What is Concrete coating pipe (CWC Pipe)

The concrete coated pipe also called concrete weight coating pipe (CWC pipe), it is the steel pipe external with concrete weight coating (Mixed with cement, aggregates, reinforced steel mesh, and water), to provide strong downward force protection (Impact from anchoring, dredging activity, fishing, ship sinking) or a negative buoyancy for the pipelines. This pipe is commonly used in sub-sea (submarine) pipelines, with adding the proper weight of the concrete coatings to support a resistant pressure against seawater.

Concrete coated pipe types and dimensions

For to use in different circumstances in the sub-sea environment, the pipe could be in different dimensions, and available with different weight/thickness/density of concrete coatings, also can be processed with anti-corrosion coatings and insulation coatings.

Below the typical ranges:

Dimensions ranges for Concrete Coated Pipe

Mother pipe standards: API 5L Grade B to Grade 80. ISO 3183 Grade L245 to L555.
Diameter range: 6” to 60”
Pipe Thickness: SCH 20, SCH 40, SCH 80
Length: Up to 12 meters

Concrete weight coating density

The concrete formulation can be tailored to any specified density specifications, normally are 140, 165, and 190 pounds per cubic foot, smaller or greater densities also applicable.
Density range: 1800-3450 kg/m3 (112-215 lbs/ft3)
Concrete compressive strength: From 3000 psi to 7200 psi. Up to 50 Mpa.
Concrete thickness: 1 inch to 8 inches. (25 mm to 200 mm)

Referred Standards

DNV-OS-F101: Submarine Pipeline Systems – SAWL 245, SAWL290, SAWL 320, SAWL 360, SAWL 415, SAWL 450, SAWL 485, SAWL 555
ISO 21809-5:2010: Petroleum and natural gas industries – External coatings for buried or submerged pipelines used in pipeline transportation systems – Part 5: External concrete coatings.

• ASTM C42 Standard Test Method for Obtaining and Testing Drilled Cores and Sawed Beams of Concrete
• ASTM C87 Test Methods for Effect of Impurities in Fine Aggregate on Strength of Mortar BS 1881 Methods of Testing Concrete
• ASTM C642 Standard Test Method for Specific Gravity, Absorption, and Voids in Hardened Concrete
• BS 3148 Test Methods for Water for Making Concrete
• BS 4449 Material Specification for Carbon Steel Bars for Concrete Reinforcement
• BS 4482 Hard Drawn Mild Steel Wire for the Reinforcement of Concrete
• BS 4483 Specification for Steel Fabric for the Reinforcement of Concrete
• ISO 4012 Test Specimen of Determination of Compressive Strength

Features of CWC pipe

CWC pipe consist of cement, water, aggregates and reinforcement materials, it’s advantage is to fix the pipeline stably performances and provides effective mechanical protection. Compared with other insulation type like pipe-in-pipe, CWC pipe is more efficient in saving cost, easy the pipeline installation and convenient the operations.

Key notes during concrete weight coating pipe manufacturing processes

(Before coating the concrete, the steel pipe normally shall be coated with an FBE coating.)

Refer to What is Hot Induction Bends and Inspection guides.

First is to calculate the proportioned quantity of cement, iron ore, sand, and granite aggregate, they mixed them together to create a specified density required; During concrete buildup processes, control the steel wire mesh position will get a certain wire depth with the coating; Weighing each joint to verify if they meet the requirements of the project; Clean the concrete coated pipe ends and trimmed the excess wire. After curing in 30 days, the material could be ready for delivery.

(The concrete coating can be done via machine or form-applied coating and can be prepared for any thickness at the job site. The external concrete coating is designed to protect the isolation coating of pipe from mechanical damage during repair, upgrading, construction, and operation. The concrete coating method is advanced and the best method of protecting pipelines which comply with regulatory procedures.)

Benefits of concrete coated pipe

• Mechanical protection and negative buoyancy
• Anti-corrosion protection
• Excellent Compatibility
• Long-term adhesion to steel
• Well suited to reel laying methods
• High resistance to cathodic disbondment
• And much more

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