[labnetwork] BCl3 Condensation

[Craig Cheney]

Sean,

   There are several things that can happen if you get BCL3 line condensation.  The first is incorrect gas flow control through an MFC, most (Gas Calibrated) MFC's are designed to work in the gaseous phase, if the gas you are flowing condensates into a liquid the MFC loses its ability to properly control.  MFC's measure gas flow using thermal mass flow, if they are calibrated for gas then flowing a liquid through them will give erratic results.  The second problem is insufficient gas supply, if you the gas delivery for the BCL3 contains numerous changes in direction then the possibility exists that you can actually create a trap if the BCL3 condensates to a level that does not permit gas to flow.   We have seen this in installations where the line run actually had a trap built into it and due to temperature differences along the line run, this line would literally stop gas flow due to the condensation building up to a point that it completely blocked the line.

  Here are industry standard designs considerations that are employed for the proper delivery of BCL3 or other low vapor pressure/low vapor temperature gases.


*         Control the temperature of the cylinder.  Most installations utilize a blanket that flows coolant through them that is connected to an independent chiller.   The temperature of the cylinder is kept at room temperature or 1 or 2 degrees warmer then room temperature.

*         The gas line itself (and it should be coaxial), should be heated and insulated.  The temperature of the gas line and gas panel components should be 10 to 15 degrees warmer then room temperature.

*         The gas line itself should be designed and built to incorporate the following;

o   Minimal changes in direction.

o   Should be located as close as possible to the use point.

o   There  should be no traps built into the line, even if run path requires it.  This will cause big problems.

o   The line (if possible) should be sloped or designed so that it would naturally drain to the delivery source.

  I hope that helps.  Let me know if you would like any more information.

Thank you,

Craig Cheney
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From: labnetwork-bounces at mtl.mit.edu [mailto:labnetwork-bounces at mtl.mit.edu] On Behalf Of Rinehart, Sean
Sent: Tuesday, February 18, 2020 8:42 AM
To: labnetwork at mtl.mit.edu
Subject: [labnetwork] BCl3 Condensation

Hi all,

I know that BCl3 condensation and line heating have been brought up several times in the past so this seemed like a good place to ask about the consequences of BCl3 condensation. Barring subsequent exposure to moisture is there any permanent damage to the delivery system, or does it just affect process gas mixture and block gas flow until it evaporates off?

Also, if the delivery pressure is regulated to below the vapor pressure at the coldest point in the delivery system would that effectively eliminate the risk of condensation?

Thank you,

Sean Rinehart
Assistant Director, Cleanroom Operations
Yale University
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