vince pitelka on sat 2 dec 00
> Vince is quite correct here, and it should benoted that the electronics to
> control the speed of an AC motor are more then cheesey, they are really
not
> reliable and do not produce a smooth electrical signal to the blower.
Thats
> why you see the typical Graingers squirel cage blowers with the added
flaps
> over the blower intakes. Both these methods are cheap, inexpensive, and
> often used, but are really poor substitutes for the correct solutions. The
> flap idea is really an inaccurate method.
Sorry Jonathan, you have my undying respect for your considerable knowledge,
but you have a great fascination for high-tech industrial equipment, and
here you are getting a little carried away. If a person has the money to
burn, then the equipment you suggest is great, but in reality the adjustable
intake flaps on the little Dayton squirrel cage blowers work great, and can
be adjusted with a high degree of precision. The old fashioned taper-seat
brass gas-cocks are worthless, but newer gas ball valves, with a stainless
steel ball closure in the center and a longer handle give a very high degree
of sensitivity and precision in gas adjustment. You can spend all the money
you want on metering valves or gate valves or butterfly valves, and the only
thing you will accomplish is a slightly greater degree of ease of operation.
For the studio artist, the mainstream high-tech industrial fix is not always
the best or most practical solution, especially when one weighs expense
against benefits.
Best wishes -
- Vince
Vince Pitelka
Home - vpitelka@dekalb.net
615/597-5376
Work - wpitelka@tntech.edu
615/597-6801 ext. 111, fax 615/597-6803
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
http://www.craftcenter.tntech.edu/
Jonathan Kaplan on sun 3 dec 00
>> Vince is quite correct here, and it should benoted that the electronics to
>> control the speed of an AC motor are more then cheesey, they are really
>not
>> reliable and do not produce a smooth electrical signal to the blower.
>Thats
>> why you see the typical Graingers squirel cage blowers with the added
>flaps
>> over the blower intakes. Both these methods are cheap, inexpensive, and
>> often used, but are really poor substitutes for the correct solutions. The
>> flap idea is really an inaccurate method.
>
>Sorry Jonathan, you have my undying respect for your considerable knowledge,
>but you have a great fascination for high-tech industrial equipment, and
>here you are getting a little carried away. If a person has the money to
>burn, then the equipment you suggest is great, but in reality the adjustable
>intake flaps on the little Dayton squirrel cage blowers work great, and can
>be adjusted with a high degree of precision. The old fashioned taper-seat
>brass gas-cocks are worthless, but newer gas ball valves, with a stainless
>steel ball closure in the center and a longer handle give a very high degree
>of sensitivity and precision in gas adjustment. You can spend all the money
>you want on metering valves or gate valves or butterfly valves, and the only
>thing you will accomplish is a slightly greater degree of ease of operation.
I think we need to disagree here Vince.
These are not high tech industrial devices. Yes they are industrial
components but they are simple ways to manually adjust the air and the gas
that offer a greater degree of accuracy then the flaps and ball valves.
Whether we use tapered gas cocks or ball valves, they are really not
designed for any type of metering other than "on" or "off." The flaps on
the blowers are grossly inaccurate and I can probably get the same air flow
at various positions of the flaps. Limit the volume of the exiting air, not
the intake. Any commercial combustion system that uses a blower would never
restrict the intake. Only the volume of air at each burner is monitored,
and can be adjusted automatically with "high tech" fuel and air balancing
systems, zero pressure systems, high velocity sealed burners, etc,( and
with great expense) or with these simple manually adjusted devices.( at a
very reasonable expense) I for one, and I think many would agree, that for
an additional few hundred dollars added on to some pipe burners would be a
small price to pay for better and more ecconomical firings.
Here is a case in point. My car kiln was equipped with some basic pipe
burners that had a tapered gas cocks for adjusting the gas on each burner
and flaps/ rheostats on the blowers. These were incredibly hard to keep
adjusted, especially the air, and it was very difficult to train staff to
fire correctly, even with a probe. With the addition of these devices, not
only have we cut our gas bill by one half, the firings are better, faster,
and I can train staff how to fire with repeatable accuracy and consistency.
