Sealed Conduit - Liable for Damage?

[JoelKline]

I have a job where I supplied an a chemical skid (with pumps and other components). One of the required components was an Isolator and a Pressure Switch. The idea is that in the event of a leak, pressure would be lost in the line and the switch would hit its lower limit and send an alarm to the nearby panel. The isolator diaphragm (Made of Alloy20 and yet compatible with acid) failed, allowing sulfuric acid to leak into the pressure switch, the switch diaphragm failed (because it wasn?t compatible with the acid). Thats why I had the isolator! Nonetheless, the acid leaked into the switch housing and fried the switch. Acid was able to leak out through the conduit and dripped on a nearby panel causing cosmetic damage.
I replaced the isolator and switch under warranty but believe that owner may say that I'm responsible for replacing the nearby panel.

Here is my question: Do you know if there is any NEC code that states that an electrician is required to seal/isolate the conduit in type of installation? If so, can you point out the that respective language and location? Where an electrical device is installed up on a pressured line. I'm not sure if it matters or not but the pumps are able to pump about 50psi.

 

[petersonra]

A lot depends on things you have not told us. Your equipment failed and damaged another piece of equipment due to a readily recognizable failure mode that you tried to deal with but failed to do so in a way that actually worked.

I have never heard of an alloy 20 isolation diaphragm that failed in this way. my suspicion is something was either designed or installed improperly.Generally, one would just buy a pressure switch that has a compatible diaphragm in the first place.

In any case, it is not an electrical problem to seal conduit to prevent acid from leaking into the conduit system from a failed piece of equipment.

 

[weressl]

I have a job where I supplied an a chemical skid (with pumps and other components). One of the required components was an Isolator and a Pressure Switch. The idea is that in the event of a leak, pressure would be lost in the line and the switch would hit its lower limit and send an alarm to the nearby panel. The isolator diaphragm (Made of Alloy20 and yet compatible with acid) failed, allowing sulfuric acid to leak into the pressure switch, the switch diaphragm failed (because it wasn?t compatible with the acid). Thats why I had the isolator! Nonetheless, the acid leaked into the switch housing and fried the switch. Acid was able to leak out through the conduit and dripped on a nearby panel causing cosmetic damage.
I replaced the isolator and switch under warranty but believe that owner may say that I'm responsible for replacing the nearby panel.

Here is my question: Do you know if there is any NEC code that states that an electrician is required to seal/isolate the conduit in type of installation? If so, can you point out the that respective language and location? Where an electrical device is installed up on a pressured line. I'm not sure if it matters or not but the pumps are able to pump about 50psi.

501.17 Process Sealing.​

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This section shall apply to processconnectedequipment, which includes, but is not limited to,canned pumps, submersible pumps, flow, pressure, temperature,or analysis measurement instruments. A process seal is adevice to prevent the migration of process fluids from thedesigned containment into the external electrical system. Processconnected electrical equipment that incorporates a singleprocess seal, such as a single compression seal, diaphragm, ortube to prevent flammable or combustible fluids from enteringa conduit or cable system capable of transmitting fluids, shallbe provided with an additional means to mitigate a singleprocess seal failure, The additional means may include, but isnot limited to the following1) A suitable barrier meeting the process temperature andpressure conditions that the barrier will be subjected toupon failure of the single process seal. There shall be avent or drain between the single process seal and thesuitable barrier. Indication of the single process sealfailure shall be provided by visible leakage, an audiblewhistle, or other means of monitoring.(2) A listed Type MI cable assembly, rated at not less than125 percent of the process pressure and not less than125 percent of the maximum process temperature (indegrees Celsius), installed between the cable or conduitand the single process seal.(3) A drain or vent located between the single process sealand a conduit or cable seal. The drain or vent shall besufficiently sized to prevent overpressuring the conduitor cable seal above 6 in. water column (1493 Pa). Indicationof the single process seal failure shall be providedby visible leakage, an audible whistle, or othermeans of monitoring.Process-connected electrical equipment that does notrely on a single process seal or is listed and marked ?singleseal? or ?dual seal? shall not be required to be provided​

with an additional means of sealing.

