How to define a pinch hazard?

[AaronH]

All,

I have a design I am working on where a moving object is going to come close to a fixed object. At this point in the design I can control how close the two objects can get. I need to get them as close as I can but avoid a pinch hazard as well. Unfortunately, the issue cannot be designed out nor guarded in any real effective way. I've done some basic research on the net and have yet to find a source that defines with dimensions what a pinch point is. I realize it's some what of a relative term as the distance require to pinch your finger is different than your fore-arm, but I am hoping there is a source that gives some insight into this topic. I've been on a couple OSHA websites and they, of course, say that pinch points have to be guarded, but I don't see anywhere where they define what IS a pinch hazard.

Anyone know of a good resource that gives dimensional data to define pinch points for machinery?

Thanks,
Aaron

 

[desertfox]

Hi AaronH

This might help but it doesn't give any dimensions only various pinch hazards.

http://docs.google.com/viewer?a=v&q=cache:7XCQChjVmXcJ:

http://www.concrete-pipe.org/safety/sa_114.pdf+pinch+hazard&hl=en&gl=uk&

pid=bl&srcid=ADGEESgcoCBqFViDaQz78PN2SLrfF2tbGGNU2_WWKfa
LGniyncCsLq2op2pDcLLvyBKdZPW2LYZoZN2BcnFixrwRArMUUG5fhj
MMDf-uyZXbPOSU1RzzDFAFg-p--IHlu84NupB5cb1G&sig=AHIEtbRMBXJ1ggxAGCye0062wy_frBb4PQ

desertfox

 

[TheTick]

Currently designing hospital beds. We have specific standards for this industry (FDA, I think). Mottorized movements within 8 inches of perimeter. No standard for manually-powered mechanisms.

 

[MadMango]

I used to work in transportation, not sure if this is applicable since you didn't state your industry, but CFR Title 49 states a min clearance of 1.5" for moving handrails and fixted surfaces.

Read Section 38.23.b.13.

http://www.fta.dot.gov/civilrights/ada/civil_rights_3905.html

"Art without engineering is dreaming; Engineering without art is calculating."

Have you read faq731-376 to make the best use of these Forums?

 

[BrianPetersen]

There is a table that talks about the distance that someone has to reach into a hazard area versus how large the opening can be. I know it's Table 3 in CSA Z432-04 but I also know that the CSA numbers are copied from OSHA, so the same table is in OSHA somewhere. This might not really address your question, though; it's really meant at the size of openings in guards that are allowable for someone to reach through.

The ANSI standard for printing presses (B65.1? could be wrong) defines the approach between rollers for it to be considered a pinch point to be 3 inches; this is in a situation where someone's arm can be inserted into the gap.

Robot standards (ANSI/RIA R15.06-1999 and CSA Z434-03) require robots to stay at least 18" (ANSI) or 500mm (CSA) clear of obstructions not directly related to the robot function, in situations where a person could be standing on the floor near the robot while teaching it. Presumably this is an indirect way of saying that 18" (ANSI) or 500mm (CSA) is sufficient to allow a person to stand there without being crushed. Yeah, I know some people are bigger than that, but it's not a perfect world.

So, it depends how much of someone's body can foreseeably get in the way of danger.

 

[berkshire]

This appears to be pretty subjective,
The OSHA rule reads : Section 4002: "Moving Parts of Machinery or Equipment".
All machines or parts of machines which "create hazardous revolving, reciprocating, running, shearing, punching, pressing, squeezing, drawing, cutting, rolling, mixing or similar action, including pinch points and sheer points, not guarded by the frame of the machine or by location" must be guarded.
Nowhere in this does it give a dimension.
Can you guard by location i.e. keep people away from it?
B.E.

 

[Wrenchbender]

No, I do not know of any references that define, but…
I believe specifying what constitutes a’pinch’ on human anatomy would be difficult because of many factors some of which are subjective. (Variables would include the sensitivity of the organs involved, the strain rate, pressure, extent of the trauma produced, how many capillaries are broken, temperature, predisposing medical conditions of the pinchee, etc, etc.)

If there are no precedents, and no standards in place, and the source of the pinch requirement cannot quantify it, I think the best approach would be common sense, engineering judgment and due diligence to avoid what could be a ‘pinch’ (whatever that is) in the worst case scenario. Maybe volunteers could be recruited for product development. Oh, have them sign a waiver.

 

[IRstuff]

While not directly related British Standard BS EN547 may provide some useful guidance, since it provides standards for access openings for various parts of the body.

While pinch hazards are not deterministically defined in broad usage, common usage does only refer to limbs and appendages as potential victims of pinch hazards. This does mean that BS EN547 could be used as a guideline for determining the smallest gap to prevent pinching a specific appendage.

For example, specification 4.10 describes the minimum opening that allows the 95th percentile finger to be inserted.

With a P95 breadth of 23 mm and the specified additional allowance of 25 mm, then opening or gap larger than 48 mm cannot be technically considered to be a pinch hazard.

Likewise BS EN547 has similar calculations for feet, arms, hands, etc.

TTFN

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