Seals - XP Enclosures, Adjacent Enclosures, Div2 Area

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bobgorno

Senior Member
Location
Colorado
Situation:
  • Class I, Div. 2 Area
  • No evaluation done for non-incendive system, components , etc. Assume not non-incendive.
  • Automated Valve, limit switches, XP enclosure, non-hermetically sealed contacts, enclosure says install seal within 18"
  • Automated Valve, solenoid valve connected to limit switch XP enclosure with LFMC, no seal at XP enclosure.
  • 2nd installation, Automated Valve, solenoid valve connected to limit switch XP enclosure with close nipple, no seal at XP enclosure.
  • See attached pictures. It appears field has installed with consideration to limit vapor, not contain explosion. If the switches were hermetically sealed, there would be no issue with these installs.

Recommended correction - Rework solenoid valve connections to include seal at XP enclosure. LFMC will not contain explosion. On 2nd installation example, XP solenoid valve cannot be used to seal the adjacent enclosure. 501.15(A)(1)(1) and (B)(1).

Comments from the group are appreciated.
Thanks,
BobG
 

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rbalex

Moderator
Staff member
Location
Mission Viejo, CA
Occupation
Professional Electrical Engineer
Bob G,

I'm sorry, but I can't seem to expand you photos to a point where I can view them clearly (my old eyes:(); nevertheless, your written analysis seems proper to me.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
hard to tell much from the pictures.

some actuators like this come with namur style sensors that are made for div 2 areas.

just because it is an XP enclosure does not mean it needs a seal. it only needs a seal if the XP enclosure is required.
 

rbalex

Moderator
Staff member
Location
Mission Viejo, CA
Occupation
Professional Electrical Engineer
I've known Bob G a long time; I trust his evaluation of whether a particular enclosure is required to be explosionproof - just as I would yours. :happyyes:
 

bobgorno

Senior Member
Location
Colorado
We have inspected the enclosures and all are mechanical limit switches, non-hermetically sealed, not NAMUR.

We have vendors who have tried to be helpful and connected these, however it does not appear they actually use electricians. Found some that actually connect the solenoid to the XP enclosure with a 316SS pipe nipple and reducer instead of conduit fittings.

We are changing our specs to prevent the vendors from being "too helpful". We will now require limit switches to be hermetically sealed when we are in a D2 area. That way whatever they do, we will be good.

In the meantime, we are evaluating another site on whether we can call it all non-incendive...

Cheers,
BobG
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
... We will now require limit switches to be hermetically sealed when we are in a D2 area. That way whatever they do, we will be good. ...
BobG

Yes, we always spec those limit switches to be the sealed magnetic reed type for Class I, Division 2 areas.

As I recall the magnetic reed switches cost a bit more than the mechanical limit switches, but after you add the labor and material that is required to seal the mechanical switches you have a total cost more than you would have if you used the sealed switches.
 
I too have old eyes, but I have worked with a lot of valve operators and limit switches. I think you will like the hermetically sealed limit switches much better from an operation perspective as well. Especially with most of the Switchpack designs. Most of these use a round cam that is placed eccentrically on the shaft with spring loaded slip splines for setting the cams. The mechanical lever switches need a good bit of travel and with an eccentric round cam that translates to a good deal of shaft rotation to actuate the limit switch. If you set them too close you sometimes have reliablity issuses with temperature change and vibration. The hermetic switches use similar cams, but they have magnets and set up with better resolution and reliability.

Some of the switchpacks that i have used had a few extra terminals and were designed to let you hang the solenoid to the exclosure and land the solenoid wires on the strip.
 
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