'snake oil'.
......and thats the final comment from me.



You again mention non resin cellulose filters falling apart when wet.
The home test I mentioned recently (I thought) would convince you
that these filter materials *don't get wet* in the intended
application?
Ever hear of gravity settling and equlibrium displacement ? Dont
consder to ever get a job as a lab tech.... you wont make it.


Brian W

I'm pretty much convinced. Traditional filter holders can be had for a
little more than
TP holders and the filters are not all that expensive. In addition I can
pick and choose
which filters to used based upon what happens in actual practice. Since the
holders
are pretty cheap, I am planning to install 2 in series so I can stage filter
porosities if
necessary. Thanks for the insite Rich. IMHO going with proven industry
equipment
just makes sense especially since it is not prohibitively expensive.
Although the TP
and PT units seem attractive, I wouldn't be comfortable with them without a
following
filter (which seems to be the norm) and that drives the cost up both in
terms of space
and also elements.

Rich, do you thing that 2 filters in series is a good idea? If so then how
about vacuum
gauges? Shoufl I install one in between the 2 filters?

Doug
s/v Callista

"Rich Hampel" wrote in message
...
We're starting to flog a dead horse here .... so my very last comment
on all this is:
... take a toilet paper roll, get a container, immerse it in any oil
that you want and let it soak, then add 1" of water to settle at the
bottom of the container with the TP .... to the bottom of whatever you
contain the toilet paper, let sit a week or more, remove and examine
that the TP has fallen apart where the water has come in contact with
the TP. Now consider that the TP in poorly designed boat system is
held in place by a knife edge seal biteing into the end of the TP
roll........ What happens later on when there is differential pressure
across 'mush' (papier mache) being held by a knife edge seal and has a
differential pressure across it.

Water in fuel oil is common, as an emulsion from the refinery (errors
in handling, etc.) and as the product of condensation on the tank farm
walls with water entering the tankage through the tank vent, etc.

I've herein posted what is the normal industry methods,
'state-of-the-art' ..... and what is 'snake oil'.
.....and thats the final comment from me.



You again mention non resin cellulose filters falling apart when wet.
The home test I mentioned recently (I thought) would convince you
that these filter materials *don't get wet* in the intended
application?
Ever hear of gravity settling and equlibrium displacement ? Dont
consder to ever get a job as a lab tech.... you wont make it.


Brian W

Rich, do you thing that 2 filters in series is a good idea?
In a delivery system that has symptoms of gross contamination ....
definitely a prefilter (@ approx 5 times the retention size) will
VASTLY extend the life the final filter.
If you have an active independent recirc. polishing (any kind) then
probably: no .... as the challenge to the delivery system filters will
approach zero. But a belt and suspenders approach is always good for
safety .... your decision.

If so then how
about vacuum
gauges? Shoufl I install one in between the 2 filters?
MOST DEFINITE YES!! The ONLY way to monitor filtation operation
performance is by gauges ---- then you can monitor WHEN to change the
filters. But you should periodically also record the pressures to see
which one is in need of replacement. What you will develop is the
state of the present entire system (history) versus engine hours ...
and then in future change before you reach a critical point .... or
ascertain that the system has degraded by bacterial contamination,
onload of bad fuel, etc. or worse.... if you see that a value has
*decreased* or is less than previous, then you know to change a filter
that has a *hole* and is now bypassing.
Without gauges .... you just wait until something inevitably "chokes"
.... or needlessly throw away a lot of filters with lots of life
remaining.

If you do have TP filters already installed, put a gauge across them
and watch for the differential pressure to vary from day to day ....
indicating bypass or unloading.

Oops! I meant to say that traditional holders a cheaper than the TP units.

Doug
s/v Callista

"doug dotson" wrote in message
...
I'm pretty much convinced. Traditional filter holders can be had for a
little more than
TP holders and the filters are not all that expensive. In addition I can
pick and choose
which filters to used based upon what happens in actual practice. Since
the
holders
are pretty cheap, I am planning to install 2 in series so I can stage
filter
porosities if
necessary. Thanks for the insite Rich. IMHO going with proven industry
equipment
just makes sense especially since it is not prohibitively expensive.
Although the TP
and PT units seem attractive, I wouldn't be comfortable with them without
a
following
filter (which seems to be the norm) and that drives the cost up both in
terms of space
and also elements.

