Improved safety for integrated granulation and drying suites
Extensive safety testing confirms pressure enhancement effects and
identifies safe design limits for integrated systems GEA Pharma Systems in
conjunction with the FSA, the safety specialist centre in Germany, have carried
out an extensive test programme involving over 100 test explosions. This
research has shown conclusively that should an explosion occur during the
transfer operation in an integrated system where a granulator is connected
directly to a fluid bed dryer without an explosion isolation valve, the
secondary explosion pressures in the granulator can be significantly higher
than in the fluid bed. These tests have enabled GEA Pharma Systems to gain
full EC type approval for a range of pressure shock resistant integrated
systems and 16-bar pressure shock resistant high shear granulators.
Safety when using organic solvents
The tests were
carried out with hybrid mixtures that behave in the same way as pharmaceutical
products containing organic solvents and showed that the final explosion
pressure in the granulator is dependent on the volumes of the two vessels and
that the length and diameter of the
interconnecting duct is critical in
ensuring that the pressure remains within safe limits.
The tests showed that where the fluid bed is designed in accordance with VDI
2263 part 5 (i.e.: for a 10-bar explosion pressure, which the standard
considers to be adequate for all pharmaceutical powders and organic solvent
combinations), then the granulator must be able to withstand an
over
pressure of at least 16 bar to provide a range of transfer duct configurations
which are both practical and safe.
Where the fluid bed is required to handle materials with explosion pressures
greater than 10 bar (e.g.: metal powders) - and hence is designed outside of
the VDI standard - or where the configuration of the interconnecting duct is
outside the safe design parameters, then either the granulator must be designed
to a higher pressure shock resistance or a hygienic fast acting valve, or some
other form of protection, is essential. The test program showed that the
pressure enhancement effects are caused by the difference in the propagation
speed between the pressure wave and the flame front. The worst cases are when
the pressure in the granulator is able to rise significantly before the flame
can reach it and ignite the pre-compressed material. For the range of transfer
duct configurations to be used with the 16-bar granulator design, the resence
of bends and obstructions such as mills was not seen to affect the increase in
pressure.
For plant processing powders, or mixtures that are not flammable at the time
of transfer between the granulator and the fluid bed, then the risk of
explosion is eliminated and hence a wider range of transfer duct designs can be
used safely. This extensive research program has significantly advanced the
state of the art in safety technology for pharmaceutical plants and confirms
GEA Pharma Systems’ commitment to introducing new products which are based
on sound research and development using solid process know how and
understanding.
Safety and the environment
For full compliance with
national, local and in-house regulations, GEA Pharma Systems offers a range of
emission control options including solvent recovery systems, outlet filters and
full containment plants. Equipment can be supplied to meet explosion-proof and
pressure shock standards as required.