Steven Shelikoff wrote:


...filter media, by definition we are ignoring the case. My question is
why does it matter strictly to the performance of the filter media
whether fuel is being pushed through by a pump or pushed through by
atmospheric pressure?

It's often a function of system and pump design. For e.g., when
using a centrifugal pump (or liquid ring, and sometimes vane), the
inlet is typically sized larger than the outlet. The result is
higher fluid velocity on the outlet side versus the 'suction'
side. Higher velocity, higher impact pressure, often resulting in
better particulate retention.

Additionally, all pump curves I've seen are, to some degree, more
dependent on suction head than discharge head, and cavitation
becomes an issue (i.e. efficiency drops more rapidly for loss of
head on the suction side than for increase in head on the
discharge side). Thus, when the filter begins to clog, you not
only lose flowrate due to loop pressure drop increasing, you lose
pump *efficiency* as well, exacerbating the problem. The result
is, typically, less allowable filter loading before the system
performance is affected, so more frequent filter changes.

Whether this is an issue with the Racors or not, I have no idea,
not being familiar with them. But if you want maximum system
efficiency, maximum filter loading capacity, and longest interval
between changeouts, discharge filtration is the way to go.

Or...just use more *wind*, and all this diesel stuff is moot :-)

Keith Hughes

On Sat, 10 Jan 2004 12:53:52 -0700, Keith Hughes
wrote:

Steven Shelikoff wrote:


...filter media, by definition we are ignoring the case. My question is
why does it matter strictly to the performance of the filter media
whether fuel is being pushed through by a pump or pushed through by
atmospheric pressure?

It's often a function of system and pump design. For e.g., when
using a centrifugal pump (or liquid ring, and sometimes vane), the
inlet is typically sized larger than the outlet. The result is
higher fluid velocity on the outlet side versus the 'suction'
side. Higher velocity, higher impact pressure, often resulting in
better particulate retention.

Sounds like we have to limit this further. Ok, I'll limit it to the
typical filter, like a Racor fuel filter, with a typical pump, like the
Walbro, with the pump either before or after the Racor attached to it by
at least a few feet of hose and in both cases, a 3 psi difference
between the outlet and inlet. How would you explain a difference in the
performance of the filter media between the pump pushing or pulling the
fuel?

Additionally, all pump curves I've seen are, to some degree, more
dependent on suction head than discharge head, and cavitation
becomes an issue (i.e. efficiency drops more rapidly for loss of
head on the suction side than for increase in head on the
discharge side). Thus, when the filter begins to clog, you not
only lose flowrate due to loop pressure drop increasing, you lose
pump *efficiency* as well, exacerbating the problem. The result
is, typically, less allowable filter loading before the system
performance is affected, so more frequent filter changes.

Basically, the above is saying that the pump can push better than it cal
pull. That I agree with. But if it can pull well enough to maintain
enough pressure differential across the filter up to the point where you
would want to change the filter anyway, it becomes a non-issue.
Especially if you're not as worried about filter element replacement
costs as you are about other aspects of the system such as polishing
ability and safety.

Whether this is an issue with the Racors or not, I have no idea,
not being familiar with them. But if you want maximum system
efficiency, maximum filter loading capacity, and longest interval
between changeouts, discharge filtration is the way to go.

And if I want maximum life out of the pump (it's always seeing clean
fuel), filtration capability (the pump isn't emulsifying the fuel just
before it gets to the filter) and safety (a leak will shut the system
down rather than pump fuel into the bilge) then I'd go the other way.

You pick the parameters you want to maximize and go with it.

Or...just use more *wind*, and all this diesel stuff is moot :-)

Yup.

Steve

Steven Shelikoff wrote:

Sounds like we have to limit this further. Ok, I'll limit it to the
typical filter, like a Racor fuel filter, with a typical pump, like the
Walbro, with the pump either before or after the Racor attached to it by
at least a few feet of hose and in both cases, a 3 psi difference
between the outlet and inlet. How would you explain a difference in the
performance of the filter media between the pump pushing or pulling the
fuel?

I did not claim there *is* a difference. As long as the DP is the
same, and fluid velocity is the same, there should be no
appreciable difference. I mean, if you continue to "limit this
further" such that all pneumatic parameters are identical,
operating in a steady state condition, then of course there's no
difference between suction and pressure filtration. There can't
be, QED.