Rich, do you thing that 2 filters in series is a good idea? If so then how
about vacuum
gauges? Shoufl I install one in between the 2 filters?

Doug
s/v Callista

"Rich Hampel" wrote in message
...
We're starting to flog a dead horse here .... so my very last comment
on all this is:
... take a toilet paper roll, get a container, immerse it in any oil
that you want and let it soak, then add 1" of water to settle at the
bottom of the container with the TP .... to the bottom of whatever you
contain the toilet paper, let sit a week or more, remove and examine
that the TP has fallen apart where the water has come in contact with
the TP. Now consider that the TP in poorly designed boat system is
held in place by a knife edge seal biteing into the end of the TP
roll........ What happens later on when there is differential pressure
across 'mush' (papier mache) being held by a knife edge seal and has a
differential pressure across it.

Water in fuel oil is common, as an emulsion from the refinery (errors
in handling, etc.) and as the product of condensation on the tank farm
walls with water entering the tankage through the tank vent, etc.

I've herein posted what is the normal industry methods,
'state-of-the-art' ..... and what is 'snake oil'.
.....and thats the final comment from me.



You again mention non resin cellulose filters falling apart when wet.
The home test I mentioned recently (I thought) would convince you
that these filter materials *don't get wet* in the intended
application?
Ever hear of gravity settling and equlibrium displacement ? Dont
consder to ever get a job as a lab tech.... you wont make it.


Brian W

Rich, do you thing that 2 filters in series is a good idea?
In a delivery system that has symptoms of gross contamination ....
definitely a prefilter (@ approx 5 times the retention size) will
VASTLY extend the life the final filter.
If you have an active independent recirc. polishing (any kind) then
probably: no .... as the challenge to the delivery system filters will
approach zero. But a belt and suspenders approach is always good for
safety .... your decision.

If so then how
about vacuum
gauges? Shoufl I install one in between the 2 filters?
MOST DEFINITE YES!! The ONLY way to monitor filtation operation
performance is by gauges ---- then you can monitor WHEN to change the
filters. But you should periodically also record the pressures to see
which one is in need of replacement. What you will develop is the
state of the present entire system (history) versus engine hours ...
and then in future change before you reach a critical point .... or
ascertain that the system has degraded by bacterial contamination,
onload of bad fuel, etc. or worse.... if you see that a value has
*decreased* or is less than previous, then you know to change a filter
that has a *hole* and is now bypassing.
Without gauges .... you just wait until something inevitably "chokes"
.... or needlessly throw away a lot of filters with lots of life
remaining.

If you do have TP filters already installed, put a gauge across them
and watch for the differential pressure to vary from day to day ....
indicating bypass or unloading.

Oops! I meant to say that traditional holders a cheaper than the TP units.

Doug
s/v Callista

"doug dotson" wrote in message
...
I'm pretty much convinced. Traditional filter holders can be had for a
little more than
TP holders and the filters are not all that expensive. In addition I can
pick and choose
which filters to used based upon what happens in actual practice. Since
the
holders
are pretty cheap, I am planning to install 2 in series so I can stage
filter
porosities if
necessary. Thanks for the insite Rich. IMHO going with proven industry
equipment
just makes sense especially since it is not prohibitively expensive.
Although the TP
and PT units seem attractive, I wouldn't be comfortable with them without
a
following
filter (which seems to be the norm) and that drives the cost up both in
terms of space
and also elements.

Rich, do you thing that 2 filters in series is a good idea? If so then how
about vacuum
gauges? Shoufl I install one in between the 2 filters?

Doug
s/v Callista

"Rich Hampel" wrote in message
...
We're starting to flog a dead horse here .... so my very last comment
on all this is:
... take a toilet paper roll, get a container, immerse it in any oil
that you want and let it soak, then add 1" of water to settle at the
bottom of the container with the TP .... to the bottom of whatever you
contain the toilet paper, let sit a week or more, remove and examine
that the TP has fallen apart where the water has come in contact with
the TP. Now consider that the TP in poorly designed boat system is
held in place by a knife edge seal biteing into the end of the TP
roll........ What happens later on when there is differential pressure
across 'mush' (papier mache) being held by a knife edge seal and has a
differential pressure across it.

