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How to meassure the pressure different of different environment.

V

Vincent

Jan 1, 1970
0
Our company intend to build a clean room with possitive pressure in the
room.We will install a blowing fan to suck the air from outside into the
clean room with the damper control.

Can anyone know how to meassure the pressure different between inside and
outside of the clean room.

Thanks

Vincent
 
J

John Gilmer

Jan 1, 1970
0
Vincent said:
Our company intend to build a clean room with possitive pressure in the
room.We will install a blowing fan to suck the air from outside into the
clean room with the damper control.

Can anyone know how to meassure the pressure different between inside and
outside of the clean room.

With a manometer.

You can buy a sensitive differential pressure guage that will do the same
thing.

In those circumstances, pressures are measured in INCHES of WATER.

SO: if you want to go the DYI route you pick a location where you want to
monitor the pressure and you bring tubes from INSIDE the enclosure and
OUTSIDE the enclosure. You connect these tubes to a U shaped glass or
plastic (transparent) section of tube with arms on the order of 10 to 18".
Before connection you put some WATER in the tubes to fill each arm about 5".
When you complete the connection the DIFFERENCE between the water level in
each side of the "U" is the pressure inside your room.

You can buy "scientific" versions of the above thay feature a large (very)
diameter tube on one side and a sloping tube on the other side. For
pressure differences of a fraction of an inch, the sloping tube permits a
more accurate measurement.

But, basically, all you need is some clear tubing, a ruler, and some water.
 
P

Perion

Jan 1, 1970
0
Vincent said:
Our company intend to build a clean room with possitive pressure in the
room.We will install a blowing fan to suck the air from outside into the
clean room with the damper control.

Can anyone know how to meassure the pressure different between inside and
outside of the clean room.

1. If all you want to do is be able to monitor the pressure difference:
search "differential pressure gauge" at http://www.google.com/ . There's
zillions of varieties and prices.

2. If you want to actually maintain (control) the pressure difference by
varying the damper postion you could use a differential pressure transducer
or transmitter as input to a PID controller. The output of the controller
would then control a proportional damper actuator. Or you could keep the
damper stationary and use the differential pressure transducer as input to a
Variable Frequency Drive (VFD) to control the blower motor speed (assuming
you have a three phase power system). Many standard VFDs have built in PID
control functionality so you wouldn't need any other control devices but the
transducer and the drive.

http://www.omega.com probably has whatever gauge, transducer, PID controller
(no VFDs), etc. you would need.

Perion
 
R

Ross Mac

Jan 1, 1970
0
I believe a magnahelic gauge is used.....the last one I purchased was from
graingers for about 50 bucks...
 
D

daestrom

Jan 1, 1970
0
tony said:
If you do opt to make your own water gauge, consider adding a little soap to
the water: surface tension effects can cause small errors.

And a drop of food coloring can make it easier to read against a ruler
background ;-)

daestrom
 
L

Louis Bybee

Jan 1, 1970
0
Vincent said:
Our company intend to build a clean room with possitive pressure in the
room.We will install a blowing fan to suck the air from outside into the
clean room with the damper control.

Can anyone know how to meassure the pressure different between inside and
outside of the clean room.

Thanks

Vincent

You've received some good answers to your question, but no one has suggested
that you will need to filter the incoming air. Although I hope you've
already taken that into consideration, outside air only appears"clean".
Check the outside air filters (if you have them) on your HVAC units for a
good example of what is in the air you intend to put into this clean room,
and that's only the big stuff! Depending on your process, material you can't
readily see with the naked eye will contaminate the area.

Without specifying your application one can only guess as to the need for
climate control (heat, and humidity, etc.), and the need to disconnect any
normal HVAC units now serving the area (this will affect the pressure
gradient measurements, and introduce contaminates).

Louis--
*********************************************
Remove the two fish in address to respond
 
W

william_b_noble

Jan 1, 1970
0
for what it's worth, I have a couple of magnahelic gauges for $15 each - if
interested, contact me off the list at william_b_noble at msn dot com

I also have this cool purge control panel that has a magnehelic gauge and a
bunch of other goodies up for auction on E-bay.

bill
 
J

John Gilmer

Jan 1, 1970
0
Mark said:
Along with the pressure you need to monitor the humidity
as well, since humidity is a factor in air density.

You monitor humidity if the process requires a certain range of humidity.

Your basic clean room is pressurized so that "leaks" take conditioned air
out and un-conditioned air doesn't come in. The "conditioned" make up air
would have to have moisture added or taken out as required by the process.
 
J

John Gilmer

Jan 1, 1970
0
Gfretwell said:
It sounds to me like the slack tube manometer may be the easiest solution with
the magnehelic guage being the most elegant. One thing with slack tubes, the
water evaporates pretty fast so you probably want a more stable operating
fluid. You can calibrate your "ruler" to anything from mercury to motor
oil.

Since oil is lighter than water, the oil gauge will be more sensitive.
 
D

daestrom

Jan 1, 1970
0
Gfretwell said:
It sounds to me like the slack tube manometer may be the easiest solution with
the magnehelic guage being the most elegant. One thing with slack tubes, the
water evaporates pretty fast so you probably want a more stable operating
fluid. You can calibrate your "ruler" to anything from mercury to motor
oil.

True. Have made them using a 'pinch' in the ends to help this. And adding
a small amount of oil on the water surface (be sure to add the same
'thickness' to both sides) will make the water last a long time. Have seen
some using a red oil that also makes reading against the scale easier.

daestrom
 
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