How much does the length of a vacuum hose affect the vacuuming suction?

Steve

On 2013-04-02, Steve B wrote:
How much does the length of a vacuum hose affect the vacuuming suction?


The longer is the hose, the thinner, and the greater the flow, the
more is the deleterious effect. It is the same as a hose offering
resistance to any other kind of flow.

i

don't forget the roughness inside. Is it a flat wall, or one
that creates turbulence. The wall must stand up to any pressure and not
collapse.
Martin

On 4/1/2013 9:46 PM, Ignoramus6646 wrote:
On 2013-04-02, Steve B wrote:
How much does the length of a vacuum hose affect the vacuuming suction?


The longer is the hose, the thinner, and the greater the flow, the
more is the deleterious effect. It is the same as a hose offering
resistance to any other kind of flow.

i

On Mon, 1 Apr 2013 19:41:45 -0700, "Steve B" wrote:

How much does the length of a vacuum hose affect the vacuuming suction?

Steve

Virtually no effect on suction - may reduce flow somewhat. My central
vac pulls the same at the unit in the basement as it does on the
second floor about 15 feet up, using the same 25 foot hose.

wrote in message
...
On Mon, 1 Apr 2013 19:41:45 -0700, "Steve B" wrote:

How much does the length of a vacuum hose affect the vacuuming suction?

Steve

Virtually no effect on suction - may reduce flow somewhat. My central
vac pulls the same at the unit in the basement as it does on the
second floor about 15 feet up, using the same 25 foot hose.

We have a Vacuflow 960--twin motors, with the unit capable of handling
18,000 square feet of building.

Length of the tubing most assuredly makes a difference. The vacuum cleaner
is located in the shop, with tubing extended (underground) to the
house--with the longest runs likely near 100'. There's an obvious
difference of performance in the house as opposed to in the shop. 2"
inside diameter pipe, if you have a question on size.

The rules of physics dictate that there will be losses.

Harold

On Mon, 01 Apr 2013 23:43:57 -0400, wrote:

On Mon, 1 Apr 2013 19:41:45 -0700, "Steve B" wrote:

How much does the length of a vacuum hose affect the vacuuming suction?

Steve

Virtually no effect on suction - may reduce flow somewhat. My central
vac pulls the same at the unit in the basement as it does on the
second floor about 15 feet up, using the same 25 foot hose.
Now before anyone says "of course, the length is the same" - no it's
not. There is an extra15 to 20 feet of "hardline" leading to the
upstairs.

wrote:

On Mon, 01 Apr 2013 23:43:57 -0400, wrote:

On Mon, 1 Apr 2013 19:41:45 -0700, "Steve B" wrote:

How much does the length of a vacuum hose affect the vacuuming suction?

Steve

Virtually no effect on suction - may reduce flow somewhat. My central
vac pulls the same at the unit in the basement as it does on the
second floor about 15 feet up, using the same 25 foot hose.
Now before anyone says "of course, the length is the same" - no it's
not. There is an extra15 to 20 feet of "hardline" leading to the
upstairs.


The line to the upper floor has the advantage of gravity and the mass
of the air in the pipe. You need a flow gauge to see the difference.


--

Politicians should only get paid if the budget is balanced, and there is
enough left over to pay them.

Sometimes Friday is just the fifth Monday of the week.

On Thu, 04 Apr 2013 07:02:44 -0400, "Michael A. Terrell"
wrote:


wrote:

On Mon, 01 Apr 2013 23:43:57 -0400, wrote:

On Mon, 1 Apr 2013 19:41:45 -0700, "Steve B" wrote:

How much does the length of a vacuum hose affect the vacuuming suction?

Steve

Virtually no effect on suction - may reduce flow somewhat. My central
vac pulls the same at the unit in the basement as it does on the
second floor about 15 feet up, using the same 25 foot hose.
Now before anyone says "of course, the length is the same" - no it's
not. There is an extra15 to 20 feet of "hardline" leading to the
upstairs.


The line to the upper floor has the advantage of gravity and the mass
of the air in the pipe. You need a flow gauge to see the difference.

Not a factor.

--
Ed Huntress

Steve B wrote:
How much does the length of a vacuum hose affect the vacuuming suction?

Steve

Short answer is alot.

the "pressure" available in a vacuum system is usually limited to that of
atmospheric, or 14.7-ish PSI.

That's all you have to work with, and that's only when you start pumping.

Since suction is the flow of gas in this case, you have to factor in the
volume you're trying to move, and it will increase as the pressure drops
making it harder and harder to evacuate.

1 cubic foot of air at sea level takes up 1 cubic foot.

Drop the pressure by half and now this gas takes up 2 cubic feet.

half that again and it's 4 cubic feet.