Water in fuel oil is common, as an emulsion from the refinery (errors
in handling, etc.) and as the product of condensation on the tank farm
walls with water entering the tankage through the tank vent, etc.

I've herein posted what is the normal industry methods,
'state-of-the-art' ..... and what is 'snake oil'.
.....and thats the final comment from me.



You again mention non resin cellulose filters falling apart when wet.
The home test I mentioned recently (I thought) would convince you
that these filter materials *don't get wet* in the intended
application?
Ever hear of gravity settling and equlibrium displacement ? Dont
consder to ever get a job as a lab tech.... you wont make it.


Brian W

On Sun, 07 Dec 2003 19:41:08 GMT, Rich Hampel
wrote:

...
... take a toilet paper roll, get a container, immerse it in any oil
that you want and let it soak, then add 1" of water to settle at the
bottom of the container with the TP .... to the bottom of whatever you
contain the toilet paper, let sit a week or more, remove and examine
that the TP has fallen apart where the water has come in contact with
the TP.

Wow: now that's a test I can relate to.
If true, it would be a strong disincentive to using unbonded cellulose
media for fuel oil. Though I have mentioned that critical applications
like aero recips and tractor engines specify a water/sediment cup
before the fuel filter - still, a filter medium that will collapse in
the presence of water is a no-no.


I am uncomfortable with the "perpetual"filters which feature narrow
gaps in metal disks. And I'm uncomfortable with bonded surface
filters that will block in a fresh storm (The approach of specifying
an oversized surface filter can postpone the inevitable, it's true)

Now consider that the TP in poorly designed boat system is
held in place by a knife edge seal biteing into the end of the TP
roll........ What happens later on when there is differential pressure
across 'mush' (papier mache) being held by a knife edge seal and has a
differential pressure across it.


Depth filters are routinely used in water-purification and
air-handlers. I don't pretend to speak for *every* industry,
but I can say is this, about the car biz:
the automobile typically uses resin bonded paper surface filters in
the oil line.
Since detergent oil suppresses sludge formation, these filters could
stay in place longer than they typically survive before replacement.

Alternative media are now growing in popularity but there is little
advantage over the resin bonded paper type for lube oil filtration
IMO.
Fuel filtration, on the other hand has become much more demanding
in the mass auto market, since the advent of high pressure fuel
injection. Dual in line filters have become the norm - discarding
the first, moving second to first, and installing new second filter
is one approach to holding down costs.

This is starting to look more like the pleasure boat with diesel power
application. But cars don't typically have to deal with the shaken-up
sediment load - and it is this that has been a continual preoccupation
in this newsgroup thread.

For people who are willing to consider reasonable approaches to diesel
fuel handling (and gasoline for that matter) there can nobody who
can pick fault with using a sampling valve at the low point of a fuel
tank. This can save so much grief from water and visible
contamination that it represents ultra-cheap insurance.

The next reasonable step is to provide a sight glass for early
detection of water and contamination (the 'tractor' approach)

For people who just cannot fit a drain/sampling valve in a sump
(though they cost under $20 typically) and have some reason to avoid a
sediment/water sight cup then using a pair of surface filters offering
large area and rotating them will save most engine outs - but not all.

For people who must do all they can to eliminate engine stoppage from
fuel contamination, then fronting a fuel system with a depth filter
that won't itself break down is cheapish insurance.
I haven't surveyed depth filters in this application recently -
but the ones that no expert could not reasonably object to would be
built something like this:
layered stockinette knit,
string bobbins.

In reviewing what I have written here today, I see I have omitted any
mention of fuel polishing - which is where the thread started.

Here's my personal opinion on this:
boaters and sailors will know if they are likely to get fuel
contamination - it only takes one nasty experience.

They will think that if they replaced all fuel tanks and took on
only clean dry fuel, they could avoid another scare - but that's not
practical for most (and even those who did could still find water in
the fuel - temperature cycling in a ventilated tank can *deposit*
water in the fuel, for sure.)

