[labnetwork] Issue with diborane in nitrogen mixture

[Leif Johansen]

Dear all,

Here at DTU Danchip we are facing some difficulties with diborane in nitrogen mixtures.

I the recent months we have made the following observations with our 3% diborane in nitrogen mixture:


·         Approximately half year ago, the safety valve opened up due to a too large overpressure on the secondary side of the regulator. Usually, the secondary pressure is set to 1-2 Bars overpressure. The safety valve will open up at pressures exceeding ca. 7 Bars.


·         At that time we believed that the incident was caused by a faulty gas panel regulator. So we changed the regulator and continued to use the gas.


·         However, in the past month or so we have seen that the pressure rises from the setpoint of 1.5 Bars to around 3 Bars. If we then consume gas from the line, the pressure has been observed to drop in discrete steps rather than in a smooth way.


·         This week the pressure suddenly increased dramatically again, leading to a new safety valve release. We have now shut down the gas line.

My questions are :


1.       The bottle is from March 2010. I have once read that over time diborane decomposes into higher order borohydrides, which, unlike diborane, are solid and can clog orifices and nozzles. This phenomenon has already been addressed by Bob Hamilton in this forum. Is our diborane bottle simply too old and emits "ear wax" into the gas line?

2.       The bottle is located in a gas bunker outside, where the temperature can vary quite a bit over the four seasons. The specified temperature range is 0°C to 40°C (32°F to 104°F ). What happens if the temperature exceeds this range?

3.       The gas panel regulator is a "Rotatrex SI 240 V" gas regulator (240 Bar primary side, 7 Bar secondary side). I have read that certain materials should be avoided inside valves and regulators used for diborane gas. As far as I can read on the data sheet, the  body is made of 316 L steel, the diaphragm is made of Hasetlloy and the valve seat is made of Vespel or PVDF. Can anyone comment on whether our present regulator is suited at all to handle diborane? If not, can anybody recommend a better alternative?

These issues are causing considerable down-times of our diborane consuming equipment, so I would very much appreciate any information you could share which could help us solve the problem.


Leif S. Johansen

Head of Operations

DTU Danchip



Technical University of Denmark

[cid:image001.gif at 01CDC3FC.D1B530E0]

Danchip

Ørsteds Plads, Byg. 347

2800  Lyngby

Direct +45 45255713
Mobile +45 25348992

lej at danchip.dtu.dk<mailto:lesjo at danchip.dtu.dk>

www.danchip.dtu.dk/<http://www.danchip.dtu.dk/>



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