Biomedical Engineering Reference
In-Depth Information
process supervision'. Furthermore, what role does this instrument take on
with respect to the major hazard of runaway reactions, whose prevention
is the main goal of the project? The fact that workers took such owner-
ship of the system placed the designers in a very uncomfortable situation.
From their point of view, it even meant that the project had failed.
Starting with the idea that unexpectedly taking ownership of the sys-
tem constituted a response on the part of the users, we carried out an anal-
ysis of work to understand this response. This analysis showed that the
evolution of the function of the artifact that took place within the activity
of the workers found its source in the strategies these workers used to con-
trol the production process. Indeed, the workers controlled the process by
maintaining it at the lowest possible temperature threshold. This strategy
'drives them away' from the major hazard of a runaway reaction (which
occurs when the temperature threshold is set high). However, running the
process at a low temperature is also hazardous: if the product becomes too
cold, it may crystallize and harden. To use the expression of the workers
themselves, this is an 'everyday hazard'
*
. The designers took into account
this need of the workers, and altered the artifact accordingly: in addition
to the initial analogical display of temperature, they included the display
of a curve, making it possible to track the history of the evolutions of tem-
perature. Indeed, the curve makes it possible to interpret trends in the
product's thermal kinetics. This emerged, from the analysis of work activ-
ity, as a variable used by the workers to prevent these everyday hazards.
In addition, the work analysis showed that the workers spent a lot
of their time trying to steer clear from the major hazard of runaway
reactions, that is, to produce while staying as far away as possible from
high temperatures. However, runaway reactions might still appear fol-
lowing, for example, a breakdown or damages to the equipment. Once
again, to use the workers' own words, they would then have to 'cope with
the unknown' - hence the idea of designing an instrument that would
allow workers to apprehend the concrete conditions of a runaway reac-
tion. The alarm was able to achieve this, since its design was based on
a model of runaway reactions. Therefore, the prototype was modified
so as to be able to simulate the temporal dynamics of such major events
(to do this, the product being manufactured was replaced with an inert
liquid). Three simulations were conducted that differed from one another
in terms of safety procedures that had been planned for that particular
site. They showed that, in two of the cases, the workers would have failed
*
As it expands, the product may cause some of the equipment, which is made of glass, to
break. Furthermore, it will be necessary to heat the product up later on, which may be
hazardous.
