compliance requirements for optical sensor in haz loc

[Fash]

We manufacture optical sensors for use in gas turbines. The sensors are passive optical devices in a hazardous location, connected to an electrical 'interrogator' which is in a safe location by an optical fibre.
In Europe the compliance regime is clear since the ATEX directive now covers non-electrical equipment.
I'm struggling to work out what the relevant standards in the US are since the product in the Haz Loc is not electrical and the only standards I can find relate to electrical equipment.
I know it's a bit off topic in an electrical forum but help really appreciated:-?

 

[weressl]

We manufacture optical sensors for use in gas turbines. The sensors are passive optical devices in a hazardous location, connected to an electrical 'interrogator' which is in a safe location by an optical fibre.
In Europe the compliance regime is clear since the ATEX directive now covers non-electrical equipment.
I'm struggling to work out what the relevant standards in the US are since the product in the Haz Loc is not electrical and the only standards I can find relate to electrical equipment.
I know it's a bit off topic in an electrical forum but help really appreciated:-?

The only area you need to be concerned about where the fibre passes from the hazardous to the non-hazardous location. You would need to prevent the passage of flammable mixture passing through the boundary. If the electrical enclosure is XP rated then the connector/bulkhead also needs to be such. Approval for both the enclosure and connector neds to be a lsited product that is acceptable in the US, eg. UL or similar. If the enclosure is pressurized according to NFPA 496, then the connector only needs to be a pressure rated connector that provides sufficient pressure retaineage in the enclosure.

 

[rbalex]

For US domestic applications, it is very likely your product will need to be "listed" whether for HazLoc locations or not. This essentially means third-party certification. There are several Nationally Recognized Testing Laboratories (NRTL) in the US. They can assist you in determining the appropriate requirements. Some also have associates in Europe that are permitted to conduct required testing ? you will probably recognize them.

 

[bobgorno]

There may be some guidance for you in this ISA Technical Report. There are some reports of optical energy igniting hazardous vapors. An abstract is pasted below.


ANSI/ISA-TR12.21.01-2004 Use of Fiber Optic Systems in Class I Hazardous (Classified) Locations (Downloadable) @ www.ISA.org

About
This Technical Report provides guidance on the safe use of fiber optic systems and their
constituent parts producing or guiding visible, near infrared, or mid infrared (maximum
wavelength of 10 micrometers) radiation in Class I hazardous (classified) locations. Hazardous
(classified) locations are described in the National Electrical Code (NEC). Limiting levels
prescribed in this document apply only to the minimum levels of optical power, optical power
density, and optical energy needed to ignite explosive gas atmospheres. In apparatus where
optical energy is transduced to electrical energy, the limiting values for the electrical energy must be determined from relevant standards for electrical apparatus (e.g. ANSI/ISA-12.00.01).

 

[weressl]

There may be some guidance for you in this ISA Technical Report. There are some reports of optical energy igniting hazardous vapors. An abstract is pasted below.


ANSI/ISA-TR12.21.01-2004 Use of Fiber Optic Systems in Class I Hazardous (Classified) Locations (Downloadable) @ www.ISA.org

About
This Technical Report provides guidance on the safe use of fiber optic systems and their
constituent parts producing or guiding visible, near infrared, or mid infrared (maximum
wavelength of 10 micrometers) radiation in Class I hazardous (classified) locations. Hazardous
(classified) locations are described in the National Electrical Code (NEC). Limiting levels
prescribed in this document apply only to the minimum levels of optical power, optical power
density, and optical energy needed to ignite explosive gas atmospheres. In apparatus where
optical energy is transduced to electrical energy, the limiting values for the electrical energy must be determined from relevant standards for electrical apparatus (e.g. ANSI/ISA-12.00.01).

Do you think this is applicable to a passive device? Eg. the device itself does not generate light energy, but it evaluates the light energy/parameters from an external source.

 

[bobgorno]

The cable is passive also. The TR discusses protection techniques for the cable. It's highly unlikely that a broken FO cable will ignite a hazardous atmosphere, but someone has gone through the trouble of testing and proving you can.

I don't know what to make of it. Don't want to agree or disagree, cuz either way you can't win on this.

I just install OFNR cable in conduit or cable tray to protect from the end of the world.

Since the cable is non-conductive, no XP seal is required. I don't believe you can push vapors through the cable, so vapor barrier in conduit or putting the cable in a tray are probably the best install techniques.

As for the passive optical end devices, FASH probabaly needs to compare it to the ISA TR and build a justification why it can't produce enough energy to ignite a hazardous area.

This is one of the reasons a NRTL independant apporval is probabaly better an ATEX manufacturers' self evaluation if the manufacturer does not have the expertise to evaluate the whole picture.

 

[weressl]

This is one of the reasons a NRTL independant apporval is probabaly better an ATEX manufacturers' self evaluation if the manufacturer does not have the expertise to evaluate the whole picture.

The ATEX self-evaluation is based on ATEX Standards. It is not unlike a manufacturer would perform a testing based on the UL Standard. The UL testing just removes the manufacturers direct liability. UL could also afford to have more elaborate a detailed testing, since it performs testing for a number of products for different manuafcturers and economy of scale comes into play.