Informational Note: For construction and testing requirementsfor process sealing for listed and marked ?singleseal? or ?dual seal? requirements, refer to ANSI/ISA-12.27.01-2003,​

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Requirements for Process Sealing BetweenElectrical Systems and Potentially Flammable or Combustible​

Process Fluids.

 

[petersonra]

I am pretty sure this only applies to classified areas and only to flammable fluids. sulfuric acid is not flammable.

501.17 Process Sealing.​

​

​

​

​

This section shall apply to processconnectedequipment, which includes, but is not limited to,canned pumps, submersible pumps, flow, pressure, temperature,or analysis measurement instruments. A process seal is adevice to prevent the migration of process fluids from thedesigned containment into the external electrical system. Processconnected electrical equipment that incorporates a singleprocess seal, such as a single compression seal, diaphragm, ortube to prevent flammable or combustible fluids from enteringa conduit or cable system capable of transmitting fluids, shallbe provided with an additional means to mitigate a singleprocess seal failure, The additional means may include, but isnot limited to the following1) A suitable barrier meeting the process temperature andpressure conditions that the barrier will be subjected toupon failure of the single process seal. There shall be avent or drain between the single process seal and thesuitable barrier. Indication of the single process sealfailure shall be provided by visible leakage, an audiblewhistle, or other means of monitoring.(2) A listed Type MI cable assembly, rated at not less than125 percent of the process pressure and not less than125 percent of the maximum process temperature (indegrees Celsius), installed between the cable or conduitand the single process seal.(3) A drain or vent located between the single process sealand a conduit or cable seal. The drain or vent shall besufficiently sized to prevent overpressuring the conduitor cable seal above 6 in. water column (1493 Pa). Indicationof the single process seal failure shall be providedby visible leakage, an audible whistle, or othermeans of monitoring.Process-connected electrical equipment that does notrely on a single process seal or is listed and marked “singleseal” or “dual seal” shall not be required to be provided​

with an additional means of sealing.

Informational Note: For construction and testing requirementsfor process sealing for listed and marked “singleseal” or “dual seal” requirements, refer to ANSI/ISA-12.27.01-2003,​

​

​

​

Requirements for Process Sealing BetweenElectrical Systems and Potentially Flammable or Combustible​

Process Fluids.

 

[growler]

I am pretty sure this only applies to classified areas and only to flammable fluids. sulfuric acid is not flammable.

Sulfuric acid is not flammable but when it reacts with metals is gives off hydrogen gas which is very flammable so the area may well have been classified or should be.


Probably the best person to ask about this situation would be the local Fire Marshal.

 

[weressl]

I am pretty sure this only applies to classified areas and only to flammable fluids. sulfuric acid is not flammable.

You're correct. The OP was talking about a chemical skid, but not that it was (formally) classified or not. The underlying problem and the solution offered in the recent addition to the NEC that I cited is the same, weather it is (in) a classified area or not. If you carefully read that paragraph, none of its provision deals with prevention or prtoection of/from an explosion, it strictly deals with limiting the process fluid migration through the system. Good installation practice would utilize that in ALL areas.

 

[petersonra]

You're correct. The OP was talking about a chemical skid, but not that it was (formally) classified or not. The underlying problem and the solution offered in the recent addition to the NEC that I cited is the same, weather it is (in) a classified area or not. If you carefully read that paragraph, none of its provision deals with prevention or prtoection of/from an explosion, it strictly deals with limiting the process fluid migration through the system. Good installation practice would utilize that in ALL areas.

Good practice and required by the NEC are not the same thing.

501.17 is part of article 501. Unclassified areas are specifically excluded.

ARTICLE 501
Class I Locations
I. General
501.1 Scope. Article 501 covers the requirements for electrical
and electronic equipment and wiring for all voltages
in Class I, Division 1 and 2 locations where fire or explosion
hazards may exist due to flammable gases or vapors or
flammable liquids.

501.17 uses the phrase "flammable or combustible fluids" when describing the process sealing requirement. Sulfuric acid is not a flammable or combustible fluid. The remote chance of getting enough hydrogen gas created by a leak into the conduit does not trigger this clause even in a classified area.

