11.1 Introduction: the hygienic performance of closed
equipment
Hygienic performance of closed processing equipment for food processing
depends on a number of aspects. Some of these aspects are surface material and
finish (roughness and topography), gasket material and gasket design, welding
quality and welding location, cleaning procedure (time, temperature and deter-
gent) and internal design of the equipment. This chapter focus on the relationship
between flow of detergent during cleaning and, as a direct consequence, the
design of the equipment. At first glance, flow of detergent might not be the most
important aspect in cleaning; nevertheless, it is an aspect that is relatively cheap
to optimise through design consideration. Additionally, increased focus on
environmental concerns (and taxes) related to energy consumption and use of
chemicals has made the obvious choice of increasing the temperature or use of
harsher chemicals unattractive from an economical point of view ± improved
cleaning is obtained more cheaply through proper design of closed equipment.
Maintenance of proper hygiene in closed process equipment is in many ways
a complex task. The interaction between the design of the equipment and the
nature of fluid flow in the equipment is the main concern. It is already known
that dead legs or other types of areas shielded from the main flow can occur and
present a hygienic risk (Anon., 1993; Lelieveldet al., 2003). During cleaning the
main task of the flow is to bring cleaning agents in the right doses to all parts of
the process plant. In turn, the adhesion mechanisms between the soil and the
surface of the process equipment must be overcome. Clearly, this is similar to
other sanitation procedures; however, in closed processes, validation proves
rather difficult, as inspection is often not possible. Hence, a greater basic
11 Improvingthe hygienic designof closed equipment
A. Friis and B.B.B. Jensen, Technical University of Denmark