My basic premis is that with all due repsect to those on the list who are
in the burner business, flaps and rheostats, ball valves and tapered gas
cocks are both inefficient and a poor solution. Cost effective, sure. But
thats only a small part of the issue. Potters need to look at the bigger
picture.
I respectfully disagree that the only thing they will accomplish is a
greater degree of ease of operation. They will provide a greater degree of
accuracy and metering, and I would submit that if we were to test these two
approaches with an oxygen probe, you would notice a greater degree of
combustion efficiency: easier excess air firings in the crutial early
stages of firing as well as proper and far less fuel usage from body
reduction to end of firing. More stochiometric combustion, not wasteful and
inefficient combustion.
>
>For the studio artist, the mainstream high-tech industrial fix is not always
>the best or most practical solution, especially when one weighs expense
>against benefits.
The studio artist needs to make the choice. As I mentioned, these changes
are not high tech, but they are more practical. The benefits of using
better metering devices far outweighs their miniscule expense. IMHO
Respectfully,
Jonathan
Jonathan Kaplan, president
Ceramic Design Group
PO Box 775112
Steamboat Springs CO 80477
voice and fax 970 879-9139
jonathan@csn,net
http://www.sni.net/ceramicdesigin
Plant Location:
1280 13th Street Unit 13
Steamboat Springs CO 80487
(please use this address for all deliveries via UPS, comman carrier, FEd
Ex, etc.)
vince pitelka on mon 4 dec 00
I think that Jonathan and I are each perhaps guilty of overstating our case
a bit. Jonathan has experience with a wide variety of industrial processes
and assisted technologies. He has a healthy fascination for such things,
which has resulted in an extensive knowledge of industrial equipment, and
thus a great exuberance for their use.
I also have a fascination for machinery and equipment, and have extensive
experience with a wide range of machinery, and while I have great admiration
for Jonathan and his knowledge, I also have great respect and admiration for
those who excel at the low-tech improvised, salvaged, invented, synthesized
solutions to studio problems. It delights me when I see potters come up
with a clever, effective low-tech fix.
Are the devices Jonathan recommends a good idea? Of course they are. Do
they make it easier for someone to operate a kiln from a set of
instructions? Of course they do. But are they necessary equipment to allow
the studio potter to fire her/his kiln with consistent accuracy? No they
are not.
Anyone who has used both the old tapered brass gas cocks and the newer
stainless-core ball-valves knows that they are completely different animals,
and the latter one allows very precise gas adjustment.
Also, I have long understood, perhaps mistakenly, that with small squirrel
cage blowers it is far better to limit blower intake than to restrict blower
output. When you restrict blower intake, the blower is essentially sucking
a very low vacuum, which reduces friction and drag within the blower
housing, reducing load on the motor, reducing heat buildup. When you
restrict the blower output, you place backpressure on the blower, increasing
load on the motor, increasing chances of heat buildup and motor damage.
If I am mistaken in these assumptions, perhaps someone on the list can
clarify this for me. If I am correct in my assumptions, then the intake
shutter (flap) on the small Dayton blowers works as well as any other
solution, particularly for the independent studio potter who is always
firing her/his own kiln. Like most studio potters, when I adjust the power
burners during a firing, I pay attention to the shape, color, and sound of
the flame, in order to compensate for any difference in the reading of the
inexpensive WCI gauges or the output of the blowers, rather than adjusting
strictly by the blower shutter opening and the reading on the WCI gauge. I
am able to get precise adjustments and very consistent results.
Best wishes -
- Vince
Vince Pitelka
Home - vpitelka@dekalb.net
615/597-5376
Work - wpitelka@tntech.edu
615/597-6801 ext. 111, fax 615/597-6803
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
http://www.craftcenter.tntech.edu/
michael wendt on tue 5 dec 00
Dear Vince and Jonathan:
You are both right about blowers to some degree. If the air system has no
sinks or sources (read: leaks) then both systems are the same under the same
atmospheric pressure. Most people assume incorrectly that restricting the
airflow through the system increases the load on the motor. The reverse is
the case. Don't take my word for it, test it with a shop vacuum. Put a stiff
piece of cardboard over the inlet as it runs and listen to the motor pitch.
