ISO/TS 15066:2016 is a standard for Collaborative Robots (COBOTS).   While 
COBOT specific, it does contain a great deal of information on risk of harm 
based not only on the mass and velocity of the moving part of the COBOT, but 
also the duration of contact with the body, body part impacted, and surface 
area of contact.   Lots of interesting equations.

Jim Hulbert

From: Douglas Powell <[email protected]>
Sent: Monday, January 29, 2024 7:04 PM
To: [email protected]
Subject: [EXTERNAL] Re: [PSES] Reduce Speed of Moving Part to Reduce Risk

All valid points; however, I was taking my information from the established 
ISO/IEC standards for machinery, with which I am familiar. I do recall another 
standrd some years ago, mentioning contact surface area when I was looking into 
finger crush as well as sharp edges. And the original question was solely about 
speed, so that's how I responded.

All the best,  ~ Doug


Douglas E Powell
Laporte, Colorado, USA
[email protected]<mailto:[email protected]>
LinkedIn<https://urldefense.com/v3/__https://www.linkedin.com/in/coloradocomplianceguy/__;!!GXa4NB5MBjHR!War-VZOuRADz3jRwOAfj5So1NgmwD3sc1s5K-N4jJksKsLhX1gOFLTp-Tw6q2ae55E8MCkKYs65my8pgddwK9g$>

(UTC-06:00, US-MDT)


On Mon, Jan 29, 2024 at 4:41 PM Richard Nute 
<[email protected]<mailto:[email protected]>> wrote:

Hi Doug and Brian:

I thought I would offer my (radical) point of view on the issue of “speed of 
moving parts.”

Consider moving aluminum foil and moving aluminum block, both at the same 
speed.  The aluminum foil has very little mass, while the aluminum block has 
relatively high mass.  The foil is not likely to cause injury, while the block 
may cause injury.

Consider an aluminum needle and an aluminum block, both having the same speed 
and mass.  The needle is likely to cause injury, while the block is not likely 
to cause injury.

Consider the time of contact with a moving part.  If the time is long, then 
injury is not likely.  If the time is short, then injury is likely.

So, in addition to speed, we must consider mass of the block, contact area, and 
duration of the contact in predicting injury.

In other words, energy per area (mv2 per area in this case) whether mechanical, 
thermal, radiant, chemical, or electrical, transferred to a body part for a 
(usually short) period of time, causes injury.  The same energy magnitude 
transferred over a long period of time is not likely to cause injury.

An injury occurs only when energy per contact area of sufficient magnitude and 
duration is imparted to a body part.  Both the safety science article and the 
IRSST paper discuss energy of moving parts and area, but do not address the 
other parameters.  Both introduce (to me) the concept of “force” on various 
body parts.  I’m not sure of how this fits into this safety discussion.

Consideration of speed alone is over-simplification.

Best regards,
Rich


From: Doug Nix <[email protected]<mailto:[email protected]>>
Sent: Monday, January 22, 2024 11:16 AM
To: [email protected]<mailto:[email protected]>
Subject: Re: [PSES] Reduce Speed of Moving Part to Reduce Risk

Hi Brian,

In the machinery sector, 250 mm/s has long been used as the threshold for 
avoidability. This figure comes from the robot standards and has been used for 
about 30 years. Studies done at the Polytechnique de Montréal [1] and IRSST [2] 
have shown that a speed closer to 140 mm/s is more universally avoidable by 
people working in various environments, but the long use of 250 mm/s has 
entrenched that higher speed. Related to that is the IRSST’s Repoer R-956. I’ve 
attached copies of these documents for you.

You can find the 250 mm/s number quoted in most machinery safety standards 
where reduced speed is considered for risk reduction. The origin is in ANSI/RIA 
R15.06 1992, which made its way into CSA Z434 and then eventually to ISO 10218.

[1]          Y. Chinniah, B. Aucourt, and R. Bourbonnière, “Study of Machine 
Safety for Reduced-Speed or Reduced-Force Work R-956,” IRRST - Institut de 
recherche Robert-Sauvé en santé et en sécurité du travail, Montreal, 2017.

[2]          Y. Chinniah, B. Aucourt, and R. Bourbonnière, “Safety of 
industrial machinery in reduced risk conditions,” Safety Science, vol. 93, pp. 
152–161, Mar. 2017, doi: 10.1016/j.ssci.2016.12.002.


Best regards,

Doug Nix
[email protected]<mailto:[email protected]>
+1 (519) 729-5704

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