Replacement of External Pipe Assembly on PFS December 21, 2014

Transcription

1 Replacement of External Pipe Assembly on PFS December 21, 2014 The pipe assembly shown in Figure 1 is currently attached to the wooden shelf on PFS. It is covered with foam that acts as insulation. There are three tubes attached to the assembly, all with tube clamps. The tube at the upper left leads to the stand pipe/fill tube. The tube at the upper right brings fluid from the wooden box to the pipe assembly. The tube at the bottom returns fluid to the wooden box. Figure 1: Old external pipe assembly/debubbler The new pipe assembly (Figure 2) is the same, but includes a new section with a Y- filter between two ball valves. On December 11, 2014, the inline filter on the inlet to the flow meter in the wooden box was removed and this new pipe assembly was installed. There were several leaks, however. They were observed for a day and a half and measured to steadily decrease in combined fluid loss. However, as a precaution against perpetual leaking, the original pipe assembly was replaced the next day. 1

2 Figure 2: New external pipe assembly/debubbler The 2 inch joints were connected using a Rectorseal sealant. This has hardened and it seems unlikely that these joints can be tightened further without compromising the integrity of the sealant. There were several leaks in these joints (e.g. Figure 3), but there were also similar leaks in the old assembly when it was first put together in 2009, and they stopped after a few days. There is hope that the leaks in the new assembly will similarly stop after a few days. The 1 inch pipes were connected with Teflon tape sealant. There were leaks in two locations (see Figure 4). These joints could potentially be tightened a bit more before reinstalling the pipe assembly. Any combination of joints along this stretch can be tightened as long as the hose barb at the right side winds up pointing approximately toward the hose entrance to the wooden box and the Y- filter and ball valves are oriented in accessible directions. 2

3 Figure 3: Leaks in Rectorseal joints (left and right) and teflon joint (right) Figure 4: Leak locations (red dots) from early December There were several in the Rectorseal joint at the upper left, one in the Rectorseal joint near the spigot, one in the Rectorseal joint near the ball valve, and one each in the two teflon joints shown. 3

4 Instructions Remove the foam insulation from the external pipe assembly. There are many small pieces taped into place. Follow the relevant procedures in the glycol replacement manual to drain the system. The insulating panels do not need to be drained this time, so be sure to close all 12 ball valves at the supply and return points on the instrument insulation panels before draining the glycol. Remove the inline filter from the inlet to the flow meter and do not put it back. Please put it in a visible spot in the PFS cabinet, or in the top try of the PFS tool box. Loosen the three tube clamps. The tube insulation will need to be pushed back by hand to reach them. There is a hex nutdriver in the PFS tool box that is the right size for the nuts on the tube clamps. It s easier to use the nutdriver than a screwdriver. Remove the top two tubes first, and the lower one last. Have a bucket nearby into which to quickly direct drainage from both the loose hose and the pipe assembly. The new pipe assembly is on top of the cabinets to the left of the PFS cabinet. It is possible that it can be installed as- is and that the small leaks in it will self- seal. However, it might be a good idea to try tightening only the 1 inch pipe pieces with the Teflon tape sealant. A vice and a large wrench will be needed, or two large wrenches. These were available in the mechanics area by the clean room. If tightening seems feasible, be careful to leave the various pipe pieces oriented in an accessible way and with the hose barb pointing at the wooden box. Loosen and remove the pipe clamps holding the assembly onto the wooden shelf. Once the whole thing is detached, the plastic pieces that wrap around the pipe can be bent and pulled off. Snap these pieces onto the new pipe assembly and reattach to the wooden shelf. Attach the hoses at the upper left and right and tighten the hose clamps. In the PFS cabinet, on the bottom shelf, there is a box labeled plumbing. There should be a length of blue tube toward the bottom of the box that is the correct length to replace the return hose after the new pipe assembly is installed. On top of the PFS or M2FS cabinet, there is a large, light box that contains insulation. There should be a length of tube insulation that is the correct length for the new blue hose. Remove the tube insulation from the return hose. Inside the wooden box, loosen the tube clamp on the return hose that leads to the external pipe assembly. Pull the hose out of the wooden box. Insert the new, shorter length of blue hose into the same hole and re- tighten the hose clamp. Slide the new tube insulation over the new tube and attach the tube to the new pipe assembly. Tighten the hose clamp. 4

5 Please save the removed pieces in case we have to revert to the original setup later. Don t bother re- covering the pipe assembly with insulation. We will want to monitor the leaks until they hopefully stop. Shec can cover the pipes with insulation at the end of the observing run, or I can do it later in January at the beginning of the next observing run. Refill the system. Since the glycol solution in there right now is brand new, you should be able to pour it back into the system at the end. However, if there is a strainer that the fluid can be poured through, that would be a good idea. Inevitably, there is going to be some spilling, so you will need to use some of the premixed glycol solution on the top shelf of the PFS cabinet. If you end up needing all of it, you will have to mix some more. There is some pure glycol in a bottle on the second shelf from the bottom, in the back. Thanks for helping with this. Jeff (home) (mobile) crane@obs.carnegiescience.edu Skype: jeffdcrane Facetime: or jeffcrane@gmail.com 5