 

[Gregg Harris]

I have a job where I supplied an a chemical skid (with pumps and other components). One of the required components was an Isolator and a Pressure Switch. The idea is that in the event of a leak, pressure would be lost in the line and the switch would hit its lower limit and send an alarm to the nearby panel. The isolator diaphragm (Made of Alloy20 and yet compatible with acid) failed, allowing sulfuric acid to leak into the pressure switch, the switch diaphragm failed (because it wasn?t compatible with the acid). Thats why I had the isolator! Nonetheless, the acid leaked into the switch housing and fried the switch. Acid was able to leak out through the conduit and dripped on a nearby panel causing cosmetic damage.
I replaced the isolator and switch under warranty but believe that owner may say that I'm responsible for replacing the nearby panel.





Here is my question: Do you know if there is any NEC code that states that an electrician is required to seal/isolate the conduit in type of installation? If so, can you point out the that respective language and location? Where an electrical device is installed up on a pressured line. I'm not sure if it matters or not but the pumps are able to pump about 50psi.

Shouldn't 300.6 be in the equation?

Acid was able to leak out through the conduit and dripped on a nearby panel causing cosmetic damage.

 

[petersonra]

Shouldn't 300.6 be in the equation?

Acid was able to leak out through the conduit and dripped on a nearby panel causing cosmetic damage.

I don't believe anything in the general sections of the code requires you to account for limiting damage in the event of a failure external to the electrical system.

It may well have been a poorly designed or installed system on the whole, but that does not make it an electrical code issue. It might even be that it violates some other code or specification that might apply.

having been around this kind of stuff for a long time, my guess is that either the seal was installed wrong, somehow got damaged, or it was not alloy 20 in the first place.

I worked on a job one time where the end user spec'd all 316SS nuts and bolts. a very mainstream valve supplier charged a bunch extra to change all the valve hardware to 316SS. in the field the bolts holding the valve bonnets together experienced severe corrosion. turned out they were all 304SS and had to be replaced in the field with the correct 316SS hardware. this kind of thing is a lot more common than you might think. usually it just does not matter.

Incidentally, the valve manufacturer paid to send a guy to an oil platform 200 miles off the coast of Africa to replace the 304SS hardware and repair the valves.

 

[JoelKline]

More info.

More info.

I don't believe anything in the general sections of the code requires you to account for limiting damage in the event of a failure external to the electrical system.

It may well have been a poorly designed or installed system on the whole, but that does not make it an electrical code issue. It might even be that it violates some other code or specification that might apply.

having been around this kind of stuff for a long time, my guess is that either the seal was installed wrong, somehow got damaged, or it was not alloy 20 in the first place.

I worked on a job one time where the end user spec'd all 316SS nuts and bolts. a very mainstream valve supplier charged a bunch extra to change all the valve hardware to 316SS. in the field the bolts holding the valve bonnets together experienced severe corrosion. turned out they were all 304SS and had to be replaced in the field with the correct 316SS hardware. this kind of thing is a lot more common than you might think. usually it just does not matter.

Incidentally, the valve manufacturer paid to send a guy to an oil platform 200 miles off the coast of Africa to replace the 304SS hardware and repair the valves.

The alloy 20 isolator had an alloy20 diaphragm (definitely not common but this was the setup). Its clearly stamped on the isolator body itself. Its 1 piece, not a split body like many isolators.
The isolator was installed corrected. The skid comprised of 2 pumps, both discharges had a pressure switch (with a Buna-N diaphragm) after the alloy-20 isolator. So yes the diaphragm on the switch was not compatible with acid but how many fail safes are required! That's why I had the isolator in the first place.

Anyway, I was worried that the other alloy-20 might be a ticking time boom so I opted to replace both isolators and switches with an alloy 20 body isolator and Teflon diaphragm (a 2 part isolator) and a pressure switch with a teflon diaphragm.

 

[JoelKline]

300.6?

300.6?

Shouldn't 300.6 be in the equation?

Acid was able to leak out through the conduit and dripped on a nearby panel causing cosmetic damage.

Gregg, specifically what does 300.6 call out? I just know that I'm going to be in a meeting in a few days to talk about this exact issue and I want to be as knowledgeable as possible.

