Mechanical Ice Cube Relays

[jap]

Let me rephrase,

If you have an explosion proof enclosure with the proper seals and you intend to install relays inside of it,there is no need for the relays to be hermetically sealed.

 

[eHunter]

Hazardous location newbie question? if the equipment in the EP enclosure are not explosion proof also, how are repairs, diagnosis and maintenance safely and easily performed on the interior of the EP enclosure in a potentially explosive atmosphere?

 

[GoldDigger]

Hazardous location newbie question? if the equipment in the EP enclosure are not explosion proof also, how are repairs, diagnosis and maintenance safely and easily performed on the interior of the EP enclosure in a potentially explosive atmosphere?

Only by de-energizing the equipment (making diagnostics difficult) or by temporarily removing whatever justified the classification in the first place.

 

[jap]

Generally, the bulk of the controls are outside the hazardous location, leaving only the pushbuttons,disconnects and Motors inside,
which helps when having to troubleshoot.

 

[weressl]

I took it that he already had an enclosure rated class 1 div 2 with a PLC inside of it and was asking if he added relays inside the enclosure did they have to be hermetically sealed.

So I'll repeat mine too,


If you have an enclosure that is Class 1 Div 2 rated with the proper seals there is no need for hermetically sealed relays.

I'll humor you by saying I work in Class 1 Division 1 areas and most all of the enclosures are explosion proof with sealoffs for every entry with non-hermetically sealed devices inside if them. Engineers design.

Mostly just the light switches are hermetically sealed and dont require sealoffs.

3 of the 4 walls are 8" reinforced concrete and the outside wall is hinged so in case of an explosion the blast blows everything outside
instead of into the plant.

I tried. There are just some who can't or won't.

 

[weressl]

Hazardous location newbie question? if the equipment in the EP enclosure are not explosion proof also, how are repairs, diagnosis and maintenance safely and easily performed on the interior of the EP enclosure in a potentially explosive atmosphere?

The vast majority of the areas are Cl. I, Div. 2 areas, meaning that normally there is no ignition hazard in the area, but even in Div. 1 areas it is seldom seen that the ignitable mixture is continously present. As a frist step, operational measures are taken to minimize the presence of ignitable mixture.

Then the the general practice is that the permit for work includes the stipulation that a portable LEL(Lower Explosive Limit) monitor is carried by the worker and it is assured that before the XP enclosure is opened there is no ignition hazard. Should the monitor indicate that there is an ignitable mixture developing, the power is immediatel removed and the work suspended. The LEL monitor is usually set at 20% of the lowest explosive limit, so there is some time before the air/fuel mixture actually reaches the ignitable level.

 

[jap]

In a nutshell its very time consuming.