Parallelling fuel pumps
 

Got it now. Was thinking about bottom discharge, or even monting pump on
same elevation as the bottom of the tank.

surfnturf

"Steve" wrote in message
From the top of the tank to the bottom is about 24", so even if I put the
pump on the tank top (not desireable since that is the bilge. Tanks are
integral.) the suction life, when the tank is low, would be more than the
1
ft spec. Might work fine as long as I don't loose suction. However the
whole
idea is to have it as a priming pump.

Steve
s/v Good Intentions

Parallelling fuel pumps
 

- Two off, three way valves.
- Don't equalise the hours on the pumps, they might both reach their end of
life at the same time.
- two plastic tags which say STANDBY PUMP. One goes on the valve, one on
the switch.
- Run on the A pump, test run on the B pump once per .... week, month ( I'd
say month )
And a jerry can with a hose attachment

It was getting too complicated.
Alternatively, two pumps in parallel with only check valves. Still run on A
and test B regularly. When something fails you will have to pull it all
apart to fix it, but there is much less to go wrong.

DF


"Doug Dotson" wrote in message
...
So perhaps a valve on both ends plus a check valve or maybe
two check valves. This is getting too complicated to be
worth it.

Doug
s/v Callista

"Rich Hampel" wrote in message
...
Further thoughts against paralleling such pumps:
If the internal check valves in one pump fails then the fluid will
flow retrograde in the pump that failed.... and damn little volume is
pumped by the pump that remains intact.
Typical industrial installation of such a 'system' would require a
block and bypass system of cocks/valves and bypass/lock-out piping.

In article , Steven Shelikoff
wrote:

On Mon, 12 Apr 2004 13:33:26 -0000, 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?

Then I wouldn't put them in parallel without isolation valves. Even
if
it works when both pumps are good, you don't know how the pump will
fail.

Steve

Parallelling fuel pumps
 

- Two off, three way valves.
- Don't equalise the hours on the pumps, they might both reach their end of
life at the same time.
- two plastic tags which say STANDBY PUMP. One goes on the valve, one on
the switch.
- Run on the A pump, test run on the B pump once per .... week, month ( I'd
say month )
And a jerry can with a hose attachment

It was getting too complicated.
Alternatively, two pumps in parallel with only check valves. Still run on A
and test B regularly. When something fails you will have to pull it all
apart to fix it, but there is much less to go wrong.

DF


"Doug Dotson" wrote in message
...
So perhaps a valve on both ends plus a check valve or maybe
two check valves. This is getting too complicated to be
worth it.

Doug
s/v Callista

"Rich Hampel" wrote in message
...
Further thoughts against paralleling such pumps:
If the internal check valves in one pump fails then the fluid will
flow retrograde in the pump that failed.... and damn little volume is
pumped by the pump that remains intact.
Typical industrial installation of such a 'system' would require a
block and bypass system of cocks/valves and bypass/lock-out piping.

In article , Steven Shelikoff
wrote:

On Mon, 12 Apr 2004 13:33:26 -0000, 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?

Then I wouldn't put them in parallel without isolation valves. Even
if
it works when both pumps are good, you don't know how the pump will
fail.

Steve

Parallelling fuel pumps
 

Constant flow through the day tank; the fuel is retained by an inverted
"dip tube" outlet. Its arranged so that only when a "bypass" cock at
the bottom is opened does the tank empty.


In article , Doug Dotson
wrote:

Answers below.

Doug
s/v Callista

"Rich Hampel" wrote in message
...
Doug,
Do you have a sailboat or a trawler/stinkpot?

Sailboat.

If you have a sailboat, you can finally raise a sail, heave-to/anchor,
go below and brew some tea, or just go to sleep until the sea-state
calms down and you can sort out what's the problem - later.

Nice theory. A lee shore and shoals might make that approach a bit
risky though. Low winds and strong currents in close quarters also
makes such an approach a bit too exciting to be worth saving a
couple hunderd bucks over.

