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.
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
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.
However details on equipment hygiene or hygienic design are limited.
With the advent of Mega Food Parks
in India, the shift to globally recognized 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 principles 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.
Elixir-T-Uni-Vibrating Fork Level Sensor's Tines with Milk Particle
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.
EHEDG Certified EL Class I with Tri-Clamp Mounting
Flush Mounting Hygienic design for a level sensor
While each level sensor variant has to individually qualify certification,
the guiding principles for design are similar. For a more detailed understanding refer
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
EHEDG in its document: EHEDG Guidelines
specifies the following criteria for selecting materials:
inhert to application media, cleaning detergents and disinfectants
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.
Tines of Vibration Type Level Sensor
Importance of Surface finish
EHEDG recommends a
Surface Roughness Average of 0.8 µm for the surface of the level sensor in
contact with the application media.
Surface Finish of Vibrating Fork Level Sensor
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 Classes
EHEDG offers two main types of equipment certification:
EL: Equipment cleaned with liquids
ED: Equipment dry cleaned only