# Dielectric union



## glen1971 (Oct 10, 2012)

Would anyone have a part number for a Zone 2 (Class1 Div 2) dielectric union? Or do they even make sure an animal?
I'm trying to electrically isolate a pressure transmitter from a pipeline with Cathodic Protection on it. There is one on the process connection, but the transmitter is still "hot" through the conduit system.
When a lightning storm rolls through we let the smoke out of the pressure transmitter. On one site, someone removed the dielectric union on the main control cable at the pipeline to the PLC, and when a storm rolled through it cost us the transmitter, PLC card and processor.


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## Peewee0413 (Oct 18, 2012)

dielectric union, class 1 div 2 never seen one lol


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## Lone Crapshooter (Nov 8, 2008)

Not exactly what you are looking for but OZ Gedney makes Phenolic couplings for breaking metallic paths ( ICC Couplings). Only approved for general areas.
You might want to check your area classification to make you are in a Class 1 Div 2 area or they just put it in with that type of equipment because that is what they had that day. You might be in a general area and not know it. I have seen that happen more than once . On the other hand you could be in a Class 1 Div 1 area. It can go ether way.
As electrical people we have to live with engineering gives us. From what I have seen it is here it is live with it.

LC


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## glen1971 (Oct 10, 2012)

Lone Crapshooter said:


> You might want to check your area classification to make you are in a Class 1 Div 2 area or they just put it in with that type of equipment because that is what they had that day. You might be in a general area and not know it. I have seen that happen more than once . On the other hand you could be in a Class 1 Div 1 area. It can go ether way.
> As electrical people we have to live with engineering gives us. From what I have seen it is here it is live with it.
> 
> LC


No I'm sure it's a Div 2 location, based on area classification and adjacent process vents.

I wasn't sure they made them, so we're gonna try a process rated one, if that works, then I'll look at a non-ferous plate to enter the cable into the PLC, which should accomplish the same thing.


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## SWDweller (Dec 9, 2020)

Could you use a schedule 80 plastic nipple? I like 80 better, take more pressure when threading in or out of the metal fittings.


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## wcord (Jan 23, 2011)

How about a Crouse Hinds CEAG cable gland?


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## CAUSA (Apr 3, 2013)

SWDweller said:


> Could you use a schedule 80 plastic nipple? I like 80 better, take more pressure when threading in or out of the metal fittings.


And use a wood plug when threading it to prevent oops on pipe shape.


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## wcord (Jan 23, 2011)

SWDweller said:


> Could you use a schedule 80 plastic nipple? I like 80 better, take more pressure when threading in or out of the metal fittings.





SWDweller said:


> Could you use a schedule 80 plastic nipple? I like 80 better, take more pressure when threading in or out of the metal fittings.


Firstly, PVC isn't approved for Zone 2, (Class 1,Div2
Secondly, can't thread pvc or screws it into metal fittings 
12-1112 Fittings 1) Rigid PVC conduit, including elbows and bends, shall not be threaded but shall be used with adapters and couplings, which shall be applied with solvent cement. 2) Female threaded PVC adapters shall be used together with a metal conduit nipple to terminate at threaded conduit entries in metal enclosures.


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## CAUSA (Apr 3, 2013)

wcord said:


> Firstly, PVC isn't approved for Zone 2, (Class 1,Div2
> Secondly, can't thread pvc or screws it into metal fittings
> 12-1112 Fittings 1) Rigid PVC conduit, including elbows and bends, shall not be threaded but shall be used with adapters and couplings, which shall be applied with solvent cement. 2) Female threaded PVC adapters shall be used together with a metal conduit nipple to terminate at threaded conduit entries in metal enclosures.


Yes you are correct.

I just though I was adding to a funny solution.🤩

I was going to use the B_t plug solution to keep its shape. But figured to rude, due to this being a family friendly site. With apprentices, viewing it. My bad. For making the statement.

thanks for the correction. Your are correct with the not PCV in the area in question. And the joining methods. For the electrical section.

I will try to keep it more serious in the future.

😎


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## CAUSA (Apr 3, 2013)

glen1971 said:


> Would anyone have a part number for a Zone 2 (Class1 Div 2) dielectric union? Or do they even make sure an animal?
> I'm trying to electrically isolate a pressure transmitter from a pipeline with Cathodic Protection on it. There is one on the process connection, but the transmitter is still "hot" through the conduit system.
> When a lightning storm rolls through we let the smoke out of the pressure transmitter. On one site, someone removed the dielectric union on the main control cable at the pipeline to the PLC, and when a storm rolled through it cost us the transmitter, PLC card and processor.


so check out the EATON products.

There is one that adapts to a existing port or re pipe it in.

See below.
I included the sales brochure for other related products in case you need them and the data sheet on the most cost effective one to install.

They are CSA approved.


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## oldsparky52 (Feb 25, 2020)

How can it be okay to break the conduit bond?


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## oldsparky52 (Feb 25, 2020)

Are these intrinsically safe components and system?


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## CAUSA (Apr 3, 2013)

oldsparky52 said:


> How can it be okay to break the conduit bond?


Not really breaking the bond but having a Rated surge protector at the closest source to protect the sensor or controller.

Yes rated for the area. But must be installed according to their instructions. 

But like always get the AHJ clearance for this application. so you do not waste your time and money.

Pg.13 if I remember correctly for other sensor protection items.


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## Peewee0413 (Oct 18, 2012)

Wireless transmitter? Batteries don't tend to do well in places that drop to Artic temperatures though.


