Aux 1 Unit 6 Q14

Let’s visualize an air reservoir (or receiver) and its typical mountings:

Visual Description

Imagine a large, cylindrical steel tank, similar in shape to a propane tank but often much bigger. Its size can vary significantly depending on the application and required air storage capacity. The tank is usually painted in a bright color, often red or blue, for visibility and safety identification.

Mountings

1. Support Structure:

• Saddles or Cradles: The most common mounting method involves saddles or cradles that support the tank horizontally along its length. These are usually made of steel and bolted securely to the deck or foundation.
• Legs or Stands: In some cases, the receiver might be mounted vertically on legs or stands, especially if space is limited.

2. Piping Connections:

• Inlet: A large-diameter pipe connection, typically located near the top of the tank, allows compressed air from the compressor to enter the receiver.
• Outlet: Another large-diameter pipe connection, usually at or near the bottom of the tank, allows compressed air to be drawn from the receiver for use.
• Other Connections: Smaller pipe connections might be present for:
  • Safety Relief Valve: Vents excess pressure to the atmosphere.
  • Drain Valve: Allows for the removal of condensate (water) from the tank.
  • Pressure Gauge: Indicates the internal pressure of the receiver.

3. Manhole or Inspection Cover:

• Access Point: A large, bolted cover on the top or side of the tank provides access for internal inspection, cleaning, and maintenance.

4. Lifting Lugs:

• Handling and Installation: Metal lugs or eyes welded to the tank’s body facilitate lifting and positioning during installation or maintenance.

5. Vibration Isolators (Optional):

• Vibration Dampening: In some installations, vibration isolators (rubber pads or springs) might be placed between the support structure and the tank to minimize vibrations transmitted to the vessel’s structure.

6. Protective Coatings:

• Corrosion Prevention: The tank’s exterior is typically coated with paint or other protective coatings to prevent corrosion, especially in marine environments.

Key Points to Note

• Secure Mounting: The mountings are designed to securely hold the receiver in place, even under the stresses of pressure fluctuations and potential ship movements.
• Accessibility: The mountings and connections should allow for easy access for inspection, maintenance, and operation of valves.
• Safety: The safety relief valve and pressure gauge are critical components for ensuring the safe operation of the receiver.
• Material and Construction: The tank is constructed from high-strength materials and welded to withstand the high internal pressures.

In summary:

The mountings on an air receiver play a vital role in ensuring its stability, accessibility, and safety. They include support structures, pipe connections, access points, and other features designed to facilitate its proper installation, operation, and maintenance.

To protect the interior surface of a large air reservoir against corrosion, several coating options are available. The most suitable coating depends on factors like the operating environment, budget, and desired maintenance interval. Here are some common choices:

1. Epoxy Coatings:

• Advantages:
  • Excellent adhesion to steel substrates.   1. Evaluation of adhesion of epoxy resin sealant to improve the corrosion resistance of thermal sprayed coatings appliedadhesionscience.springeropen.com
  • High resistance to corrosion, chemicals, and abrasion.   1. Epoxy Surface & Wet Tolerant Protective Coating – Cactus Industrial www.cactusindustrial.com
  • Wide range of formulations available for different environments.
  • Long service life.
• Disadvantages:
  • Surface preparation is critical for proper adhesion.
  • Application requires specialized equipment and expertise.
  • Can be sensitive to UV degradation if exposed to sunlight.   1. Does UV Resistant Epoxy Exist? – Zeraus www.zeraus.com

2. Polyurethane Coatings:

• Advantages:
  • Good resistance to corrosion, chemicals, and abrasion.
  • Flexible and can withstand some degree of expansion and contraction.   1. Flexibility and elasticity of polyurethane – POLIMIX www.polimix.eu
  • Easier to apply than epoxy coatings.
• Disadvantages:
  • May not be as durable as epoxy coatings in harsh environments.
  • Can be sensitive to moisture during application and curing.   1. Effect of Humidity & Temperature on Painting www.paintcenter.org

3. Zinc-Rich Coatings:

• Advantages:
  • Provides cathodic protection to the steel, sacrificing itself to protect the base metal.   1. Zinc and Corrosion thermalsprayzinc.zinc.org
  • Highly effective in preventing corrosion, even in harsh environments.   1. Corrosion Protective Zinc Coating Systems – Baril Coatings USA barilcoatings.us
  • Can be used as a primer for other coatings.   1. Best Zinc-Rich Primers in 2022 — Including Phosphates and Chromates www.ippmagazine.com
• Disadvantages:
  • Requires proper surface preparation and application techniques.   1. Frequently Asked Questions on Surface Preparation for Zinc-Rich Coatings www.zrcworldwide.com
  • Can be susceptible to damage if not top-coated.

4. Hot-Dip Galvanizing:

• Advantages:
  • Provides a thick, durable zinc coating that offers excellent corrosion protection.   1. Coatings & Finishes: The Differences Between Hot Dip Galvanising And Zinc Plating – Accu www.accu.co.uk
  • Relatively low cost compared to other coatings.   1. Excellent reasons to hot dip galvanize steel www.premiergalvanizing.co.uk
  • Long service life.   1. Longevity | American Galvanizers Association galvanizeit.org
• Disadvantages:
  • Not suitable for all air receiver designs due to size and shape limitations.
  • Can create a rough surface that might require additional smoothing for certain applications.   1. Materials for Hot-Dip Galvanizing www.duncangalvanizing.com

5. Other Coatings:

• Inorganic Zinc Silicate: Provides excellent corrosion resistance and high-temperature tolerance, but requires specialized application.
• Fluoropolymer Coatings: Offer exceptional chemical and corrosion resistance, but are generally more expensive.
• Ceramic Coatings: Can provide excellent abrasion and corrosion resistance, but might be less flexible and more prone to cracking.

Factors to Consider When Choosing a Coating:

• Operating Environment: Consider the specific environment the air receiver will be exposed to (e.g., humidity, temperature, presence of corrosive gases or chemicals).
• Surface Preparation: The quality of surface preparation significantly impacts the coating’s adhesion and long-term performance.   1. The Effect of Surface Preparation on Coating Performance – KTA-Tator kta.com
• Application Method: Some coatings require specialized equipment or application techniques.
• Maintenance: Consider the ease of repair and touch-up in case of damage to the coating.
• Cost: Factor in both the initial cost of the coating and the potential long-term savings due to reduced maintenance and extended service life.

Recommendation:

For most large air receivers on marine vessels, epoxy coatings or hot-dip galvanizing are often preferred due to their excellent corrosion resistance, durability, and long service life. However, the final choice should be made in consultation with a coatings expert and considering the specific requirements of the application.