Hygienic Design of Level Sensors
Maintainance of hygiene in Food and Drug industries is critical to a plant's operation. Use of a non-compliant equipment or a non-compliant cleaning process can lead to health and safety risks for consumers.
The primary goal of hygienic design is to ensure validity of efficient sanitation processes. In other words, if an equipment with hygienic design is used, efficient clean-in-place methods should be considered valid in order to ensure hygiene.
EHEDG Certified Level Sensor
Vibrating fork Elixir-T-UNI DN51: Level Sensor for liquids, Certified EL Class I
Regulartory Environment for hygienic equipments
Regulatory bodies such as FDA(Food and Drug Authority) in United States have laid down standards and good practices for manufacturing.
EHEDG: European Hygience and Design Group is not a regulatory body but a consortium of companies devoted to the advancement of hygienic design and food engineering
FSSAI(Food Safety and Standards Authority of India) in last few years has been increasingly active in promoting hygiene amongst business involved in food products. A license regulation has been released. The documents covers all aspects of hygiene. Hoever details on equipment hygiene or hygienic design are limited.
With the advent of Mega Food Parks in India, the shift to globally recongnized manufacturing practices will be the way forward. Therefore, even if hygiene regulation for equipments in India is still catching with internationally accepted practices, the norms accepted by FDA and EHEDG would naturally apply for export of edible processed goods.
Why hygienic design matters for a level sensor
Buildup of application media and Bacterial growth
Level sensors based vibronic or capacitive pricinples are directly in contact with the application media. Even with free-flowing liquids some build up is expected. If not specially designed, application media particles get deposited on the surface and crevices of the level sensor.
If left uncleaned, these pockets of particles can act as breeding grounds for batcteria. e.g. In dairy plants, this could lead to curdling of the entire batch of raw milk. In pharmaceutical plants, such an incedent can put consumers at risk.
Pipe Fittings and Mounting arrangement
Mounting arrangement may come in contact with the application media, irrespective of the the principle of level measurement. Crevices created by threads or joints between two surfaces provide area for bacterial growth.
Hygienic Design for a level sensor
While each level sensor variant has to individually qualify certification, the guiding prciples for design are similar. For a more detailed understanding refer to EHEDG Free Documents. Primary design and manufacturing criteria considered by Sapcon Instruments have been briefly explained below.
Selecting Material of Construction
Level Sensors used in hygienic applications are primiarily made of SS316 grade stainless steel. EHEDG in its document: EHEDG Guidelines specifies the following criteria for selecting materials:
- inhert to application media, cleaning detergents and disinfectants
- corrosion resistant
- mechanically stable
Material such as Plastics, Glass, Ceramic may be used under certain conditions. Devices such as Pressure Transmitters must use non-toxic signal-transfer liquids.
Standardization of Manufacturing Process
Although, EHEDG does not mandate a process qualification for manufacturing; standardization and qualification of the manufacturing process can help ensure sustainable quality.
The surface geometry of level sensors may have a curves, acute angles and crevices in a way which could lead to deposition of food particles. If such surfaces are unavoidable in the sensor, then the product needs to go through a hygienic evaluation test.
Importance of Surface finish
Hygienic Pipe Fittings for level sensors
EHEDG releases its approved set of pipe fittings periodically. Using standard pipe fittings has the benefit of being compatible with several makes of level sensors. Some manufacturers of level sensors offer EHEDG approved pipe fittings which have been customized for their make. This can cause vendor-lockin issues when looking for replacement.
EHEDG Certfication Types and ClassesEHEDG offers two main types of equipment certification:
- EL: Equipment cleaned with liquids
- ED: Equipment dry cleaned only