Arcing through a nylon tube running natural gas

[bhzimmer]

My issue is the concern of running natural gas through a nylon tubing instrumentation line. I'm concerned that a static charge may build up and cause arcing through the tube which would lead to an explosion. The pressure in the line is low, around 30-60 psi, with flow rates/velocities which are undetermined as of yet. The tubing is 1/4" ID with a wall thickness of .040".

Based on the dielectric strength of the nylon, it seems that a voltage of 14000 V will be enough to cause arcing.

Is there any way to measure the strength of the electric field, to get an idea of how high the voltage levels are? Is a maximum voltage that the tube could collect? (is there a way to determine that maximum?)
And is there any way to know the velocity above which conditions will be unsafe?

Any help in this matter is greatly appreciated.

 

[VEBill]

Is there oxygen inside the same tube?

 

[bhzimmer]

No, there is not enough oxygen in the tube for an explosion to occur (unless a leak occurs through the arcing).

 

[bogeyman]

Three questions for you

Is it legal to pass NG through a nylon tube in your place of work?
Does nylon have the qualities required to resist any chemical attack that the gas may present?
Does nylon tube allow NG to pass through its walls? it wont stop helium.

A specialy developed plastics pipe is used in UK underground gas supplies which does resist any form of attack from the gas, I would suggest that you use a similar material and cover it if you wish with a metalic screen bonded to ground to prevent arcing from the outside of the tube.

 

[OperaHouse]

I don't think this would be a problem in the tube itself. The problem would exist at the first metal transition piece if it is not grounded. I have seen this in rubber hoses that carried a very light oil. A metal T was placed in the line and a one inch arc would jump to the nearest grounded metal.

 

[bhzimmer]

Bogeyman: There is no law to prevent us from using nylon tubing for this application, any standards that I have found relating to this issue have been specific to higher operating pressures.

From a chemical resistance standpoint, the nylon is compatible with NG.

 

[nbucska]

Without O2 there can't be any explosion and even if there
would be, it may not damage the elastic nylon tube.

I used some unknown 6mm plastic tube for H2+O2 torch and it exploded back several times without any effect.

Why don't you try adding O2, and exploding it, to see what
if any damage an explosion would cause ?


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