instrument application - hazloc approval needed?

[DoReMi]

Do instruments in following applications need to be approved for hazardous location?

NFPA 820 defines haz.location area (class I, group D, Div.2) of some open basins in WWTP: "interior of the tank from the minimum operating water surface to the top of the tank wall; envelope 18in (0.46m) above the the top of the tank and extending 18in (0.46m) beyond the exterior wall..."
There are several instruments (in-situ analyzer) on the market, that will be installed so that the transmitter is mounted above the haz.envelope, a probe cable will run vertical through the envelope and the probe will normally submerged in wastewater. There are some instances in which the probe would be exposed in the haz.envelope:
- (abnormal) low water level
- the probe is pulled for maintenance/ cleaning
- at the clarifier: the rake arm lifts the probe out of the water

Do instruments in application as described are required to be approved for used in class I, div.2 haz.location?

The instrument manufacturers list the application in their manuals, but can not provide a certification.

Also I'd have liked to see an answer to question 02-25-2004, tgifreddy (low and limited energy).

Thanks
DoReMi

 

[petersonra]

If the probe is electric in nature, and it extends into or through a classifed area, you would need to do something to prevent the ignition of gases that the probe might cause.

I am familiar with a few such instruments that have EExn ratings for Zone 2. you could use them in an area rated zone 2 if the EExn rating is a US EExn rating. There is some difference between the US and Eurpean EExn rating and only the US version is acceptable here.

There are also several instruments that have IS barriers built into the instrument where the probe is connected.

Without more information, I don't think there is an answer to your question.

 

[DoReMi]

Reversing your answer would mean that several manufacturers of sludge blanket level monitors, DO & ORP probes, nitrate probes etc. selling instruments for applications in wastewater treatment plant, seemingly unaware of NFPA 820 and the conclusion therefrom.

As far as I could find out:
- the probes are housed in watertight as there are usually submerged
- the probes need either more than 1.5V or 1.3W or store energy (so they can not be considered a "simple appartus"
- the probes have no make-or-break components or otherwise sparking or arcing components
- intrinsically safety or I.S.barriers have not been mentined, some manufacturers said the probe can be considered a non-incendive device (w/o proof of certification)

Does this help?
DoReMi

 

[petersonra]

Reversing your answer would mean that several manufacturers of sludge blanket level monitors, DO & ORP probes, nitrate probes etc. selling instruments for applications in wastewater treatment plant, seemingly unaware of NFPA 820 and the conclusion therefrom.

As far as I could find out:
- the probes are housed in watertight as there are usually submerged
- the probes need either more than 1.5V or 1.3W or store energy (so they can not be considered a "simple appartus"
- the probes have no make-or-break components or otherwise sparking or arcing components
- intrinsically safety or I.S.barriers have not been mentined, some manufacturers said the probe can be considered a non-incendive device (w/o proof of certification)

Does this help?
DoReMi

It can be listed for use in a div 2 area without the need for IS barriers, but it needs to be listed that way. You can't just "consider it" that way.

 

[DoReMi]

Lets summarize:
For the application I'm concerned about, the instruments need to be listed.

Thanks.
DoReMi

 

[petersonra]

Lets summarize:
For the application I'm concerned about, the instruments need to be listed.

Thanks.
DoReMi

Listed as suitable for use in a Class1Div2 area, not just listed.

 

[weressl]

Do instruments in following applications need to be approved for hazardous location?

NFPA 820 defines haz.location area (class I, group D, Div.2) of some open basins in WWTP: "interior of the tank from the minimum operating water surface to the top of the tank wall; envelope 18in (0.46m) above the the top of the tank and extending 18in (0.46m) beyond the exterior wall..."
There are several instruments (in-situ analyzer) on the market, that will be installed so that the transmitter is mounted above the haz.envelope, a probe cable will run vertical through the envelope and the probe will normally submerged in wastewater. There are some instances in which the probe would be exposed in the haz.envelope:
- (abnormal) low water level
- the probe is pulled for maintenance/ cleaning
- at the clarifier: the rake arm lifts the probe out of the water

Do instruments in application as described are required to be approved for used in class I, div.2 haz.location?