So you really have to pump out 3 cubic feet of air to drop the pressure in
a 1 foot cube to 1/4th atmospheric pressure.

The resitance of tube or pipe is a big deal at lower pressures. A shopvac
with a 2" hose seems pretty powerful out in the open, but if the pressure
is 0.1" Hg you're just going to get a gentle breeze if even across the
same hose. The same thing happens once pressure in your vacuum system
starts to drop. Everything gets harder and harder to do the more gas you
remove.

So the other short answer is you want the shortest, fattest pipes for
vacuum work, whithin reason for what you're doing.

On Tue, 2 Apr 2013 19:12:16 +0000 (UTC), Cydrome Leader
wrote:

Steve B wrote:
How much does the length of a vacuum hose affect the vacuuming suction?

Steve

Short answer is alot.

the "pressure" available in a vacuum system is usually limited to that of
atmospheric, or 14.7-ish PSI.

That's all you have to work with, and that's only when you start pumping.

Since suction is the flow of gas in this case, you have to factor in the
volume you're trying to move, and it will increase as the pressure drops
making it harder and harder to evacuate.

1 cubic foot of air at sea level takes up 1 cubic foot.

Drop the pressure by half and now this gas takes up 2 cubic feet.

half that again and it's 4 cubic feet.

So you really have to pump out 3 cubic feet of air to drop the pressure in
a 1 foot cube to 1/4th atmospheric pressure.

The resitance of tube or pipe is a big deal at lower pressures. A shopvac
with a 2" hose seems pretty powerful out in the open, but if the pressure
is 0.1" Hg you're just going to get a gentle breeze if even across the
same hose. The same thing happens once pressure in your vacuum system
starts to drop. Everything gets harder and harder to do the more gas you
remove.

So the other short answer is you want the shortest, fattest pipes for
vacuum work, whithin reason for what you're doing.





Except then you have to remove all the air from the fat pipe too - it
is a catch-22.

wrote:
On Tue, 2 Apr 2013 19:12:16 +0000 (UTC), Cydrome Leader
wrote:

Steve B wrote:
How much does the length of a vacuum hose affect the vacuuming suction?

Steve

Short answer is alot.

the "pressure" available in a vacuum system is usually limited to that of
atmospheric, or 14.7-ish PSI.

That's all you have to work with, and that's only when you start pumping.

Since suction is the flow of gas in this case, you have to factor in the
volume you're trying to move, and it will increase as the pressure drops
making it harder and harder to evacuate.

1 cubic foot of air at sea level takes up 1 cubic foot.

Drop the pressure by half and now this gas takes up 2 cubic feet.

half that again and it's 4 cubic feet.

So you really have to pump out 3 cubic feet of air to drop the pressure in
a 1 foot cube to 1/4th atmospheric pressure.

The resitance of tube or pipe is a big deal at lower pressures. A shopvac
with a 2" hose seems pretty powerful out in the open, but if the pressure
is 0.1" Hg you're just going to get a gentle breeze if even across the
same hose. The same thing happens once pressure in your vacuum system
starts to drop. Everything gets harder and harder to do the more gas you
remove.

So the other short answer is you want the shortest, fattest pipes for
vacuum work, whithin reason for what you're doing.





Except then you have to remove all the air from the fat pipe too - it
is a catch-22.

yup.

There's got to be some sort of "vacuum impedance" or conductance to volume
matching formula out there, although I can't figure out what's it's even
called.

The Lesker Company has good docs on stuff like that on their website:

http://www.lesker.com/newweb/menu_te...v=ok&le vel=2

It looks like "Effective Pumping Speed" is the matter at hand:

http://www.lesker.com/newweb/Technic...ping&init=skip

The tech support person or people there are REALLY good.

"Cydrome Leader" wrote in message
news:kjfr4n$g26

There's got to be some sort of "vacuum impedance" or conductance to
volume
matching formula out there, although I can't figure out what's it's
even
called.


http://www.engineeringtoolbox.com/fl...nts-d_277.html

jsw

Jim Wilkins wrote:
"Cydrome Leader" wrote in message
news:kjfr4n$g26

There's got to be some sort of "vacuum impedance" or conductance to
volume
matching formula out there, although I can't figure out what's it's
even
called.


http://www.engineeringtoolbox.com/fl...nts-d_277.html

jsw

The ones listed there seen to be for the constant flow of
gas/steam/liquid. The problem is the pressure isn't constant in a pumpdown
scenario.

On 4/1/2013 10:41 PM, Steve B wrote:
How much does the length of a vacuum hose affect the vacuuming suction?


An example: my 5 hp leaf vac has a 6" dia hose, 6' long. The "vacuuming
suction" is very good. I thought a 12' hose would be more convenient
and added another 6'. The resulting vacuuming suction was so poor as to
be useless.

Bob