Food safety considerations for robot system - overall hygienic design principles

Hygienic design of robotic automation solution helps food companies to eliminate the risk of microbial contamination. In a four-part series of articles, we zoom in the best hygienic practices to design robotic automation solutions. In this fourth part we outline some specific principles for hygienic design for robot systems as specified by 3-A Sanitary Standards.

Within the framework of the project ColRobFood, we were interested in the challenges faced by Flemish companies in integrating robots in food production with the hygiene constraints in mind. We noticed that the problem of designing 'food-ready' robotic automation solutions is still open. With these blog series we will give you a summary of tips and tricks promoted by well-known organisations in hygienic design as EHEDG and 3-A SSI.

Previously we listed some risks of contamination of food by the equipment. How can we now manage these hazards by design ?

As a follow-up to part 2 and part 3 of this blog series, we here below propose an overview of additional and specific points you should look at to evaluate the quality of a robot system from a hygienic point of view.

Special fabrication requirements 

  • Moveable joint specifically developed for low pressure washing or easily removable for manual cleaning

An area with two moving components is always hygienically critical. Designing robot axes from the point of view of hygiene is difficult because seals cannot impair axis manoeuvrability. This problem can be solved effectively by using shaft seals. The gap between the axes should be wide enough to allow cleaning and disinfection agents to work effectively. The shaft seals should fit tightly enough to prevent the entry of microorganisms and contamination.

  • Low internal air-pressurisation of the arm

As the robot operates, it heats up to 60 to 70°C. When reducing its speed, or when static, it cools down quickly, producing condensation, and drawing the environment (air, humidity and bacteria) into the robot.

The ideal conditions for bacterial growth inside a robot are in place : medium temperatures between 15°C and 40°C; water presence and activity; vapour condensation drawn from the environment directly inside the robot; neutral pH; and most significantly, lack of access for cleaning the inner parts of the equipment.

With uncontrolled air pressurisation, bacteria and corrosion can develop within a few weeks. A low internal air-pressurisation of the arm is the best solution during and after production periods to prevent ingress of contaminants.
When purge air is used, it shall not come in contact with products or product contact surfaces. If used, product contact surfaces shall be protected from potential purge air leakage by an air flow sensor and shielding or other effective means.

Wiring/robot dressing requirements

Robot dressing concerns cabling, tubing and other fitments affixed to the robot and required to power and control the end of effector. This includes the cabling, tubing and other fitments from the internal ports to the end of effector termination and any that must be run on the exterior of the robot itself. Dressing includes tool changer connections. 

(Source: DENSO Robotics)

Robot wiring and pneumatic lines should be located inside the robot mechanism, except that when robot wiring and dressing are required external to the robot mechanism. These external items accumulate contamination and they shall be installed in a manner that promotes effective cleaning - dismantling or special cleaning procedures. They shall also be designed and constructed to meet the requirements for product contact surfaces.
Exhaust air from pneumatic equipment shall be piped away from product contact surfaces.

Controller requirements

The robot controller or robot controller components should not be located in the product contact zone except where they meet all of the accepted product contact criteria. This location should be away from a location where it could be affected by moisture or condensation.

Flexible robot covers shall not be used

Robot protective jacket shall not be used

Some robot manufacturers recommend the use of traditional robot covers to protect the robot, but these typically employ folds to allow freedom of motion, or elastic bands to provide a seal, therefore these covers actually introduce liquid collection areas. Another concern with covers is that the operator removes the cover for cleaning and reinstalls it. If this cover is not re-installed properly, your product can be exposed to the unprotected robot, and the robot can also be exposed to the environment.

Programming requirements

The robot shall have the ability to be programmed in order to allow for specific positions that ensure safe food handling. For example, home, wait, maintenance or robotic tasks, not directly involved with food handling, should be conducted with the entirety of the robot and end effector in a non-food zone position (see part 3 for definition).

If there is not accessibility for cleaning, inspection, maintenance or other support activities while in a non-food zone position, those tasks may be performed with the equipment in a food zone position provided that no food is present and the activity is followed by appropriate cleaning.

Robots should be programmed to prohibit exhausting of pneumatic air or liquid (except food dispensed as part of operations) in the product zone. 

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