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## wcord (Jan 23, 2011)

oldsparky52 said:


> How can it be okay to break the conduit bond?


I did an air traffic control center, where the main room was shielded with lead and all of our conduits had to convert to PVC where they went thru the lead shield.
If I remember (40 yes ago), we had to pull a bond wire in every conduit. 
At the time, the reasoning was explained, but I don't recall what it was


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## Peewee0413 (Oct 18, 2012)

I don't see lightning being an exception to the conduit or cable requirements. Protect what you can from lighting using some of the many different tactics.


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## glen1971 (Oct 10, 2012)

oldsparky52 said:


> Are these intrinsically safe components and system?


The system we are working on is not IS. It is just a PLC, with one cable going to the valve on a pipeline. There is a solenoid and 3 limit switches on the valve and a pressure transmitter on the pipeline. All are 24 vdc.


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## glen1971 (Oct 10, 2012)

Peewee0413 said:


> I don't see lightning being an exception to the conduit or cable requirements. Protect what you can from lighting using some of the many different tactics.


Right or wrong the original installations all had an insulating union (I believe they are a process rated one) where the cable enters a condulet tee. Top of the tee goes to the discrete devices, and the other opening on the tee goes to the transmitter.
A run of heat trace has rubber around the pipeline to separate it from the power kit box (Thermon metal style), so that install was pretty easy to wrap my head around. Yes a non-metallic junction box would have been better, but I didn't do the original install.


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## Peewee0413 (Oct 18, 2012)

glen1971 said:


> Right or wrong the original installations all had an insulating union (I believe they are a process rated one) where the cable enters a condulet tee. Top of the tee goes to the discrete devices, and the other opening on the tee goes to the transmitter.
> A run of heat trace has rubber around the pipeline to separate it from the power kit box (Thermon metal style), so that install was pretty easy to wrap my head around. Yes a non-metallic junction box would have been better, but I didn't do the original install.


Can you show me a non-metallic Class 1 div 2 enclosure?


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## glen1971 (Oct 10, 2012)

Peewee0413 said:


> Can you show me a non-metallic Class 1 div 2 enclosure?


Any fiberglass gasketted Junction box.
Thermon DP power kits.
Are a couple of examples.


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## Peewee0413 (Oct 18, 2012)

glen1971 said:


> Any fiberglass gasketted Junction box.
> Thermon DP power kits.
> Are a couple of examples.


I've never installed fiberglass anything inside a class 1 div 2. I'll take your word for it.


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## aznmoktx (10 mo ago)

glen1971 said:


> Would anyone have a part number for a Zone 2 (Class1 Div 2) dielectric union? Or do they even make sure an animal?
> I'm trying to electrically isolate a pressure transmitter from a pipeline with Cathodic Protection on it. There is one on the process connection, but the transmitter is still "hot" through the conduit system.
> When a lightning storm rolls through we let the smoke out of the pressure transmitter. On one site, someone removed the dielectric union on the main control cable at the pipeline to the PLC, and when a storm rolled through it cost us the transmitter, PLC card and processor.


Try this: Dielectric Insulated Unions - HART Industrial Unions (hartindustries.com) ; or if your txr is tubed Swagelok makes a di-electric tube union: Unions | Dielectric Fittings | Fittings | Swagelok ; that's what we use.


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## glen1971 (Oct 10, 2012)

aznmoktx said:


> Try this: Dielectric Insulated Unions - HART Industrial Unions (hartindustries.com) ; or if your txr is tubed Swagelok makes a di-electric tube union: Unions | Dielectric Fittings | Fittings | Swagelok ; that's what we use.


Thank you for your help! The process side ones were easy to find. I was wondering if they made one for the electrical side.


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## kb1jb1 (Nov 11, 2017)

aznmoktx said:


> Try this: Dielectric Insulated Unions - HART Industrial Unions (hartindustries.com) ; or if your txr is tubed Swagelok makes a di-electric tube union: Unions | Dielectric Fittings | Fittings | Swagelok ; that's what we use.


I have to keep this for future reference although I probably will never need it. Years ago I did but that customer is long gone.


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## glen1971 (Oct 10, 2012)

Minor update..
So we installed the surge protectors as shown in post #10 on 2 of the most problematic sites. They made it through one lightning storm, but Sunday we took out another analog card due to lightning. Looking at it, I think we inadvertently left in an insulating union on the electrical side, so there may not have been a decent ground connection. We pulled out the second union on one site, and will catch the second one tomorrow, as I need a longer length of LT flex. I'm finding that troubleshooting lightning is a bit of a challenge, when there is none in the forecast. Judging by our forecast, Mother Nature is going to cooperate for a day or two.


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## glen1971 (Oct 10, 2012)

Minor update #2.
Mother Nature cooperated and gave a pretty good lightning show last night. There must have been lightning in the area of a problem site, as we saw a process trip. The transmitter and PLC took zero damage. Today I added a ground from the transmitter, and connected it back to the #2 at the PLC. While there, I found an insulating coupling that may have been giving us some grief. 
I'm not sure if the surge protectors we added were doing their job last night and interrupted the 4-20 mA signal. So today, we are adding a 5 second delay to the shutdown control logic in the PLC. Usually when we see issues both an alarm and shutdown are generated at the same time. Out thought is if we delay the shutdown and leave the alarm with no delay, we should be able to see a bit better of what's going on. We'll see what Mother Nature dishes out today.


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