open to the atmosphere vessels

Hi Rich,

I assume you mean 14.9 PSIA.

Go to the Protectoseal web site ( ) and look at "emergency vents and conservation vents". Get a copy of their sizing software for vents.

Also look at the API Standard for emergency vents, API 2000 Venting Atmospheric and Low-Pressure Storage Tanks.

Maybe, just for completeness, check out NFPA 30 (Code-National Fire Protection Agency )Guidance Code, Flammable and Combustible Liquids Code Handbook, with Guidance notes for fire protection professionals world wide Referred to in OSHA 1910.106

Oh well, here is a list (some just for reference):

•API 2000 (Code-American Petroleum Institute )
Venting Atmospheric and Low-Pressure Storage Tanks.
Standard written by the American Petroleum Institute for above ground storage tanks. Designed for operation at pressures from vacuum through 1.034 bar gauge
Internationally accepted standard
Used as the basis for OSHA 1910.106

Equipment Covered
Normal Vents
Emergency Vents
Flame Arresters
Blanketing Valves


•NFPA 30 (Code-National Fire Protection Agency )
Guidance Code
Flammable and Combustible Liquids Code Handbook
Guidance notes for fire protection professionals world wide
Referred to in OSHA 1910.106

Equipment Covered
Normal Vents
Emergency Vents
Flame Arresters
Blanketing Systems

•OSHA 1910.106 20 CFR (Occupational Safety & Health Association )
Code of Federal Regulations relating to adequate provision of normal venting for above ground tanks and emergency
relief venting for fire exposure for above ground tanks.

Equipment Covered
Normal Vents
Emergency Vents
Flame Arresters
Blanketing Systems

•EPA 40 CFR (Environmental Protection Agency)
- 95 Subchapter C Code of Federal Regulations for control - 'Air Programs'
Each part deals with specific subjects.

Part 50 has two levels
1) National Primary Ambient Air Quality Standards. Levels of air quality necessary to protect public health.
2) National Secondary Ambient Air Quality Standards. Levels of air quality necessary to protect the public from any known or
anticipated adverse effects of pollutants.

Part 60 - Standards of Performance for New Stationary Sources.
Applies to any new structure, building, facility or installation including those refurbished after July 23 1984.
Synthetic Organic Chemical Manufacturing Industry and Volatile Organic Liquid Storage Vessels and Handling Equipment.
Industrial Surface Coating: Cans.
Petroleum Refineries:Fugitive Sources.

Storage Tanks Affected:
1) Fixed roof tank in combination with an internal floating roof that meets strict design perameters.
2) External floating roof tank meeting specified design perameters
3) Fixed roof tank with a closed vent system and control device. With the third option; the system must
be monitored to ensure that no part of the system leaks more than 500 parts per million

•UL 525 (Underwriters Laboratories - Standard 525 )
Flame\Detonation Arresters for Use on Vents of Storage Tanks for Petroleum Oil and Gasoline
Commonly used test protocol for vent line and end of line flame arresters.
Includes new listing category for detonation arresters.

•FM Research Class 7371 (Factory Mutual Research Class 7371 )
Test Procedure for Detonation Arresters.
Internationally respected testing and approval organisation.
Has developed a distinct test protocol to qualify detonation arresters.
Also tests vent line and end of line flame arresters.

•USCG 33 CFR Part 154 (United States Coast Guard )
Marine Vapour control Systems
Test Procedure for Detonation Arresters only.
Licensing authority stating that arresters must be tested by an independent laboratory.
Defines requirements for design, installation and safe operation of systems.
Tests for overdriven detonation as well as detonations and deflagrations.
Does not test itself.

Regards, John.

Holy cow!(or Santa Vaca) to John's reply...

My guess is you're trying to figure out when enough condensate will form inside the vapor space to dilute the contents. This normally would not be a corrosion accelerator for HCl or caustic, depending on the tank material. (HCl would obviously NOT be stored in carbon steel.)

The problem needs to be better described for help to be provided.

Thanks John... but way to much information. Rustbuster, you are right on target for my question. Let me know what information is required and I will get it. The HCl is stored in a pressure vessel looking object that is rated for 14.9 psi. There is no "g" or "a" on the end. The HCl is supposed to 98% which should not be a problem for CS @ ambiant temps I'm told. Richard Schram
Mechanical Integrity Specialist
Pharmacia Global Supply Arecibo-P. Rico
rschram@pharmacia.com

Hi guys,

Sorry about the info-flood, sometimes I get carried away. I guess I was thinking that with the right conservation vent, the ingress of moist air during the fill-empty cycle could be eliminated (the vent would filter-out the moisture). If the installed vent is just a pipe "goose-neck" you would expect to pick up some humidity. I will be watching for rustbuster's reply.

Regards, John.

Hi,

My first question would be do you have access to a chemical engineer? Rate of evaporation/condensation calculations are usually one of their specialties.

Second, my experience with caustic and HCL would be manufacturing plastic tanks. Lots of plastic tank suppliers will be willing to add the necessary number of connectors as per your design specification. From my corrosion charts, Hydrochloric Acid and Carbon Steel are poorly rated.

Can you build a shelter (supported roof) to protect your tanks from direct sunlight?

Is someone mixing a batch of HCL and then storing it in a tank, or will the tank be continuously feed with HCL?

Sincerely,
Babyyoda

babyyoda,

There will be constant feed to the vessel. Richard Schram
Mechanical Integrity Specialist
Pharmacia Global Supply Arecibo-P. Rico
rschram@pharmacia.com

Caustic solutions are not made more corrosive to carbon steel or stainless steel by dilution, so if you formed a layer of diluted (lower density)solution on top of the tank contents, no corrosion consequences will ensue. So for these tanks, formation of internal condensate is a "who cares!" This is not always so. Some FRP, for example, can experience more attack at lower caustic concentrations.

On the acid side of things, SULFURIC ACID loses its oxidizing nature and becomes very aggressive to carbon steel when it is diluted, which can occur rapidly from ambient humidity because concentrated sulfuric acid is very hygroscopic.

This does not apply to HCl, and, as I said before, you should not be storing HCl in carbon or stainless steel. Reducing the concentration of HCl by condensate reentry will tend to decrease its aggressiveness. However, this is such a slight effect that the situation is similar to above - i.e. there is no effect worth caring about if you have selected the correct material for the HCL in the first place.

Therefore, APIGUY, your search for condensing volumes etc,. is not warranted.

Are you sure the acid is HCl? What you describe sounds like Sulfuric Acid (H2SO4. Sulfuric acid is commonly supplied in concentrations of 93 to 98 % and at those concentrations carbon steel is commonly used. For your climate, HCl is probably supplied at 28 to 32 % concentration (thermodynamically limited). It is usually stored in fiberglass or lined tanks.

In any case, there are vent driers available which use a dessicant material which absorbs water vapor from the air.
Sizing depends on the rates and volumes of in-breathing of air into the tank.