These are the people who could consider fuel polishing.
So the question is: does fuel-polishing work?
I don't see how you can avoid the conclusion that a reasonable
fuel-polishing design makes things better - if not perfect.

So I would not want people to confuse the idea of polishing fuel
with the idea of paper depth filters - the two ideas don't have to go
together. It seems to me you can polish perfectly well with surface
filters.

Arguably, the surface filter, which might block with sediment is
*still* OK in a (by-pass) fuel polishing layout. If it blocks - so
long as you know it, it does not stop you dead (yet) so long as you
get some warning that the bypass is blocked and the same is likely to
hit the main fuel filtration soon.

What you positively don't want is a main fuel feed blocking.
So strangely enough, I think a depth pre-filter is *most* helpful
here. And it is reasonable to take account of objections to
unbonded paper filter media if they can decompose in water.

As a labor of love, I'll take a look around to see what industrial
depth filters may prove helpful in this application.

Brian W

This is starting to look more like the pleasure boat with diesel power
application. But cars don't typically have to deal with the shaken-up
sediment load - and it is this that has been a continual preoccupation
in this newsgroup thread.

It is this that this trhead is addressing. We have a diesel bus for our
business
and have had no problems with the fuel problems we have had on our boat.
Preoccupation seems to have a negative connotation in that it generally
infers that the issure is not necessarily real or is blown out of
proportion.

For people who are willing to consider reasonable approaches to diesel
fuel handling (and gasoline for that matter) there can nobody who
can pick fault with using a sampling valve at the low point of a fuel
tank. This can save so much grief from water and visible
contamination that it represents ultra-cheap insurance.

Unfortunately, a sample valve at the low point in a fuel system is
very much in violation of CG rules. That said, my tanks have them
and I wouldn't be without them.

The next reasonable step is to provide a sight glass for early
detection of water and contamination (the 'tractor' approach)


The transparent bowl in a Raycor fills that bill.

For people who just cannot fit a drain/sampling valve in a sump
(though they cost under $20 typically) and have some reason to avoid a
sediment/water sight cup then using a pair of surface filters offering
large area and rotating them will save most engine outs - but not all.

For people who must do all they can to eliminate engine stoppage from
fuel contamination, then fronting a fuel system with a depth filter
that won't itself break down is cheapish insurance.
I haven't surveyed depth filters in this application recently -
but the ones that no expert could not reasonably object to would be
built something like this:
layered stockinette knit,
string bobbins.

In reviewing what I have written here today, I see I have omitted any
mention of fuel polishing - which is where the thread started.

Here's my personal opinion on this:
boaters and sailors will know if they are likely to get fuel
contamination - it only takes one nasty experience.

The realistic view is that it is not 'if' but 'when'. Bad fuel can be
obtained
anywhere. But what is the reality it that fuel can go bad just sitting in
the
tanl. So the best supply of fuel in the world will become bad. Sailboats
are especially prone to this since we tend to use little fuel.

They will think that if they replaced all fuel tanks and took on
only clean dry fuel, they could avoid another scare - but that's not
practical for most (and even those who did could still find water in
the fuel - temperature cycling in a ventilated tank can *deposit*
water in the fuel, for sure.)

Water is easily removed by a normal Raycor. It's the water that provides
the interface for critters to grow that becomes the problem.

These are the people who could consider fuel polishing.
So the question is: does fuel-polishing work?

Yes.

I don't see how you can avoid the conclusion that a reasonable
fuel-polishing design makes things better - if not perfect.

Nothing is perfect, that is fur shur!

So I would not want people to confuse the idea of polishing fuel
with the idea of paper depth filters - the two ideas don't have to go
together. It seems to me you can polish perfectly well with surface
filters.

It appears you can. But the filters do not last nearly as long.

Arguably, the surface filter, which might block with sediment is
*still* OK in a (by-pass) fuel polishing layout. If it blocks - so
long as you know it, it does not stop you dead (yet) so long as you
get some warning that the bypass is blocked and the same is likely to
hit the main fuel filtration soon.


My vision of a polishing systemn is that it is iundependent of the engine
system. But I suspect that the engine system will block prior to a
polishing system if the polishing system is not adequate.

