Table of Contents
CPC Problems and Solutions
Problem
CPC was not getting butanol after hooking up the butanol fill bottle on January 31, 2012.
Cause
There was a vacuum in the butanol fill bottle.
Solution
Open the fill bottle briefly before hooking it up to the cpc.
Problem
During the March 26, 2010 flight, there was no air flow through the CPC. Near the end of the flight the external CPC pump and exhaust lines were flooded with butanol.
During the December 29, 2010 flight, there was no output voltage from the CPC to the A/D board.
Cause
The CPC had a critical orifice regulating the air flow through the instrument. At altitude, the external pump cannot pull enough air through the orifice to maintain proper flow rates. The butanol in the pump and the exhaust line is probably due to this problem as well.
December 29/2010 Upon further investigation found that the ground wire from the CPC to the A/D board had a broken connection at the A/D board.
Solution
Removed the critical orifice and installed a valve between the instrument and the pump to regulate flow through the CPC.
October 15, 2010 Opened the valve fully, and re-installed into center rack. Checked for leaks. A charcoal filter was installed before the pump to ensure pump does not get saturated from butanol.
December 29, 2010 Stripped ground wire at the A/D board and re-pinned to fix.
Problem
CPC did not pass a leak test on May 1st, 2015.
Cause
Both ends of the charcoal filter attached to the CPC and the inlet pipe were not properly sealed or were leaking air.
Solution
Disassembled the charcoal filter and replaced the metal grates designed to keep the charcoal pellets out of the tubing with steel wool. The rubber seals now make a seal at both ends of the filter. Also cut the inlet tube so fresh metal could be used to make a better-fitting Swagelock end.
Problem
Failed leak test of the whole system at pressure on November 11, 2015
Cause
On November 13, 2015 a lot of butanol was sucked into the system even getting into the DMT. Anything that looked like a leak after this was probably just flooded optics. Tested for leaks throughout the system and in CPC and replaced all o-rings. The CPC was still found to be “leaking” (probably still flooded optics) on December 22, 2015. Dried the instrument according to the manual and a pretty bad actual leak was still present. Put in a new inlet tube on December 30, 2015 and optics flooded. There was no pinhole in this tube which I later found through speaking with TSI Inc. that the pinhole in the inlet tube T's off from the pressure transducer lines to a line that ventilates the butanol reservoir. Without this ventilation, the reservoir will continue to fill and eventually flood the optics. Drilled a hole in the new inlet tube and the CPC still leaked pretty badly. ~100 counts at 915 mb.
Solution
The o-rings that were replaced in the CPC were slightly larger than they were supposed to be. The leak was coming from the manifold around the pinhole in the inlet tube primarily, so when the proper o-rings were installed the leak rate dropped to only ~3 counts at 500 mb on March 8th, 2016. O-rings from the same manufacturer will be put into the saturator block to fully fix the leak.
Problem
CPC from WMI continues to flood when attempting to drop the pressure of the system in the lab throughout January 2016.
Cause
One thing to note first of all is that this CPC has the critical orifice in it whereas our CPC's flow is controlled by the alicat flow controller. This could amplify the problems that were not noticeable when using our CPC to do the same experiment. When pressure is dropped, no matter how slowly, the butanol liquid level (command rll) raises. The amount it raises is proportional to how quickly the pressure is lowered. However, at a certain level when the butanol liquid level raises at all it will flood the optics. This is because the butanol in the instrument is pulled down into the aerosol stream when pressure is dropped. Although this happens no matter what, we want to keep it to a minimum to prevent flooding.
Solution
The necessary liquid level to keep the instrument at when reducing pressure is around 1830. I believe this is the level when the butanol reservoir is nearly empty, if not, empty. Counts should be closely monitored because if the saturator wick begins to dry the counts will be low.