Installation of an Orbitally Welded Hygienic Piping System
Image courtesy of ATW Services
In response to increased demand for the production of an asthma drug, an expanded hygienic piping system was installed in a UK manufacturing plant. The system was designed to provide process services for two blow-fill-seal (BFS) packaging machines, and to replace the original hand-welded system with an orbitally welded one. Several advanced design concepts were incorporated into the installation to satisfy the goals of cleanability and sterilizability. The packaging suite was designated as a clean room to prevent contamination of the product during the BFS process. Some of the implemented features, and guidelines for similar projects, are presented in this article.
Figure 1: Details of the clean steam generator and header that deliver clean steam to the process piping and vessels for sterilization. The piping and header are jacketed to conserve heat.
Figure 2: Details of piping system, showing swing bends used to select routing of product. Completely welded systems must be physically connected. Such a design should prevent operator error.
To be effective as a sterilant, clean steam must be delivered dry, saturated and without entrained air. Clean steam condensate must not be allowed to flow back into aseptic process systems during or after sterilization. In this system, connection to the 4 in. drain was made only when dumping water from the system, so that accidental backflow cannot occur. Steam traps were used to remove condensate and air from the system. Engineering of the system, including selection of piping diameters, was based on the temperature calculations for heat loss.
Figure 3: Tank bottoms and piping are sloped to promote complete drainability (image provided by ATW Services).
Drainability is an essential feature of any hygienic piping system. Retained fluid in the piping provides a medium where bacteria could grow, adding an unacceptable bioburden to the system. Retained fluid could also promote corrosion, leading to product contamination. The utilization of gravity has been found to be the most effective method of removing all traces of liquid from a process system. The piping system was therefore designed with falls or slopes to ensure complete drainability. The tong runs of piping leading to drains were sloped to provide a 1:100 fall, which is equivalent to approximately 0.125 in./ft, and the bottoms of the tanks were sloped to ensure that pools of liquid do not accumulate on the vessel bottoms.