Tank Blanketing

Tank blanketing (also called nitrogen blanketing or inert gas blanketing) is a process used to protect the contents of a storage tank by maintaining a layer of inert gas (commonly nitrogen) over the product surface. This protects the tank’s contents from contamination, oxidation, fire risk, and vapor loss.

Purpose of Tank Blanketing

1. Prevent oxidation - Especially for oxygen-sensitive products (e.g., food oils, pharmaceuticals, fuels).
2. Reduce explosion risk - Keeps flammable vapors below explosive limits by displacing oxygen.
3. Avoid contamination - Blocks moisture, dust, and microbes from entering.
4. Minimize vapor loss - Reduces emissions and product evaporation.
5. Prevent tank collapse - Maintains pressure during pump-out or thermal contraction.

How It Works

A tank blanketing system maintains a low-pressure blanket of inert gas in the tank’s vapor space above the medium. A tank blanketing system typically includes:

• Reducing Valve (Inlet Side) - Opens to admit nitrogen when internal pressure drops below setpoint.

• Sustaining Valve (Outlet Side) - Opens to relieve excess pressure during filling or heating.

• Safety Valve / Pressure & vacuum relief valve (PVRV) - Backup safety device to prevent rupture or implosion.

Common Inert Gases Used

• Nitrogen (N₂) – Most common, inexpensive, non-reactive.
• Carbon dioxide (CO₂) – Used in food and beverage applications.
• Argon – Used for highly reactive chemicals, but more costly.

Industries Using Tank Blanketing

• Food & beverage (e.g., oils, juices, beer)
• Pharmaceuticals
• Petrochemicals and refineries
• Cosmetics
• Paints and coatings
• Chemical storage (flammables, solvents)

Advantages

• Enhanced safety (fire/explosion prevention)
• Better product quality
• Reduced emissions
• Extended shelf life
• Complies with environmental and safety standards (e.g., API 2000)

Typical Example

In a Brewery CO2 is commonly used as the blanketing medium. The reducing valve is set at 3.5 Barg and the sustaining valve at 3.8 Barg.

1. On startup the tank is completely empty and is pre-charged with CO2 to 3.5 Barg by the reducing valve.

2. As the tank is filled with beer, the CO2 compresses and when the pressure reaches 3.8 Barg, it is vented out of the tank through the sustaining valve. The CO2 is often reused and not vented to the atmosphere.

3. When the tank is emptied of beer, the CO2 pressure reduces and consequently the reducing valve lets in more CO2.

4. The valve sizes are determined by the rate at which the tank can be filled and emptied and not by the size of the tank.

For further help or information about these products please contact us on +44 (0)1482 601030 or email sales@flowstar.co.uk.