Yearbook 2013/2014 - ehedg

44 Hygienic design of floor drainage components
That drains might contribute to segregation or zoning, and
indeed their impact hygienically on the facility, is a matter
for debate, though reference to drainage is made in a
number of EHEDG derived publications (Lelieveld, Mostert,
Holah: 2003; 2005; 2011). Zhoa et al. (2006) in their study
of Listeria in poultry plants noted the importance of drains:
“Floor drains in food processing facilities are a particularly
important niche for the persistence of Listeria and can be a
point of contamination in the processing plant environment
and possibly in food products” (ibid, p. 3314).
However, even when the provisions contained in component
standards are adopted, these are not necessarily aligned
with best hygienic practice. For example, the standard EN
1253 permits the design of gullies with an effective sump, as
illustrated in Figure 6. Here, the obvious sump provides all of
the potential ingredients for bacterial growth.
More recent work by Berrang et al. (2012) studied Listeria
mobilization from the drain by inadvertent water spray during
cleaning operations, with subsequent potential to transfer to
food contact surfaces. Of note, Berrang cites studies where
such bacteria have been detected in floor drainage even
after extensive plant sanitation (ibid p. 1328).
Reducing the potential for harbourage of such pathogens
should be a key concern of any floor drainage product
manufacturer concerned with hygienic principles.
Floor drainage issues in practice
Generally, two main issues give rise to hygienic concern:
issues related to installation, and in particular the floor-todrain
interface, and issues related to the component design
itself. Here, the latter is considered.
The choice of materials for drainage component manufacture
is extensive and not necessarily constrained by the key
European standard (EN 1253). Typically, where hygienic
considerations apply, stainless steels are advocated. With
the readily available supply of appropriate grade sheet,
it should come as no surprise that many components are
fabricated by none drainage-specific companies. Linear
channels in basic form, especially, can be easily fabricated,
as can simple ‘box’ type gullies. It is estimated that more
than 200 suppliers fabricate drainage components in the
European Union (EU) alone (ACO 2009), the vast majority
of which are primarily fabrication companies with no specific
expertise in drainage. Consequently, there is huge variation
in how floor drains are fabricated, two examples are shown
in Figure 5.
Figure 6. Horizontal gully as portrayed in BS EN 1253.
It thus becomes necessary to supplement general standards
with further guidance. In the case of the floor gully, many
of the design aspects of European Hygienic Engineering
Design Group (EHEDG) guidance documents, particularly
Document 13, may be economically incorporated in product
design.
ACO has sought to incorporate in its components:
• Continuous welding of joints
• Radiused corners
• Drainability
The new horizontal gully in Figure 7 shows a floor drain
body that addresses the above points.
Figure 5. A case for improved drainage component design.
For the facility operator, specification of components that
meet appropriate standards – Euronorms or their regional
counterparts – ensures compliance with a number of criteria,
not the least of which are load bearing and hydraulic capacity.
As a matter of course, certification should be requested from
component suppliers (e.g., for the internal floor gully the
recommended reference is EN 1253 [2003]).
Figure 7. Floor gully body addressing key principles of hygienic
design.