Measuring Surface Areas in Square Meters for Paint Calculation on an FPSO

Introduction

In an FPSO (Floating Production Storage and Offloading) unit, surface preparation and painting are critical for corrosion protection. Proper measurement of surface areas in square meters (m2) is essential for estimating the quantity of paint required. This guide provides step-by-step procedures for measuring beams, vessels, piping, the hull, and accommodation areas, along with practical examples and references.

General Formula for Area Calculation

To determine the surface area of any structure, the following basic formulas are used:

• Flat Surfaces: Length (L) × Width (W)
• Cylindrical Surfaces (e.g., Piping, Vessels): Circumference (C) × Length (L), where C = π × Diameter (D)
• Complex Shapes: Break down into basic shapes, calculate separately, then sum up the areas.

1. Measuring Beams

Beams in an FPSO are typically I-beams, H-beams, or box beams. The surface area includes the top flange, bottom flange, and web.

• I-Beam/H-Beam:
• Box Beam:

Example: A box beam with a height of 0.5m, width of 0.3m, and length of 10m:

• Total Area = 2(0.5 × 10) + 2(0.3 × 10) + 2(0.5 × 0.3) = 10 + 6 + 0.3 = 16.3 m2

2. Measuring Pressure Vessels and Storage Tanks

Vessels are usually cylindrical, and their surface area is calculated using:

• Lateral Surface Area: π × Diameter × Height
• End Caps (Hemispherical or Ellipsoidal Heads): π × (Diameter2 / 2) per cap
• Total Area: Lateral Surface Area + 2 × End Cap Area

Example: A cylindrical vessel with a diameter of 2m and height of 5m:

• Lateral Surface Area = π × 2 × 5 = 31.42 m2
• End Caps = 2 × (π × (22 / 2)) = 12.57 m2
• Total Area = 31.42 + 12.57 = 43.99 m2

3. Measuring Piping

Piping systems run across various sections of the FPSO, requiring accurate measurement to estimate paint quantity.

• Surface Area of Pipe = π × Diameter × Length
• Valves, Flanges, and Fittings: These must be estimated separately using manufacturer specifications or a factor of 1.2 to 1.5 times the calculated area.
• Multiple Pipes: Measure and sum all sections.

Example: A pipe with a diameter of 0.5m and length of 20m:

• Surface Area = π × 0.5 × 20 = 31.42 m2

4. Measuring the FPSO Hull

The hull is a vast surface requiring breakdown into sections:

• Flat Sections (Sides, Bottom, and Deck):
• Curved Sections (Bow and Stern):
• Total Area: Sum of all sections

Example: An FPSO hull with a side length of 100m and height of 20m:

• Total Area (both sides) = 2 × (100 × 20) = 4000 m2

5. Measuring the Accommodation Area

The accommodation area consists of walls, ceilings, and floors:

• Walls: Height × Width of each wall
• Ceilings and Floors: Length × Width
• Doors and Windows: Deduct from total wall area
• Total Area: (Walls + Ceilings + Floors) - (Doors + Windows)

Example: An accommodation room with four walls (each 5m wide and 3m high), a ceiling of 5m × 5m, and a door of 2m2:

• Walls = 4 × (5 × 3) = 60 m2
• Ceiling = 5 × 5 = 25 m2
• Total Area = 60 + 25 - 2 = 83 m2

Surface Measurement Tools

Accurate measurement requires the use of the right tools. The most commonly used tools for surface area calculations in an FPSO include:

• Measuring Tape: For direct measurement of flat and accessible surfaces.
• Laser Distance Meter: Provides accurate readings for large or hard-to-reach areas.
• Ultrasonic Thickness Gauge: Used for measuring the thickness of coatings and metal surfaces.
• Flexible Ruler: Useful for measuring curved surfaces like piping.
• Drones and 3D Scanners: Advanced technology for large-area and high-altitude measurements.

Paint Calculation and Allowances

Once the surface areas are determined:

• Paint Coverage: Check the manufacturer’s specifications (e.g., 1 liter covers 8-10 m2 at a specified thickness).
• Number of Coats: Multiply by the required coats (e.g., primer, intermediate, topcoat).
• Wastage Factor: Add 10-20% to account for overspray and surface irregularities.

Example: If total calculated area is 500m2 and paint coverage is 8m2/liter:

• Required Paint = 500 / 8 = 62.5 liters
• With 2 coats: 62.5 × 2 = 125 liters
• Including 10% wastage: 125 × 1.1 = 137.5 liters

Conclusion

Accurate surface measurement in square meters ensures precise estimation of paint requirements, reducing waste and ensuring optimal corrosion protection. Following these guidelines will enhance efficiency in planning and executing painting projects on FPSOs.

References

• ASTM D609: Standard Practice for Preparation of Cold-Rolled Steel Panels for Testing Paint, Varnish, Conversion Coatings, and Related Coating Products.
• SSPC-PA 2: Procedure for Determining Conformance to Dry Coating Thickness Requirements.
• NACE SP0188: Standard Recommended Practice for Discontinuity (Holiday) Testing of New Protective Coatings on Conductive Substrates.