Thats why I advocate a small capacity gravity feed 'day tank' .... NO
bleed or lift pumps, NO filters, NO electricity .... just nature's
gravity to feed oil to the injector pump; single cock to switch it
online to the fuel system .... 2-1/2 to 3 gallons of clean
prefiltered fuel oil can take you a looooong way in an emergency.
KISS. ;-)

I agree, but as I said before, I have no practical space at a level
above the engine for a day tank. I suppose that in an emergency
I can set a jerry can in the pilot house and gravity feed it though.
Wish I had though of that a year ago when we lost our engine due
to a failed lift pump half way across the Gulf Stream :)

It seem that you reserve your day tank for emergencies only. What
prevents the prefiltered fuel from going stale and getting growth?





In article , Larry W4CSC
wrote:

"Doug Dotson" wrote in
:

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


I'll also vote for a manual valve on both in parallel......

We're in a seaway, big waves. The pump goes into failure mode, we
switch
on the backup and are back in business. Wouldn't it be good if we could
isolate the failed pump for repairs, remove/replace or tear it down for
that new diaphram while the other pump has the load and the first mate
or
autopilot is driving? Sure would be nice to be able to get that failed
pump offline while the boat's still underway for repairs. Can't do that
on
the series pumps without some crazy plumbing bypasses and lots of
valves....

Larry W4CSC

Parallelling fuel pumps
 

Constant flow through the day tank; the fuel is retained by an inverted
"dip tube" outlet. Its arranged so that only when a "bypass" cock at
the bottom is opened does the tank empty.


In article , Doug Dotson
wrote:

Answers below.

Doug
s/v Callista

"Rich Hampel" wrote in message
...
Doug,
Do you have a sailboat or a trawler/stinkpot?

Sailboat.

If you have a sailboat, you can finally raise a sail, heave-to/anchor,
go below and brew some tea, or just go to sleep until the sea-state
calms down and you can sort out what's the problem - later.

Nice theory. A lee shore and shoals might make that approach a bit
risky though. Low winds and strong currents in close quarters also
makes such an approach a bit too exciting to be worth saving a
couple hunderd bucks over.

Thats why I advocate a small capacity gravity feed 'day tank' .... NO
bleed or lift pumps, NO filters, NO electricity .... just nature's
gravity to feed oil to the injector pump; single cock to switch it
online to the fuel system .... 2-1/2 to 3 gallons of clean
prefiltered fuel oil can take you a looooong way in an emergency.
KISS. ;-)

I agree, but as I said before, I have no practical space at a level
above the engine for a day tank. I suppose that in an emergency
I can set a jerry can in the pilot house and gravity feed it though.
Wish I had though of that a year ago when we lost our engine due
to a failed lift pump half way across the Gulf Stream :)

It seem that you reserve your day tank for emergencies only. What
prevents the prefiltered fuel from going stale and getting growth?





In article , Larry W4CSC
wrote:

"Doug Dotson" wrote in
:

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


I'll also vote for a manual valve on both in parallel......

We're in a seaway, big waves. The pump goes into failure mode, we
switch
on the backup and are back in business. Wouldn't it be good if we could
isolate the failed pump for repairs, remove/replace or tear it down for
that new diaphram while the other pump has the load and the first mate
or
autopilot is driving? Sure would be nice to be able to get that failed
pump offline while the boat's still underway for repairs. Can't do that
on
the series pumps without some crazy plumbing bypasses and lots of
valves....

Larry W4CSC

Parallelling fuel pumps
 

I spoke to the tech rep at Walbro regarding the wobble plate blockage.
His reply was that Yes, the stopped wobble plate can block the free
flow of fuel to the second pump in series. But, the blockage can be
overcome by 1.5 psi of push or suction.


On Mon, 12 Apr 2004 15:43:41 GMT, Rich Hampel
wrote:

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

Parallelling fuel pumps
 

I spoke to the tech rep at Walbro regarding the wobble plate blockage.
His reply was that Yes, the stopped wobble plate can block the free
flow of fuel to the second pump in series. But, the blockage can be
overcome by 1.5 psi of push or suction.


