Principal engineer
- Thread starter john2684
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- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Do you mean do they need to be UL listed?
Are these being used as part of an industrial process or machine? Will they be individually sold or only used by your company?
Only the AHJ can approve something. In some localities the AHJ must always approve Listed equipment, in other localities AHJ seem to always reject non-Listed equipment. In both of these situations it would be preferable to have your device Listed
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petersonra
Senior Member
- Location
- Northern illinois
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- engineer
UL lists stuff. It does not approve them.
Since there are plenty of such devices available that are UL listed, why screw around with some that aren't? Some where, some day you will get in a pi&&ing contest with some one over it. Why create a future hassle for yourself.
Safety-critical components of a UL-Listed product must be UL-Recognized (backwards UR mark). These items would be considered "safety critical." As petersonra says, just use UR parts, it's easier in the long run.
Anyone please correct me.
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
why would these be a safety issue at all?
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
A U and a backwards R only indicate that the device is UL recognized instead of listed. A recognized component must be used with some other device rather than being used just by itself. For example, a plug-in relay must be used with the correct relay base.
Safety critical devices may or may not be recognized components, they could be listed instead.
What if one fails? Might bad things happen (e.g. conveyor continues to run when it should have stopped)?
1.) Does not the UR imply some level of testing?
2.) I'm not sure why my immediate assumption was UR rather than UL/UR.
Thanks,
Doug
Our company is a UL 508a listed panel builder and the only time UL listing is an issue is if an application specification or customer defines it as a requirement.
That said, any reputable electrical component is going to be either UL listed or UL recognized. I doubt the conveyor is UL listed as a complete assembly.
As far as the 24 volt conveyors go, they are typically low torque powered rollers which are very safe for use where operators will be present. Far better safety wise than belt conveyors or high power roller units driven by chains or friction belts. Each zone has the torque needed to move a box the distance of that zone and pass it to the next. Very low torque requirements=safer operaton. Not to mention you are dealing with low voltage rather than 240/480 induction motor driven units.
That said, any reputable electrical component is going to be either UL listed or UL recognized. I doubt the conveyor is UL listed as a complete assembly.
As far as the 24 volt conveyors go, they are typically low torque powered rollers which are very safe for use where operators will be present. Far better safety wise than belt conveyors or high power roller units driven by chains or friction belts. Each zone has the torque needed to move a box the distance of that zone and pass it to the next. Very low torque requirements=safer operaton. Not to mention you are dealing with low voltage rather than 240/480 induction motor driven units.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Yes UL recognized components have gone through some UL process.
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
If it is truly a "safety" issue, you might have a point. However, my suspicion is that its more an equipment or product damage issue, or mere inconvenience.
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