What you positively don't want is a main fuel feed blocking.
So strangely enough, I think a depth pre-filter is *most* helpful
here. And it is reasonable to take account of objections to
unbonded paper filter media if they can decompose in water.
Ithink a separate polishing system is better. Prefiltering may lead
to lift-pump failure as things clog up.

As a labor of love, I'll take a look around to see what industrial
depth filters may prove helpful in this application.

Thanks! Much appreciated!

Brian W

This is starting to look more like the pleasure boat with diesel power
application. But cars don't typically have to deal with the shaken-up
sediment load - and it is this that has been a continual preoccupation
in this newsgroup thread.

It is this that this trhead is addressing. We have a diesel bus for our
business
and have had no problems with the fuel problems we have had on our boat.
Preoccupation seems to have a negative connotation in that it generally
infers that the issure is not necessarily real or is blown out of
proportion.

For people who are willing to consider reasonable approaches to diesel
fuel handling (and gasoline for that matter) there can nobody who
can pick fault with using a sampling valve at the low point of a fuel
tank. This can save so much grief from water and visible
contamination that it represents ultra-cheap insurance.

Unfortunately, a sample valve at the low point in a fuel system is
very much in violation of CG rules. That said, my tanks have them
and I wouldn't be without them.

The next reasonable step is to provide a sight glass for early
detection of water and contamination (the 'tractor' approach)


The transparent bowl in a Raycor fills that bill.

For people who just cannot fit a drain/sampling valve in a sump
(though they cost under $20 typically) and have some reason to avoid a
sediment/water sight cup then using a pair of surface filters offering
large area and rotating them will save most engine outs - but not all.

For people who must do all they can to eliminate engine stoppage from
fuel contamination, then fronting a fuel system with a depth filter
that won't itself break down is cheapish insurance.
I haven't surveyed depth filters in this application recently -
but the ones that no expert could not reasonably object to would be
built something like this:
layered stockinette knit,
string bobbins.

In reviewing what I have written here today, I see I have omitted any
mention of fuel polishing - which is where the thread started.

Here's my personal opinion on this:
boaters and sailors will know if they are likely to get fuel
contamination - it only takes one nasty experience.

The realistic view is that it is not 'if' but 'when'. Bad fuel can be
obtained
anywhere. But what is the reality it that fuel can go bad just sitting in
the
tanl. So the best supply of fuel in the world will become bad. Sailboats
are especially prone to this since we tend to use little fuel.

They will think that if they replaced all fuel tanks and took on
only clean dry fuel, they could avoid another scare - but that's not
practical for most (and even those who did could still find water in
the fuel - temperature cycling in a ventilated tank can *deposit*
water in the fuel, for sure.)

Water is easily removed by a normal Raycor. It's the water that provides
the interface for critters to grow that becomes the problem.

These are the people who could consider fuel polishing.
So the question is: does fuel-polishing work?

Yes.

I don't see how you can avoid the conclusion that a reasonable
fuel-polishing design makes things better - if not perfect.

Nothing is perfect, that is fur shur!

So I would not want people to confuse the idea of polishing fuel
with the idea of paper depth filters - the two ideas don't have to go
together. It seems to me you can polish perfectly well with surface
filters.

It appears you can. But the filters do not last nearly as long.

Arguably, the surface filter, which might block with sediment is
*still* OK in a (by-pass) fuel polishing layout. If it blocks - so
long as you know it, it does not stop you dead (yet) so long as you
get some warning that the bypass is blocked and the same is likely to
hit the main fuel filtration soon.


My vision of a polishing systemn is that it is iundependent of the engine
system. But I suspect that the engine system will block prior to a
polishing system if the polishing system is not adequate.

What you positively don't want is a main fuel feed blocking.
So strangely enough, I think a depth pre-filter is *most* helpful
here. And it is reasonable to take account of objections to
unbonded paper filter media if they can decompose in water.
Ithink a separate polishing system is better. Prefiltering may lead
to lift-pump failure as things clog up.

As a labor of love, I'll take a look around to see what industrial
depth filters may prove helpful in this application.

Thanks! Much appreciated!

Brian W