Looking for Hazardous Area Hourmeter

[apatjr]

Has anyone had any luck finding an hourmeter that can be used in a Class 1, Div 2 Area and has the certificate to back it up.

Thanks in advance.

 

[peebee]

Hmmm. . . . I'd think you should be able to find an intrinsically safe meter pretty easily. . . .

Please clarify your exact requirements -- you're simply looking for an elapsed time meter that will count run time or some such? Based on an external contact closure?

 

[bklauba]

Would an elapsed time meter mounted in a NEMA 4,7,9 enclosure with an appropriate sight glass do the trick?

bk

 

[apatjr]

We presently seal a standard hourmeter inside a NEMA 7 instumenatation enclosure. However, this means either using a pour fitting or a cable terminator. In most cases this forces the hourmeter outside our control panel. We are trying to eliminate this extra step.

An instrinsically safe device wouldn't cut it as everything is located in the hazardous zone. At present every device is rated for a hazardous area less the hourmeter.

 

[DRWeig]

apatjr,

You can use an intrinsically safe device, just put the barrier inside your NEMA 7 enclosure and pipe out to the meter through a seal.

I'd contact the major barrier manufacturers (MTL, R Stahl, Pepprl&Fuchs, Turck). They'll be able to point you at an IS rated device (or they might have one of their own).

You actually have another option. If the counter were electronic (no contacts or other "arc and spark" devices), and it doesn't in normal operation produce a spark, you can use it as-is in a Division 2 area per the NEC. Not much stuff is actually labeled non-incendive for Div 2.

Let us know what you find out!

Old Dave

 

[apatjr]

Old Dave,

Thanks for the input. However, we're trying to eliminate the use on any NEMA 7 enclosures.

We get our control panels inspected by UL and as such we have to supply documentation proving the components are suitable for the area.

I've been told that if our hourmeter is fed power through a PLC that is rated for a hazardous area then the PLC will limit the current which in turn make the end device intrinsically safe. Personally, I don't buy this.

Again, thanks for the input.

 

[DRWeig]

apatjr,

You're right to not buy into the "if the power supply is intrinsically safe, the load is too" argument. There are things that this is true for -- they're termed "simple apparatus" and are defined by the following parameters:

Less than 1.2V (US) or 1.5V (elsewhere)
Less than 100 mA
Less than 25 mW
There's also a stored-energy restriction of something like 20 microjoules.
Surface temperature less than ignition temperature under all conditions

However, if something is not obviously a simple device (thermistor, RTD, switch, LED) then it needs a label as intrinsically safe, with associated safety parameters.

I betya the folks at MTL will have a lead for you.

Good luck with it!

Old Dave

 

[resqcapt19]

Look at the exception to 501.3(B)(2). This would permit the use of most electronic type meters without an explosion proof enclosure and special documentation would not be required. Also most motor driven hourmeters would be permitted per 501.8(B) without documentation.
Don

 

[apatjr]

Resqcapt19

I'll have to address this with UL. I noticed that the exception also mentions solenoids and yet all our solenoids are rated for hazardous areas.

Thanks for the insight.