Vince Pitelka on sat 6 mar 04
> The most my gauge reads is about 3". The gas company says that 7" is the
> static or standing pressure and that when the gas is "flowing" the gauge
> will not read the true full pressure. That does not seem right.
> Is this correct and if so how does one ever know if the true 7" water
column
> pressure is actually being delivered?
Bruce -
In order to measure the line pressure, you would have to install a WCI gauge
before the valve, so that it measures the pressure in the gas line when the
valve is turned off. But 7 WCI is the lowest pressure that municipal gas
companies will deliver, so you certainly have at least that.
When you have a WCI gauge between the valve and the orifice, the pressure
reading is of course going to be quite a bit lower than the line pressure,
because of the gas escaping through the orifice. Even when you have your
pressure turned up all the way, the pressure reading couldn't be anywhere
near the line pressure, again because of all the pressure that is escaping
through the orifice. When a WCI gauge is located between the valve and the
orifice, the only way you could get it to read 7 WCI would be to completely
block the orifice.
Best wishes -
- Vince
Vince Pitelka
Appalachian Center for Craft
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Home - vpitelka@dtccom.net
615/597-5376
Office - wpitelka@tntech.edu
615/597-6801 x111, FAX 615/597-6803
http://iweb.tntech.edu/wpitelka/
http://www.tntech.edu/craftcenter/
Dave Finkelnburg on sat 6 mar 04
Bruce,
Your gas company people have told you the truth.
To tell the true supply pressure of your gas, you have to have a gauge
between a valve and the supply source, and have the valve closed. If, as is
most often the case, your gauge is downstream of the valve controlling gas
flow to the burner, then you are measuring the pressure after it has been
lowered by passing through the valve.
When you just start firing, your gauge reads very low, almost nothing.
The gauge is showing the pressure produced by the air at the end of the
burner, which is the pressure present inside the burner pipe, and the gauge
considers atmospheric pressure as zero. As the gas flow increases during
the firing, the gauge begins to register more and more velocity pressure
from the flowing gas. However, unless the gauge is very, very many pipe
diameters from the end of the gas pipe, the gauge indication will never
approach the supply pressure because the open pipe is there to allow the
pressure to drop.
Does this compute yet? :-)
Good firing,
Dave Finkelnburg, scrambling to make schedule adjustments since
I have just learned today I have the opportunity to go to
Indianapolis...just goes to show, sometimes good things happen even to the
undeserving!
----- Original Message -----
From: "Bruce Freund"
Sent: Saturday, March 06, 2004 8:31 AM
> If your city gas pressure is supposed to be 7" water column is that the
> pressure your gas gauge should read when the burners are full heat.
>
> The most my gauge reads is about 3". The gas company says that 7" is the
> static or standing pressure and that when the gas is "flowing" the gauge
> will not read the true full pressure. That does not seem right.
>
> Is this correct and if so how does one ever know if the true 7" water
column
> pressure is actually being delivered?
Bruce Freund on sat 6 mar 04
If your city gas pressure is supposed to be 7" water column is that the
pressure your gas gauge should read when the burners are full heat.
The most my gauge reads is about 3". The gas company says that 7" is the
static or standing pressure and that when the gas is "flowing" the gauge
will not read the true full pressure. That does not seem right.
Is this correct and if so how does one ever know if the true 7" water column
pressure is actually being delivered?
Best of the best,
bruce
| |
|
