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Sight Glass (EX area)

Sight Glass (EX area)

Sight Glass (EX area)


Is it possible to used Sight glass in ATEX area (Zone 1 group 2)? Glass is sometimes not recommended in EX area.
A low conudctivity fluid (lubricating oil) will flow through the sight glass.
This oil may be charger by a fine filtration upstream filter.

I would like to avoid potential static external static discharges (ESD) creater by a charged lube oil flow (by induction effect).



RE: Sight Glass (EX area)

You don't describe which kind of sight glass. I'm aware of
- in-line, flow sight glass
- tank/vessel sight glass
- bypasss level sight glass

The first has lots of flow, the 2nd has flow if the medium in the tank is agitated, both the (unagitated) 2nd and 3rd only has liquid movement as the level changes, relatively low movement compared to the first.

I had a college summer job doing lab work where the disposal of liquids require the use a grounded metal canister in order to avoid static discharge. Of course, the open canister had a mix of liquid fumes and air and the danger was reaching the LEL concentration level and then having a spark discharge. I found this article that shows the type of equipment at the time.


It would seem that any flow induced static charge would be dissipated when the fluid contacts grounded, exposed, conductive metal pipe. I would think that a flow in grounded metallic pipe with a flow sight indicator with materials of construction of exposed, conductive metal surrounding the transparent sight glass would dissipate any static charge. I have to admit, I'm speculating, I do not know if there hazardous area regs regarding this.

In-line flow sight glass indicators are available in both thermoplastic or metallic construction.

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