Flammable liquid - sparks 2

[SrChemE]

Dear All,
I am in the process of installing a pressure transmitter on a toluene tank (highly flammable).
A question came up regarding the fact that when opening the 4" nozzle to install the transmitter sparks could develop by something being dropped.
The technicians already use no-spark tools to work on this tank.
What can be done to handle the installation of a new instrument on this tank nozzle that contains flammable liquid?
Are there any procedures identifying how to prevent these sparks? Any particular special cautions?
Thank you!

 

[Latexman]

Watch out for static electricity, especially with toluene! It is non-conductive and it stores static. Is the tank grounded? Ground the worker and their tools to the tank so they are at the same potential. Is the tank inerted?

Good luck,
Latexman

To a ChE, the glass is always full - 1/2 air and 1/2 water.

 

[SrChemE]

yes, the tank is grounded, but not inerted. We use spark-free tools for any job around the toluene tank.
Thanks!

 

[georgeverghese]

Toluene is highly carcinogenic, so breathing gear would be required.

 

[Compositepro]

"EPA has concluded that that there is inadequate information to assess the carcinogenic potential of toluene."

 

[georgeverghese]

Compositepro, Would err on the side of caution with this ambigous stance from the US EPA - in my mind, most simple aromatic compounds are carcinogenic - benzene, toluene, xylenes, ethylbenzene and others.

 

[Latexman]

IMHO, "there is inadequate information to assess the carcinogenic potential of toluene" + "err on the side of caution" [≠] "Toluene is highly carcinogenic". Yes, one does not want to be exposed to toluene vapors, but lets be realistic. The OP wants to put a PT on a 4" nozzle. How many seconds of potential exposure is that during a well planned and executed job with experienced personnel? Add a half-face respirator to the required PPE and get on with it.

Good luck,
Latexman

To a ChE, the glass is always full - 1/2 air and 1/2 water.

 

[LittleInch]

The fact you're installing a pressure transmitter implies significant pressure. How much pressure are we talking about? Only them can anyone make some sensible comments? Can you hot tap this instead of removing what I assume is a blank flame?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Latexman]

It could be, that wasn't my perception though. SrChemE, what kind of tank? Pressure? Temperature?

Good luck,
Latexman

To a ChE, the glass is always full - 1/2 air and 1/2 water.

 

[moltenmetal]

How often is this operation being considered?

If only once, consider inerting the tank with something dense like CO2 or argon to reduce the risk while doing the installation.

If this is a routine operation, consider a way to avoid having to do it- install it and valve it off for instance when not required.

Toluene is NOT "highly carcinogenic"- you're thinking of benzene, which can be shown to be a contributing cause to a very specific cancer (aplastic anemia). Toluene is widely used in consumer products. Benzene is not. The primary concern here is the flammability, and that's a very serious concern.

 

[SrChemE]

I appreciate all of your comments. All information you share will be helpful for the development of this task. Sorry for not getting back to you all earlier, but I was ISO auditing all morning.

The toluene tank in question is not under pressure during normal operation. The tank is set up with a Flame Arrester that has adequate capacity for these scenarios:
 
Pressure relief for accidental line clearing into tank using utility N2
Pressure relief for maximum fill-in rate + thermal outbreathing
Vacuum relief for maximum pump out rate + thermal inbreathing
We also have a Blowoff Manway with 1.0 psig set pressure. (Tank is rated 3 psig.) It operates at amb temp.
The Toluene tank is an above ground tank that has a capacity of ~ 15,000 gallons. Design Temp and Pressure = 200F & 3 psig. This tank is located inside a containment area that provides for containment in the event of a large spill. Whenever routine maintenance is performed on the system, personnel must use spark resistant tools. In line spark arrestor is installed on the inside of the off-loading line and a flame arrestor is designed on the top of the storage tank to prevent outside flame sources from entering the storage tank vent.
The tank is also set-up with Fire Safe Valves on Suction to each pump. Fusible linked valves provide protection in the event of an external fire. If temp reaches 165F, valves automatically CLOSE and shuts off toluene flow to the process.[Not to be confused with in line spark arrestor & vent flame arrestor also installed to keep external fires from entering into the toluene storage tank.]

* The main reason to install a pressure transmitter is to comply with a new plant initiative to monitor design limit exceedances, therefore the transmitter. The maintenance superintendent voiced a concern about sparks during the installation of the instrument and I was just wondering if other sites have a good way of handling this.
Thank you all for your comments and ideas.

 

[georgeverghese]

Agreed, I see a half face respirator is recommended in documentation off the net for short term exposure to TOL vapors. Also beware of the benzene content in this grade of TOL, if any.

 

[chicopee]

Make sure that the instrument is designed for either class 1A, 1B or 1c hazardous atmosphere. The classes mentioned are based on the flash point and boiling point of toluene which I don't have.

 

[moltenmetal]

The atmosphere inside the headspace of that tank is normally hazardous, so that would be a Class 1 Division 1 (likely zone 0) environment. The transmitter must have approvals accordingly. But the original question asked was how to avoid blowing the place up while installing the transmitter, not how to specify one which will be safe once installed.

 

[SrChemE]

Thank you for the heads up.
The selected instrument meets the requirement for flammability.
Thanks again.

 

[EdStainless]

Given that hard impact from non-sparking tools will generate enough local heat to trigger ignition I would rig an inerting system for this process.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[PyroLoe]

Some info I found through NFPA

With respect to frictional heat or sparks, it is recognized that there is a need to control sources of ignition, including mechanical sparks from hand tools, that have sufficient energy to ignite flammable vapors. Studies, anecdotes, codes, and referenced standards (e.g., API 2214, Spark Ignition Properties of Hand Tools) show that there is a potential for hand tool sparks to ignite flammable vapors from a limited number of chemicals and under certain unique conditions. These include flammable liquids with low minimum ignition energies, operations in which flammable or combustible liquids are heated, and a typical spark generation that can occur between specific types of hand tools and struck surfaces (i.e., thermite reactions or impact of steel tools on quartzitic materials).

Even spark-resistant tools might not provide suitable protection against ignition. For example, hard metal particles can become imbedded in the relatively soft metal of spark-resistant tools, and these particles can cause sparks when the tools are used.
Over the years, it has become more accepted that ordinary steel hand tools cannot generate ignition-capable sparks, except under unusual circumstances. (See API RP 2214, Spark Ignition Properties of Hand Tools.)”

 

[SrChemE]

PyroLore, many thanks for your information. I will definitely look into this.
I will also share this info with our I&E and mechanics in the plant.
Greetings