The point I was making is that in real world applications,
parameters will not be identical, and the system is not steady
state. So you have to factor in the overall system design (pump
curves, filter cartridge design, flow rates, velocities, etc.) to
determine if there may be an impact, since the filter does *not*
operate independently of the overall system. For your basic
'rock-n-alligator' filters, I would not expect any differences.

And if I want maximum life out of the pump

You put a strainer in front of it.

You pick the parameters you want to maximize and go with it.

So true...

Keith Hughes

On Sat, 10 Jan 2004 16:29:32 -0700, Keith Hughes
wrote:

Steven Shelikoff wrote:

Sounds like we have to limit this further. Ok, I'll limit it to the
typical filter, like a Racor fuel filter, with a typical pump, like the
Walbro, with the pump either before or after the Racor attached to it by
at least a few feet of hose and in both cases, a 3 psi difference
between the outlet and inlet. How would you explain a difference in the
performance of the filter media between the pump pushing or pulling the
fuel?

I did not claim there *is* a difference. As long as the DP is the
same, and fluid velocity is the same, there should be no
appreciable difference. I mean, if you continue to "limit this
further" such that all pneumatic parameters are identical,
operating in a steady state condition, then of course there's no
difference between suction and pressure filtration. There can't
be, QED.

Exactly my point. I don't see how there could be a difference between
pushing and pulling "all else being equal". But Rich keeps saying there
is a difference and that the difference is unexplainable and is just
waiting for a doctoral thesis in filterology to explain it.

The point I was making is that in real world applications,
parameters will not be identical, and the system is not steady
state. So you have to factor in the overall system design (pump
curves, filter cartridge design, flow rates, velocities, etc.) to
determine if there may be an impact, since the filter does *not*
operate independently of the overall system. For your basic
'rock-n-alligator' filters, I would not expect any differences.

And if I want maximum life out of the pump

You put a strainer in front of it.

The pump already comes with a strainer. But it's a royal PITA to
replace and really only gets out the largest of crud. For a "strainer"
to be effective, it's just another filtration stage and we're back to
sucking fuel through a filter rather than pushing it through.

You pick the parameters you want to maximize and go with it.

So true...

Steve

I'm building my system with one filter (10uM) in front of the pump and
one (1uM) after the pump. That way the pump is protected. Incidently,
are the regular Apollo ball valves available at West Marine suitable
for diesel? I have noticed Apollo valves in a number of the pics of
systems folks have sent me but not sure if they are the typical ones.
I had planned on using the small Tempo valves that are specifically
made for fuel and are alot smaller.

Doug
s/v Callista

"Steven Shelikoff" wrote in message
...
On Sat, 10 Jan 2004 16:29:32 -0700, Keith Hughes
wrote:

Steven Shelikoff wrote:

Sounds like we have to limit this further. Ok, I'll limit it to the
typical filter, like a Racor fuel filter, with a typical pump, like the
Walbro, with the pump either before or after the Racor attached to it
by
at least a few feet of hose and in both cases, a 3 psi difference
between the outlet and inlet. How would you explain a difference in
the
performance of the filter media between the pump pushing or pulling the
fuel?

I did not claim there *is* a difference. As long as the DP is the
same, and fluid velocity is the same, there should be no
appreciable difference. I mean, if you continue to "limit this
further" such that all pneumatic parameters are identical,
operating in a steady state condition, then of course there's no
difference between suction and pressure filtration. There can't
be, QED.

Exactly my point. I don't see how there could be a difference between
pushing and pulling "all else being equal". But Rich keeps saying there
is a difference and that the difference is unexplainable and is just
waiting for a doctoral thesis in filterology to explain it.

The point I was making is that in real world applications,
parameters will not be identical, and the system is not steady
state. So you have to factor in the overall system design (pump
curves, filter cartridge design, flow rates, velocities, etc.) to
determine if there may be an impact, since the filter does *not*
operate independently of the overall system. For your basic
'rock-n-alligator' filters, I would not expect any differences.

And if I want maximum life out of the pump

You put a strainer in front of it.

The pump already comes with a strainer. But it's a royal PITA to
replace and really only gets out the largest of crud. For a "strainer"
to be effective, it's just another filtration stage and we're back to
sucking fuel through a filter rather than pushing it through.

You pick the parameters you want to maximize and go with it.

So true...

