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Safety Questions

Question Asked:

I'm trying to determine if I need to have a safety rated dump valve or just a regular dump valve for an application. The dump valve is used on a shuttle table. This shuttle table is loaded by the operator, the operator pushes a button, and the table enters the cell at which point the robot unloads the table. The table is enclosed by guarding and a light curtain, so the operator is protected by pinch points. However, when the integrator/tech is teaching the robot in the cell, there may be a scenario where injury could occur. What's your thoughts? Thank you!!

2 Answers

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Christopher Scott - Controls Integration Manager
Lincoln Electric, Automation Division
christopher_scott [at] lincolnelectric [dot] com
(423) 643-2406

I do not believe that the information provided is adequate enough to fully answer your question. A risk assessment would be needed to fully understand the initial risk level that this moving table represents. Along with that, I would need to know the intended operation of the system along with any maintenance requirements. With all of that information, we could then determine the best possible solution to your problem. Speaking in generalities, for high risk applications where trapped air and unintended motion could cause an injury to personnel, I would make sure that the air provided to that part of system was controlled by a safety rated dump valve. Feel free to reach out to me if you have any further questions.

Lee Burk - Manager, Training & Standards
Pilz Automation Safety L.P.
l [dot] burk [at] pilzusa.com
(734) 354-0272

Indeed, the safety performance will need to be determined by a risk assessment, but assuming your description means the potential harm is significant, you will require a higher performance level than that provided by a single valve. In this case it sounds like you already have a redundant control, the dump valve and the directional valve. Both can be used to safely prevent motion while the zone is accessed, provided the directional valve releases the pressure in its off position. Just drive and monitor both with your interlocking device and safety control logic.


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