Diff pumps help keep the water OUT!
Posted: Fri Sep 18, 2015 3:00 pm
One reason I like the diff pump is that water in the system can and does wind up in the diff pump and its oil and is pumped out of it as the boiler reaches its operating range between 140-180 degees C. Once a first pumping and long run occurs, the water and volitiles are pretty much out of my system, unless I leave it un-attended for a month or more. (common after HEAS)
The common water signature and assurance that it is gone is as folllows:
Turn on the forepump and open the basllast valve fully and evacuate the fore line to about 25 microns or, hopefully, better. Open the valve to the diff pump and pump it down to a foreline indication of about 25 microns or better. Open the fusor valve and this raises the foreline pressure to almost a full torr, but instantly plunges back to about 25 microns and stabilizes there. Now turn on the diff pump boiler. As the boiler temp reaches about 80 deg C. the foreline pressure rises, (yes, I have a PID controller on the boiler to read the temp and control the fan)
This pressure continues to rise to about 40-50 microns as the boiler temp goes above 120 deg C. (volitiles and water being removed from the diff pump and its oil) The pressure in the fusor doesn't seem to rise more than about 2 microns during all this as the jets in diff pump go active and the mechanical pump ditches the water. Quickly, within seconds, the fusor chamber pressure plunges to 0.5 microns or (5X10e-4 torr). At this point I let the boiler continue to heat to about 160 deg C and by this time the foreline is back to about 20 microns and I shut the forepump ballast off.
As the ballast is closed I'll usually see about another 3 or 4 micron drop in the foreline to 15 microns or so. Ultimately, the diff pump drags the system down to the 7X10e-5 range and fusor operation with flowing D2 commences.
Fusion will heat the fusor to about 100 deg C and water molecules are continuously boiled out of the fusor walls. This is, inturn, pumped out of the system. Thus, a three day group of separate runs will have the bulk of the water out of my system, and, hopefully yours.
Note: I never use S.I. pressure units and also refuse to use torr in my discussion unless well below 1 micron. The fusor, in operation, and in most pump down scenarios, is always in the "micron range" It is a micron device. I religiously go to scientific notation torr for diff pump bottoming figures. However the fusor system never, ever dwells there long as fusor operation shoots back to the multi-micron level of real fusion operations due to flowing deuterium.
Richard Hull
The common water signature and assurance that it is gone is as folllows:
Turn on the forepump and open the basllast valve fully and evacuate the fore line to about 25 microns or, hopefully, better. Open the valve to the diff pump and pump it down to a foreline indication of about 25 microns or better. Open the fusor valve and this raises the foreline pressure to almost a full torr, but instantly plunges back to about 25 microns and stabilizes there. Now turn on the diff pump boiler. As the boiler temp reaches about 80 deg C. the foreline pressure rises, (yes, I have a PID controller on the boiler to read the temp and control the fan)
This pressure continues to rise to about 40-50 microns as the boiler temp goes above 120 deg C. (volitiles and water being removed from the diff pump and its oil) The pressure in the fusor doesn't seem to rise more than about 2 microns during all this as the jets in diff pump go active and the mechanical pump ditches the water. Quickly, within seconds, the fusor chamber pressure plunges to 0.5 microns or (5X10e-4 torr). At this point I let the boiler continue to heat to about 160 deg C and by this time the foreline is back to about 20 microns and I shut the forepump ballast off.
As the ballast is closed I'll usually see about another 3 or 4 micron drop in the foreline to 15 microns or so. Ultimately, the diff pump drags the system down to the 7X10e-5 range and fusor operation with flowing D2 commences.
Fusion will heat the fusor to about 100 deg C and water molecules are continuously boiled out of the fusor walls. This is, inturn, pumped out of the system. Thus, a three day group of separate runs will have the bulk of the water out of my system, and, hopefully yours.
Note: I never use S.I. pressure units and also refuse to use torr in my discussion unless well below 1 micron. The fusor, in operation, and in most pump down scenarios, is always in the "micron range" It is a micron device. I religiously go to scientific notation torr for diff pump bottoming figures. However the fusor system never, ever dwells there long as fusor operation shoots back to the multi-micron level of real fusion operations due to flowing deuterium.
Richard Hull