static free solvent extraction line
static free solvent extraction line
(OP)
Hi
what type of pipes would you recoment for a solvent extraction line? the solvent been pumped contain NO3, Cl, Na2CO3, H2SO4 and Entrained Organic Solvent.
the solvent is highly flammable and any sparks should be avoided at all cost. The pipes must be completely static free.
where can i find guidelines/ rules of thumb on static free pipelines regarding
-material
-flov velocity
-earthing
-others?
thks
what type of pipes would you recoment for a solvent extraction line? the solvent been pumped contain NO3, Cl, Na2CO3, H2SO4 and Entrained Organic Solvent.
the solvent is highly flammable and any sparks should be avoided at all cost. The pipes must be completely static free.
where can i find guidelines/ rules of thumb on static free pipelines regarding
-material
-flov velocity
-earthing
-others?
thks





RE: static free solvent extraction line
Of greater concern would be the locations where phase separation occurs, where the dangerous charge separation can develop. It depends on geometry, transfer rate, etc. as to the magnitude of the hazard. Avoid free floating conductive objects or long probes in the vessel. Multiphase materials should be introduced into vessels through dip tubes or via bottom entry. Velocity should be controlled and splashing/spraying avoided. Vel of <1 m/s is usually safe for homogeneous fluids without dip pipes but yours is heterogeneous. Decelerate fluids upstream of discharge points. To know how far upstream requires knowing the relaxation time of the accumlated charge.
Insulative piping and vessels can be used by experienced industrial practitioners, but really pay attention to controlling intensity of motion, avoiding liquid surfaces that can accumulate charges, and providing pathways to ground, to remove eletrostatic charges. Electrostaticly conductive non-metals are preferred.
NFPA is a good source and API has a guide as well but I do not recall much specific advice on multiphase solutions.
There are books like "Avoiding Static Ignition Hazards in Chemical Operations" (a CCPS Concept Book)by L. Britton
that may be useful.
RE: static free solvent extraction line
what is your opinion of using GRP (glass fibre) piping for such an application?
RE: static free solvent extraction line
RE: static free solvent extraction line
Steamguy2
www.SteamPlantEngineering.com - Discussion & resources for professionals in the Power Generation Industry
RE: static free solvent extraction line
Solvents with some water solubility or contaminants will tend to be conductive. If the bulk is the aqueous phase you are in relatively good shape as long as the solvents are compatible with the resin. Excluding oxygen is also required if there is any scenario that would place the vapor space in the flammable range (above the LEL and below the UEL). I myself would be willing to use it but follow-up after maintenance is important. Leaving bonding and grounding disconnected would create a hazard that would not be obvious. Unless a heptane, toluene or hexane type of material is the solvent, the rest may not apply but it is useful context for you.
What I would also be careful of is the transitions between systems, metallic to nonmetallic piping, and operations e.g. pipeline to vessel, flow thorough a filter media).
Again it is the issue of charge separation occurring at transitions, S to L, L to L, conductive wall to nonconductive wall and the condition of the receiving vessel.
Having a conductive fluid may not be enough protection. For instance, if this were a batch system and the receiving vessel were also an insulator, the charge may not have a path to ground, due to an air gap from the inlet pipe to the liquid surface and a nonconductive closed block valve on the vessel outlet.
Construction that can create a capacitor also can be a problem. Glass reactors are often damaged by static discharges that punch holes through non-conductive glass to the steel, from mixing or filling with low conductivity fluids
Even with a path to ground, a low conductivity solvent phase that settles out (or to the top) may have a significant relaxation time. This would mean that activities like dipping a sample immediately after filling could be hazardous, regardless of whether the vessel or pipe was conductive or not.
Metal has the advantage of providing most of the path to ground. With nonmetals, dissipative or conductive construction is preferred, if feasible. Otherwise careful earthing and bonding is necessary to assure that induced charges and capacitors are not formed.
Gary
RE: static free solvent extraction line
RE: static free solvent extraction line
The answer is that this material is handled safely, day in, day out at numerous metal purification facilities worldwide, using non-metallic piping in properly designed equipment. There have also been some recent, catastrophic fires at such facilities. Others will know the details of the fires far better than I do. But the principal problem seems to be inadequate inerting and other design flaws rather than a lack of consideration for the possibility of static discharge, or the mere use of non-metallic piping.
The organic diluant used also matters greatly. If the diluant is being used sufficiently below its flash point, there's no issue because a static discharge will not generate a fire.
RE: static free solvent extraction line
RE: static free solvent extraction line
RE: static free solvent extraction line
A common example is a plastic bucket or gasoline container that gets filled. The gasoline gets charged by flowing though a pipe and then falls into the bucket. The charge will accumulate in the bucket and be attacted to the bottom which is close to the ground. The charged liquid cannot flow back up the falling column of liquid. However, if the fill pipe is conductive and lowered to the bottom of the bucket, the charged liquid will be attracted to the pipe (or any ground wire) and be neutralized. In the case where the charge has accumulated on the bottom of the bucket it will slowly bleed-off by various mechanisms. If the bucket is immediately lifted off the ground after filling the electrical capacitance of the bucket falls drastically and the voltage of the accumulated charge will rise proportionally. The charge will now be attacted to the nearest ground which is likely to be the wire bail on the bucket and a spark is likely to occur at the surface of the gasoline which will result in an ignition.
RE: static free solvent extraction line
I take note.
What is your oppinion regarding the use of HDPE?
RE: static free solvent extraction line
RE: static free solvent extraction line
Our application is a relative long line (1.2 km) and I want to ensure the liquid remain below its flash point