Question: Proper transfer of flammable liquid to storage tank 1

[CarlaRyan]

I have a problem. We have to pump 20 gals of a
diesel fuel additive with a flash point of -20 celcius (low flashpoint) from a 55 gal metal drum using a chemically resistant plastic hand operated drum pump into a 12,000 gal diesel fuel storage tank every day. The drum pump is attached to the 12,000 gal diesel fuel storage tank via a chemically resistive rubber hose that uses brass threaded hose nipples. (The end of the hose is attached to the plastic pump via a threaded brass hose nipple. The other end of the hose is attached to the 12,000 gal diesel fuel storage tank via a threaded brass hose nipple thats threaded into a stainless "T" fitting on top of the 15 ft high fuel storage tank. My concern is twofold. First Problem: we are splash filling 20 gals of a -20 celcius flashpoint liquid into a 12,000 gal tank that already has about 1000 gals of diesel fuel in it by the time we pump the 20 gals every day. The hand pump is capable of pumping 32oz per revolution about 32oz every 2 secs). I'm terrified to do this wrong and I know splash filling low flashpoint liquids is typically wrong but is it probable that an issue
will occur pumping such a small amount (20 gals) into that large a tank (12,000 gal) when about 1000 gals of diesel is already in the tank? Will an unsafe amount of vapor be likely to build up? and, Second Problem: This
problem is easier. Where on earth do I ground this setup? My plan was to make certain the diesel fuel storage tank is properly (earth) grounded, then ground the 55 gal metal drum to earth ground, then bond the plastic pump to the 55
gal metal drum. The proplem is what about the hose? The hose is rubber with brass threaded fittings so the fitting is attached to the tank but there's rubber between that fitting and the drum pump, the hose is NOT metal lined
and the drum pump is plastic anyway so it seems to me there's a ton of room for unequal potential. I'm lost with the second problem as well now that I'm typing it. Any help would be greatly appreciated. I want to be as safe as
possible and definitely within requirements.

Carla

 

[Montemayor]

Carla:

Every storage tank I worked on as a project and process engineer when I was working projects for DuPont had to have a fill dip pipe (with a 3/8" anti-syphon hole at the top of the dip pipe and under the tank roof). Dupont has specific engineering standards for this construction and fill method. I did this over 20 years ago and I've seen just about everyone I know, and have worked for, using it. The reasons for its use is that it was discovered (over 40 years ago) that a static electrical charge is generated when dumping or spraying hydrocarbons in a free-fall inside a storage tank. This immediately presents the second necessary ingredient as relates to the infamous "triangle" of Fuel-Oxidant-Ignition. The dip pipe has proven itself as a device that arrests the potential to buildup an electrical charge and potential spark.

The generation of vapors in the tank has no hazard related to the fill method. Over-pressure is normally handled with a conservation vent. The rate of filling the tank also has no related hazard attached to it. However, as per my experience and a lot of other engineers who have been around a lot less than I, what you are doing is hazardous. It is hazardous because it has the propensity to generate an electrical static charge inside the tank. This potential charge should be safely grounded.

I would also seriously criticize the use of plastic components in this type of industrial installation. Not only are they weak, prone to leakage and rupture - but they are insulators that often stonewall any effort to ground the equipment.

The first thing I would do in install a dip pipe feeding method for the fuel additive.

I hope this experience helps out.

 

[CarlaRyan]

Monte,

Thank you so much you saved my life...and quite possibly lierally lol. Tommorow morning I will immediately order a cast iron housing pump (I have one in mind) as well as begin work on the fill dip pipe. Is there a company that sells an off the shelf dip pipe or can I just fabricate a stainless pipe and thread it into the existing port? How far down from the entry port should the 3/8" hole be? How far up from the tank floor should the bottom of the pipe be? Is it ok if the pump is always emersed in the existing diesel fuel in the tank? Also when we fill the tank with the additives we are only pumping 20 gals into a 12,000 tank via a hand pump so won't it just hit the fuel then not penetrate the the fuel? Should we change the rubber hose that currently has no metal lining to a hose that's conductable?

Thanks for the first rate info

 

[25362]

Carla, just to satisfy my curiosity:

[•] is it an anti-static additive ?
[•] do you have an inert gas blanket in the tank ?

 

[MJCronin]

carla....

My two cents..

It might also be possible to include a recirc loop ino your piping system and to inject your additive somewhere in the loop.

This configuration would ensure mixing as well as solve your static charge problem.

Additionally, the rules of the US piping codes ASME B31.1 and B31.3 ban the use of plastic piping in permanently installed systems. NFPA-30 also has mention of plastic piping systems.

Perhaps you could explore the use of a small chemical addition system or "shot feeder" with the use of a circulating pump.

http://216.197.108.105/EP/2 Chemical Feed System/Form8400.pdf

Let us know your final decision

regards..

-MJC

 

[Compositepro]

The dip pipe must extend to below the surface of the fluid in the tank. Static is not generated by freefall. It is generated by fluid flowing against a pipe or tank wall. The problem with freefall is the gap in the pipe which interupts the conductive path for charge to flow back up the pipe to where it was created by charge separation.

A large tank containing a flammable concentration is a bomb waiting for a spark. Diesel has a high flash point and is not explosive. Gasoline is typically above its flammble limit. If the vapor space in a tank is in its flammable range it should be inerted. Standard safe practice is to eliminate two sides of the fire triangle (oxygen - fuel - ignition source).

 

[dcasto]

You do not ground the system, you bond the tank to the pump so there is no electrical potential, hence, do not use plastic insulators between the pump and tank.

 

[CarlaRyan]

Thanks to all. 2562 we are not using an antistatic additive nor are we pumping an inert gas. Both of those are not options. MLcronin, since your message about the "shot feeder" I have begun talking to the company for the URL you gave me and we are planning on setting up a "shot feeder" connected to the "Loop". That pumping solution wont be installed for at least a month so we have to go with my plan until then. MJcronin; I looked at the US piping codes you suggested and I changed both the hose and pump from plastic to stainless. Everything seems to be right now the only question I have is as follows. After pumping the additive into the storage tank there will be un-needed additive in the 15 ft hose line. We plan to instruct the person that is pumping to reverse pump the un-needed contents left in the hose back in to the 55 gal additive drum. He'll be pumping 20 gals of additive every day so he'll be back pumping about a half gal of the un-needed contents of the hose back into the 55 gal drum every day. Should I be worried about him back pumping diesel fumes back into the 55 gal drum when he's back pumping the contents of the hose. Is it likely that would present any problems? The additive is a Class 3 hazard.