As you cover more of the inlet, the pitch gets higher and since pitch is
related to motor speed, that means you have reduced the load on the motor.
Now cover the outlet and notice the same change of pitch. What happens when
you reach cut off is the air cannot move through the fan impeller and simply
spins in a circle inside the housing so the load on the motor decreases and
the motor speeds up. The rule with fans is: the free air (no restriction of
inlet or outlet) delivery condition requires the most power and places the
greatest load on the motor. As you approach cut off, the load on the motor
declines. Where you place that restriction makes no difference.
You are both right.
Regards,
Michael Wendt wendtpot@lewiston.com
Also, I have long understood, perhaps mistakenly, that with small squirrel
cage blowers it is far better to limit blower intake than to restrict blower
output. When you restrict blower intake, the blower is essentially sucking
a very low vacuum, which reduces friction and drag within the blower
housing, reducing load on the motor, reducing heat buildup. When you
restrict the blower output, you place backpressure on the blower, increasing
load on the motor, increasing chances of heat buildup and motor damage.
If I am mistaken in these assumptions, perhaps someone on the list can
clarify this for me. If I am correct in my assumptions, then the intake
shutter (flap) on the small Dayton blowers works as well as any other
solution, particularly for the independent studio potter who is always
firing her/his own kiln.
-----Original Message-----
From: vince pitelka
To: CLAYART@LSV.CERAMICS.ORG
Date: Monday, December 04, 2000 8:02 PM
Subject: Re: fancy industrial regulation of air and gas supply
>I think that Jonathan and I are each perhaps guilty of overstating our case
>a bit. Jonathan has experience with a wide variety of industrial processes
>and assisted technologies. He has a healthy fascination for such things,
>which has resulted in an extensive knowledge of industrial equipment, and
>thus a great exuberance for their use.
>
>I also have a fascination for machinery and equipment, and have extensive
>experience with a wide range of machinery, and while I have great
admiration
>for Jonathan and his knowledge, I also have great respect and admiration
for
>those who excel at the low-tech improvised, salvaged, invented, synthesized
>solutions to studio problems. It delights me when I see potters come up
>with a clever, effective low-tech fix.
>
>Are the devices Jonathan recommends a good idea? Of course they are. Do
>they make it easier for someone to operate a kiln from a set of
>instructions? Of course they do. But are they necessary equipment to
allow
>the studio potter to fire her/his kiln with consistent accuracy? No they
>are not.
>
>Anyone who has used both the old tapered brass gas cocks and the newer
>stainless-core ball-valves knows that they are completely different
animals,
>and the latter one allows very precise gas adjustment.
>
>Also, I have long understood, perhaps mistakenly, that with small squirrel
>cage blowers it is far better to limit blower intake than to restrict
blower
>output. When you restrict blower intake, the blower is essentially sucking
>a very low vacuum, which reduces friction and drag within the blower
>housing, reducing load on the motor, reducing heat buildup. When you
>restrict the blower output, you place backpressure on the blower,
increasing
>load on the motor, increasing chances of heat buildup and motor damage.
>
>If I am mistaken in these assumptions, perhaps someone on the list can
>clarify this for me. If I am correct in my assumptions, then the intake
>shutter (flap) on the small Dayton blowers works as well as any other
>solution, particularly for the independent studio potter who is always
>firing her/his own kiln. Like most studio potters, when I adjust the power
>burners during a firing, I pay attention to the shape, color, and sound of
>the flame, in order to compensate for any difference in the reading of the
>inexpensive WCI gauges or the output of the blowers, rather than adjusting
>strictly by the blower shutter opening and the reading on the WCI gauge. I
>am able to get precise adjustments and very consistent results.
>Best wishes -
>- Vince
>
>Vince Pitelka
>Home - vpitelka@dekalb.net
>615/597-5376
>Work - wpitelka@tntech.edu
>615/597-6801 ext. 111, fax 615/597-6803
>Appalachian Center for Crafts
>Tennessee Technological University
>1560 Craft Center Drive, Smithville TN 37166
>http://www.craftcenter.tntech.edu/
>
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