 

[gadfly56]

I have a job where I supplied an a chemical skid (with pumps and other components). One of the required components was an Isolator and a Pressure Switch. The idea is that in the event of a leak, pressure would be lost in the line and the switch would hit its lower limit and send an alarm to the nearby panel. The isolator diaphragm (Made of Alloy20 and yet compatible with acid) failed, allowing sulfuric acid to leak into the pressure switch, the switch diaphragm failed (because it wasn?t compatible with the acid). Thats why I had the isolator! Nonetheless, the acid leaked into the switch housing and fried the switch. Acid was able to leak out through the conduit and dripped on a nearby panel causing cosmetic damage.
I replaced the isolator and switch under warranty but believe that owner may say that I'm responsible for replacing the nearby panel.

Here is my question: Do you know if there is any NEC code that states that an electrician is required to seal/isolate the conduit in type of installation? If so, can you point out the that respective language and location? Where an electrical device is installed up on a pressured line. I'm not sure if it matters or not but the pumps are able to pump about 50psi.

Were you responsible for the skid design and component selection, or did you just install what was shipped?

 

[petersonra]

The alloy 20 isolator had an alloy20 diaphragm (definitely not common but this was the setup). Its clearly stamped on the isolator body itself. Its 1 piece, not a split body like many isolators.
The isolator was installed corrected. The skid comprised of 2 pumps, both discharges had a pressure switch (with a Buna-N diaphragm) after the alloy-20 isolator. So yes the diaphragm on the switch was not compatible with acid but how many fail safes are required! That's why I had the isolator in the first place.

Anyway, I was worried that the other alloy-20 might be a ticking time boom so I opted to replace both isolators and switches with an alloy 20 body isolator and Teflon diaphragm (a 2 part isolator) and a pressure switch with a teflon diaphragm.

were you able to determine the failure mode?

 

[Gregg Harris]

Gregg, specifically what does 300.6 call out? I just know that I'm going to be in a meeting in a few days to talk about this exact issue and I want to be as knowledgeable as possible.

Equipment in a corrosive atmosphere.

 

[petersonra]

Equipment in a corrosive atmosphere.

the atmosphere is not corrosive in this case. what is corrosive is inside a sealed pipe.

 

[JoelKline]

Failure Cause

Failure Cause

were you able to determine the failure mode?

When I removed the isolotor and look from the process end I didnt see a diaphram. Its like the acid had eaten the thin alloy20 diaphram!

 

[JoelKline]

Were you responsible for the skid design and component selection, or did you just install what was shipped?

I was responsible for the skid and all components on that skid (which include the switch and isolator). I selected the make/model of isolator. I obviously will not use this type again, but in the meantime I may be liable for damage for something that I indirectly supplied. ?!

 

[GoldDigger]

When I removed the isolotor and look from the process end I didnt see a diaphram. Its like the acid had eaten the thin alloy20 diaphram!

What about the possibility that either the diaphragm was not actually Alloy20 or was not even present at all in the first place? Disassembly of the isolator should show traces of the edge of the diaphragm where it was captured between the mating pieces of the isolator shell and protected from corrosion. Is it worth sending the isolator back to the manufacturer or a lab for a post-mortem analysis?
If it failed because of manufacturing defect, the liability would shift to them.

 

[gadfly56]

I was responsible for the skid and all components on that skid (which include the switch and isolator). I selected the make/model of isolator. I obviously will not use this type again, but in the meantime I may be liable for damage for something that I indirectly supplied. ?!

Alloy 20 should be just fine for this application. It sounds as if someone dropped the wrong diaphram material into the isolator. Unless there is a remnant available for forensic analysis you'll never know for sure.

That said, the customer is likely to look to you to repair/replace the damaged elements of his work. You'll have to look to the company who supplied the isolator to make you whole. That may be tricky; usually the terms of purchase severely limit what you can go after them for, although state law may modify your potential recovery in you favor.

 

[petersonra]

it sounds a lot like someone used the wrong material especially to be eaten that fast. on would think there would be some remnant of it left though.

I think i would probably have used a Teflon coated diaphragm but alloy 20 should have worked fine.