Steve

On Sun, 11 Jan 2004 10:52:16 -0500, "Doug Dotson"
wrote:

I'm building my system with one filter (10uM) in front of the pump and
one (1uM) after the pump. That way the pump is protected. Incidently,
are the regular Apollo ball valves available at West Marine suitable
for diesel? I have noticed Apollo valves in a number of the pics of
systems folks have sent me but not sure if they are the typical ones.
I had planned on using the small Tempo valves that are specifically
made for fuel and are alot smaller.

The valves would have letters stamped on it for what they're rated for.
I forget the order of the initials but they're ones for gas, water, oil,
air, etc. If it's rated for oil (has an O in the rating) it should work
fine for diesel fuel.

Steve

On Sun, 11 Jan 2004 10:52:16 -0500, "Doug Dotson"
wrote:

I'm building my system with one filter (10uM) in front of the pump and
one (1uM) after the pump. That way the pump is protected. Incidently,
are the regular Apollo ball valves available at West Marine suitable
for diesel? I have noticed Apollo valves in a number of the pics of
systems folks have sent me but not sure if they are the typical ones.
I had planned on using the small Tempo valves that are specifically
made for fuel and are alot smaller.

The valves would have letters stamped on it for what they're rated for.
I forget the order of the initials but they're ones for gas, water, oil,
air, etc. If it's rated for oil (has an O in the rating) it should work
fine for diesel fuel.

Steve

Make sure the Apollo valves are specifically rated for fuel. Something
about the seats is different.
I noticed this when I was building my polishing system.

"Doug Dotson" wrote in message
...
I'm building my system with one filter (10uM) in front of the pump and
one (1uM) after the pump. That way the pump is protected. Incidently,
are the regular Apollo ball valves available at West Marine suitable
for diesel? I have noticed Apollo valves in a number of the pics of
systems folks have sent me but not sure if they are the typical ones.
I had planned on using the small Tempo valves that are specifically
made for fuel and are alot smaller.

Doug
s/v Callista

"Steven Shelikoff" wrote in message
...
On Sat, 10 Jan 2004 16:29:32 -0700, Keith Hughes
wrote:

Steven Shelikoff wrote:

Sounds like we have to limit this further. Ok, I'll limit it to the
typical filter, like a Racor fuel filter, with a typical pump, like
the
Walbro, with the pump either before or after the Racor attached to it
by
at least a few feet of hose and in both cases, a 3 psi difference
between the outlet and inlet. How would you explain a difference in
the
performance of the filter media between the pump pushing or pulling
the
fuel?

I did not claim there *is* a difference. As long as the DP is the
same, and fluid velocity is the same, there should be no
appreciable difference. I mean, if you continue to "limit this
further" such that all pneumatic parameters are identical,
operating in a steady state condition, then of course there's no
difference between suction and pressure filtration. There can't
be, QED.

Exactly my point. I don't see how there could be a difference between
pushing and pulling "all else being equal". But Rich keeps saying there
is a difference and that the difference is unexplainable and is just
waiting for a doctoral thesis in filterology to explain it.

The point I was making is that in real world applications,
parameters will not be identical, and the system is not steady
state. So you have to factor in the overall system design (pump
curves, filter cartridge design, flow rates, velocities, etc.) to
determine if there may be an impact, since the filter does *not*
operate independently of the overall system. For your basic
'rock-n-alligator' filters, I would not expect any differences.

And if I want maximum life out of the pump

You put a strainer in front of it.

The pump already comes with a strainer. But it's a royal PITA to
replace and really only gets out the largest of crud. For a "strainer"
to be effective, it's just another filtration stage and we're back to
sucking fuel through a filter rather than pushing it through.

You pick the parameters you want to maximize and go with it.

So true...

Steve

I decide to go with the Tempo type. Already had one and picked
up a 3-way last spring at the used boat parts place in St. Augustine.
Assembled the filters and most of the plumbing today, pump should
arrive on Tuesday ($81 brand new on eBay). I;ll take a digipic when
done for anyone that is interested in seeing it.

Doug
s/v Callista

"Keith" wrote in message
...
Make sure the Apollo valves are specifically rated for fuel. Something
about the seats is different.
I noticed this when I was building my polishing system.

"Doug Dotson" wrote in message
...
I'm building my system with one filter (10uM) in front of the pump and
one (1uM) after the pump. That way the pump is protected. Incidently,
are the regular Apollo ball valves available at West Marine suitable
for diesel? I have noticed Apollo valves in a number of the pics of
systems folks have sent me but not sure if they are the typical ones.
I had planned on using the small Tempo valves that are specifically
made for fuel and are alot smaller.

