Helium Purifier Work Done 25,26-August-2022 ----------------------------------------------- Original Rev. 29-Aug-2022 Current Rev. 31-Aug-2022 Summary: this note describes work done on the Purifier for the Helium Recovery System on 25,26-August-2022. - Remove the single water filter in the Purifier cooling circuit and replace it with dual filters that can individually be valved out of the circuit also install a flow-meter. - Pump out the Vacuum Jacket on the Purifier both its top and side ports. Dual Water Filters and Flow-meter: ---------------------------------- The new dual water filters for the Purifier and the new flow-meter were installed on the south wall of room B111 about where the original single filter had been. At the same time the Parker quick disconnects were removed from the front of the Purifier and replaced with straight through standard barbs for 1/2" ID hose and 3/8" NPT pipe. All of the Purifier's cooling circuit remains 1/2" ID hose. The intent is to maximize the flow rate and to make it easy to change water filters without turning Off the Purifier and to allow one to monitor the flow rate. The flow-meter indicates about 8 Liters per Minute. I do not know how accurate this flow-meter is. It is the old flow-meter from the Main Compressor and is 15 LPM maximum flow. If we really are getting an 8 LPM flow through the Purifier that should be fine for its 3.1 k Watts of heat dissipation. With new filter cartridges the flow rate was the same with both filters in parallel or with just either one of the filters in the circuit by itself. Purifier Vacuum Jacket Pump Out: -------------------------------- The cold temperatures in the Purifier had gotten up to about 122 and 77 degrees K for its heat exchanger and trap temperatures. I think that the upper limit for the trap temperature is 80 deg K - but I'm not certain about this. Reza gave me guidance in installing the pump out setup. Specifically: by using a "T" one can pump on both ports at once and that the pump out port adapters feel some what loose even when they are correctly installed. Using the port adapters to pull the plug out of the port takes a bit of a fine touch. It was easy to feel the side plug come out but much harder to feel the top plug. Suggestions: Do not over tighten the adapter tool screw into the plug before pulling it out - doing so just makes it hard to un-screw the tool from the plug after you re-install it. When un-screwing the tool from the plug, once you think that you have it un-screwed, push it in lightly while turning it CCW and feel for the click as the threads come around on each turn. The port adapter tool handle will suck back into the tool and partly block the port thus preventing a good pump out. There are some scrap plastic shims to put between the tool handle (knob) and the body of the tool to keep the handle fully out, i.e. to keep the plug fully out of the port. Observations during the pump out: When pumping with just the dry pump on both ports with both plugs still in the Pirani gauge on the pump cart's vacuum manifold (gauge 5) got down to 5.0 E-2 in about 30 minutes. Note that I had previously pumped on just the long KF-25 bellows hose with just the dry pump for most of the day. Pulling the side plug made this gauge jump up to 9.5 E-2 From when the side plug was pulled it took the dry pump about 3 minutes to get this Pirani gauge back down to 5.0 E-2 I did not see this gauge jump when I pulled the top plug but I may have missed it. The turbo pump was turned ON when the Pirani gauge on the vacuum manifold had reached 2.0 E-2 After 4 hours of turbo pumping the vacuum manifold Pirani gauge was 6.5 E-4 and the Ionization gauge (gauge 6) was 4.5 E-6. After 18 hours of turbo pumping the vacuum manifold Pirani gauge was 7.3 E-4 and the Ionization gauge was 2.4 E-6. The Pirani gauge at the output of the turbo pump / input to the dry pump was 2.2 E-3 At this point I put the plugs back in and I remove the pump out equipment. Observations during Cool Down: 13:15 301 K and 282 K just started cool down mode 11 14:30 265 K and 216 K mode 11 15:30 239 K and 176 K mode 11 16:30 215 K and 138 K mode 11 17:40 189 K and 106 K mode 21 21:45 75 K and 45 K mode 35 So by 21:45 it had been cooling down for 8.5 hours it was fully cold, there was 105 psi of gas in the recovery tanks, and it should have switched from mode 35 to mode 41 but it did not. Instead I saw it switch from mode 35 to mode 51, i.e. warm up for a "regenerate" cycle. I was to thick and stupid to look at the purity monitor current while it was in mode 35 to see if it was high. The purity monitor is turned off when it made the change to mode 51. The Cryo-Mech control system makes the un-forgivable sin of not telling the user why it made this un-expected switch to mode 51 and the regenerate cycle. I think this may be an example of what Reza has seen before, i.e. if the purity monitor sits for a long time with no gas moving through it then its current climbs up because it's just smelling its own stink. All of this was confused because early the next AM the display screen / control computer for the Liquefier froze and I did not recognize that as the road block to getting everything running again for about 24 hours. Eventually once everything was running and it had been making liquid for about 12 hours the cold temperatures were: exchanger 86 K and trap 58 K. Over the next day things got a little colder: exchanger 80 K and trap 57 K. It may make sense that the exchanger takes a long time to cool as I assume that this temperature measurement is just made some place along the length of the exchanger and cold gas from the trap may need to flow for a long time to fully cool it. Purifier Vacuum Jacket Pump Out while the Purifier Is in a Regenerate Cycle: The idea is to put the Purifier into a 24 hour "Regenerate" cycle, i.e. it warms up its Trap and Heat Exchanger with their built in heaters and then it pumps on them with its built in dry pump while from the outside we pump on the Purifier's vacuum jacket. The intent is to get the trap nice and clean and this process gets things warmed up quickly (by using the built in heaters) so that the vacuum jacket pump out can get started promptly. By doing this you do not have to wait 12 or 24 hours for the Purifier to warm up after you turn its power Off. In a standard Regenerate cycle (which is run every so often during normal purifier operation) the built in dry pump only pumps on the warmed up Trap for 30 minutes. But its easy to tell the Purifier to pump on its Trap for 24 hours by the touch panel sequence starting from the Home Screen: tap Menu in the upper left-hand corner tap Control, tap Advanced, tap Extended Pump ON, tap Menu, tap Home You are now back at the Home Screen and to start a Regenerate cycle just: tap Regen along the right-hand edge. To return the Purifier to a normal 30 minute Regenerate cycle pump time do the following: tap Menu in the upper left-hand corner tap Control, tap Advanced, tap Extended Pump OFF, tap Menu, tap Home You can end the Regenerate cycle by tapping ON at the right-hand edge of the Home Screen. If you do not want the Purifier to pump on its Trap for 24 hours, but just want the quick warm up of a Regenerate cycle, then from the Home Screen just tap Regen and once the mode 51 heater assisted warm up is complete, you could either tap OFF on the Home Screen, or let it pump on its Trap for 30 minutes (in mode 71) and then tap OFF on the Home Screen. For details seen the Cryo-Mech Purifier manual in our MSU Physics Dept. Helium Liquefier web pages. Look in the Cryo_Mech_Manuals sub-director for the file name: Cryo_Mech_PT60_Automatic_Purifier_Manual_17Jul17.pdf The description of using the touch screen starts in section 6-1 starting on page 9. A description of the automatically initiated Regenerate cycle during normal operation is in e.g. section A.1 on page 3.