Doc. 37. Hygienic design and application of sensors | EN-English

EHEDG 2022
Seiten / pages: 114

DOC No.37 – Part 1, Second Edition

Summary
The document focusses on sensors that are actually used in the food and beverage industry. All food contact processes are covered: wet processes, but also dry matter and powder. The guideline focusses on the product contact area of the sensor.
The document helps to define the hygienic requirements for the sensors and give guidance how to use them. It will point out if the aim of the measurement may cause hygienic difficulties. Installation and integration are covered as well. Besides the food contact area, the document covers where applicable as well as applications in the splash area, like housings, holder and wiring devices.
For each sensor technology, the section describes the range of application, the details of design and construction that have an impact on the hygienic purpose, the correct integration into the process, the consequences in case of a damaged sensor and the impact on the process and the cleanability during the installation. Besides the certified sensor itself, it is as important to ensure the hygienic integration.

Contents

1 Objectives and scope
2 Normative References
3 Definition of Terms
4 General Considerations and external parts of process sensors
4.1 General
5 Sensors
5.1 Sensors for wet applications and slurries
5.1.1 Temperature
5.1.1.1 Contact free temperature sensors
5.1.1.1.1 Laser and Infrared Temperature
5.1.1.1.2 Clamp on
5.1.1.2 Contact temperature sensors
5.1.1.2.1 Weld in spud / Thermowell
5.1.1.2.2 Direct integration
5.1.2 Flow
5.1.2.1 Electronically measured
5.1.2.1.1 Magnetic-inductive measurement devices
5.1.2.1.2 Coriolis mass flow measurement
5.1.2.1.3 Thermal flow measurement
5.1.2.1.4 Ultrasonic Flow (Clamp on and ingressing)
5.1.2.1.5 Surface acoustic wave (SAW)
5.1.2.1.6 Vortex Flow Sensors
5.1.2.1.7 Differential Pressure Flow
5.1.2.2 Mechanically measured
5.1.2.2.1 Mechanical flow measurement, here: oval wheel meters
5.1.2.2.2 Float-type flow meters, variable area flow
5.1.3 Level
5.1.3.1 Limit Switches
5.1.3.1.1 Vibronic
5.1.3.1.2 Capacitance
5.1.3.1.3 Conductivity level switches
5.1.3.1.4 Microwave level switches
5.1.3.1.5 Optical level switches
5.1.3.1.6 Float switches
5.1.3.2 Continuous level in tanks
5.1.3.2.1 Hydrostatic
5.1.3.2.2 Continuous Optical Level  Camera Laser level measurement
5.1.3.2.3 Magnet resistance level measurement
5.1.3.2.4 Time of flight/transit time level measurement, contactless Microwave (radar) Ultrasonic
5.1.3.2.5 Contact level systems  Guided microwave Capacitance
5.1.3.2.6 By-pass systems and external level Displacer Magnetic gauge Load cell
5.1.4 Pressure
5.1.4.1 Metal membrane, oil filled
5.1.4.2 Ceramic membrane
5.1.4.3 Mechanical systems
5.1.5 Analytical
5.1.5.1 Optical systems
5.1.5.1.1 Ingressing with direct product contact
5.1.5.1.2 Colour.Oxygen NIR
5.1.5.1.3 Analytical in pipe installation / flow housing Colour Turbidity
5.1.5.2 Conductivity  
5.1.5.2.1-Pole conductivity
5.1.5.2.2-Pole conductive
5.1.5.2.3 Inductive conductivity  
5.1.5.3 pH
5.1.5.3.1 Glass sensor
5.1.5.3.2 ISFET sensor / plastic / PEEK / ISFET pH sensor
5.1.5.4 Physical systems inline analytical
5.1.5.4.1 Vibronic density
5.1.5.4.2 Coriolis density
5.1.5.4.3 Time of flight/transition time, ultrasonic and microwave density
5.1.5.4.4 Coriolis viscosity
5.1.5.5 Amperometric Oxygen
5.1.5.6 Fittings for analytical sensors
5.2 Sensors for dry applications and powder
5.2.1 Dry matter Temperature
5.2.1.1 Contact free temperature sensors
5.2.1.1.1 Laser
5.2.1.1.2 Clamp on
5.2.1.2 Contact temperature sensors
5.2.1.2.1 Weld-in spud
5.2.1.2.2 Direct integration
5.2.2 Level measurement in dry matter
5.2.2.1 Switches
5.2.2.1.1 Vibronic
5.2.2.1.2 Capacitance
5.2.2.1.3 Microwave level switches
5.2.2.2 Continuous level in Silos ad dry matter
5.2.2.2.1 Optical Camera Laser dry Level
5.2.2.2.2 Time of flight /trasit time level measurement, contactless in silos and dry matter Microwave (Radar), dry Ultrasonic
5.2.2.2.3 Level in Silos and dry matter with ingressing parts systems  Guided microwave.Capacitance dry
5.2.2.2.4 Mechanical systems Load cells Electromechanical
5.2.3 Dry Flow
5.2.3.1 Optical / Laser flow
5.2.4 Analytical of dry matter
5.2.4.1 NIR analysis
5.3 Sensors in the indirect product contact area
5.3.1 Presence detection
5.3.1.1 Optical
5.3.2 Distance detection
5.3.2.1 Inductive
5.3.2.2 Laser distance detection
5.3.3 Encoder and positioner
5.4 Requirements for non-food contact areas
5.4.1 Housings
5.4.2 Cables, cable entries and plugs
5.4.3 Holder and mechanical support
6 References
7 Key Learning Points