The instrument manufacturers list the application in their manuals, but can not provide a certification.

Also I'd have liked to see an answer to question 02-25-2004, tgifreddy (low and limited energy).

Thanks
DoReMi

According to NFPA 70:

500.8 Equipment.
......​

​

​

(B) Approval for Class and Properties.​

......

(3)​

​

Where specifically permitted in Articles 501 through 503, general-purpose equipment or equipment in generalpurpose
enclosures shall be permitted to be installed in Division 2 locations if the equipment does not constitute a source of ignition under normal operating conditions.​

501.105 Meters, Instruments, and Relays.​

........​

(B) Class I, Division 2.​

.......​

(2) Resistors and Similar Equipment.​

Resistors, resistance devices, thermionic tubes, rectifiers, and similar equipment that are used in or in connection with meters,
instruments, and relays shall comply with 501.105(A).​

Exception: General-purpose-type enclosures shall be permitted if such equipment is without make-and-break or sliding

contacts [other than as provided in 501.105(B)(1)] and if the maximum operating temperature of any exposed surface
will not exceed 80 percent of the ignition temperature in degrees Celsius of the gas or vapor involved or has been
tested and found incapable of igniting the gas or vapor.
This exception shall not apply to thermionic tubes.
......​

(4) General-Purpose Assemblies.​

Where an assembly is made up of components for which general-purpose enclosures are acceptable as provided in 501.105(B)(1), (B)(2),
and (B)(3), a single general-purpose enclosure shall be acceptable for the assembly. Where such an assembly includes any of the equipment described in 501.105(B)(2), the maximum obtainable surface temperature of any component of the assembly shall be clearly and permanently
indicated on the outside of the enclosure. Alternatively, equipment shall be permitted to be marked to indicate the temperature class for which it is suitable, using the temperature class (T Code) of Table 500.8(C).​

_________________________________________

Should the manufacturer attest that the equipment meets the above criteria by design then the equipment does not need to be listed.​

You may want to verify the above with the AHJ in advance or get your insurers' Code compliance officers agreement.​

 

[DoReMi]

The paragraphs which Laszlo listed are the ones I tried to exploit too.
The problem is, that the manufacturers don't state the "maximum operating temperature of any exposed surface" on the datasheet of their devices. I think these (NEC) exceptions rather aim at the manufacturer of devices in order to be able to design an ex-proof device/ instrument and/or provide "self-evidence of suitability" for installation in haz.locations.
Most manufacturers of instruments for my application could not or didn't want to provide this "self-evidence of suitability" although they list that same application in their manuals and that application is per NFPA820 defined as CID2.
Getting in touch with the AHJ is another way I'm following.

At least your answers confirm my findings.

Thanks.
DoReMi

 

[weressl]

The paragraphs which Laszlo listed are the ones I tried to exploit too.
The problem is, that the manufacturers don't state the "maximum operating temperature of any exposed surface" on the datasheet of their devices. I think these (NEC) exceptions rather aim at the manufacturer of devices in order to be able to design an ex-proof device/ instrument and/or provide "self-evidence of suitability" for installation in haz.locations.
Most manufacturers of instruments for my application could not or didn't want to provide this "self-evidence of suitability" although they list that same application in their manuals and that application is per NFPA820 defined as CID2.
Getting in touch with the AHJ is another way I'm following.

At least your answers confirm my findings.

Thanks.
DoReMi

You could request the design data as to what normal operating temperatures are expected to develop, even if it is a statement that the 'instrument components are designed to operate at not greater than XXFarenheit/Celsius'. This does not put anybody in any legal bind. It is and informative, not contractual statement.