On Mon, 12 Apr 2004 15:43:41 GMT, Rich Hampel
wrote:

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

Parallelling fuel pumps
 

"Rich Hampel" wrote in message
...
Doug,

Thats why I advocate a small capacity gravity feed 'day tank' .... NO
bleed or lift pumps, NO filters, NO electricity .... just nature's
gravity to feed oil to the injector pump; single cock to switch it
online to the fuel system ....

I have 16 gal TEMPO tank for gravity feed to my galley stove. I have a 3 way
valve that will allow me to switch it over to the engine and generator
suction manifold.. Not only is it available for emergency fuel source, but
it is presently very handy for purging the air after I change fuel filter or
open an injector line. (problem is, I have to remember to turn off the valve
to the normal service tank that is below the engine).

Steve
s/v Good Intentions

Parallelling fuel pumps
 

"Rich Hampel" wrote in message
...
Doug,

Thats why I advocate a small capacity gravity feed 'day tank' .... NO
bleed or lift pumps, NO filters, NO electricity .... just nature's
gravity to feed oil to the injector pump; single cock to switch it
online to the fuel system ....

I have 16 gal TEMPO tank for gravity feed to my galley stove. I have a 3 way
valve that will allow me to switch it over to the engine and generator
suction manifold.. Not only is it available for emergency fuel source, but
it is presently very handy for purging the air after I change fuel filter or
open an injector line. (problem is, I have to remember to turn off the valve
to the normal service tank that is below the engine).

Steve
s/v Good Intentions

Parallelling fuel pumps --- better to use a 'day tank'
 

Just my experience in using Walbro pumps in recirculation systems,
pulling through 2 filters instead of pushing. Not sure amp draw, but
going on 3 years now 100% running with shut-downs only when I really
want it quite. (maybe 50-100hr out of a year).

One pump, still a ticking :-)

-al-


On Tue, 13 Apr 2004 00:41:24 GMT, Rich Hampel
wrote:

Just my experience in using Walbro pumps in recirculation systems. But
to be fair Im pushing a hefty differential pressure through a major
filter bank. With a 6 psid load I only get ~700 hrs. on my Walbro
pumps, I havent measured the amps draw but I wager its 50% of rated amp
capacity.

In article , Doug Dotson
wrote:

Interesting. Can you point me to some supporting docs that
indicates the WALBRO is not suitable as a primary pump.
This is counter to all I have heard from numerous sources
including reputable marine service outfits. Actually, the
WALBRO docs that come with the pump includes only
instructions for installing it as a list pump.

More below.

Doug
s/v Callista

"Rich Hampel" wrote in message
...
Instead of parelleling electrical lift pumps, better to install a 'day
tank' that is constantly supplied by freshly filtered fuel oil but with
a lock-out cock (to an inverted dip tube in the day tank) so that the
day tank always keeps a full load of fuel. Then if you have electrical
failure or filter blockage you will be able to use the 3 or 4 gallons
in the day tank to keep moving and make repairs, etc. If worse
becomes worse, you can always siphon fuel from the main tank(s) and
manually load a gravity feed 'day tank'.

Not practical in my case.

FWIW ... A Walbro IMHO is NOT a constant duty delivery pump.

Not my understanding. This pump seems to have been used for many
years as a primary fuel pump and seems to have a very reputation.

A better
solution for that application is simply an automotive 12v impulse fuel
pump. The Walbro is an intermittent transfer or recirculation pump;
but, can be so piped that if the engine mounted diaphragm lift pump AND
the inline priming pump BOTH fail then the recirculation pump can be
used to either pressurize the system or deliver to the 'day tank'.

That is sort of what I have now. Engine mounted mechanical lift
pump with the WALBRO ahead of it. WALBRO can be used
as a backup in the case of a failure although some plumbing
has to be moved to bypass a failed mechanical pump.