Static Electric Discharge Hazard 9

[MotoGP]

I'm rapidly getting in over my head on this subject.

My specific concern pertains to Bulk Oil Tank Vessels, but, I'm rapidly becoming interested in the "any given piping" scenario, to wit, and "borrowing" from the disconcerting language of NFPA 77, "...under certain conditions, particularly with liquid hydrocarbons, static (electricity) may accumulate in the liquid...The generation of static electricity can not be prevented absolutely, because its instrinsic origins are present at every interface". Oh gee, that's swell...

So, the pipe material, the physical properties of the fluid contained within the pipe and the velocity that it travels, the pipe dimensions, the action of fluid, let's say discharging through an open end of piping (and at a given distance over a fluid level within a tank, if a fluid is present),etc, should all play a role, in contributing to a "certain condition"...maybe?

I have looked through all of the "McGraw-Hill" Handbooks on Piping and done internet searches "ad nauseum", albeit with some "near misses"...any help to steer me in the right direction will be greatly appreaciated.

I am in search of a "recipe", or a "flowchart" or something similar to understand when, where and why there exists a need to ground a piping span in order to remediate a "misadventure" due to a hazardous electrostatic discharge.

 

[oxilume]

MotoGP

I wrote a Best Management Practice for preventing static electricity discharge while pneumatically conveying drill cuttings containing synthetic drilling fluids on offshore drilling rigs. Here are a few of the references I used.

Links:

http://www.woodweb.com/knowledge_base/PVC_piping.html

http://www.electrostatic.com/Luttgen.htm

http://home.att.net/~waterfront-woods/Articles/Electricity/static.htm

http://www.chevronphillips.matweb.com/brochures/ethylbro.pdf

http://www.chem.mtu.edu/org/aiches&h/pdf/Abstract2002.pdf

http://www.api.org/step/newsletter/November98.htm

API RP 2003, Protection Against Ignitions Arising Out of Static, Lightning, and Stray Currents, Sixth Edition, September 1998. This document provides guidance on safe operating practices to prevent hydrocarbon ignition arising from static, lightning and stray currents. Major operations covered include tank truck & tank car loading, marine operations and storage tanks. [Order No. K20036]

http://www.marinecompliance.org/newsletters/uscgnewsDEC.html

Todd

http://www.oxilume.com

 

[ddace]

This tread is quite interesting and has provided me some good information on the subjet. I am curently desining the fuel system, including the day tank, for a mobile diesel genset (approx 100gal/400l).

I would like to know how these concerns are avoided in the transport industry ? I.E. Most fuel tanks on vehicules are filled from the top at high velocity with no dip pipe. Doe's all this matter have to do with the volume of the fuel tank and/or quantity of fuel transfered in a given period ?

My tank is well grounded to the trailer but filled from the top. Should I consider a dip pipe? The consumption of the engine (when running at full load) will require a transfert of approx 150 l. every 15 minutes. A tranfert pump will supplie it to the day tank from a bulk tank in about 1.5 min?

 

[rmw]

To all thread participants:

This has been one of the most informative and professionally handled threads that I have read recently.

Congrats to all who contributed. I benefitted greatly from reading it.

rmw

 

[leveles]

You CANNOT prevent static buildup in purely dielectric
fluids flowing thru pipes (fluid shear condition), BUT
Metal pipes or any section with even high resistance,
like carbon fibre matrix is sufficient to dissipate it.
If you have high insulator piping like glass, passing
the charged fluid thru a grounded metal nonreactive mesh
removes the concern.

 

[Fizzhead]

First I want to echo the comment of rmw, this forum has gone to great lengths not only to explain the why's and wherefore's of a somewhat difficult subject, but has done so with a significant degree of professionalism. Kudos to all who have contributed here.

ddace:

You ask "should I use a dip pipe?" I would say that if you haven't gotten that impression from the contents of this thread, then you have wasted all the time you spent reading it! I know plenty of people who have assumed that because diesel has a very low vapor pressure there should be no such concern. One even has the scars to prove the falsehood!

Your question about vehicle fueling is a good one. One big difference is that vehicle fuel tanks vent out through the fill piping, not a standard design elsewhere in hydrocarbon liquids transport engineering. Given that the most common fuel is gasoline which is highly volatile and flammable, I would postulate that the difference is related to the difference in venting systems, not the volume of fluid transferred or volume of the tank. I will very much look forward to the contributions of some of the other commenters here on this question.

 

[25362]

The following site provided by Google:
Electrostatic ignition hazards in motor cars - occurrence, detection and avoidance by Ulrich von Pidoll, may be helpful.

 

[BoBliness]

To anyone interested, the Australian Standard concerned is:
" AS 1020:1995 - The control of undesirable static electricity"

Sorry it took me so long to get this post up, but i had some trouble joining the site

Cheers