Backup, of course.

"Steven Shelikoff" wrote in message
...
On Sun, 11 Apr 2004 21:57:42 -0400, "Doug Dotson"
wrote:

Is it possible/advisable to place 2 WALBRO fuel pumps
in parallel without any valves? My goal is to be able
to switch between pumps by just applying power to one
or the other without having to adjust valves.

That begs the question why are you going to put two pumps in parallel if
you only want to run one at a time?

Steve

Is there no failure mode that would prevent flow through?

Doug
s/v Callista

"Kelton Joyner" wrote in message
.. .
Unless you have isolation valves to allow servicing of a parallel pump,
series works just as well for backup.
fuel wil flow through the unpowered pump.
Kelton
W4IND
s/v Isle Escape

Larry W4CSC wrote:
(Steven Shelikoff) wrote in
:


That begs the question why are you going to put two pumps in parallel if
you only want to run one at a time?

Steve



Backup?

Larry W4CSC

Is there no failure mode that would prevent flow through?

Doug
s/v Callista

"Kelton Joyner" wrote in message
.. .
Unless you have isolation valves to allow servicing of a parallel pump,
series works just as well for backup.
fuel wil flow through the unpowered pump.
Kelton
W4IND
s/v Isle Escape

Larry W4CSC wrote:
(Steven Shelikoff) wrote in
:


That begs the question why are you going to put two pumps in parallel if
you only want to run one at a time?

Steve



Backup?

Larry W4CSC

I believe I mentioned WALBRO as the pump in use. Not sure what
technology it uses.

Doug
s/v Callista

"Steve" wrote in message
...

"Kelton Joyner" wrote in message
.. .
Unless you have isolation valves to allow servicing of a parallel pump,
series works just as well for backup.
fuel wil flow through the unpowered pump.

Depends on the type of pump. A possitive displacement pump (roller, vane,
etc.) will block the flow from the other pump.. This isn't a problem with
a
diaphram or centrifigal it would work, however would subject the idle pump
components to pressure or could be a source of leakage once it failed.

Steve
s/v Good Intentions

I believe I mentioned WALBRO as the pump in use. Not sure what
technology it uses.

Doug
s/v Callista

"Steve" wrote in message
...

"Kelton Joyner" wrote in message
.. .
Unless you have isolation valves to allow servicing of a parallel pump,
series works just as well for backup.
fuel wil flow through the unpowered pump.

Depends on the type of pump. A possitive displacement pump (roller, vane,
etc.) will block the flow from the other pump.. This isn't a problem with
a
diaphram or centrifigal it would work, however would subject the idle pump
components to pressure or could be a source of leakage once it failed.

Steve
s/v Good Intentions

That is interesting because the electric pump which is now
used for priming is installed in series with the mechanical
lift pump. Never had any problem with things not working.
This setup was done by a reputable outfit and has been done
on hundreds of boat from what I understand.

Doug
s/v Callista

"Rich Hampel" wrote in message
...
The Walbro is a 'wobble plate' diaphragm and therefore not suitable for
series installation. If the wobble plate stops in a position such
that one pump is blocked then both pumps will not flow.

For parallel installation application - a simple thumb-cock on the
outlet of each pump would be sufficient.


In article , Kelton Joyner
wrote:

Unless you have isolation valves to allow servicing of a parallel pump,
series works just as well for backup.
fuel wil flow through the unpowered pump.
Kelton
W4IND
s/v Isle Escape

Larry W4CSC wrote:
(Steven Shelikoff) wrote in
:


That begs the question why are you going to put two pumps in parallel
if
you only want to run one at a time?

Steve



Backup?

Larry W4CSC

That is interesting because the electric pump which is now
used for priming is installed in series with the mechanical
lift pump. Never had any problem with things not working.
This setup was done by a reputable outfit and has been done
on hundreds of boat from what I understand.

Doug
s/v Callista

"Rich Hampel" wrote in message
...
The Walbro is a 'wobble plate' diaphragm and therefore not suitable for
series installation. If the wobble plate stops in a position such
that one pump is blocked then both pumps will not flow.

For parallel installation application - a simple thumb-cock on the
outlet of each pump would be sufficient.


In article , Kelton Joyner
wrote:

Unless you have isolation valves to allow servicing of a parallel pump,
series works just as well for backup.
fuel wil flow through the unpowered pump.
Kelton
W4IND
s/v Isle Escape

Larry W4CSC wrote:
(Steven Shelikoff) wrote in
:


That begs the question why are you going to put two pumps in parallel
if
you only want to run one at a time?

Steve



Backup?

Larry W4CSC

Doug,

The way the Walbro is built, the flow may or may not be blocked
depending on the position that the wobble plate is in. Bottom line if
you want fully automatic change over for backup, plumb them in parallel
with a check valve on the output of each. Then you can wire them to a
SPDT center off switch to shift from one to the other.

Doug Dotson wrote:
Is there no failure mode that would prevent flow through?

Doug
s/v Callista

"Kelton Joyner" wrote in message
.. .

Unless you have isolation valves to allow servicing of a parallel pump,
series works just as well for backup.
fuel wil flow through the unpowered pump.
Kelton
W4IND
s/v Isle Escape

Larry W4CSC wrote:

(Steven Shelikoff) wrote in
:



That begs the question why are you going to put two pumps in parallel if
you only want to run one at a time?

Steve



Backup?

Larry W4CSC




--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

Doug,

The way the Walbro is built, the flow may or may not be blocked
depending on the position that the wobble plate is in. Bottom line if
you want fully automatic change over for backup, plumb them in parallel
with a check valve on the output of each. Then you can wire them to a
SPDT center off switch to shift from one to the other.

Doug Dotson wrote:
Is there no failure mode that would prevent flow through?

Doug
s/v Callista

"Kelton Joyner" wrote in message
.. .

Unless you have isolation valves to allow servicing of a parallel pump,
series works just as well for backup.
fuel wil flow through the unpowered pump.
Kelton
W4IND
s/v Isle Escape

Larry W4CSC wrote:

(Steven Shelikoff) wrote in
:



That begs the question why are you going to put two pumps in parallel if
you only want to run one at a time?

Steve



Backup?

Larry W4CSC




--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

Glenn,

That is pretty much what I was figuring on other than the
check valves. Not sure I want a center off switch though.
I would prefer that one or the other be on at all times. I'm
also considering putting an hours-meter on each so that I
can balance the use.

Doug
s/v Callista

"Glenn Ashmore" wrote in message
news:7wzec.16$uF3.13@lakeread04...
Doug,

The way the Walbro is built, the flow may or may not be blocked
depending on the position that the wobble plate is in. Bottom line if
you want fully automatic change over for backup, plumb them in parallel
with a check valve on the output of each. Then you can wire them to a
SPDT center off switch to shift from one to the other.

Doug Dotson wrote:
Is there no failure mode that would prevent flow through?

Doug
s/v Callista

"Kelton Joyner" wrote in message
.. .

Unless you have isolation valves to allow servicing of a parallel pump,
series works just as well for backup.
fuel wil flow through the unpowered pump.
Kelton
W4IND
s/v Isle Escape

Larry W4CSC wrote:

(Steven Shelikoff) wrote in
:



That begs the question why are you going to put two pumps in parallel
if
you only want to run one at a time?

Steve



Backup?

Larry W4CSC




--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com