Doug
s/v Callista

"Steven Shelikoff" wrote in message
...
On Sat, 10 Jan 2004 16:29:32 -0700, Keith Hughes
wrote:

Steven Shelikoff wrote:

Sounds like we have to limit this further. Ok, I'll limit it to
the
typical filter, like a Racor fuel filter, with a typical pump, like
the
Walbro, with the pump either before or after the Racor attached to
it
by
at least a few feet of hose and in both cases, a 3 psi difference
between the outlet and inlet. How would you explain a difference
in
the
performance of the filter media between the pump pushing or pulling
the
fuel?

I did not claim there *is* a difference. As long as the DP is the
same, and fluid velocity is the same, there should be no
appreciable difference. I mean, if you continue to "limit this
further" such that all pneumatic parameters are identical,
operating in a steady state condition, then of course there's no
difference between suction and pressure filtration. There can't
be, QED.

Exactly my point. I don't see how there could be a difference between
pushing and pulling "all else being equal". But Rich keeps saying
there
is a difference and that the difference is unexplainable and is just
waiting for a doctoral thesis in filterology to explain it.

The point I was making is that in real world applications,
parameters will not be identical, and the system is not steady
state. So you have to factor in the overall system design (pump
curves, filter cartridge design, flow rates, velocities, etc.) to
determine if there may be an impact, since the filter does *not*
operate independently of the overall system. For your basic
'rock-n-alligator' filters, I would not expect any differences.

And if I want maximum life out of the pump

You put a strainer in front of it.

The pump already comes with a strainer. But it's a royal PITA to
replace and really only gets out the largest of crud. For a
"strainer"
to be effective, it's just another filtration stage and we're back to
sucking fuel through a filter rather than pushing it through.

You pick the parameters you want to maximize and go with it.

So true...

Steve

I decide to go with the Tempo type. Already had one and picked
up a 3-way last spring at the used boat parts place in St. Augustine.
Assembled the filters and most of the plumbing today, pump should
arrive on Tuesday ($81 brand new on eBay). I;ll take a digipic when
done for anyone that is interested in seeing it.

Doug
s/v Callista

"Keith" wrote in message
...
Make sure the Apollo valves are specifically rated for fuel. Something
about the seats is different.
I noticed this when I was building my polishing system.

"Doug Dotson" wrote in message
...
I'm building my system with one filter (10uM) in front of the pump and
one (1uM) after the pump. That way the pump is protected. Incidently,
are the regular Apollo ball valves available at West Marine suitable
for diesel? I have noticed Apollo valves in a number of the pics of
systems folks have sent me but not sure if they are the typical ones.
I had planned on using the small Tempo valves that are specifically
made for fuel and are alot smaller.

Doug
s/v Callista

"Steven Shelikoff" wrote in message
...
On Sat, 10 Jan 2004 16:29:32 -0700, Keith Hughes
wrote:

Steven Shelikoff wrote:

Sounds like we have to limit this further. Ok, I'll limit it to
the
typical filter, like a Racor fuel filter, with a typical pump, like
the
Walbro, with the pump either before or after the Racor attached to
it
by
at least a few feet of hose and in both cases, a 3 psi difference
between the outlet and inlet. How would you explain a difference
in
the
performance of the filter media between the pump pushing or pulling
the
fuel?

I did not claim there *is* a difference. As long as the DP is the
same, and fluid velocity is the same, there should be no
appreciable difference. I mean, if you continue to "limit this
further" such that all pneumatic parameters are identical,
operating in a steady state condition, then of course there's no
difference between suction and pressure filtration. There can't
be, QED.

Exactly my point. I don't see how there could be a difference between
pushing and pulling "all else being equal". But Rich keeps saying
there
is a difference and that the difference is unexplainable and is just
waiting for a doctoral thesis in filterology to explain it.

The point I was making is that in real world applications,
parameters will not be identical, and the system is not steady
state. So you have to factor in the overall system design (pump
curves, filter cartridge design, flow rates, velocities, etc.) to
determine if there may be an impact, since the filter does *not*
operate independently of the overall system. For your basic
'rock-n-alligator' filters, I would not expect any differences.

And if I want maximum life out of the pump

You put a strainer in front of it.

The pump already comes with a strainer. But it's a royal PITA to
replace and really only gets out the largest of crud. For a
"strainer"
to be effective, it's just another filtration stage and we're back to
sucking fuel through a filter rather than pushing it through.

You pick the parameters you want to maximize and go with it.

So true...

Steve