[My apologies to Bruker users who receive this note twice.]
Awareness Warning - Bruker Automatic Sample Changer Belt Failure
Eastman Chemical Company purchased a Bruker DRX-500 NMR with a 60-sample
automatic sample changer (BACS) about 3 years ago. We also purchased a
total of 30 individual sample heaters for use with this system. This is
the maximum number of individual sample heaters that Bruker says can be
used without causing belt damage or misalignment problems.
The purpose of this Awareness Warning is to inform other Bruker users
and the NMR community of our recent belt failure on the BACS. With 26
individual sample heaters and about 10 samples (5-mm tubes) with ceramic
spinners in the BACS, the belt broke while we were repositioning the
belt manually by pushing the buttons on the side of the unit. About
one-half of the samples were dissolved in o-dichlorobenzene (ODCB) and
heated to 130 C. Only one person was in the room at the time of the
failure and did not get injured even though he was standing nearly under
the BACS unit as he was moving the belt. When the failure occurred, the
entire belt fell from the support wheels and most of the belt ended up
on the floor, breaking many of the NMR sample tubes, releasing hot ODCB
fumes into the room. The operator turned off the power to the sample
heaters and vacated the room immediately. With the help of our
emergency response personnel, we cleaned up the area and allowed it to
air out before returning to work in the area. Clearly, this failure
could have been far more severe if we had been using some of the more
dangerous solvents we routinely use to dissolve polymers.
It is our conclusion that this failure occurred because of plastic
fatigue due to excessive stress on the belt. This level of stress on
the belt was required to allow the sample heaters to all be on the BACS
simultaneously and not allow the belt to sag in the long unsupported
segments between the large wheels. We are thankful to Bruker for their
rapid response to provide us with a replacement belt, for getting our
system back on the air quickly, and for assistance in construction and
implementation of a remote button box described below.
Our plans for reducing the likelihood of this type of accident in the
future include any or all of the following:
(1) replace the BACS belt every 2 years with a new belt,
(2) load the BACS from the top from a platform built along
side of the magnet and BACS,
(3) reduce the number of individual sample heaters in use at
any one time until a better belt design can be developed and
implemented,
(4) build a remote button box to allow repositioning of the
sample belt without standing under or near the BACS (this modification
to the system was accomplished quickly by the Bruker service engineer
and our electronic shop during the repair visit),
(5) begin to use the sx command in XWINNMR to reposition the
belt in place of using the buttons on the side of the BACS,
(6) work with our engineering staff to determine if a better
belt configuration can be designed including an improved choice of belt
material, and
(7) discuss with Bruker whether or not a better BACS design
can be developed that incorporates better support for the belt and a
better belt design.
We encourage other Bruker users with a similar configuration to consider
the consequences of a sample changer belt failure. As you can imagine,
we are carefully reviewing all of our operational procedures around
loading samples to the BACS and will be developing detailed procedures
for more safe operation of this unit. We were very lucky and are very
thankful that no one was injured.
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Douglas W. Lowman, Research Associate
Physical and Analytical Chemistry Research Division
Technological Innovation Group, Eastman Chemical Company
P. O. Box 1972, Building 95, 200 South Wilcox Drive
Kingsport, TN 37662-5150 USA
e-mail: dwlowman@eastman.com
Telephone: (423) 229-4728
FAX: (423) 229-4558
http://www.eastman.com
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