Re: [PSES] UL 61010-1 7.4 stabilty

Mon, 22 Jul 2019 22:41:21 -0700

Thanks Rich,

This is helpful. I think I know how to deal with this. And I will argue against a broken wheel test which would be an unwarranted abnormal operations test in my view. In this case, the wheels are rated for the load; if they were underrated then a test like that might be in order. 

Best regards, Doug



Currently out of the office and working from my Android phone

Sent: July 22, 2019 8:44 PM
Subject: Re: [PSES] UL 61010-1 7.4 stabilty


Hi Doug:

See IEC 61010, 3rd edition, Clause 7.4 d) and e).

The 4X load is only applied to the support or castor that has the greatest load (independent of the equipment) (d).  I guess the pass criterion is no failure of the support or castor.  (If the support or castor is rated 4X or more of its load, then no test is necessary.)

The maximum load support or castor is removed; the equipment shall not overbalance (but without the 4X load) (e).  (Hmm.  If the support or castor meets (d), then what is the value of assuming its failure?) 

The inspector has not written the two requirements correctly.

Best regards,
Rich
 

On 7/22/2019 5:11 PM, Doug Powell wrote:
An interesting requirement came up today on a system that uses wheels for mobility. The inspector says clause 7.4 requires "... the unit be stable in the upright orientation, with wheels augmented with floor-braces or other such parts as necessary such that each wheel or brace can withstand four times the weight normally applied to it and the unit will remain stable and upright if any wheel or support is removed or broken." This is the exact in the letter report.

I have no problem with stability requirements but I checked the third edition of UL 61010-1 and the national differences. I found nothing like this statement in the standard.  It didn't even mention the words wheels or castors. I am familiar with the four times requirements for handles, lifting rings and the like but not for wheels in particular. Also, I do know about various topple tests and the like are performed but a broken wheel or broken support test?  

This made me wonder if the certifying agency has internal requirements or possibly the inspector is confusing wheel requirements from IEC 60601-1 for "transportable equipment" .  

Does anyone know where the above may have originated? 

Thanks everyone!

Doug

--
Douglas E Powell

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